# read method

1. @override

Future<int> read(

1. List<int> cbuf, [
2. int offset = 0,
3. int? length

])
override

Reads characters into an array.

This method will block until some input is available, an I/O error occurs, or the end of the stream is reached.

## Parameters

- `cbuf`: Destination buffer
- `offset`: Offset at which to start storing characters (default: 0)
- `length`: Maximum number of characters to read (default: remaining buffer space)

## Returns

The number of characters read, or -1 if the end of the stream has been reached.

## Example

    final reader = FileReader('text.txt');
    try {
      final buffer = List<int>.filled(1024, 0);
      final charsRead = await reader.read(buffer);
      if (charsRead != -1) {
        final text = String.fromCharCodes(buffer.sublist(0, charsRead));
        print('Read: $text');
      }
    } finally {
      await reader.close();
    }

Throws InvalidArgumentException if `offset` or `length` is negative, or if `offset` + `length` is greater than the length of `cbuf`. Throws IOException if an I/O error occurs. Throws StreamClosedException if the reader has been closed.

## Implementation

    @override
    Future<int> read(List<int> cbuf, [int offset = 0, int? length]) async {
      length ??= cbuf.length - offset;

      if (offset < 0 || length < 0 || offset + length > cbuf.length) {
        throw InvalidArgumentException('Invalid offset or length');
      }

      if (length == 0) {
        return 0;
      }

      await _ensureOpen();

      if (_buffer == null || _bufferPosition >= _buffer!.length) {
        return -1; // End of file
      }

      final availableChars = _buffer!.length - _bufferPosition;
      final charsToRead = length.clamp(0, availableChars);

      for (int i = 0; i < charsToRead; i++) {
        cbuf[offset + i] = _buffer!.codeUnitAt(_bufferPosition + i);
      }

      _bufferPosition += charsToRead;
      return charsToRead;
    }