getColumn method Null safety

int getColumn(
  1. int offset,
  2. {int? line}
)

Gets the 0-based column corresponding to offset.

If line is passed, it's assumed to be the line containing offset and is used to more efficiently compute the column.

Implementation

int getColumn(int offset, {int? line}) {
  if (offset < 0) {
    throw RangeError('Offset may not be negative, was $offset.');
  } else if (offset > length) {
    throw RangeError('Offset $offset must be not be greater than the '
        'number of characters in the file, $length.');
  }

  if (line == null) {
    line = getLine(offset);
  } else if (line < 0) {
    throw RangeError('Line may not be negative, was $line.');
  } else if (line >= lines) {
    throw RangeError('Line $line must be less than the number of '
        'lines in the file, $lines.');
  }

  final lineStart = _lineStarts[line];
  if (lineStart > offset) {
    throw RangeError('Line $line comes after offset $offset.');
  }

  return offset - lineStart;
}