Add base64 decoder and change existing base64 encoder.

sdk/lib/crypto/crypto_utils.dart

 // Copyright (c) 2012, 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.crypto;
 
-class _LineWrappingStringBuffer {
-  _LineWrappingStringBuffer(int this._lineLength) : _sb = new StringBuffer();
-
-  void write(String s) {
-    if (_lineLength != null && _currentLineLength == _lineLength) {
-      _sb.write('\r\n');
-      _currentLineLength = 0;
-    }
-    _sb.write(s);
-    _currentLineLength++;
-  }
-
-  String toString() => _sb.toString();
-
-  int _lineLength;
-  StringBuffer _sb;
-  int _currentLineLength = 0;
-}
-
 abstract class _CryptoUtils {
   static String bytesToHex(List<int> bytes) {
     var result = new StringBuffer();
     for (var part in bytes) {
       result.write('${part < 16 ? '0' : ''}${part.toRadixString(16)}');
     }
     return result.toString();
   }
 
-  static String bytesToBase64(List<int> bytes, [int lineLength]) {
-    final table =
-        const [ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L',
-                'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
-                'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j',
-                'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
-                'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
-                '8', '9', '+', '/' ];
+  static final int PAD = '='.codeUnitAt(0);

[floitsch, 2013/03/22 17:22:05]

I would make this a const. Even if that means that we cannot use codeUnitAt.
something like:
static const int PAD = 100; // '='.

[mdakin1, 2013/03/25 17:05:02]

Done.

+  static final int CR = '\r'.codeUnitAt(0);
+  static final int LF = '\n'.codeUnitAt(0);
 
-    var result = new _LineWrappingStringBuffer(lineLength);
+  static final String _encodeTable =

[floitsch, 2013/03/22 17:22:05]

const, even though it shouldn't matter much.

[mdakin1, 2013/03/25 17:05:02]

Done.

+      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
 
-    // Encode all full 24-bit blocks.
-    var i = 0;
-    for (; (i + 2) < bytes.length; i += 3) {
-      var b0 = bytes[i] & 0xff;
-      var b1 = bytes[i + 1] & 0xff;
-      var b2 = bytes[i + 2] & 0xff;
-      result.write(table[b0 >> 2]);
-      result.write(table[((b0 << 4) | (b1 >> 4)) & 0x3f]);
-      result.write(table[((b1 << 2) | (b2 >> 6)) & 0x3f]);
-      result.write(table[b2 & 0x3f]);
+  static final String _encodeTableUrlSafe =

[floitsch, 2013/03/22 17:22:05]

ditto.

[mdakin1, 2013/03/25 17:05:02]

Done.

+      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
+
+  // Lookup table used for finding Base 64 alphabet index of a given byte.
+  // -2 : Outside base64 alphabet
+  // -1 : \r or \n
+  //  0 : = (Padding character).
+  // >0 : base64 alphabet index of given byte.
+  static 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 ];
+
+  static String bytesToBase64(List<int> bytes,
+                              [bool urlSafe = false,
+                              bool addLineSeparator = false,

[floitsch, 2013/03/22 17:22:05]

nit: add one space in front of the "bool addLi..." and the next line.

[mdakin1, 2013/03/25 17:05:02]

Done.

+                              bool usePadding = true]) {
+    int len = bytes.length;
+    if (len == 0) {
+      return "";
+    }
+    final String lookup = urlSafe ? _encodeTable : _encodeTableUrlSafe;
+    // Size of 24 bit chunks.
+    final int padLength = len % 3;
+    final int chunkLength = len - padLength;
+    // Size of base output.
+    int outputLen = ((len ~/ 3) * 4) + ((padLength > 0 && usePadding) ? 4 : 0);
+    // Add extra for line separators.
+    if (addLineSeparator) {
+      outputLen += ((outputLen - 1) ~/ 76) << 1;

[floitsch, 2013/03/22 17:22:05]

Maybe put 76 in a constant?

[mdakin1, 2013/03/25 17:05:02]

Done.

+    }
+    List<int> out = new List<int>(outputLen);
+
+    // Encode 24 bit chunks.
+    int j = 0, i = 0, cc = 0;
+    while (i < chunkLength) {
+      int x = (bytes[i++] << 16) | (bytes[i++] << 8) | bytes[i++];

[floitsch, 2013/03/22 17:22:05]

I wonder if you could help the VM and dart2js if you bit-anded with 24bits.

[mdakin1, 2013/03/25 17:05:02]

Done. 
I added a 0xFFFFFF mask per << operation, hope that was what you meant.

[floitsch, 2013/03/25 17:45:37]

Yes. that's what I wanted.

+      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 && ++cc == 19 && j < outputLen - 2) {
+          out[j++] = CR;
+          out[j++] = LF;
+          cc = 0;
+      }
     }
 
-    // Deal with the last non-full block if any and add padding '='.
-    if (i == bytes.length - 1) {
-      var b0 = bytes[i] & 0xff;
-      result.write(table[b0 >> 2]);
-      result.write(table[(b0 << 4) & 0x3f]);
-      result.write('=');
-      result.write('=');
-    } else if (i == bytes.length - 2) {
-      var b0 = bytes[i] & 0xff;
-      var b1 = bytes[i + 1] & 0xff;
-      result.write(table[b0 >> 2]);
-      result.write(table[((b0 << 4) | (b1 >> 4)) & 0x3f]);
-      result.write(table[(b1 << 2) & 0x3f]);
-      result.write('=');
+    // If input length if not a multiple of 3, encode remaining add padding.

[floitsch, 2013/03/22 17:22:05]

encode the remaining bytes and add padding.

[mdakin1, 2013/03/25 17:05:02]

Done.

+    if (padLength == 1) {
+      int x = bytes[i++];
+      out[j++] = lookup.codeUnitAt(x >> 2);
+      out[j++] = lookup.codeUnitAt((x & 0x3) << 4);
+      if (usePadding) {
+        out[j++] = PAD;
+        out[j++] = PAD;
+      }
+    } else if (padLength == 2) {
+      int x = (bytes[i++] << 10) | (bytes[i++] << 2);
+      out[j++] = lookup.codeUnitAt((x >> 12) & 0x3F);
+      out[j++] = lookup.codeUnitAt((x >> 6) & 0x3f);
+      out[j++] = lookup.codeUnitAt(x & 0x3F);
+      if (usePadding) out[j++] = PAD;
     }
 
-    return result.toString();
+    return new String.fromCharCodes(out);
   }
+
+  static List<int> base64StringToBytes(String input, [bool ignoreErrors]) {
+    int len = input.length;
+    if (len == 0) {
+      return new List<int>(0);
+    }
+
+    // Count '\r', '\n' and illegal characters,
+    // For illegal characters, if [ignoreErrors] is false, throw an exception.
+    int extrasLen = 0;
+    for (int i = 0; i < len; i++) {
+      int c = _decodeTable[input.codeUnitAt(i)];
+      if (c < 0) {
+          if (c == -1) {

[floitsch, 2013/03/22 17:22:05]

indentation. (2chars)

[mdakin1, 2013/03/25 17:05:02]

Done.

[mdakin1, 2013/03/25 17:05:02]

Done.

+            extrasLen++;
+          } else if (c == -2 && !ignoreErrors) {

[floitsch, 2013/03/22 17:22:05]

Change this if to:
if (c < 0) {
  extrasLen++;
  if (c == -2 && !ignoreErrors) {
    throw new FormatException ...;
  }
}

Otherwise the test (len - extrasLen) % 4 != 0 won't work if there are
non-new-line characters.

[mdakin1, 2013/03/25 17:05:02]

Done.

+            throw new FormatException('Invalid character: ${input[i]}');
+          }
+      }
+    }
+
+    if ((len - extrasLen) % 4 != 0) {

[floitsch, 2013/03/22 17:22:05]

Needs change above to work.
Add test for it.

[mdakin1, 2013/03/25 17:05:02]

Done.

+      throw new FormatException('Invalid input.');
+    }
+
+    // Count pad characters, ignore illegal characters at the end.
+    int padLength = 0;
+    for (int i = len; i > 1 && _decodeTable[input.codeUnitAt(--i)] <= 0;) {

[floitsch, 2013/03/22 17:22:05]

I prefer:
for (int i = len - 1; i >= 0; i--) {
  int currentCodeUnit = input.codeUnitAt(i);
  if (_decodeTable[currentCodeUnit] > 0) break;
  if (currentCodeUnit == PAD) padLength++;
}

[mdakin1, 2013/03/25 17:05:02]

Done.
Cleaner, thanks.

+      if (input.codeUnitAt(i) == PAD) {
+        padLength++;
+      }
+    }
+    int outputLen = (((len - extrasLen) * 6) >> 3) - padLength;
+    List<int> out = new List<int>(outputLen);
+
+    for (int i = 0, o = 0; o < outputLen;) {
+      // Accumulate 4 valid 6 bit base64 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) | c;

[floitsch, 2013/03/22 17:22:05]

I would bit-and to help the vm and dart2js.
Otherwise they need to verify that the left-shifting won't hurt them.

[mdakin1, 2013/03/25 17:05:02]

Done.

+          j--;
+        }
+      }
+      out[o++] = x >> 16;
+      if (o < outputLen) {
+        out[o++] = (x >> 8) & 0xFF;
+        if (o < outputLen) out[o++] = x & 0xFF;
+      }
+    }
+    return out;
+  }
+
 }