Index: lib/src/base64/encoder.dart |
diff --git a/lib/src/base64/encoder.dart b/lib/src/base64/encoder.dart |
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+++ b/lib/src/base64/encoder.dart |
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+// 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. |
+ |
+library crypto.base64.encoder; |
+ |
+import 'dart:convert'; |
+ |
+import 'package:charcode/ascii.dart'; |
+ |
+import 'encoder_sink.dart'; |
+ |
+/// 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 _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 _encodeTable = |
+ "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; |
+ |
+/// The line length for Base64 strings with line separators. |
+const _lineLength = 76; |
+ |
+/// 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; |
+ |
+ /// 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, |
+ _pad = encodePaddingCharacter |
+ ? const [$percent, $3, $D] |
+ : const [$equal]; |
+ |
+ /// 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]) { |
+ RangeError.checkValidRange(start, end, bytes.length); |
+ if (end == null) end = bytes.length; |
+ |
+ var length = end - start; |
+ if (length == 0) return ""; |
+ |
+ var lookup = _urlSafe ? _encodeTableUrlSafe : _encodeTable; |
+ |
+ // The total length of the 24-bit chunks. |
+ var remainderLength = length.remainder(3); |
+ var chunkLength = length - remainderLength; |
+ |
+ // The size of the base output. |
+ var baseOutputLength = (length ~/ 3) * 4; |
+ var remainderOutputLength = remainderLength > 0 ? 3 + _pad.length : 0; |
+ |
+ var outputLength = baseOutputLength + remainderOutputLength; |
+ if (_addLineSeparator) { |
+ // Add extra expected length to account for line separators. |
+ outputLength += ((outputLength - 1) ~/ _lineLength) * 2; |
+ } |
+ var out = new List<int>(outputLength); |
+ |
+ // Encode 24 bit chunks. |
+ var input = start; |
+ var output = 0; |
+ var chunks = 0; |
+ while (input < chunkLength) { |
+ // Get a 24-bit chunk from the next three input bytes. Mask each byte to |
+ // make sure we don't do something bad if the user passes in non-byte |
+ // ints. |
+ var chunk = (bytes[input++] << 16) & 0x00FF0000; |
+ chunk |= (bytes[input++] << 8) & 0x0000FF00; |
+ chunk |= bytes[input++] & 0x000000FF; |
+ |
+ // Split the 24-bit chunk into four 6-bit sections to encode as |
+ // characters. |
+ out[output++] = lookup.codeUnitAt(chunk >> 18); |
+ out[output++] = lookup.codeUnitAt((chunk >> 12) & 0x3F); |
+ out[output++] = lookup.codeUnitAt((chunk >> 6) & 0x3F); |
+ out[output++] = lookup.codeUnitAt(chunk & 0x3F); |
+ |
+ // Add an optional line separator for every 76 characters we emit; that |
+ // is, every 19 chunks. |
+ chunks++; |
+ if (_addLineSeparator && chunks == 19 && output < outputLength - 2) { |
+ out[output++] = $cr; |
+ out[output++] = $lf; |
+ chunks = 0; |
+ } |
+ } |
+ |
+ // If the input length isn't a multiple of 3, encode the remaining bytes and |
+ // add padding. |
+ if (remainderLength == 1) { |
+ var byte = bytes[input]; |
+ out[output++] = lookup.codeUnitAt(byte >> 2); |
+ out[output++] = lookup.codeUnitAt((byte << 4) & 0x3F); |
+ out.setRange(output, output + _pad.length, _pad); |
+ out.setRange(output + _pad.length, output + 2 * _pad.length, _pad); |
+ } else if (remainderLength == 2) { |
+ var byte1 = bytes[input++]; |
+ var byte2 = bytes[input]; |
+ out[output++] = lookup.codeUnitAt(byte1 >> 2); |
+ out[output++] = lookup.codeUnitAt(((byte1 << 4) | (byte2 >> 4)) & 0x3F); |
+ out[output++] = lookup.codeUnitAt((byte2 << 2) & 0x3F); |
+ out.setRange(output, output + _pad.length, _pad); |
+ } |
+ |
+ return new String.fromCharCodes(out); |
+ } |
+ |
+ Base64EncoderSink startChunkedConversion(Sink<String> sink) { |
+ StringConversionSink stringSink = sink is StringConversionSink |
+ ? sink |
+ : new StringConversionSink.from(sink); |
+ |
+ return new Base64EncoderSink(stringSink, _urlSafe, _addLineSeparator); |
+ } |
+} |