Improve the style of code in lib/.

lib/src/base64.dart

Index: lib/src/base64.dart
diff --git a/lib/src/base64.dart b/lib/src/base64.dart
index b3896b6075b60c3ca2b5c6d2123f154d020a6092..4c06cb4814ec2741bcdf13988156a14378be5162 100644
--- a/lib/src/base64.dart
+++ b/lib/src/base64.dart
@@ -5,71 +5,15 @@
 library crypto.base64;
 
 import 'dart:convert';
-import 'dart:typed_data';
+
+import 'base64/decoder.dart';
+import 'base64/encoder.dart';
 
 /// An instance of the default implementation of [Base64Codec].
 ///
 /// This provides convenient access to most common Base64 use-cases.
 const Base64Codec BASE64 = const Base64Codec();
 
-/// A mapping from ASCII character codes to their corresponding Base64 values.
-///
-/// Characters with a value of -2 are invalid. Characters with a value of -1
-/// should be ignored. The padding character, "=", is represented as 0.
-const List<int> _decodeTable = const [
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -1, -2, -2, -1, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, 62, -2, 62, -2, 63,
-  52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -2, -2, -2,  0, -2, -2,
-  -2,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
-  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -2, -2, -2, -2, 63,
-  -2, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
-  41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2,
-  -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2
-];
-
-/// A String representing a mapping from numbers between 0 and 63, inclusive, to
-/// their corresponding encoded character.
-///
-/// This is the table for URL-safe encodings.
-const String _encodeTableUrlSafe =
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
-
-/// A String representing a mapping from numbers between 0 and 63, inclusive, to
-/// their corresponding encoded character.
-///
-/// This is the table for URL-unsafe encodings.
-const String _encodeTable =
-    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-
-/// The line length for Base64 strings with line separators.
-const int _LINE_LENGTH = 76;
-
-/// A carriage return.
-const int _CR = 13; // '\r'
-
-/// A line feed.
-const int _LF = 10; // '\n'
-
-/// The byte sequence representing non-URL-encoded padding.
-const List<int> _PAD_BYTES = const [61]; // '='
-
-/// The byte sequence representing URL-encoded padding.
-const List<int> _ENCODED_PAD_BYTES = const [37, 51, 68]; // '%3D'
-
-/// The string representing non-URL-encoded padding.
-const String _PAD = "=";
-
-/// The string representing URL-encoded padding.
-const String _ENCODED_PAD = "%3D";
-
 /// A codec that converts between binary data and [Base64][rfc]-encoded strings.
 ///
 /// [rfc]: https://tools.ietf.org/html/rfc4648
@@ -124,6 +68,7 @@ class Base64Codec extends Codec<List<int>, String> {
     if (encodePaddingCharacter == null) {
       encodePaddingCharacter = _encodePaddingCharacter;
     }
+
     return new Base64Encoder(
         urlSafe: urlSafe,
         addLineSeparator: addLineSeparator,
@@ -135,308 +80,5 @@ class Base64Codec extends Codec<List<int>, String> {
       addLineSeparator: _addLineSeparator,
       encodePaddingCharacter: _encodePaddingCharacter);
 
-  Base64Decoder get decoder => new Base64Decoder();
-}
-
-/// An encoder that converts sequences of bytes to strings using [Base64][rfc].
-///
-/// [rfc]: https://tools.ietf.org/html/rfc4648
-class Base64Encoder extends Converter<List<int>, String> {
-  /// Whether this encoder generates URL-safe strings.
-  final bool _urlSafe;
-
-  /// Whether this encoder adds line breaks to the output.
-  final bool _addLineSeparator;
-
-  /// Whether this encoder URL-encodes trailing padding characters.
-  final bool _encodePaddingCharacter;
-
-  /// The sequence of bytes to use as a padding character.
-  final List<int> _pad;
-
-  /// Creates a new [Base64Encoder].
-  ///
-  /// The default [BASE64.encoder] will be good enough for most cases. A new
-  /// codec only needs to be instantiated when you want to do multiple
-  /// conversions with the same configuration.
-  ///
-  /// If [urlSafe] is `true`, a URL-safe alphabet will be used. Specifically,
-  /// the characters `-` and `_` will be used instead of `+` and `/`.
-  ///
-  /// If [addLineSeparator] is `true`, `\r\n` line separators will be added
-  /// every 76 characters.
-  ///
-  /// If [encodePaddingCharacter] is `true`, the padding character `=` will be
-  /// written as `%3D`.
-  const Base64Encoder(
-      {bool urlSafe: false,
-      bool addLineSeparator: false,
-      bool encodePaddingCharacter: false})
-      : _urlSafe = urlSafe,
-        _addLineSeparator = addLineSeparator,
-        _encodePaddingCharacter = encodePaddingCharacter,
-        _pad = encodePaddingCharacter == true ? _ENCODED_PAD_BYTES : _PAD_BYTES;
-
-  /// Converts [bytes] to Base64.
-  ///
-  /// If [start] and [end] are provided, only the sublist `bytes.sublist(start,
-  /// end)` is converted.
-  String convert(List<int> bytes, [int start = 0, int end]) {
-    int bytes_length = bytes.length;
-    RangeError.checkValidRange(start, end, bytes_length);
-    if (end == null) end = bytes_length;
-    int length = end - start;
-    if (length == 0) {
-      return "";
-    }
-    final String lookup = _urlSafe ? _encodeTableUrlSafe : _encodeTable;
-    // Size of 24 bit chunks.
-    final int remainderLength = length.remainder(3);
-    final int chunkLength = length - remainderLength;
-    // Size of base output.
-    int baseOutputLength = ((length ~/ 3) * 4);
-    int remainderOutputLength;
-    if (_encodePaddingCharacter) {
-      remainderOutputLength = ((remainderLength > 0) ? 6 : 0);
-    } else {
-      remainderOutputLength = ((remainderLength > 0) ? 4 : 0);
-    }
-
-    int outputLength = baseOutputLength + remainderOutputLength;
-    // Add extra for line separators.
-    if (_addLineSeparator) {
-      outputLength += ((outputLength - 1) ~/ _LINE_LENGTH) << 1;
-    }
-    List<int> out = new List<int>(outputLength);
-
-    // Encode 24 bit chunks.
-    int j = 0, i = start, c = 0;
-    while (i < chunkLength) {
-      int x = ((bytes[i++] << 16) & 0x00FFFFFF) |
-          ((bytes[i++] << 8) & 0x00FFFFFF) |
-          bytes[i++];
-      out[j++] = lookup.codeUnitAt(x >> 18);
-      out[j++] = lookup.codeUnitAt((x >> 12) & 0x3F);
-      out[j++] = lookup.codeUnitAt((x >> 6) & 0x3F);
-      out[j++] = lookup.codeUnitAt(x & 0x3F);
-      // Add optional line separator for each 76 char output.
-      if (_addLineSeparator && ++c == 19 && j < outputLength - 2) {
-        out[j++] = _CR;
-        out[j++] = _LF;
-        c = 0;
-      }
-    }
-
-    // If input length if not a multiple of 3, encode remaining bytes and
-    // add padding.
-    if (remainderLength == 1) {
-      int x = bytes[i];
-      out[j++] = lookup.codeUnitAt(x >> 2);
-      out[j++] = lookup.codeUnitAt((x << 4) & 0x3F);
-      out.setRange(j, j + _pad.length, _pad);
-      out.setRange(j + _pad.length, j + 2 * _pad.length, _pad);
-    } else if (remainderLength == 2) {
-      int x = bytes[i];
-      int y = bytes[i + 1];
-      out[j++] = lookup.codeUnitAt(x >> 2);
-      out[j++] = lookup.codeUnitAt(((x << 4) | (y >> 4)) & 0x3F);
-      out[j++] = lookup.codeUnitAt((y << 2) & 0x3F);
-      out.setRange(j, j + _pad.length, _pad);
-    }
-
-    return new String.fromCharCodes(out);
-  }
-
-  _Base64EncoderSink startChunkedConversion(Sink<String> sink) {
-    StringConversionSink stringSink;
-    if (sink is StringConversionSink) {
-      stringSink = sink;
-    } else {
-      stringSink = new StringConversionSink.from(sink);
-    }
-    return new _Base64EncoderSink(stringSink, _urlSafe, _addLineSeparator);
-  }
-}
-
-/// A [ChunkedConversionSink] for encoding chunks of data to Base64.
-class _Base64EncoderSink extends ChunkedConversionSink<List<int>> {
-  /// The encoder used to encode each chunk.
-  final Base64Encoder _encoder;
-
-  /// The underlying sink to which to emit the encoded strings.
-  final ChunkedConversionSink<String> _outSink;
-
-  /// The buffer of as-yet-unconverted bytes.
-  ///
-  /// This is used to ensure that we don't generate interstitial padding
-  /// characters.
-  final List<int> _buffer = new List<int>();
-
-  /// The length of [_buffer]; that is, the number of unconverted bytes.
-  int _bufferCount = 0;
-
-  _Base64EncoderSink(this._outSink, urlSafe, addLineSeparator)
-      : _encoder = new Base64Encoder(
-            urlSafe: urlSafe, addLineSeparator: addLineSeparator);
-
-  void add(List<int> chunk) {
-    var nextBufferCount = (chunk.length + _bufferCount) % 3;
-
-    int decodableLength = _bufferCount + chunk.length - nextBufferCount;
-
-    if (_bufferCount + chunk.length > _buffer.length) {
-      _buffer.replaceRange(_bufferCount, _buffer.length,
-          chunk.sublist(0, _buffer.length - _bufferCount));
-      _buffer.addAll(chunk.sublist(_buffer.length - _bufferCount));
-    } else {
-      _buffer.replaceRange(_bufferCount, _bufferCount + chunk.length, chunk);
-    }
-
-    _outSink.add(_encoder.convert(_buffer, 0, decodableLength));
-    _buffer.removeRange(0, decodableLength);
-    _bufferCount = nextBufferCount;
-  }
-
-  void close() {
-    if (_bufferCount > 0) {
-      _outSink.add(_encoder.convert(_buffer.sublist(0, _bufferCount)));
-    }
-    _outSink.close();
-  }
-}
-
-/// An encoder that converts [Base64][rfc] strings to sequences of bytes.
-///
-/// [rfc]: https://tools.ietf.org/html/rfc4648
-class Base64Decoder extends Converter<String, List<int>> {
-  const Base64Decoder();
-
-  List<int> convert(String input) {
-    int length = input.length;
-    if (length == 0) {
-      return new Uint8List(0);
-    }
-
-    int normalLength = 0;
-    int i = 0;
-    // Count '\r', '\n' and illegal characters, check if
-    // '/', '+' / '-', '_' are used consistently, for illegal characters,
-    // throw an exception.
-
-    while (i < length) {
-      int codeUnit = input.codeUnitAt(i);
-      int c = _decodeTable[codeUnit];
-      if (c == -2) {
-        if (codeUnit == _ENCODED_PAD_BYTES[0] &&
-            i < length - 2 &&
-            input.codeUnitAt(i + 1) == _ENCODED_PAD_BYTES[1] &&
-            input.codeUnitAt(i + 2) == _ENCODED_PAD_BYTES[2]) {
-          normalLength++;
-          i += 2;
-        } else {
-          throw new FormatException('Invalid character', input, i);
-        }
-      }
-      if (c >= 0) normalLength++;
-      i++;
-    }
-
-    if (normalLength % 4 != 0) {
-      throw new FormatException(
-          '''Size of Base 64 characters in Input
-          must be a multiple of 4''',
-          input,
-          normalLength);
-    }
-
-    // Count pad characters.
-    int padLength = 0;
-    i = length - 1;
-    while (i >= 0) {
-      int currentCodeUnit = input.codeUnitAt(i);
-      if (currentCodeUnit == _ENCODED_PAD_BYTES[2] &&
-          i >= 2 &&
-          input.codeUnitAt(i - 1) == _ENCODED_PAD_BYTES[1] &&
-          input.codeUnitAt(i - 2) == _ENCODED_PAD_BYTES[0]) {
-        padLength++;
-        i -= 2;
-      } else if (_decodeTable[currentCodeUnit] > 0) {
-        break;
-      } else if (currentCodeUnit == _PAD_BYTES[0]) {
-        padLength++;
-      }
-      i--;
-    }
-    int outputLength = ((normalLength * 6) >> 3) - padLength;
-    List<int> out = new Uint8List(outputLength);
-
-    for (int i = 0, o = 0; o < outputLength;) {
-      // Accumulate 4 valid 6 bit Base 64 characters into an int.
-      int x = 0;
-      for (int j = 4; j > 0;) {
-        int c = _decodeTable[input.codeUnitAt(i++)];
-        if (c >= 0) {
-          x = ((x << 6) & 0x00FFFFFF) | c;
-          j--;
-        }
-      }
-      out[o++] = x >> 16;
-      if (o < outputLength) {
-        out[o++] = (x >> 8) & 0xFF;
-        if (o < outputLength) out[o++] = x & 0xFF;
-      }
-    }
-
-    return out;
-  }
-
-  _Base64DecoderSink startChunkedConversion(Sink<List<int>> sink) {
-    if (sink is! ByteConversionSink) {
-      sink = new ByteConversionSink.from(sink);
-    }
-    return new _Base64DecoderSink(sink);
-  }
-}
-
-/// A [ChunkedConversionSink] for decoding chunks of Base64 strings to data.
-class _Base64DecoderSink extends ChunkedConversionSink<String> {
-  /// The encoder used to decode each chunk.
-  final Base64Decoder _decoder = new Base64Decoder();
-
-  /// The underlying sink to which to emit the decoded strings.
-  final ChunkedConversionSink<List<int>> _outSink;
-
-  /// The as-yet-unconverted text.
-  ///
-  /// This is used to handle a chunk stopping partway in the middle of a
-  /// URL-encoded `=` character.
-  String _unconverted = "";
-
-  _Base64DecoderSink(this._outSink);
-
-  void add(String chunk) {
-    if (chunk.isEmpty) return;
-    if (_unconverted.isNotEmpty) {
-      chunk = _unconverted + chunk;
-    }
-    chunk = chunk.replaceAll(_ENCODED_PAD, _PAD);
-    int decodableLength = chunk.length;
-    // If chunk ends in "%" or "%3", it may be a partial encoded pad.
-    // If chunk is smaller than 4 characters, don't bother checking.
-    if (chunk.length > 3 && chunk.contains(_ENCODED_PAD[0], chunk.length - 2)) {
-      decodableLength = chunk.lastIndexOf(_ENCODED_PAD[0]);
-    }
-    decodableLength -= decodableLength % 4;
-    _unconverted = chunk.substring(decodableLength);
-    if (decodableLength > 0) {
-      _outSink.add(_decoder.convert(chunk.substring(0, decodableLength)));
-    }
-  }
-
-  void close() {
-    if (_unconverted.isNotEmpty) {
-      _outSink.add(_decoder.convert(_unconverted));
-    }
-    _outSink.close();
-  }
+  Base64Decoder get decoder => const Base64Decoder();
 }