/* lnodelib.c
   
   Copyright 2006-2010 Taco Hoekwater <taco@luatex.org>

   This file is part of LuaTeX.

   LuaTeX is free software; you can redistribute it and/or modify it under
   the terms of the GNU General Public License as published by the Free
   Software Foundation; either version 2 of the License, or (at your
   option) any later version.

   LuaTeX is distributed in the hope that it will be useful, but WITHOUT
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
   License for more details.

   You should have received a copy of the GNU General Public License along
   with LuaTeX; if not, see <http://www.gnu.org/licenses/>. */

static const char _svn_version[] =
    "$Id: lnodelib.c 3851 2010-09-03 11:55:16Z taco $ "
    "$URL: http://foundry.supelec.fr/svn/luatex/tags/beta-0.63.0/source/texk/web2c/luatexdir/lua/lnodelib.c $";

#include "lua/luatex-api.h"
#include "ptexlib.h"

#define init_luaS_index(a) do {                                         \
    lua_pushliteral(L,#a);                                              \
    luaS_##a##_ptr = lua_tostring(L,-1);                                \
    luaS_##a##_index = luaL_ref (L,LUA_REGISTRYINDEX);                  \
  } while (0)

#define make_luaS_index(a)                                              \
  static int luaS_##a##_index = 0;                                      \
  static const char * luaS_##a##_ptr = NULL

#define luaS_index(a)   luaS_##a##_index

#define luaS_ptr_eq(a,b) (a==luaS_##b##_ptr)

#define NODE_METATABLE  "luatex_node"

make_luaS_index(luatex_node);

halfword *check_isnode(lua_State * L, int ud)
{
    register halfword *p = lua_touserdata(L, ud);
    if (p != NULL) {
        if (lua_getmetatable(L, ud)) {
            lua_rawgeti(L, LUA_REGISTRYINDEX, luaS_index(luatex_node));
            lua_gettable(L, LUA_REGISTRYINDEX);
            if (lua_rawequal(L, -1, -2)) {
                lua_pop(L, 2);
                return p;
            }
        }
    }
    luaL_typerror(L, ud, NODE_METATABLE);
    return NULL;
}

/* This routine finds the numerical value of a string (or number) at
   lua stack index |n|. If it is not a valid node type, returns -1 */

static
int do_get_node_type_id(lua_State * L, int n, node_info * data)
{
    register int j;
    if (lua_type(L, n) == LUA_TSTRING) {
        const char *s = lua_tostring(L, n);
        for (j = 0; data[j].id != -1; j++) {
            if (strcmp(s, data[j].name) == 0)
                return j;
        }
    } else if (lua_type(L, n) == LUA_TNUMBER) {
        register int i = (int) lua_tointeger(L, n);
        for (j = 0; data[j].id != -1; j++) {
            if (data[j].id == i)
                return j;
        }
    }
    return -1;
}

#define get_node_type_id(L,n)    do_get_node_type_id(L,n,node_data)
#define get_node_subtype_id(L,n) do_get_node_type_id(L,n,whatsit_node_data)

static
int get_valid_node_type_id(lua_State * L, int n)
{
    int i = get_node_type_id(L, n);
    if (i == -1) {
        if (lua_type(L, n) == LUA_TSTRING) {
            luaL_error(L, "Invalid node type id: %s", lua_tostring(L, n));
        } else {
            luaL_error(L, "Invalid node type id: %d", lua_tonumber(L, n));
        }
    }
    return i;
}

static
int get_valid_node_subtype_id(lua_State * L, int n)
{
    int i = get_node_subtype_id(L, n);
    if (i == -1) {
        if (lua_type(L, n) == LUA_TSTRING) {
            luaL_error(L, "Invalid whatsit node id: %s",
                            lua_tostring(L, n));
        } else {
	    luaL_error(L, "Invalid whatsit node id: %d",
                            lua_tonumber(L, n));
        }
    }
    return i;
}



/* Creates a userdata object for a number found at the stack top, 
  if it is representing a node (i.e. an pointer into |varmem|). 
  It replaces the stack entry with the new userdata, or pushes
  |nil| if the number is |null|, or if the index is definately out of
  range. This test could be improved.
*/

void lua_nodelib_push(lua_State * L)
{
    halfword n;
    halfword *a;
    n = -1;
    if (lua_isnumber(L, -1)) {
        n = (int) lua_tointeger(L, -1);
    }
    lua_pop(L, 1);
    if ((n == null) || (n < 0) || (n > var_mem_max)) {
        lua_pushnil(L);
    } else {
        a = lua_newuserdata(L, sizeof(halfword));
        *a = n;
        lua_rawgeti(L, LUA_REGISTRYINDEX, luaS_index(luatex_node));
        lua_gettable(L, LUA_REGISTRYINDEX);
        lua_setmetatable(L, -2);
    }
    return;
}

/* |spec_ptr| fields can legally be zero, which is why there is a special function. */

static void lua_nodelib_push_spec(lua_State * L)
{
    halfword n;
    halfword *a;
    n = -1;
    if (lua_isnumber(L, -1)) {
        n = (halfword) lua_tointeger(L, -1);
    }
    lua_pop(L, 1);
    if ((n < 0) || (n > var_mem_max)) {
        lua_pushnil(L);
    } else {
        a = lua_newuserdata(L, sizeof(halfword));
        *a = n;
        lua_rawgeti(L, LUA_REGISTRYINDEX, luaS_index(luatex_node));
        lua_gettable(L, LUA_REGISTRYINDEX);
        lua_setmetatable(L, -2);
    }
    return;
}

void lua_nodelib_push_fast(lua_State * L, halfword n)
{
    halfword *a;
    a = lua_newuserdata(L, sizeof(halfword));
    *a = n;
    lua_rawgeti(L, LUA_REGISTRYINDEX, luaS_index(luatex_node));
    lua_gettable(L, LUA_REGISTRYINDEX);
    lua_setmetatable(L, -2);
    return;
}


/* converts type strings to type ids */

static int lua_nodelib_id(lua_State * L)
{
    int i = get_node_type_id(L, 1);
    if (i >= 0) {
        lua_pushnumber(L, i);
    } else {
        lua_pushnil(L);
    }
    return 1;
}


static int lua_nodelib_subtype(lua_State * L)
{
    int i = get_node_subtype_id(L, 1);
    if (i >= 0) {
        lua_pushnumber(L, i);
    } else {
        lua_pushnil(L);
    }
    return 1;
}

/* converts id numbers to type names */

static int lua_nodelib_type(lua_State * L)
{
    int i = get_node_type_id(L, 1);
    if (i >= 0) {
        lua_pushstring(L, node_data[i].name);
    } else {
        lua_pushnil(L);
    }
    return 1;
}


/* allocate a new node */

static int lua_nodelib_new(lua_State * L)
{
    int i, j;
    halfword n = null;
    i = get_valid_node_type_id(L, 1);

    if (i == whatsit_node) {
        j = -1;
        if (lua_gettop(L) > 1) {
            j = get_valid_node_subtype_id(L, 2);
        }
        if (j < 0) {
            luaL_error(L,
                           "Creating a whatsit requires the subtype number as a second argument");
        }
    } else {
        j = 0;
        if (lua_gettop(L) > 1) {
            j = (int) lua_tointeger(L, 2);
        }
    }
    n = new_node(i, j);
    lua_nodelib_push_fast(L, n);
    return 1;
}


/* Free a node.
   This function returns the 'next' node, because that may be helpful */

static int lua_nodelib_free(lua_State * L)
{
    halfword *n;
    halfword p;
    if (lua_gettop(L) < 1) {
        lua_pushnil(L);
        return 1;
    } else if (lua_isnil(L, 1)) {
        return 1;               /* the nil itself */
    }
    n = check_isnode(L, 1);
    p = vlink(*n);
    flush_node(*n);
    lua_pushnumber(L, p);
    lua_nodelib_push(L);
    return 1;
}

/* Free a node list */

static int lua_nodelib_flush_list(lua_State * L)
{
    halfword *n_ptr;
    if ((lua_gettop(L) < 1) || lua_isnil(L, 1))
        return 0;
    n_ptr = check_isnode(L, 1);
    flush_node_list(*n_ptr);
    return 0;
}

/* find prev, and fix backlinks */

#define set_t_to_prev(head,current)             \
  t = head;                                     \
  while (vlink(t)!=current && t != null) {      \
    if (vlink(t)!=null)                         \
      alink(vlink(t)) = t;                      \
    t = vlink(t);                               \
  }

/* remove a node from a list */


static int lua_nodelib_remove(lua_State * L)
{
    halfword head, current, t;
    if (lua_gettop(L) < 2) {
        luaL_error(L, "Not enough arguments for node.remove()");
    }
    head = *(check_isnode(L, 1));
    if (lua_isnil(L, 2)) {
        return 2;               /* the arguments, as they are */
    }
    current = *(check_isnode(L, 2));

    if (head == current) {
        if (alink(head) != null && vlink(current) != null) {
            alink(vlink(current)) = alink(head);
        }
        head = vlink(current);
        current = head;
    } else {                    /* head != current */
        t = alink(current);
        if (t == null || vlink(t) != current) {
            set_t_to_prev(head, current);
            if (t == null) {    /* error! */
		luaL_error(L,
                               "Attempt to node.remove() a non-existing node");
            }
        }
        /* t is now the previous node */
        vlink(t) = vlink(current);
        if (vlink(current) != null) {
            alink(vlink(current)) = t;
        }
        current = vlink(current);
    }
    lua_pushnumber(L, head);
    lua_nodelib_push(L);
    lua_pushnumber(L, current);
    lua_nodelib_push(L);
    return 2;
}

/* Insert a node in a list */

static int lua_nodelib_insert_before(lua_State * L)
{
    halfword head, current, n, t;
    if (lua_gettop(L) < 3) {
        luaL_error(L, "Not enough arguments for node.insert_before()");
    }
    if (lua_isnil(L, 3)) {
        lua_pop(L, 1);
        return 2;
    } else {
        n = *(check_isnode(L, 3));
    }
    if (lua_isnil(L, 1)) {      /* no head */
        vlink(n) = null;
        alink(n) = null;
        lua_nodelib_push_fast(L, n);
        lua_pushvalue(L, -1);
        return 2;
    } else {
        head = *(check_isnode(L, 1));
    }
    if (lua_isnil(L, 2)) {
        current = tail_of_list(head);
    } else {
        current = *(check_isnode(L, 2));
    }
    if (head != current) {
        t = alink(current);
        if (t == null || vlink(t) != current) {
            set_t_to_prev(head, current);
            if (t == null) {    /* error! */
                luaL_error(L,
                               "Attempt to node.insert_before() a non-existing node");
            }
        }
        couple_nodes(t, n);
    }
    couple_nodes(n, current);
    if (head == current) {
        lua_nodelib_push_fast(L, n);
    } else {
        lua_nodelib_push_fast(L, head);
    }
    lua_nodelib_push_fast(L, n);
    return 2;
}


static int lua_nodelib_insert_after(lua_State * L)
{
    halfword head, current, n;
    if (lua_gettop(L) < 3) {
        luaL_error(L, "Not enough arguments for node.insert_after()");
    }
    if (lua_isnil(L, 3)) {
        lua_pop(L, 1);
        return 2;
    } else {
        n = *(check_isnode(L, 3));
    }
    if (lua_isnil(L, 1)) {      /* no head */
        vlink(n) = null;
        alink(n) = null;
        lua_nodelib_push_fast(L, n);
        lua_pushvalue(L, -1);
        return 2;
    } else {
        head = *(check_isnode(L, 1));
    }
    if (lua_isnil(L, 2)) {
        current = head;
        while (vlink(current) != null)
            current = vlink(current);
    } else {
        current = *(check_isnode(L, 2));
    }
    try_couple_nodes(n, vlink(current));
    couple_nodes(current, n);

    lua_pop(L, 2);
    lua_nodelib_push_fast(L, n);
    return 2;
}


/* Copy a node list */

static int lua_nodelib_copy_list(lua_State * L)
{
    halfword n, s = null;
    halfword m;
    if (lua_isnil(L, 1))
        return 1;               /* the nil itself */
    n = *check_isnode(L, 1);
    if ((lua_gettop(L) > 1) && (!lua_isnil(L,2))) {
        s = *check_isnode(L, 2);
    }
    m = do_copy_node_list(n, s);
    lua_pushnumber(L, m);
    lua_nodelib_push(L);
    return 1;
}

/* (Deep) copy a node */

static int lua_nodelib_copy(lua_State * L)
{
    halfword *n;
    halfword m;
    if (lua_isnil(L, 1))
        return 1;               /* the nil itself */
    n = check_isnode(L, 1);
    m = copy_node(*n);
    lua_nodelib_push_fast(L, m);
    return 1;
}

/* output (write) a node to tex's processor */

static int lua_nodelib_append(lua_State * L)
{
    halfword *n;
    halfword m;
    int i, j;
    j = lua_gettop(L);
    for (i = 1; i <= j; i++) {
        n = check_isnode(L, i);
        m = *n;
        tail_append(m);
        while (vlink(m) != null) {
            m = vlink(m);
            tail_append(m);
        }
    }
    return 0;
}

static int lua_nodelib_last_node(lua_State * L)
{
    halfword m;
    m = pop_tail();
    lua_pushnumber(L, m);
    lua_nodelib_push(L);
    return 1;
}



/* build a hbox */

static int lua_nodelib_hpack(lua_State * L)
{
    halfword n, p;
    const char *s;
    int w = 0;
    int m = 1;
    int d = -1;
    n = *(check_isnode(L, 1));
    if (lua_gettop(L) > 1) {
        w = (int) lua_tointeger(L, 2);
        if (lua_gettop(L) > 2) {
            if (lua_type(L, 3) == LUA_TSTRING) {
                s = lua_tostring(L, 3);
                if (strcmp(s, "additional") == 0)
                    m = 1;
                else if (strcmp(s, "exactly") == 0)
                    m = 0;
                else if (strcmp(s, "cal_expand_ratio") == 0)
                    m = 2;
                else if (strcmp(s, "subst_ex_font") == 0)
                    m = 3;
                else {
                    luaL_error(L,
                                   "3rd argument should be either additional or exactly");
                }
            } else if (lua_type(L, 3) == LUA_TNUMBER) {
                lua_number2int(m, lua_tonumber(L, 3));
            } else {
                lua_pushstring(L, "incorrect 3rd argument");
            }
            if (lua_gettop(L) > 3) {
                if (lua_type(L, 4) == LUA_TSTRING) {
                    d = nodelib_getdir(L, 4);
                } else {
                    lua_pushstring(L, "incorrect 4th argument");
                }
            }
        }
    }
    p = hpack(n, w, m, d);
    lua_nodelib_push_fast(L, p);
    lua_pushnumber(L, last_badness);
    return 2;
}


static int lua_nodelib_dimensions(lua_State * L)
{
    int top;
    top = lua_gettop(L);
    if (top > 0) {
        scaled_whd siz;
        glue_ratio g_mult = 1.0;
        int g_sign = normal;
        int g_order = normal;
        int i = 1;
        int d = -1;
        halfword n = null, p = null;
        if (lua_isnumber(L, 1)) {
            if (top < 4) {
                lua_pushnil(L);
                return 1;
            }
            i += 3;
            g_mult = (glue_ratio) lua_tonumber(L, 1);
            lua_number2int(g_sign, lua_tonumber(L, 2));
            lua_number2int(g_order, lua_tonumber(L, 3));
        }
        n = *(check_isnode(L, i));
        if (lua_gettop(L) > i && !lua_isnil(L, (i + 1))) {
            if (lua_type(L, (i + 1)) == LUA_TSTRING) {
                d = nodelib_getdir(L, (i + 1));
            } else {
                p = *(check_isnode(L, (i + 1)));
            }
        }
        if (lua_gettop(L) > (i + 1) && lua_type(L, (i + 2)) == LUA_TSTRING) {
            d = nodelib_getdir(L, (i + 2));
        }
        siz = natural_sizes(n, p, g_mult, g_sign, g_order, d);
        lua_pushnumber(L, siz.wd);
        lua_pushnumber(L, siz.ht);
        lua_pushnumber(L, siz.dp);
        return 3;
    } else {
        luaL_error(L,
                       "missing  argument to 'dimensions' (luatex_node expected)");
    }
    return 0;                   /* not reached */
}


/* build a vbox */
static int lua_nodelib_vpack(lua_State * L)
{
    halfword n, p;
    const char *s;
    int w = 0;
    int m = 1;
    int d = -1;
    n = *(check_isnode(L, 1));
    if (lua_gettop(L) > 1) {
        w = (int) lua_tointeger(L, 2);
        if (lua_gettop(L) > 2) {
            if (lua_type(L, 3) == LUA_TSTRING) {
                s = lua_tostring(L, 3);
                if (strcmp(s, "additional") == 0)
                    m = 1;
                else if (strcmp(s, "exactly") == 0)
                    m = 0;
                else {
                    luaL_error(L,
                                   "3rd argument should be either additional or exactly");
                }
                if (lua_gettop(L) > 3) {
                    if (lua_type(L, 4) == LUA_TSTRING) {
                        d = nodelib_getdir(L, 4);
                    } else {
                        lua_pushstring(L, "incorrect 4th argument");
                    }
                }
            }

            else if (lua_type(L, 3) == LUA_TNUMBER) {
                lua_number2int(m, lua_tonumber(L, 3));
            } else {
                lua_pushstring(L, "incorrect 3rd argument");
            }
        }
    }
    p = vpackage(n, w, m, max_dimen, d);
    lua_nodelib_push_fast(L, p);
    lua_pushnumber(L, last_badness);
    return 2;
}


/* create a hlist from a formula */

static int lua_nodelib_mlist_to_hlist(lua_State * L)
{
    halfword n;
    int w;
    boolean m;
    n = *(check_isnode(L, 1));
    w = luaL_checkoption(L, 2, "text", math_style_names);
    luaL_checkany(L, 3);
    m = lua_toboolean(L, 3);
    mlist_to_hlist_args(n, w, m);
    lua_nodelib_push_fast(L, vlink(temp_head));
    return 1;
}

static int lua_nodelib_mfont(lua_State * L)
{
    int f, s;
    f = (int) luaL_checkinteger(L, 1);
    if (lua_gettop(L) == 2)
        s = (int) lua_tointeger(L, 2);  /* this should be a multiple of 256 ! */
    else
        s = 0;
    lua_pushnumber(L, fam_fnt(f, s));
    return 1;
}



/* This function is similar to |get_node_type_id|, for field
   identifiers.  It has to do some more work, because not all
   identifiers are valid for all types of nodes.
*/

/* this inlining is an optimisation trick. it would be even faster to
   compare string pointers on the lua stack, but that would require a
   lot of code reworking that I don't have time for right now.
*/


make_luaS_index(id);
make_luaS_index(next);
make_luaS_index(char);
make_luaS_index(font);
make_luaS_index(attr);
make_luaS_index(prev);
make_luaS_index(lang);
make_luaS_index(subtype);
make_luaS_index(left);
make_luaS_index(right);
make_luaS_index(uchyph);
make_luaS_index(components);
make_luaS_index(xoffset);
make_luaS_index(yoffset);
make_luaS_index(width);
make_luaS_index(height);
make_luaS_index(depth);
make_luaS_index(expansion_factor);


static void initialize_luaS_indexes(lua_State * L)
{
    init_luaS_index(id);
    init_luaS_index(next);
    init_luaS_index(char);
    init_luaS_index(font);
    init_luaS_index(attr);
    init_luaS_index(prev);
    init_luaS_index(lang);
    init_luaS_index(subtype);
    init_luaS_index(left);
    init_luaS_index(right);
    init_luaS_index(uchyph);
    init_luaS_index(components);
    init_luaS_index(xoffset);
    init_luaS_index(yoffset);
    init_luaS_index(width);
    init_luaS_index(height);
    init_luaS_index(depth);
    init_luaS_index(expansion_factor);
}

static int get_node_field_id(lua_State * L, int n, int node)
{
    register int t = type(node);
    register const char *s = lua_tostring(L, n);
    if (luaS_ptr_eq(s, next)) {
        return 0;
    } else if (luaS_ptr_eq(s, id)) {
        return 1;
    } else if (luaS_ptr_eq(s, attr) && nodetype_has_attributes(t)) {
        return 3;
    } else if (t == glyph_node) {
        if (luaS_ptr_eq(s, subtype)) {
            return 2;
        } else if (luaS_ptr_eq(s, font)) {
            return 5;
        } else if (luaS_ptr_eq(s, char)) {
            return 4;
        } else if (luaS_ptr_eq(s, prev)) {
            return -1;
        } else if (luaS_ptr_eq(s, lang)) {
            return 6;
        } else if (luaS_ptr_eq(s, left)) {
            return 7;
        } else if (luaS_ptr_eq(s, right)) {
            return 8;
        } else if (luaS_ptr_eq(s, uchyph)) {
            return 9;
        } else if (luaS_ptr_eq(s, components)) {
            return 10;
        } else if (luaS_ptr_eq(s, xoffset)) {
            return 11;
        } else if (luaS_ptr_eq(s, yoffset)) {
            return 12;
        } else if (luaS_ptr_eq(s, width)) {
            return 13;
        } else if (luaS_ptr_eq(s, height)) {
            return 14;
        } else if (luaS_ptr_eq(s, depth)) {
            return 15;
        } else if (luaS_ptr_eq(s, expansion_factor)) {
            return 16;
        }
    } else if (luaS_ptr_eq(s, prev)) {
        return -1;
    } else if (luaS_ptr_eq(s, subtype)) {
        return 2;
    } else {
        int j;
        const char **fields = node_data[t].fields;
        if (t == whatsit_node)
            fields = whatsit_node_data[subtype(node)].fields;
        for (j = 0; fields[j] != NULL; j++) {
            if (strcmp(s, fields[j]) == 0) {
                return j + 3;
            }
        }
    }
    return -2;
}


static int get_valid_node_field_id(lua_State * L, int n, int node)
{
    int i = get_node_field_id(L, n, node);
    if (i == -2) {
        const char *s = lua_tostring(L, n);
        luaL_error(L, "Invalid field id %s for node type %s (%d)", s,
                        node_data[type(node)].name, subtype(node));
    }
    return i;
}

static int lua_nodelib_has_field(lua_State * L)
{
    int i = -2;
    if (!lua_isnil(L, 1)) {
        i = get_node_field_id(L, 2, *(check_isnode(L, 1)));
    }
    lua_pushboolean(L, (i != -2));
    return 1;
}


/* fetch the list of valid node types */

static int do_lua_nodelib_types(lua_State * L, node_info * data)
{
    int i;
    lua_newtable(L);
    for (i = 0; data[i].id != -1; i++) {
        lua_pushstring(L, data[i].name);
        lua_rawseti(L, -2, data[i].id);
    }
    return 1;
}

static int lua_nodelib_types(lua_State * L)
{
    return do_lua_nodelib_types(L, node_data);
}

static int lua_nodelib_whatsits(lua_State * L)
{
    return do_lua_nodelib_types(L, whatsit_node_data);
}


/* fetch the list of valid fields */

static int lua_nodelib_fields(lua_State * L)
{
    int i = -1;
    const char **fields;
    int t = get_valid_node_type_id(L, 1);
    if (t == whatsit_node) {
        t = get_valid_node_subtype_id(L, 2);
        fields = whatsit_node_data[t].fields;
    } else {
        fields = node_data[t].fields;
    }
    lua_checkstack(L, 2);
    lua_newtable(L);
    lua_pushstring(L, "next");
    lua_rawseti(L, -2, 0);
    lua_pushstring(L, "id");
    lua_rawseti(L, -2, 1);
    lua_pushstring(L, "subtype");
    lua_rawseti(L, -2, 2);
    if (fields != NULL) {
        lua_pushstring(L, "prev");
        lua_rawseti(L, -2, -1);
        for (i = 0; fields[i] != NULL; i++) {
            lua_pushstring(L, fields[i]);
            lua_rawseti(L, -2, (i + 3));
        }
    }
    return 1;
}

/* find the end of a list */

static int lua_nodelib_tail(lua_State * L)
{
    halfword *n;
    halfword t;
    if (lua_isnil(L, 1))
        return 1;               /* the nil itself */
    n = check_isnode(L, 1);
    t = *n;
    if (t == null)
        return 1;               /* the old userdata */
    alink(t) = null;
    while (vlink(t) != null) {
        alink(vlink(t)) = t;
        t = vlink(t);
    }
    lua_nodelib_push_fast(L, t);
    return 1;
}

static int lua_nodelib_tail_only(lua_State * L)
{
    halfword *n;
    halfword t;
    if (lua_isnil(L, 1))
        return 1;               /* the nil itself */
    n = check_isnode(L, 1);
    t = *n;
    if (t == null)
        return 1;               /* the old userdata */
    while (vlink(t) != null) {
        t = vlink(t);
    }
    lua_nodelib_push_fast(L, t);
    return 1;
}


/* a few utility functions for attribute stuff */

static int lua_nodelib_has_attribute(lua_State * L)
{
    halfword *n;
    int i, val;
    n = check_isnode(L, 1);
    if (n != NULL) {
        i = (int) lua_tointeger(L, 2);
        val = (int) luaL_optinteger(L, 3, UNUSED_ATTRIBUTE);
        if ((val = has_attribute(*n, i, val)) > UNUSED_ATTRIBUTE) {
            lua_pushnumber(L, val);
            return 1;
        }
    }
    lua_pushnil(L);
    return 1;
}

static int lua_nodelib_set_attribute(lua_State * L)
{
    halfword *n;
    int i, val;
    if (lua_gettop(L) == 3) {
        i = (int) lua_tointeger(L, 2);
        val = (int) lua_tointeger(L, 3);
        n = check_isnode(L, 1);
        if (val == UNUSED_ATTRIBUTE) {
            (void) unset_attribute(*n, i, val);
        } else {
            set_attribute(*n, i, val);
        }
    } else {
        luaL_error(L, "incorrect number of arguments");
    }
    return 0;
}


static int lua_nodelib_unset_attribute(lua_State * L)
{
    halfword *n;
    int i, val, ret;
    if (lua_gettop(L) <= 3) {
        lua_number2int(i, luaL_checknumber(L, 2));
        lua_number2int(val, luaL_optnumber(L, 3, UNUSED_ATTRIBUTE));
        n = check_isnode(L, 1);
        ret = unset_attribute(*n, i, val);
        if (ret > UNUSED_ATTRIBUTE) {
            lua_pushnumber(L, ret);
        } else {
            lua_pushnil(L);
        }
        return 1;
    } else {
        return luaL_error(L, "incorrect number of arguments");
    }
}


/* iteration */

static int nodelib_aux_nil(lua_State * L)
{
    lua_pushnil(L);
    return 1;
}

static int nodelib_aux_next_filtered(lua_State * L)
{
    register halfword t;        /* traverser */
    register int i = (int) lua_tointeger(L, lua_upvalueindex(1));
    if (lua_isnil(L, 2)) {      /* first call */
        t = *check_isnode(L, 1);
    } else {
        t = *check_isnode(L, 2);
        t = vlink(t);
    }
    while (t != null && type(t) != i) {
        t = vlink(t);
    }
    if (t == null) {
        lua_pushnil(L);
    } else {
        lua_nodelib_push_fast(L, t);
    }
    return 1;
}


static int lua_nodelib_traverse_filtered(lua_State * L)
{
    halfword n;
    if (lua_isnil(L, 2)) {
        lua_pushcclosure(L, nodelib_aux_nil, 0);
        return 1;
    }
    n = *(check_isnode(L, 2));
    lua_pop(L, 1);              /* the node, integer remains */
    lua_pushcclosure(L, nodelib_aux_next_filtered, 1);
    lua_nodelib_push_fast(L, n);
    lua_pushnil(L);
    return 3;
}

static int nodelib_aux_next(lua_State * L)
{
    register halfword t;        /* traverser */
    if (lua_isnil(L, 2)) {      /* first call */
        t = *check_isnode(L, 1);
    } else {
        t = *check_isnode(L, 2);
        t = vlink(t);
    }
    if (t == null) {
        lua_pushnil(L);
    } else {
        lua_nodelib_push_fast(L, t);
    }
    return 1;
}

static int lua_nodelib_traverse(lua_State * L)
{
    halfword n;
    if (lua_isnil(L, 1)) {
        lua_pushcclosure(L, nodelib_aux_nil, 0);
        return 1;
    }
    n = *(check_isnode(L, 1));
    lua_pushcclosure(L, nodelib_aux_next, 0);
    lua_nodelib_push_fast(L, n);
    lua_pushnil(L);
    return 3;
    ;
}



static int
do_lua_nodelib_count(lua_State * L, halfword match, int i, halfword first)
{
    int count = 0;
    int t = first;
    while (t != match) {
        if (i < 0 || type(t) == i) {
            count++;
        }
        t = vlink(t);
    }
    lua_pushnumber(L, count);
    return 1;
}

static int lua_nodelib_length(lua_State * L)
{
    halfword n;
    halfword m = null;
    if (lua_isnil(L, 1)) {
        lua_pushnumber(L, 0);
        return 1;
    }
    n = *(check_isnode(L, 1));
    if (lua_gettop(L) == 2) {
        m = *(check_isnode(L, 2));
    }
    return do_lua_nodelib_count(L, m, -1, n);
}


static int lua_nodelib_count(lua_State * L)
{
    halfword n;
    halfword m = null;
    int i = -1;
    i = (int) lua_tointeger(L, 1);
    if (lua_isnil(L, 2)) {
        lua_pushnumber(L, 0);
        return 1;
    }
    n = *(check_isnode(L, 2));
    if (lua_gettop(L) == 3)
        m = *(check_isnode(L, 3));
    return do_lua_nodelib_count(L, m, i, n);
}

/* fetching a field from a node */

#define nodelib_pushlist(L,n) { lua_pushnumber(L,n); lua_nodelib_push(L); }
#define nodelib_pushattr(L,n) { lua_pushnumber(L,n); lua_nodelib_push(L); }
#define nodelib_pushspec(L,n) { lua_pushnumber(L,n); lua_nodelib_push_spec(L); }
#define nodelib_pushaction(L,n) { lua_pushnumber(L,n); lua_nodelib_push(L); }
#define nodelib_pushstring(L,n) { char *ss=makecstring(n); lua_pushstring(L,ss); free(ss); }

static void nodelib_pushdir(lua_State * L, int n, boolean dirnode)
{
    char s[2];
    if (dirnode) {
        s[0] = (char) (n < 0 ? '-' : '+');
        s[1] = 0;
    } else {
        s[0] = 0;
    }
    if (n < 0)
        n += 64;
    if (n == dir_TLT) {
        lua_pushfstring(L, "%sTLT", s);
    } else if (n == dir_TRT) {
        lua_pushfstring(L, "%sTRT", s);
    } else if (n == dir_LTL) {
        lua_pushfstring(L, "%sLTL", s);
    } else if (n == dir_RTT) {
        lua_pushfstring(L, "%sRTT", s);
    } else {
        lua_pushstring(L, "???");
    }
}

static void lua_nodelib_getfield_whatsit(lua_State * L, int n, int field)
{
    if (field == 2) {
        lua_pushnumber(L, subtype(n));
    } else {
        switch (subtype(n)) {
        case open_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, write_stream(n));
                break;
            case 5:
                nodelib_pushstring(L, open_name(n));
                break;
            case 6:
                nodelib_pushstring(L, open_area(n));
                break;
            case 7:
                nodelib_pushstring(L, open_ext(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case write_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, write_stream(n));
                break;
            case 5:
                tokenlist_to_lua(L, write_tokens(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case close_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, write_stream(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case special_node:
            switch (field) {
            case 4:
                tokenlist_to_luastring(L, write_tokens(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case local_par_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, local_pen_inter(n));
                break;
            case 5:
                lua_pushnumber(L, local_pen_broken(n));
                break;
            case 6:
                nodelib_pushdir(L, local_par_dir(n), false);
                break;
            case 7:
                nodelib_pushlist(L, local_box_left(n));
                break;
            case 8:
                lua_pushnumber(L, local_box_left_width(n));
                break;
            case 9:
                nodelib_pushlist(L, local_box_right(n));
                break;
            case 10:
                lua_pushnumber(L, local_box_right_width(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case dir_node:
            switch (field) {
            case 4:
                nodelib_pushdir(L, dir_dir(n), true);
                break;
            case 5:
                lua_pushnumber(L, dir_level(n));
                break;
            case 6:
                lua_pushnumber(L, dir_dvi_ptr(n));
                break;
            case 7:
                lua_pushnumber(L, dir_dvi_h(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_literal_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, pdf_literal_mode(n));
                break;
            case 5:
                if (pdf_literal_type(n) == lua_refid_literal) {
                    lua_rawgeti(Luas, LUA_REGISTRYINDEX, pdf_literal_data(n));
                } else {
                    tokenlist_to_luastring(L, pdf_literal_data(n));
                }
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_refobj_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, pdf_obj_objnum(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_refxform_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, width(n));
                break;
            case 5:
                lua_pushnumber(L, depth(n));
                break;
            case 6:
                lua_pushnumber(L, height(n));
                break;
            case 7:
                lua_pushnumber(L, pdf_xform_objnum(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_refximage_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, width(n));
                break;
            case 5:
                lua_pushnumber(L, depth(n));
                break;
            case 6:
                lua_pushnumber(L, height(n));
                break;
            case 7:
                lua_pushnumber(L, pdf_ximage_transform(n));
                break;
            case 8:
                lua_pushnumber(L, pdf_ximage_index(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_annot_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, width(n));
                break;
            case 5:
                lua_pushnumber(L, depth(n));
                break;
            case 6:
                lua_pushnumber(L, height(n));
                break;
            case 7:
                lua_pushnumber(L, pdf_annot_objnum(n));
                break;
            case 8:
                tokenlist_to_luastring(L, pdf_annot_data(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_start_link_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, width(n));
                break;
            case 5:
                lua_pushnumber(L, depth(n));
                break;
            case 6:
                lua_pushnumber(L, height(n));
                break;
            case 7:
                lua_pushnumber(L, pdf_link_objnum(n));
                break;
            case 8:
                tokenlist_to_luastring(L, pdf_link_attr(n));
                break;
            case 9:
                nodelib_pushaction(L, pdf_link_action(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_dest_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, width(n));
                break;
            case 5:
                lua_pushnumber(L, depth(n));
                break;
            case 6:
                lua_pushnumber(L, height(n));
                break;
            case 7:
                lua_pushnumber(L, pdf_dest_named_id(n));
                break;
            case 8:
                if (pdf_dest_named_id(n) == 1)
                    tokenlist_to_luastring(L, pdf_dest_id(n));
                else
                    lua_pushnumber(L, pdf_dest_id(n));
                break;
            case 9:
                lua_pushnumber(L, pdf_dest_type(n));
                break;
            case 10:
                lua_pushnumber(L, pdf_dest_xyz_zoom(n));
                break;
            case 11:
                lua_pushnumber(L, pdf_dest_objnum(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_thread_node:
        case pdf_start_thread_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, width(n));
                break;
            case 5:
                lua_pushnumber(L, depth(n));
                break;
            case 6:
                lua_pushnumber(L, height(n));
                break;
            case 7:
                lua_pushnumber(L, pdf_thread_named_id(n));
                break;
            case 8:
                if (pdf_thread_named_id(n) == 1)
                    tokenlist_to_luastring(L, pdf_thread_id(n));
                else
                    lua_pushnumber(L, pdf_thread_id(n));
                break;
            case 9:
                tokenlist_to_luastring(L, pdf_thread_attr(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case late_lua_node:
            switch (field) {
            case 4: /* regid (obsolete?)*/
                lua_pushnumber(L, late_lua_reg(n));
                break;
            case 6: /* name */
                tokenlist_to_luastring(L, late_lua_name(n));
                break;
            case 5: /* data */
            case 7: /* string */
                if (late_lua_type(n) == lua_refid_literal) {
                    lua_rawgeti(Luas, LUA_REGISTRYINDEX, late_lua_data(n));
                } else {
                    tokenlist_to_luastring(L, late_lua_data(n));
                }
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case close_lua_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, late_lua_reg(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_colorstack_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, pdf_colorstack_stack(n));
                break;
            case 5:
                lua_pushnumber(L, pdf_colorstack_cmd(n));
                break;
            case 6:
                tokenlist_to_luastring(L, pdf_colorstack_data(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case pdf_setmatrix_node:
            switch (field) {
            case 4:
                tokenlist_to_luastring(L, pdf_setmatrix_data(n));
                break;
            default:
                lua_pushnil(L);
            }
            break;
        case user_defined_node:
            switch (field) {
            case 4:
                lua_pushnumber(L, user_node_id(n));
                break;
            case 5:
                lua_pushnumber(L, user_node_type(n));
                break;
            case 6:
                switch (user_node_type(n)) {
                case 'a':
                    nodelib_pushlist(L, user_node_value(n));
                    break;
                case 'd':
                    lua_pushnumber(L, user_node_value(n));
                    break;
                case 'n':
                    nodelib_pushlist(L, user_node_value(n));
                    break;
                case 's':
                    nodelib_pushstring(L, user_node_value(n));
                    break;
                case 't':
                    tokenlist_to_lua(L, user_node_value(n));
                    break;
                default:
                    lua_pushnumber(L, user_node_value(n));
                    break;
                }
                break;
            default:
                lua_pushnil(L);
            }
            break;
        default:
            lua_pushnil(L);
            break;
        }
    }
}


static int lua_nodelib_getfield(lua_State * L)
{
    register halfword n;
    register int field;
    n = *((halfword *) lua_touserdata(L, 1));
    field = get_valid_node_field_id(L, 2, n);
    if (field == 0) {
        lua_pushnumber(L, vlink(n));
        lua_nodelib_push(L);
        return 1;
    }
    if (field == 1) {
        lua_pushnumber(L, type(n));
        return 1;
    }
    if (field == -1) {
        lua_pushnumber(L, alink(n));
        lua_nodelib_push(L);
        return 1;
    }
    if (field == 3 && nodetype_has_attributes(type(n))) {
        nodelib_pushattr(L, node_attr(n));
        return 1;
    }
    if (field < -1)
        return 0;
    switch (type(n)) {
    case hlist_node:
    case vlist_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, width(n));
            break;
        case 5:
            lua_pushnumber(L, depth(n));
            break;
        case 6:
            lua_pushnumber(L, height(n));
            break;
        case 7:
            nodelib_pushdir(L, box_dir(n), false);
            break;
        case 8:
            lua_pushnumber(L, shift_amount(n));
            break;
        case 9:
            lua_pushnumber(L, glue_order(n));
            break;
        case 10:
            lua_pushnumber(L, glue_sign(n));
            break;
        case 11:
            lua_pushnumber(L, (double) glue_set(n));
            break;
        case 12:
            nodelib_pushlist(L, list_ptr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case unset_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, 0);
            break;
        case 4:
            lua_pushnumber(L, width(n));
            break;
        case 5:
            lua_pushnumber(L, depth(n));
            break;
        case 6:
            lua_pushnumber(L, height(n));
            break;
        case 7:
            nodelib_pushdir(L, box_dir(n), false);
            break;
        case 8:
            lua_pushnumber(L, glue_shrink(n));
            break;
        case 9:
            lua_pushnumber(L, glue_order(n));
            break;
        case 10:
            lua_pushnumber(L, glue_sign(n));
            break;
        case 11:
            lua_pushnumber(L, glue_stretch(n));
            break;
        case 12:
            lua_pushnumber(L, span_count(n));
            break;
        case 13:
            nodelib_pushlist(L, list_ptr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case rule_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, 0);
            break;
        case 4:
            lua_pushnumber(L, width(n));
            break;
        case 5:
            lua_pushnumber(L, depth(n));
            break;
        case 6:
            lua_pushnumber(L, height(n));
            break;
        case 7:
            nodelib_pushdir(L, rule_dir(n), false);
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case ins_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, float_cost(n));
            break;
        case 5:
            lua_pushnumber(L, depth(n));
            break;
        case 6:
            lua_pushnumber(L, height(n));
            break;
        case 7:
            nodelib_pushspec(L, split_top_ptr(n));
            break;
        case 8:
            nodelib_pushlist(L, ins_ptr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case mark_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, mark_class(n));
            break;
        case 5:
            tokenlist_to_lua(L, mark_ptr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case adjust_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushlist(L, adjust_ptr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case disc_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushlist(L, vlink(pre_break(n)));
            break;
        case 5:
            nodelib_pushlist(L, vlink(post_break(n)));
            break;
        case 6:
            nodelib_pushlist(L, vlink(no_break(n)));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case math_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, surround(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case glue_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushspec(L, glue_ptr(n));
            break;
        case 5:
            nodelib_pushlist(L, leader_ptr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case glue_spec_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, 0);
            break;
        case 3:
            lua_pushnumber(L, width(n));
            break;
        case 4:
            lua_pushnumber(L, stretch(n));
            break;
        case 5:
            lua_pushnumber(L, shrink(n));
            break;
        case 6:
            lua_pushnumber(L, stretch_order(n));
            break;
        case 7:
            lua_pushnumber(L, shrink_order(n));
            break;
        case 8:
            lua_pushnumber(L, glue_ref_count(n));
            break;
        case 9:
            lua_pushboolean(L, valid_node(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case kern_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, width(n));
            break;
        case 5:
            lua_pushnumber(L, ex_kern(n));
        default:
            lua_pushnil(L);
        }
        break;
    case penalty_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, 0);
            break;
        case 4:
            lua_pushnumber(L, penalty(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case glyph_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, character(n));
            break;
        case 5:
            lua_pushnumber(L, font(n));
            break;
        case 6:
            lua_pushnumber(L, char_lang(n));
            break;
        case 7:
            lua_pushnumber(L, char_lhmin(n));
            break;
        case 8:
            lua_pushnumber(L, char_rhmin(n));
            break;
        case 9:
            lua_pushnumber(L, char_uchyph(n));
            break;
        case 10:
            nodelib_pushlist(L, lig_ptr(n));
            break;
        case 11:
            lua_pushnumber(L, x_displace(n));
            break;
        case 12:
            lua_pushnumber(L, y_displace(n));
            break;
        case 13:
            lua_pushnumber(L, char_width(font(n),character(n)));
            break;
        case 14:
            lua_pushnumber(L, char_height(font(n),character(n)));
            break;
        case 15:
            lua_pushnumber(L, char_depth(font(n),character(n)));
            break;
        case 16:
            lua_pushnumber(L, ex_glyph(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case style_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, 0);
            break;
        case 4:
            lua_pushstring(L, math_style_names[subtype(n)]);
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case choice_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushlist(L, display_mlist(n));
            break;
        case 5:
            nodelib_pushlist(L, text_mlist(n));
            break;
        case 6:
            nodelib_pushlist(L, script_mlist(n));
            break;
        case 7:
            nodelib_pushlist(L, script_script_mlist(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case simple_noad:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushlist(L, nucleus(n));
            break;
        case 5:
            nodelib_pushlist(L, subscr(n));
            break;
        case 6:
            nodelib_pushlist(L, supscr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case radical_noad:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushlist(L, nucleus(n));
            break;
        case 5:
            nodelib_pushlist(L, subscr(n));
            break;
        case 6:
            nodelib_pushlist(L, supscr(n));
            break;
        case 7:
            nodelib_pushlist(L, left_delimiter(n));
            break;
        case 8:
            nodelib_pushlist(L, degree(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case fraction_noad:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, thickness(n));
            break;
        case 5:
            nodelib_pushlist(L, numerator(n));
            break;
        case 6:
            nodelib_pushlist(L, denominator(n));
            break;
        case 7:
            nodelib_pushlist(L, left_delimiter(n));
            break;
        case 8:
            nodelib_pushlist(L, right_delimiter(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case accent_noad:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushlist(L, nucleus(n));
            break;
        case 5:
            nodelib_pushlist(L, subscr(n));
            break;
        case 6:
            nodelib_pushlist(L, supscr(n));
            break;
        case 7:
            nodelib_pushlist(L, accent_chr(n));
            break;
        case 8:
            nodelib_pushlist(L, bot_accent_chr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case fence_noad:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushlist(L, delimiter(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case math_char_node:
    case math_text_char_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, math_fam(n));
            break;
        case 5:
            lua_pushnumber(L, math_character(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case sub_box_node:
    case sub_mlist_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            nodelib_pushlist(L, math_list(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case delim_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, small_fam(n));
            break;
        case 5:
            lua_pushnumber(L, small_char(n));
            break;
        case 6:
            lua_pushnumber(L, large_fam(n));
            break;
        case 7:
            lua_pushnumber(L, large_char(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case inserting_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 3:
            nodelib_pushlist(L, last_ins_ptr(n));
            break;
        case 4:
            nodelib_pushlist(L, best_ins_ptr(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case split_up_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 3:
            nodelib_pushlist(L, last_ins_ptr(n));
            break;
        case 4:
            nodelib_pushlist(L, best_ins_ptr(n));
            break;
        case 5:
            nodelib_pushlist(L, broken_ptr(n));
            break;
        case 6:
            nodelib_pushlist(L, broken_ins(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case margin_kern_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, subtype(n));
            break;
        case 4:
            lua_pushnumber(L, width(n));
            break;
        case 5:
            nodelib_pushlist(L, margin_char(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case action_node:
        switch (field) {
        case 2:
            lua_pushnil(L);     /* dummy subtype */
            break;
        case 3:
            lua_pushnumber(L, pdf_action_type(n));
            break;
        case 4:
            lua_pushnumber(L, pdf_action_named_id(n));
            break;
        case 5:
            if (pdf_action_named_id(n) == 1) {
                tokenlist_to_luastring(L, pdf_action_id(n));
            } else {
                lua_pushnumber(L, pdf_action_id(n));
            }
            break;
        case 6:
            tokenlist_to_luastring(L, pdf_action_file(n));
            break;
        case 7:
            lua_pushnumber(L, pdf_action_new_window(n));
            break;
        case 8:
            tokenlist_to_luastring(L, pdf_action_tokens(n));
            break;
        case 9:
            lua_pushnumber(L, pdf_action_refcount(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case attribute_list_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, 0);
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case attribute_node:
        switch (field) {
        case 2:
            lua_pushnumber(L, 0);
            break;
        case 3:
            lua_pushnumber(L, attribute_id(n));
            break;
        case 4:
            lua_pushnumber(L, attribute_value(n));
            break;
        default:
            lua_pushnil(L);
        }
        break;
    case whatsit_node:
        lua_nodelib_getfield_whatsit(L, n, field);
        break;
    default:
        lua_pushnil(L);
        break;
    }
    return 1;
}




static int nodelib_getlist(lua_State * L, int n)
{
    halfword *m;
    if (lua_isuserdata(L, n)) {
        m = check_isnode(L, n);
        return *m;
    } else {
        return null;
    }
}

int nodelib_getdir(lua_State * L, int n)
{
    const char *s = NULL;
    int d = 32;                 /* invalid number */
    if (lua_type(L, n) == LUA_TSTRING) {
        s = lua_tostring(L, n);
        if (strlen(s) == 3) {
            d = 0;
        }
        if (strlen(s) == 4) {
            if (*s == '-')
                d = -64;
            else if (*s == '+')
                d = 0;
            s++;
        }
        if (strlen(s) == 3) {
            if (strcmp(s, "TLT") == 0) {
                d += dir_TLT;
            } else if (strcmp(s, "TRT") == 0) {
                d += dir_TRT;
            } else if (strcmp(s, "LTL") == 0) {
                d += dir_LTL;
            } else if (strcmp(s, "RTT") == 0) {
                d += dir_RTT;
            }
        }
    } else {
        luaL_error(L, "Direction specifiers have to be strings");
    }
    if ((d > 31) || (d < -64) || (d < 0 && (d + 64) > 31)) {
        d = 0;
        luaL_error(L, "Bad direction specifier %s", lua_tostring(L, n));
    }
    return d;
}


#define nodelib_getspec        nodelib_getlist
#define nodelib_getaction      nodelib_getlist


static str_number nodelib_getstring(lua_State * L, int a)
{
    size_t k;
    const char *s = lua_tolstring(L, a, &k);
    return maketexlstring(s, k);
}

#define nodelib_gettoks(L,a)   tokenlist_from_lua(L)

static void nodelib_setattr(lua_State * L, int stackindex, halfword n)
{
    halfword p;
    p = nodelib_getlist(L, stackindex);
    if (node_attr(n) != p) {
        if (node_attr(n) != null)
            delete_attribute_ref(node_attr(n));
        node_attr(n) = p;
	if (p != null)
	    attr_list_ref(p)++;
    }
}

static int nodelib_cantset(lua_State * L, int field, int n)
{
    luaL_error(L, "You cannot set field %d in a node of type %s",
                    field, node_data[type(n)].name);
    return 0;
}

static int lua_nodelib_setfield_whatsit(lua_State * L, int n, int field)
{
    switch (subtype(n)) {
    case open_node:
        switch (field) {
        case 4:
            write_stream(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            open_name(n) = nodelib_getstring(L, 3);
            break;
        case 6:
            open_area(n) = nodelib_getstring(L, 3);
            break;
        case 7:
            open_ext(n) = nodelib_getstring(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case write_node:
        switch (field) {
        case 4:
            write_stream(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            write_tokens(n) = nodelib_gettoks(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case close_node:
        switch (field) {
        case 4:
            write_stream(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case special_node:
        switch (field) {
        case 4:
            write_tokens(n) = nodelib_gettoks(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case local_par_node:
        switch (field) {
        case 4:
            local_pen_inter(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            local_pen_broken(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            local_par_dir(n) = nodelib_getdir(L, 3);
            break;
        case 7:
            local_box_left(n) = nodelib_getlist(L, 3);
            break;
        case 8:
            local_box_left_width(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 9:
            local_box_right(n) = nodelib_getlist(L, 3);
            break;
        case 10:
            local_box_right_width(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case dir_node:
        switch (field) {
        case 4:
            dir_dir(n) = nodelib_getdir(L, 3);
            break;
        case 5:
            dir_level(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            dir_dvi_ptr(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 7:
            dir_dvi_h(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_literal_node:
        switch (field) {
        case 4:
            pdf_literal_mode(n) = (quarterword) lua_tointeger(L, 3);
            break;
        case 5:
            if (ini_version) {
                pdf_literal_data(n) = nodelib_gettoks(L, 3);
            } else {
                lua_pushvalue(L, 3);
                pdf_literal_data(n) = luaL_ref(L, LUA_REGISTRYINDEX);
                pdf_literal_type(n) = lua_refid_literal;
            }
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_refobj_node:
        switch (field) {
        case 4:
            pdf_obj_objnum(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_refxform_node:
        switch (field) {
        case 4:
            width(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            depth(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            height(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 7:
            pdf_xform_objnum(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_refximage_node:
        switch (field) {
        case 4:
            width(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            depth(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            height(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 7:
            pdf_ximage_transform(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 8:
            pdf_ximage_index(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_annot_node:
        switch (field) {
        case 4:
            width(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            depth(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            height(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 7:
            pdf_annot_objnum(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 8:
            pdf_annot_data(n) = nodelib_gettoks(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_start_link_node:
        switch (field) {
        case 4:
            width(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            depth(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            height(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 7:
            pdf_link_objnum(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 8:
            pdf_link_attr(n) = nodelib_gettoks(L, 3);
            break;
        case 9:
            pdf_link_action(n) = nodelib_getaction(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_end_link_node:
        switch (field) {
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_dest_node:
        switch (field) {
        case 4:
            width(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            depth(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            height(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 7:
            pdf_dest_named_id(n) = (quarterword) lua_tointeger(L, 3);
            break;
        case 8:
            if (pdf_dest_named_id(n) == 1)
                pdf_dest_id(n) = nodelib_gettoks(L, 3);
            else
                pdf_dest_id(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 9:
            pdf_dest_type(n) = (quarterword) lua_tointeger(L, 3);
            break;
        case 10:
            pdf_dest_xyz_zoom(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 11:
            pdf_dest_objnum(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_thread_node:
    case pdf_start_thread_node:
        switch (field) {
        case 4:
            width(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            depth(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            height(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 7:
            pdf_thread_named_id(n) = (quarterword) lua_tointeger(L, 3);
            break;
        case 8:
            if (pdf_thread_named_id(n) == 1)
                pdf_thread_id(n) = nodelib_gettoks(L, 3);
            else
                pdf_thread_id(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 9:
            pdf_thread_attr(n) = nodelib_gettoks(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_end_thread_node:
    case pdf_save_pos_node:
        return nodelib_cantset(L, field, n);
        break;
    case late_lua_node:
        switch (field) {
        case 4:
            late_lua_reg(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5: /* data */
            late_lua_data(n) = nodelib_gettoks(L, 3);
            late_lua_type(n) = normal;
            break;
        case 6:
            late_lua_name(n) = nodelib_gettoks(L, 3);
            break;
        case 7: /* string */
            if (ini_version) {
                late_lua_data(n) = nodelib_gettoks(L, 3);
                late_lua_type(n) = normal;
            } else {
                lua_pushvalue(L, 3);
                late_lua_data(n) = luaL_ref(L, LUA_REGISTRYINDEX);
                late_lua_type(n) = lua_refid_literal;
            }
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case close_lua_node:
        switch (field) {
        case 4:
            late_lua_reg(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_colorstack_node:
        switch (field) {
        case 4:
            pdf_colorstack_stack(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            pdf_colorstack_cmd(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            pdf_colorstack_data(n) = nodelib_gettoks(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_setmatrix_node:
        switch (field) {
        case 4:
            pdf_setmatrix_data(n) = nodelib_gettoks(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    case pdf_save_node:
    case pdf_restore_node:
    case cancel_boundary_node:
        return nodelib_cantset(L, field, n);
        break;
    case user_defined_node:
        switch (field) {
        case 4:
            user_node_id(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            user_node_type(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            switch (user_node_type(n)) {
            case 'a':
                user_node_value(n) = nodelib_getlist(L, 3);
                break;
            case 'd':
                user_node_value(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 'n':
                user_node_value(n) = nodelib_getlist(L, 3);
                break;
            case 's':
                user_node_value(n) = nodelib_getstring(L, 3);
                break;
            case 't':
                user_node_value(n) = nodelib_gettoks(L, 3);
                break;
            default:
                user_node_value(n) = (halfword) lua_tointeger(L, 3);
                break;
            }
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
        break;
    default:
        /* do nothing */
        break;
    }
    return 0;
}

static int lua_nodelib_setfield(lua_State * L)
{
    register halfword n;
    register int field;
    n = *((halfword *) lua_touserdata(L, 1));
    field = get_valid_node_field_id(L, 2, n);
    if (field < -1)
        return 0;
    if (field !=0 && /* .next assignments are always allowed */
	!valid_node(n)) {
	return luaL_error(L, "You can't assign to this %s node (%d)\n", node_data[type(n)].name, n);
	/* return implied */
    }
    if (field == 0) {
        vlink(n) = nodelib_getlist(L, 3);
    } else if (field == -1) {
        alink(n) = nodelib_getlist(L, 3);
    } else if (field == 3 && nodetype_has_attributes(type(n))) {
        nodelib_setattr(L, 3, n);
    } else if (type(n) == glyph_node) {
        switch (field) {
        case 2:
            subtype(n) = (quarterword) lua_tointeger(L, 3);
            break;
        case 4:
            character(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 5:
            font(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 6:
            set_char_lang(n, (halfword) lua_tointeger(L, 3));
            break;
        case 7:
            set_char_lhmin(n, (halfword) lua_tointeger(L, 3));
            break;
        case 8:
            set_char_rhmin(n, (halfword) lua_tointeger(L, 3));
            break;
        case 9:
            set_char_uchyph(n, (halfword) lua_tointeger(L, 3));
            break;
        case 10:
            lig_ptr(n) = nodelib_getlist(L, 3);
            break;
        case 11:
            x_displace(n) = (halfword) lua_tointeger(L, 3);
            break;
        case 12:
            y_displace(n) = (halfword) lua_tointeger(L, 3);
            break;
	    /* 13,14,15 are virtual width, height, depth */
        case 16:
            ex_glyph(n) = (halfword) lua_tointeger(L, 3);
            break;
        default:
            return nodelib_cantset(L, field, n);
        }
    } else {
        switch (type(n)) {
        case hlist_node:
        case vlist_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                width(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                depth(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 6:
                height(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 7:
                box_dir(n) = nodelib_getdir(L, 3);
                break;
            case 8:
                shift_amount(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 9:
                glue_order(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 10:
                glue_sign(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 11:
                glue_set(n) = (glue_ratio) lua_tonumber(L, 3);
                break;
            case 12:
                list_ptr(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case unset_node:
            switch (field) {
            case 2:            /* dummy subtype */
                break;
            case 4:
                width(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                depth(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 6:
                height(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 7:
                box_dir(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 8:
                glue_shrink(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 9:
                glue_order(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 10:
                glue_sign(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 11:
                glue_stretch(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 12:
                span_count(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 13:
                list_ptr(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case rule_node:
            switch (field) {
            case 2:            /* dummy subtype */
                break;
            case 4:
                width(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                depth(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 6:
                height(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 7:
                rule_dir(n) = nodelib_getdir(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case ins_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                float_cost(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                depth(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 6:
                height(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 7:
                split_top_ptr(n) = nodelib_getspec(L, 3);
                break;
            case 8:
                ins_ptr(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case mark_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                mark_class(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                mark_ptr(n) = nodelib_gettoks(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case adjust_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                adjust_ptr(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case disc_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                set_disc_field(pre_break(n), nodelib_getlist(L, 3));
                break;
            case 5:
                set_disc_field(post_break(n), nodelib_getlist(L, 3));
                break;
            case 6:
                set_disc_field(no_break(n), nodelib_getlist(L, 3));
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case math_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                surround(n) = (halfword) lua_tointeger(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case glue_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                glue_ptr(n) = nodelib_getspec(L, 3);
                break;
            case 5:
                leader_ptr(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case glue_spec_node:
            switch (field) {
            case 2:            /* dummy subtype */
                break;
            case 3:
                width(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 4:
                stretch(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                shrink(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 6:
                stretch_order(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 7:
                shrink_order(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 8:
                glue_ref_count(n) = (halfword) lua_tointeger(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);

            }
            break;
        case kern_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                width(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                ex_kern(n) = (halfword) lua_tointeger(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case penalty_node:
            switch (field) {
            case 2:            /* dummy subtype */
                break;
            case 4:
                penalty(n) = (halfword) lua_tointeger(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case action_node:
            switch (field) {
            case 2:            /* dummy subtype */
                break;
            case 3:
                pdf_action_type(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                pdf_action_named_id(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 5:
                if (pdf_action_named_id(n) == 1) {
                    pdf_action_id(n) = nodelib_gettoks(L, 3);
                } else {
                    pdf_action_id(n) = (halfword) lua_tointeger(L, 3);
                }
                break;
            case 6:
                pdf_action_file(n) = nodelib_gettoks(L, 3);
                break;
            case 7:
                pdf_action_new_window(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 8:
                pdf_action_tokens(n) = nodelib_gettoks(L, 3);
                break;
            case 9:
                pdf_action_refcount(n) = (halfword) lua_tointeger(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case style_node:
            switch (field) {
            case 2:            /* dummy subtype */
                break;
            case 4:
                subtype(n) =
                    (quarterword) luaL_checkoption(L, 3, "text",
                                                   math_style_names);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case choice_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                display_mlist(n) = nodelib_getlist(L, 3);
                break;
            case 5:
                text_mlist(n) = nodelib_getlist(L, 3);
                break;
            case 6:
                script_mlist(n) = nodelib_getlist(L, 3);
                break;
            case 7:
                script_script_mlist(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case simple_noad:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                nucleus(n) = nodelib_getlist(L, 3);
                break;
            case 5:
                subscr(n) = nodelib_getlist(L, 3);
                break;
            case 6:
                supscr(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case radical_noad:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                nucleus(n) = nodelib_getlist(L, 3);
                break;
            case 5:
                subscr(n) = nodelib_getlist(L, 3);
                break;
            case 6:
                supscr(n) = nodelib_getlist(L, 3);
                break;
            case 7:
                left_delimiter(n) = nodelib_getlist(L, 3);
                break;
            case 8:
                degree(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case fraction_noad:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                thickness(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                numerator(n) = nodelib_getlist(L, 3);
                break;
            case 6:
                denominator(n) = nodelib_getlist(L, 3);
                break;
            case 7:
                left_delimiter(n) = nodelib_getlist(L, 3);
                break;
            case 8:
                right_delimiter(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case accent_noad:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                nucleus(n) = nodelib_getlist(L, 3);
                break;
            case 5:
                subscr(n) = nodelib_getlist(L, 3);
                break;
            case 6:
                supscr(n) = nodelib_getlist(L, 3);
                break;
            case 7:
                accent_chr(n) = nodelib_getlist(L, 3);
                break;
            case 8:
                bot_accent_chr(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case fence_noad:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                delimiter(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case math_char_node:
        case math_text_char_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                math_fam(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                math_character(n) = (halfword) lua_tointeger(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case sub_box_node:
        case sub_mlist_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                math_list(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case delim_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                small_fam(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                small_char(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 6:
                large_fam(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 7:
                large_char(n) = (halfword) lua_tointeger(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case margin_kern_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 4:
                width(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 5:
                margin_char(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case inserting_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 3:
                last_ins_ptr(n) = nodelib_getlist(L, 3);
                break;
            case 4:
                best_ins_ptr(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case split_up_node:
            switch (field) {
            case 2:
                subtype(n) = (quarterword) lua_tointeger(L, 3);
                break;
            case 3:
                last_ins_ptr(n) = nodelib_getlist(L, 3);
                break;
            case 4:
                best_ins_ptr(n) = nodelib_getlist(L, 3);
                break;
            case 5:
                broken_ptr(n) = nodelib_getlist(L, 3);
                break;
            case 6:
                broken_ins(n) = nodelib_getlist(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case attribute_list_node:
            switch (field) {
            case 2:            /* dummy subtype */
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case attribute_node:
            switch (field) {
            case 2:            /* dummy subtype */
                break;
            case 3:
                attribute_id(n) = (halfword) lua_tointeger(L, 3);
                break;
            case 4:
                attribute_value(n) = (halfword) lua_tointeger(L, 3);
                break;
            default:
                return nodelib_cantset(L, field, n);
            }
            break;
        case whatsit_node:
            lua_nodelib_setfield_whatsit(L, n, field);
            break;
        default:
            /* do nothing */
            break;
        }
    }
    return 0;
}

static int lua_nodelib_print(lua_State * L)
{
    char *msg;
    char a[7] = { ' ', ' ', ' ', 'n', 'i', 'l', 0 };
    char v[7] = { ' ', ' ', ' ', 'n', 'i', 'l', 0 };
    halfword *n;
    n = check_isnode(L, 1);
    msg = xmalloc(256);
    if (alink(*n) != null)
        snprintf(a, 7, "%6d", (int) alink(*n));
    if (vlink(*n) != null)
        snprintf(v, 7, "%6d", (int) vlink(*n));
    snprintf(msg, 255, "<node %s < %6d > %s : %s %d>", a, (int) *n, v,
             node_data[type(*n)].name, subtype(*n));
    lua_pushstring(L, msg);
    free(msg);
    return 1;
}


static int lua_nodelib_equal(lua_State * L)
{
    register halfword n, m;
    n = *((halfword *) lua_touserdata(L, 1));
    m = *((halfword *) lua_touserdata(L, 2));
    lua_pushboolean(L, (n == m));
    return 1;
}

static int font_tex_ligaturing(lua_State * L)
{
    /* on the stack are two nodes and a direction */
    halfword tmp_head;
    halfword *h;
    halfword t = null;
    if (lua_gettop(L) < 1) {
        lua_pushnil(L);
        lua_pushboolean(L, 0);
        return 2;
    }
    h = check_isnode(L, 1);
    if (lua_gettop(L) > 1) {
        t = *(check_isnode(L, 2));
    }
    tmp_head = new_node(nesting_node, 1);
    couple_nodes(tmp_head, *h);
    tlink(tmp_head) = t;
    t = handle_ligaturing(tmp_head, t);
    lua_pushnumber(L, vlink(tmp_head));
    flush_node(tmp_head);
    lua_nodelib_push(L);
    lua_pushnumber(L, t);
    lua_nodelib_push(L);
    lua_pushboolean(L, 1);
    return 3;
}

static int font_tex_kerning(lua_State * L)
{
    /* on the stack are two nodes and a direction */

    halfword tmp_head;
    halfword *h;
    halfword t = null;
    if (lua_gettop(L) < 1) {
        lua_pushnil(L);
        lua_pushboolean(L, 0);
        return 2;
    }
    h = check_isnode(L, 1);
    if (lua_gettop(L) > 1) {
        t = *(check_isnode(L, 2));
    }
    tmp_head = new_node(nesting_node, 1);
    couple_nodes(tmp_head, *h);
    tlink(tmp_head) = t;
    t = handle_kerning(tmp_head, t);
    lua_pushnumber(L, vlink(tmp_head));
    flush_node(tmp_head);
    lua_nodelib_push(L);
    lua_pushnumber(L, t);
    lua_nodelib_push(L);
    lua_pushboolean(L, 1);
    return 3;
}

static int lua_nodelib_protect_glyphs(lua_State * L)
{
    int t = 0;
    halfword head = *(check_isnode(L, 1));
    while (head != null) {
        if (type(head) == glyph_node) {
            register int s = subtype(head);
            if (s <= 256) {
                t = 1;
                subtype(head) = (quarterword) (s == 1 ? 256 : 256 + s);
            }
        }
        head = vlink(head);
    }
    lua_pushboolean(L, t);
    lua_pushvalue(L, 1);
    return 2;
}

static int lua_nodelib_unprotect_glyphs(lua_State * L)
{
    int t = 0;
    halfword head = *(check_isnode(L, 1));
    while (head != null) {
        if (type(head) == glyph_node) {
            register int s = subtype(head);
            if (s > 256) {
                t = 1;
                subtype(head) = (quarterword) (s - 256);
            }
        }
        head = vlink(head);
    }
    lua_pushboolean(L, t);
    lua_pushvalue(L, 1);
    return 2;
}


static int lua_nodelib_first_character(lua_State * L)
{
    /* on the stack are two nodes and a direction */
    halfword h, savetail = null, t = null;
    if (lua_gettop(L) < 1) {
        lua_pushnil(L);
        lua_pushboolean(L, 0);
        return 2;
    }
    h = *(check_isnode(L, 1));
    if (lua_gettop(L) > 1) {
        t = *(check_isnode(L, 2));
        savetail = vlink(t);
        vlink(t) = null;
    }
    while (h != null && !is_simple_character(h)) {
        h = vlink(h);
    }
    if (savetail != null) {
        vlink(t) = savetail;
    }
    lua_pushnumber(L, h);
    lua_nodelib_push(L);
    lua_pushboolean(L, (h == null ? 0 : 1));
    return 2;
}


/* this is too simplistic, but it helps Hans to get going */

static halfword do_ligature_n(halfword prev, halfword stop, halfword lig)
{
    vlink(lig) = vlink(stop);
    vlink(stop) = null;
    lig_ptr(lig) = vlink(prev);
    vlink(prev) = lig;
    return lig;
}



/* node.do_ligature_n(node prev, node last, node lig) */
static int lua_nodelib_do_ligature_n(lua_State * L)
{
    halfword n, m, o, p, tmp_head;
    n = *(check_isnode(L, 1));
    m = *(check_isnode(L, 2));
    o = *(check_isnode(L, 3));
    if (alink(n) == null || vlink(alink(n)) != n) {
        tmp_head = new_node(temp_node, 0);
        couple_nodes(tmp_head, n);
        p = do_ligature_n(tmp_head, m, o);
        flush_node(tmp_head);
    } else {
        p = do_ligature_n(alink(n), m, o);
    }
    lua_pushnumber(L, p);
    lua_nodelib_push(L);
    return 1;
}

static int lua_nodelib_usedlist(lua_State * L)
{
    lua_pushnumber(L, list_node_mem_usage());
    lua_nodelib_push(L);
    return 1;
}

/* node.protrusion_skipable(node m) */
static int lua_nodelib_cp_skipable(lua_State * L)
{
    halfword n;
    n = *(check_isnode(L, 1));
    lua_pushboolean(L, cp_skipable(n));
    return 1;
}

static const struct luaL_reg nodelib_f[] = {
    {"id", lua_nodelib_id},
    {"subtype", lua_nodelib_subtype},
    {"type", lua_nodelib_type},
    {"new", lua_nodelib_new},
    {"length", lua_nodelib_length},
    {"count", lua_nodelib_count},
    {"traverse", lua_nodelib_traverse},
    {"traverse_id", lua_nodelib_traverse_filtered},
    {"tail", lua_nodelib_tail_only},
    {"slide", lua_nodelib_tail},
    {"types", lua_nodelib_types},
    {"whatsits", lua_nodelib_whatsits},
    {"fields", lua_nodelib_fields},
    {"has_field", lua_nodelib_has_field},
    {"free", lua_nodelib_free},
    {"flush_list", lua_nodelib_flush_list},
    {"remove", lua_nodelib_remove},
    {"insert_before", lua_nodelib_insert_before},
    {"insert_after", lua_nodelib_insert_after},
    {"write", lua_nodelib_append},
    {"last_node", lua_nodelib_last_node},
    {"copy", lua_nodelib_copy},
    {"copy_list", lua_nodelib_copy_list},
    {"dimensions", lua_nodelib_dimensions},
    {"hpack", lua_nodelib_hpack},
    {"vpack", lua_nodelib_vpack},
    {"mlist_to_hlist", lua_nodelib_mlist_to_hlist},
    {"family_font", lua_nodelib_mfont},
    {"has_attribute", lua_nodelib_has_attribute},
    {"set_attribute", lua_nodelib_set_attribute},
    {"unset_attribute", lua_nodelib_unset_attribute},
    {"do_ligature_n", lua_nodelib_do_ligature_n},
    {"ligaturing", font_tex_ligaturing},
    {"kerning", font_tex_kerning},
    {"first_character", lua_nodelib_first_character},
    {"usedlist", lua_nodelib_usedlist},
    {"protect_glyphs", lua_nodelib_protect_glyphs},
    {"unprotect_glyphs", lua_nodelib_unprotect_glyphs},
    {"protrusion_skipable", lua_nodelib_cp_skipable},
    {"protrusion_skippable", lua_nodelib_cp_skipable},
   {NULL, NULL}                /* sentinel */
};

static const struct luaL_reg nodelib_m[] = {
    {"__index", lua_nodelib_getfield},
    {"__newindex", lua_nodelib_setfield},
    {"__tostring", lua_nodelib_print},
    {"__eq", lua_nodelib_equal},
    {NULL, NULL}                /* sentinel */
};



int luaopen_node(lua_State * L)
{
    luaL_newmetatable(L, NODE_METATABLE);
    luaL_register(L, NULL, nodelib_m);
    luaL_register(L, "node", nodelib_f);
    init_luaS_index(luatex_node);
    initialize_luaS_indexes(L);
    return 1;
}

void nodelist_to_lua(lua_State * L, int n)
{
    lua_pushnumber(L, n);
    lua_nodelib_push(L);
}

int nodelist_from_lua(lua_State * L)
{
    halfword *n;
    if (lua_isnil(L, -1))
        return null;
    n = check_isnode(L, -1);
    return *n;
}
