Index: tool/input_sdk/lib/convert/base64.dart |
diff --git a/tool/input_sdk/lib/convert/base64.dart b/tool/input_sdk/lib/convert/base64.dart |
new file mode 100644 |
index 0000000000000000000000000000000000000000..f3d7019af55b81f8bead51d2b55382aa34134228 |
--- /dev/null |
+++ b/tool/input_sdk/lib/convert/base64.dart |
@@ -0,0 +1,752 @@ |
+// Copyright (c) 2015, 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. |
+ |
+part of dart.convert; |
+ |
+/** |
+ * A [base64](https://tools.ietf.org/html/rfc4648) encoder and decoder. |
+ * |
+ * It encodes using the default base64 alphabet, |
+ * decodes using both the base64 and base64url alphabets, |
+ * does not allow invalid characters and requires padding. |
+ * |
+ * Examples: |
+ * |
+ * var encoded = BASE64.encode([0x62, 0x6c, 0xc3, 0xa5, 0x62, 0xc3, 0xa6, |
+ * 0x72, 0x67, 0x72, 0xc3, 0xb8, 0x64]); |
+ * var decoded = BASE64.decode("YmzDpWLDpnJncsO4ZAo="); |
+ */ |
+const Base64Codec BASE64 = const Base64Codec(); |
+ |
+/** |
+ * A [base64url](https://tools.ietf.org/html/rfc4648) encoder and decoder. |
+ * |
+ * It encodes and decodes using the base64url alphabet, |
+ * decodes using both the base64 and base64url alphabets, |
+ * does not allow invalid characters and requires padding. |
+ * |
+ * Examples: |
+ * |
+ * var encoded = BASE64URL.encode([0x62, 0x6c, 0xc3, 0xa5, 0x62, 0xc3, 0xa6, |
+ * 0x72, 0x67, 0x72, 0xc3, 0xb8, 0x64]); |
+ * var decoded = BASE64URL.decode("YmzDpWLDpnJncsO4ZAo="); |
+ */ |
+const Base64Codec BASE64URL = const Base64Codec.urlSafe(); |
+ |
+// Constants used in more than one class. |
+const int _paddingChar = 0x3d; // '='. |
+ |
+/** |
+ * A [base64](https://tools.ietf.org/html/rfc4648) encoder and decoder. |
+ * |
+ * A [Base64Codec] allows base64 encoding bytes into ASCII strings and |
+ * decoding valid encodings back to bytes. |
+ * |
+ * This implementation only handles the simplest RFC 4648 base64 and base64url |
+ * encodings. |
+ * It does not allow invalid characters when decoding and it requires, |
+ * and generates, padding so that the input is always a multiple of four |
+ * characters. |
+ */ |
+class Base64Codec extends Codec<List<int>, String> { |
+ final Base64Encoder _encoder; |
+ const Base64Codec() : _encoder = const Base64Encoder(); |
+ const Base64Codec.urlSafe() : _encoder = const Base64Encoder.urlSafe(); |
+ |
+ Base64Encoder get encoder => _encoder; |
+ |
+ Base64Decoder get decoder => const Base64Decoder(); |
+} |
+ |
+// ------------------------------------------------------------------------ |
+// Encoder |
+// ------------------------------------------------------------------------ |
+ |
+/** |
+ * Base64 and base64url encoding converter. |
+ * |
+ * Encodes lists of bytes using base64 or base64url encoding. |
+ * |
+ * The results are ASCII strings using a restricted alphabet. |
+ */ |
+class Base64Encoder extends |
+ ChunkedConverter<List<int>, String, List<int>, String> { |
+ final bool _urlSafe; |
+ |
+ const Base64Encoder() : _urlSafe = false; |
+ const Base64Encoder.urlSafe() : _urlSafe = true; |
+ |
+ String convert(List<int> input) { |
+ if (input.isEmpty) return ""; |
+ var encoder = new _Base64Encoder(_urlSafe); |
+ Uint8List buffer = encoder.encode(input, 0, input.length, true); |
+ return new String.fromCharCodes(buffer); |
+ } |
+ |
+ ByteConversionSink startChunkedConversion(Sink<String> sink) { |
+ if (sink is StringConversionSink) { |
+ return new _Utf8Base64EncoderSink(sink.asUtf8Sink(false), _urlSafe); |
+ } |
+ return new _AsciiBase64EncoderSink(sink, _urlSafe); |
+ } |
+} |
+ |
+/** |
+ * Helper class for encoding bytes to base64. |
+ */ |
+class _Base64Encoder { |
+ /** The RFC 4648 base64 encoding alphabet. */ |
+ static const String _base64Alphabet = |
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; |
+ |
+ /** The RFC 4648 base64url encoding alphabet. */ |
+ static const String _base64urlAlphabet = |
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_"; |
+ |
+ /** Shift-count to extract the values stored in [_state]. */ |
+ static const int _valueShift = 2; |
+ |
+ /** Mask to extract the count value stored in [_state]. */ |
+ static const int _countMask = 3; |
+ |
+ static const int _sixBitMask = 0x3F; |
+ |
+ /** |
+ * Intermediate state between chunks. |
+ * |
+ * Encoding handles three bytes at a time. |
+ * If fewer than three bytes has been seen, this value encodes |
+ * the number of bytes seen (0, 1 or 2) and their values. |
+ */ |
+ int _state = 0; |
+ |
+ /** Alphabet used for encoding. */ |
+ final String _alphabet; |
+ |
+ _Base64Encoder(bool urlSafe) |
+ : _alphabet = urlSafe ? _base64urlAlphabet : _base64Alphabet; |
+ |
+ /** Encode count and bits into a value to be stored in [_state]. */ |
+ static int _encodeState(int count, int bits) { |
+ assert(count <= _countMask); |
+ return bits << _valueShift | count; |
+ } |
+ |
+ /** Extract bits from encoded state. */ |
+ static int _stateBits(int state) => state >> _valueShift; |
+ |
+ /** Extract count from encoded state. */ |
+ static int _stateCount(int state) => state & _countMask; |
+ |
+ /** |
+ * Create a [Uint8List] with the provided length. |
+ */ |
+ Uint8List createBuffer(int bufferLength) => new Uint8List(bufferLength); |
+ |
+ /** |
+ * Encode [bytes] from [start] to [end] and the bits in [_state]. |
+ * |
+ * Returns a [Uint8List] of the ASCII codes of the encoded data. |
+ * |
+ * If the input, including left over [_state] from earlier encodings, |
+ * are not a multiple of three bytes, then the partial state is stored |
+ * back into [_state]. |
+ * If [isLast] is true, partial state is encoded in the output instead, |
+ * with the necessary padding. |
+ * |
+ * Returns `null` if there is no output. |
+ */ |
+ Uint8List encode(List<int> bytes, int start, int end, bool isLast) { |
+ assert(0 <= start); |
+ assert(start <= end); |
+ assert(bytes == null || end <= bytes.length); |
+ int length = end - start; |
+ |
+ int count = _stateCount(_state); |
+ int byteCount = (count + length); |
+ int fullChunks = byteCount ~/ 3; |
+ int partialChunkLength = byteCount - fullChunks * 3; |
+ int bufferLength = fullChunks * 4; |
+ if (isLast && partialChunkLength > 0) { |
+ bufferLength += 4; // Room for padding. |
+ } |
+ var output = createBuffer(bufferLength); |
+ _state = encodeChunk(_alphabet, bytes, start, end, isLast, |
+ output, 0, _state); |
+ if (bufferLength > 0) return output; |
+ // If the input plus the data in state is still less than three bytes, |
+ // there may not be any output. |
+ return null; |
+ } |
+ |
+ static int encodeChunk(String alphabet, |
+ List<int> bytes, int start, int end, bool isLast, |
+ Uint8List output, int outputIndex, int state) { |
+ int bits = _stateBits(state); |
+ // Count number of missing bytes in three-byte chunk. |
+ int expectedChars = 3 - _stateCount(state); |
+ |
+ // The input must be a list of bytes (integers in the range 0..255). |
+ // The value of `byteOr` will be the bitwise or of all the values in |
+ // `bytes` and a later check will validate that they were all valid bytes. |
+ int byteOr = 0; |
+ for (int i = start; i < end; i++) { |
+ int byte = bytes[i]; |
+ byteOr |= byte; |
+ bits = ((bits << 8) | byte) & 0xFFFFFF; // Never store more than 24 bits. |
+ expectedChars--; |
+ if (expectedChars == 0) { |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt((bits >> 18) & _sixBitMask); |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt((bits >> 12) & _sixBitMask); |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt((bits >> 6) & _sixBitMask); |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt(bits & _sixBitMask); |
+ expectedChars = 3; |
+ bits = 0; |
+ } |
+ } |
+ if (byteOr >= 0 && byteOr <= 255) { |
+ if (isLast && expectedChars < 3) { |
+ writeFinalChunk(alphabet, output, outputIndex, 3 - expectedChars, bits); |
+ return 0; |
+ } |
+ return _encodeState(3 - expectedChars, bits); |
+ } |
+ |
+ // There was an invalid byte value somewhere in the input - find it! |
+ int i = start; |
+ while (i < end) { |
+ int byte = bytes[i]; |
+ if (byte < 0 || byte > 255) break; |
+ i++; |
+ } |
+ throw new ArgumentError.value(bytes, |
+ "Not a byte value at index $i: 0x${bytes[i].toRadixString(16)}"); |
+ } |
+ |
+ /** |
+ * Writes a final encoded four-character chunk. |
+ * |
+ * Only used when the [_state] contains a partial (1 or 2 byte) |
+ * input. |
+ */ |
+ static void writeFinalChunk(String alphabet, |
+ Uint8List output, int outputIndex, |
+ int count, int bits) { |
+ assert(count > 0); |
+ if (count == 1) { |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt((bits >> 2) & _sixBitMask); |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt((bits << 4) & _sixBitMask); |
+ output[outputIndex++] = _paddingChar; |
+ output[outputIndex++] = _paddingChar; |
+ } else { |
+ assert(count == 2); |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt((bits >> 10) & _sixBitMask); |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt((bits >> 4) & _sixBitMask); |
+ output[outputIndex++] = |
+ alphabet.codeUnitAt((bits << 2) & _sixBitMask); |
+ output[outputIndex++] = _paddingChar; |
+ } |
+ } |
+} |
+ |
+class _BufferCachingBase64Encoder extends _Base64Encoder { |
+ /** |
+ * Reused buffer. |
+ * |
+ * When the buffer isn't released to the sink, only used to create another |
+ * value (a string), the buffer can be reused between chunks. |
+ */ |
+ Uint8List bufferCache; |
+ |
+ _BufferCachingBase64Encoder(bool urlSafe) : super(urlSafe); |
+ |
+ Uint8List createBuffer(int bufferLength) { |
+ if (bufferCache == null || bufferCache.length < bufferLength) { |
+ bufferCache = new Uint8List(bufferLength); |
+ } |
+ // Return a view of the buffer, so it has the reuested length. |
+ return new Uint8List.view(bufferCache.buffer, 0, bufferLength); |
+ } |
+} |
+ |
+abstract class _Base64EncoderSink extends ByteConversionSinkBase { |
+ void add(List<int> source) { |
+ _add(source, 0, source.length, false); |
+ } |
+ |
+ void close() { |
+ _add(null, 0, 0, true); |
+ } |
+ |
+ void addSlice(List<int> source, int start, int end, bool isLast) { |
+ if (end == null) throw new ArgumentError.notNull("end"); |
+ RangeError.checkValidRange(start, end, source.length); |
+ _add(source, start, end, isLast); |
+ } |
+ |
+ void _add(List<int> source, int start, int end, bool isLast); |
+} |
+ |
+class _AsciiBase64EncoderSink extends _Base64EncoderSink { |
+ final Sink<String> _sink; |
+ final _Base64Encoder _encoder; |
+ |
+ _AsciiBase64EncoderSink(this._sink, bool urlSafe) |
+ : _encoder = new _BufferCachingBase64Encoder(urlSafe); |
+ |
+ void _add(List<int> source, int start, int end, bool isLast) { |
+ Uint8List buffer = _encoder.encode(source, start, end, isLast); |
+ if (buffer != null) { |
+ String string = new String.fromCharCodes(buffer); |
+ _sink.add(string); |
+ } |
+ if (isLast) { |
+ _sink.close(); |
+ } |
+ } |
+} |
+ |
+class _Utf8Base64EncoderSink extends _Base64EncoderSink { |
+ final ByteConversionSink _sink; |
+ final _Base64Encoder _encoder; |
+ |
+ _Utf8Base64EncoderSink(this._sink, bool urlSafe) |
+ : _encoder = new _Base64Encoder(urlSafe); |
+ |
+ void _add(List<int> source, int start, int end, bool isLast) { |
+ Uint8List buffer = _encoder.encode(source, start, end, isLast); |
+ if (buffer != null) { |
+ _sink.addSlice(buffer, 0, buffer.length, isLast); |
+ } |
+ } |
+} |
+ |
+// ------------------------------------------------------------------------ |
+// Decoder |
+// ------------------------------------------------------------------------ |
+ |
+/** |
+ * Decoder for base64 encoded data. |
+ * |
+ * This decoder accepts both base64 and base64url ("url-safe") encodings. |
+ * |
+ * The encoding is required to be properly padded. |
+ */ |
+class Base64Decoder extends |
+ ChunkedConverter<String, List<int>, String, List<int>> { |
+ |
+ const Base64Decoder(); |
+ |
+ List<int> convert(String input, [int start = 0, int end]) { |
+ end = RangeError.checkValidRange(start, end, input.length); |
+ if (start == end) return new Uint8List(0); |
+ var decoder = new _Base64Decoder(); |
+ Uint8List buffer = decoder.decode(input, start, end); |
+ decoder.close(input, end); |
+ return buffer; |
+ } |
+ |
+ StringConversionSink startChunkedConversion(Sink<List<int>> sink) { |
+ return new _Base64DecoderSink(sink); |
+ } |
+} |
+ |
+/** |
+ * Helper class implementing base64 decoding with intermediate state. |
+ */ |
+class _Base64Decoder { |
+ /** Shift-count to extract the values stored in [_state]. */ |
+ static const int _valueShift = 2; |
+ |
+ /** Mask to extract the count value stored in [_state]. */ |
+ static const int _countMask = 3; |
+ |
+ /** Invalid character in decoding table. */ |
+ static const int _invalid = -2; |
+ |
+ /** Padding character in decoding table. */ |
+ static const int _padding = -1; |
+ |
+ // Shorthands to make the table more readable. |
+ static const int __ = _invalid; |
+ static const int _p = _padding; |
+ |
+ /** |
+ * Mapping from ASCII characters to their index in the base64 alphabet. |
+ * |
+ * Uses [_invalid] for invalid indices and [_padding] for the padding |
+ * character. |
+ * |
+ * Accepts the "URL-safe" alphabet as well (`-` and `_` are the |
+ * 62nd and 63rd alphabet characters), and considers `%` a padding |
+ * character, which mush then be followed by `3D`, the percent-escape |
+ * for `=`. |
+ */ |
+ static final List<int> _inverseAlphabet = new Int8List.fromList([ |
+ __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, |
+ __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, |
+ __, __, __, __, __, _p, __, __, __, __, __, 62, __, 62, __, 63, |
+ 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, __, __, __, _p, __, __, |
+ __, 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, __, __, __, __, 63, |
+ __, 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, __, __, __, __, __, |
+ ]); |
+ |
+ // Character constants. |
+ static const int _char_percent = 0x25; // '%'. |
+ static const int _char_3 = 0x33; // '3'. |
+ static const int _char_d = 0x64; // 'd'. |
+ |
+ /** |
+ * Maintains the intermediate state of a partly-decoded input. |
+ * |
+ * Base64 is decoded in chunks of four characters. If a chunk does not |
+ * contain a full block, the decoded bits (six per character) of the |
+ * available characters are stored in [_state] until the next call to |
+ * [_decode] or [_close]. |
+ * |
+ * If no padding has been seen, the value is |
+ * `numberOfCharactersSeen | (decodedBits << 2)` |
+ * where `numberOfCharactersSeen` is between 0 and 3 and decoded bits |
+ * contains six bits per seen character. |
+ * |
+ * If padding has been seen the value is negative. It's the bitwise negation |
+ * of the number of remanining allowed padding characters (always ~0 or ~1). |
+ * |
+ * A state of `0` or `~0` are valid places to end decoding, all other values |
+ * mean that a four-character block has not been completed. |
+ */ |
+ int _state = 0; |
+ |
+ /** |
+ * Encodes [count] and [bits] as a value to be stored in [_state]. |
+ */ |
+ static int _encodeCharacterState(int count, int bits) { |
+ assert(count == (count & _countMask)); |
+ return (bits << _valueShift | count); |
+ } |
+ |
+ /** |
+ * Extracts count from a [_state] value. |
+ */ |
+ static int _stateCount(int state) { |
+ assert(state >= 0); |
+ return state & _countMask; |
+ } |
+ |
+ /** |
+ * Extracts value bits from a [_state] value. |
+ */ |
+ static int _stateBits(int state) { |
+ assert(state >= 0); |
+ return state >> _valueShift; |
+ } |
+ |
+ /** |
+ * Encodes a number of expected padding characters to be stored in [_state]. |
+ */ |
+ static int _encodePaddingState(int expectedPadding) { |
+ assert(expectedPadding >= 0); |
+ assert(expectedPadding <= 5); |
+ return -expectedPadding - 1; // ~expectedPadding adapted to dart2js. |
+ } |
+ |
+ /** |
+ * Extracts expected padding character count from a [_state] value. |
+ */ |
+ static int _statePadding(int state) { |
+ assert(state < 0); |
+ return -state - 1; // ~state adapted to dart2js. |
+ } |
+ |
+ static bool _hasSeenPadding(int state) => state < 0; |
+ |
+ /** |
+ * Decodes [input] from [start] to [end]. |
+ * |
+ * Returns a [Uint8List] with the decoded bytes. |
+ * If a previous call had an incomplete four-character block, the bits from |
+ * those are included in decoding |
+ */ |
+ Uint8List decode(String input, int start, int end) { |
+ assert(0 <= start); |
+ assert(start <= end); |
+ assert(end <= input.length); |
+ if (_hasSeenPadding(_state)) { |
+ _state = _checkPadding(input, start, end, _state); |
+ return null; |
+ } |
+ if (start == end) return new Uint8List(0); |
+ Uint8List buffer = _allocateBuffer(input, start, end, _state); |
+ _state = decodeChunk(input, start, end, buffer, 0, _state); |
+ return buffer; |
+ } |
+ |
+ /** Checks that [_state] represents a valid decoding. */ |
+ void close(String input, int end) { |
+ if (_state < _encodePaddingState(0)) { |
+ throw new FormatException("Missing padding character", input, end); |
+ } |
+ if (_state > 0) { |
+ throw new FormatException("Invalid length, must be multiple of four", |
+ input, end); |
+ } |
+ _state = _encodePaddingState(0); |
+ } |
+ |
+ /** |
+ * Decodes [input] from [start] to [end]. |
+ * |
+ * Includes the state returned by a previous call in the decoding. |
+ * Writes the decoding to [output] at [outIndex], and there must |
+ * be room in the output. |
+ */ |
+ static int decodeChunk(String input, int start, int end, |
+ Uint8List output, int outIndex, |
+ int state) { |
+ assert(!_hasSeenPadding(state)); |
+ const int asciiMask = 127; |
+ const int asciiMax = 127; |
+ const int eightBitMask = 0xFF; |
+ const int bitsPerCharacter = 6; |
+ |
+ int bits = _stateBits(state); |
+ int count = _stateCount(state); |
+ // String contents should be all ASCII. |
+ // Instead of checking for each character, we collect the bitwise-or of |
+ // all the characters in `charOr` and later validate that all characters |
+ // were ASCII. |
+ int charOr = 0; |
+ for (int i = start; i < end; i++) { |
+ var char = input.codeUnitAt(i); |
+ charOr |= char; |
+ int code = _inverseAlphabet[char & asciiMask]; |
+ if (code >= 0) { |
+ bits = ((bits << bitsPerCharacter) | code) & 0xFFFFFF; |
+ count = (count + 1) & 3; |
+ if (count == 0) { |
+ assert(outIndex + 3 <= output.length); |
+ output[outIndex++] = (bits >> 16) & eightBitMask; |
+ output[outIndex++] = (bits >> 8) & eightBitMask; |
+ output[outIndex++] = bits & eightBitMask; |
+ bits = 0; |
+ } |
+ continue; |
+ } else if (code == _padding && count > 1) { |
+ if (charOr < 0 || charOr > asciiMax) break; |
+ if (count == 3) { |
+ if ((bits & 0x03) != 0) { |
+ throw new FormatException( |
+ "Invalid encoding before padding", input, i); |
+ } |
+ output[outIndex++] = bits >> 10; |
+ output[outIndex++] = bits >> 2; |
+ } else { |
+ if ((bits & 0x0F) != 0) { |
+ throw new FormatException( |
+ "Invalid encoding before padding", input, i); |
+ } |
+ output[outIndex++] = bits >> 4; |
+ } |
+ // Expected padding is the number of expected padding characters, |
+ // where `=` counts as three and `%3D` counts as one per character. |
+ // |
+ // Expect either zero or one padding depending on count (2 or 3), |
+ // plus two more characters if the code was `%` (a partial padding). |
+ int expectedPadding = (3 - count) * 3; |
+ if (char == _char_percent) expectedPadding += 2; |
+ state = _encodePaddingState(expectedPadding); |
+ return _checkPadding(input, i + 1, end, state); |
+ } |
+ throw new FormatException("Invalid character", input, i); |
+ } |
+ if (charOr >= 0 && charOr <= asciiMax) { |
+ return _encodeCharacterState(count, bits); |
+ } |
+ // There is an invalid (non-ASCII) character in the input. |
+ int i; |
+ for (i = start; i < end; i++) { |
+ int char = input.codeUnitAt(i); |
+ if (char < 0 || char > asciiMax) break; |
+ } |
+ throw new FormatException("Invalid character", input, i); |
+ } |
+ |
+ /** |
+ * Allocates a buffer with room for the decoding of a substring of [input]. |
+ * |
+ * Includes room for the characters in [state], and handles padding correctly. |
+ */ |
+ static Uint8List _allocateBuffer(String input, int start, int end, |
+ int state) { |
+ assert(state >= 0); |
+ int paddingStart = _trimPaddingChars(input, start, end); |
+ int length = _stateCount(state) + (paddingStart - start); |
+ // Three bytes per full four bytes in the input. |
+ int bufferLength = (length >> 2) * 3; |
+ // If padding was seen, then this is the last chunk, and the final partial |
+ // chunk should be decoded too. |
+ int remainderLength = length & 3; |
+ if (remainderLength != 0 && paddingStart < end) { |
+ bufferLength += remainderLength - 1; |
+ } |
+ if (bufferLength > 0) return new Uint8List(bufferLength); |
+ // If the input plus state is less than four characters, and it's not |
+ // at the end of input, no buffer is needed. |
+ return null; |
+ } |
+ |
+ /** |
+ * Returns the position of the start of padding at the end of the input. |
+ * |
+ * Returns the end of input if there is no padding. |
+ * |
+ * This is used to ensure that the decoding buffer has the exact size |
+ * it needs when input is valid, and at least enough bytes to reach the error |
+ * when input is invalid. |
+ * |
+ * Never count more than two padding sequences since any more than that |
+ * will raise an error anyway, and we only care about being precise for |
+ * successful conversions. |
+ */ |
+ static int _trimPaddingChars(String input, int start, int end) { |
+ // This may count '%=' as two paddings. That's ok, it will err later, |
+ // but the buffer will be large enough to reach the error. |
+ int padding = 0; |
+ int index = end; |
+ int newEnd = end; |
+ while (index > start && padding < 2) { |
+ index--; |
+ int char = input.codeUnitAt(index); |
+ if (char == _paddingChar) { |
+ padding++; |
+ newEnd = index; |
+ continue; |
+ } |
+ if ((char | 0x20) == _char_d) { |
+ if (index == start) break; |
+ index--; |
+ char = input.codeUnitAt(index); |
+ } |
+ if (char == _char_3) { |
+ if (index == start) break; |
+ index--; |
+ char = input.codeUnitAt(index); |
+ } |
+ if (char == _char_percent) { |
+ padding++; |
+ newEnd = index; |
+ continue; |
+ } |
+ break; |
+ } |
+ return newEnd; |
+ } |
+ |
+ /** |
+ * Check that the remainder of the string is valid padding. |
+ * |
+ * Valid padding is a correct number (0, 1 or 2) of `=` characters |
+ * or `%3D` sequences depending on the number of preceding base64 characters. |
+ * The [state] parameter encodes which padding continuations are allowed |
+ * as the number of expected characters. That number is the number of |
+ * expected padding characters times 3 minus the number of padding characters |
+ * seen so far, where `=` counts as 3 counts as three characters, |
+ * and the padding sequence `%3D` counts as one character per character. |
+ * |
+ * The number of missing characters is always between 0 and 5 because we |
+ * only call this function after having seen at least one `=` or `%` |
+ * character. |
+ * If the number of missing characters is not 3 or 0, we have seen (at least) |
+ * a `%` character and expects the rest of the `%3D` sequence, and a `=` is |
+ * not allowed. When missing 3 characters, either `=` or `%` is allowed. |
+ * |
+ * When the value is 0, no more padding (or any other character) is allowed. |
+ */ |
+ static int _checkPadding(String input, int start, int end, int state) { |
+ assert(_hasSeenPadding(state)); |
+ if (start == end) return state; |
+ int expectedPadding = _statePadding(state); |
+ assert(expectedPadding >= 0); |
+ assert(expectedPadding < 6); |
+ while (expectedPadding > 0) { |
+ int char = input.codeUnitAt(start); |
+ if (expectedPadding == 3) { |
+ if (char == _paddingChar) { |
+ expectedPadding -= 3; |
+ start++; |
+ break; |
+ } |
+ if (char == _char_percent) { |
+ expectedPadding--; |
+ start++; |
+ if (start == end) break; |
+ char = input.codeUnitAt(start); |
+ } else { |
+ break; |
+ } |
+ } |
+ // Partial padding means we have seen part of a "%3D" escape. |
+ int expectedPartialPadding = expectedPadding; |
+ if (expectedPartialPadding > 3) expectedPartialPadding -= 3; |
+ if (expectedPartialPadding == 2) { |
+ // Expects '3' |
+ if (char != _char_3) break; |
+ start++; |
+ expectedPadding--; |
+ if (start == end) break; |
+ char = input.codeUnitAt(start); |
+ } |
+ // Expects 'D' or 'd'. |
+ if ((char | 0x20) != _char_d) break; |
+ start++; |
+ expectedPadding--; |
+ if (start == end) break; |
+ } |
+ if (start != end) { |
+ throw new FormatException("Invalid padding character", |
+ input, start); |
+ } |
+ return _encodePaddingState(expectedPadding); |
+ } |
+} |
+ |
+class _Base64DecoderSink extends StringConversionSinkBase { |
+ /** Output sink */ |
+ final Sink<List<int>> _sink; |
+ final _Base64Decoder _decoder = new _Base64Decoder(); |
+ |
+ _Base64DecoderSink(this._sink); |
+ |
+ void add(String string) { |
+ if (string.isEmpty) return; |
+ Uint8List buffer = _decoder.decode(string, 0, string.length); |
+ if (buffer != null) _sink.add(buffer); |
+ } |
+ |
+ void close() { |
+ _decoder.close(null, null); |
+ _sink.close(); |
+ } |
+ |
+ void addSlice(String string, int start, int end, bool isLast) { |
+ end = RangeError.checkValidRange(start, end, string.length); |
+ if (start == end) return; |
+ Uint8List buffer = _decoder.decode(string, start, end); |
+ if (buffer != null) _sink.add(buffer); |
+ if (isLast) { |
+ _decoder.close(string, end); |
+ _sink.close(); |
+ } |
+ } |
+} |