sdk/pkg/string_scanner/lib/src/utils.dart

// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

library string_scanner.utils;

/// Validates the arguments passed to [StringScanner.error].
void validateErrorArgs(String string, Match match, int position, int length) {
  if (match != null && (position != null || length != null)) {
    throw new ArgumentError("Can't pass both match and position/length.");
  }

  if (position != null) {
    if (position < 0) {
      throw new RangeError("position must be greater than or equal to 0.");
    } else if (position > string.length) {
      throw new RangeError("position must be less than or equal to the "
          "string length.");
    }
  }

  if (length != null && length < 0) {
    throw new RangeError("length must be greater than or equal to 0.");
  }

  if (position != null && length != null && position + length > string.length) {
    throw new RangeError("position plus length must not go beyond the end of "
        "the string.");
  }
}