Revert "Remove dependency on package:charcode (#29)" (#33)

This reverts commit 7e41395d327e93b432f380aaf4c9668f0d952ef3.

Since this has not been published or rolled through to the SDK or
Flutter we will hold it back to reduce risk.
7 files changed
tree: 26ed0a8a492e6a9f8dac7a6ea58c00d99b976e83
  1. .github/
  2. .gitignore
  3. CHANGELOG.md
  4. LICENSE
  5. README.md
  6. analysis_options.yaml
  7. example/
  8. lib/
  9. pubspec.yaml
  10. test/
README.md

This package exposes a StringScanner type that makes it easy to parse a string using a series of Patterns. For example:

import 'dart:math' as math;

import 'package:string_scanner/string_scanner.dart';

num parseNumber(String source) {
  // Scan a number ("1", "1.5", "-3").
  final scanner = StringScanner(source);

  // [Scanner.scan] tries to consume a [Pattern] and returns whether or not it
  // succeeded. It will move the scan pointer past the end of the pattern.
  final negative = scanner.scan('-');

  // [Scanner.expect] consumes a [Pattern] and throws a [FormatError] if it
  // fails. Like [Scanner.scan], it will move the scan pointer forward.
  scanner.expect(RegExp(r'\d+'));

  // [Scanner.lastMatch] holds the [MatchData] for the most recent call to
  // [Scanner.scan], [Scanner.expect], or [Scanner.matches].
  var number = num.parse(scanner.lastMatch[0]);

  if (scanner.scan('.')) {
    scanner.expect(RegExp(r'\d+'));
    final decimal = scanner.lastMatch[0];
    number += int.parse(decimal) / math.pow(10, decimal.length);
  }

  // [Scanner.expectDone] will throw a [FormatError] if there's any input that
  // hasn't yet been consumed.
  scanner.expectDone();

  return (negative ? -1 : 1) * number;
}