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c04236c7deccf2fd81c002ae79aa5fe1bc646c0e
frameworks_base/common/java/com/android/common/Base64.java
Doug Zongker 6123eafa2c a new java implementation of base64 for android-common 
A new Base64 encoder/decoder class.  Some benchmarks comparing the
decoder it to those from android.os.Base64Utils (a decode-only native
implementation not accessible to apps) and
org.apache.commons.codec.binary.Base64, all with the JIT enabled:

  1k encoded data
  APACHE   avg:   811 us    min:   244 us    max: 13671 us
  COMMON   avg:   263 us    min:    30 us    max:  4730 us
  NATIVE   avg:   102 us    min:    61 us    max:  5493 us

  10k encoded data
  APACHE   avg:  3624 us    min:  2746 us    max: 23895 us
  COMMON   avg:   979 us    min:   518 us    max:  7751 us
  NATIVE   avg:   817 us    min:   762 us    max:  3143 us

  100k encoded data
  APACHE   avg: 33167 us    min: 31829 us    max: 140411 us
  COMMON   avg:  6047 us    min:  5493 us    max: 45227 us
  NATIVE   avg: 10109 us    min: 10009 us    max: 12451 us

Change-Id: Ic622e3a967a62d57d30bd25b80cbe4e0dd60e764
2010-02-04 15:54:00 -08:00

498 lines
19 KiB
Java
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/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.common;
/**
* Utilities for encoding and decoding the Base64 encoding. See RFCs
* 2045 and 3548.
*/
public class Base64 {
/**
* Encoder flag bit to indicate you want the padding '='
* characters at the end (if any) to be omitted.
*/
public static final int NO_PADDING = 1;
/**
* Encoder flag bit to indicate you want all line terminators to
* be omitted (ie, the output will be on one long line).
*/
public static final int NO_WRAP = 2;
/**
* Encoder flag bit to indicate you want lines to be ended with
* CRLF instead of just LF.
*/
public static final int CRLF = 4;
/**
* Encoder/decoder flag bit to indicate using the "web safe"
* variant of Base64 (see RFC 3548 section 4) where '-' and '_'
* are used in place of '+' and '/'.
*/
public static final int WEB_SAFE = 8;
/**
* Lookup table for turning bytes into their position in the
* Base64 alphabet.
*/
private static final int DECODE[] = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
-1, 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, -1, -1, -1, -1, -1,
-1, 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, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};
/**
* Decode lookup table for the "web safe" variant (RFC 3548
* sec. 4) where - and _ replace + and /.
*/
private static final int DECODE_WEBSAFE[] = {
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1,
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
-1, 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, -1, -1, -1, -1, 63,
-1, 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, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};
/** Non-data values in the DECODE arrays. */
private static final int SKIP = -1;
private static final int EQUALS = -2;
/**
* Decode the Base64-encoded data in input and return the data in
* a new byte array.
*
* The padding '=' characters at the end are considered optional, but
* if any are present, there must be the correct number of them.
*
* @param input the input String to decode, which is converted to
* bytes using the default charset
* @param flags controls certain features of the decoded output.
* Passing 0 to decode standard Base64.
*
* @throws IllegalArgumentException if the input contains
* incorrect padding
*/
public static byte[] decode(String str, int flags) {
return decode(str.getBytes(), flags);
}
/**
* Decode the Base64-encoded data in input and return the data in
* a new byte array.
*
* The padding '=' characters at the end are considered optional, but
* if any are present, there must be the correct number of them.
*
* @param input the input array to decode
* @param flags controls certain features of the decoded output.
* Passing 0 to decode standard Base64.
*
* @throws IllegalArgumentException if the input contains
* incorrect padding
*/
public static byte[] decode(byte[] input, int flags) {
return decode(input, 0, input.length, flags);
}
/**
* Decode the Base64-encoded data in input and return the data in
* a new byte array.
*
* The padding '=' characters at the end are considered optional, but
* if any are present, there must be the correct number of them.
*
* @param input the data to decode
* @param offset the position within the input array at which to start
* @param len the number of bytes of input to decode
* @param flags controls certain features of the decoded output.
* Passing 0 to decode standard Base64.
*
* @throws IllegalArgumentException if the input contains
* incorrect padding
*/
public static byte[] decode(byte[] input, int offset, int len, int flags) {
int p = offset;
// Allocate space for the most data the input could represent.
// (It could contain less if it contains whitespace, etc.)
byte[] output = new byte[len*3/4];
len += offset;
int op = 0;
final int[] decode = ((flags & WEB_SAFE) == 0) ?
DECODE : DECODE_WEBSAFE;
int state = 0;
int value = 0;
while (p < len) {
// Try the fast path: we're starting a new tuple and the
// next four bytes of the input stream are all data
// bytes. This corresponds to going through states
// 0-1-2-3-0. We expect to use this method for most of
// the data.
//
// If any of the next four bytes of input are non-data
// (whitespace, etc.), value will end up negative. (All
// the non-data values in decode are small negative
// numbers, so shifting any of them up and or'ing them
// together will result in a value with its top bit set.)
//
// You can remove this whole block and the output should
// be the same, just slower.
if (state == 0 && p+4 <= len &&
(value = ((decode[input[p] & 0xff] << 18) |
(decode[input[p+1] & 0xff] << 12) |
(decode[input[p+2] & 0xff] << 6) |
(decode[input[p+3] & 0xff]))) >= 0) {
output[op+2] = (byte) value;
output[op+1] = (byte) (value >> 8);
output[op] = (byte) (value >> 16);
op += 3;
p += 4;
continue;
}
// The fast path isn't available -- either we've read a
// partial tuple, or the next four input bytes aren't all
// data, or whatever. Fall back to the slower state
// machine implementation.
//
// States 0-3 are reading through the next input tuple.
// State 4 is having read one '=' and expecting exactly
// one more.
// State 5 is expecting no more data or padding characters
// in the input.
int d = decode[input[p++] & 0xff];
switch (state) {
case 0:
if (d >= 0) {
value = d;
++state;
} else if (d != SKIP) {
throw new IllegalArgumentException("bad base-64");
}
break;
case 1:
if (d >= 0) {
value = (value << 6) | d;
++state;
} else if (d != SKIP) {
throw new IllegalArgumentException("bad base-64");
}
break;
case 2:
if (d >= 0) {
value = (value << 6) | d;
++state;
} else if (d == EQUALS) {
// Emit the last (partial) output tuple;
// expect exactly one more padding character.
output[op++] = (byte) (value >> 4);
state = 4;
} else if (d != SKIP) {
throw new IllegalArgumentException("bad base-64");
}
break;
case 3:
if (d >= 0) {
// Emit the output triple and return to state 0.
value = (value << 6) | d;
output[op+2] = (byte) value;
output[op+1] = (byte) (value >> 8);
output[op] = (byte) (value >> 16);
op += 3;
state = 0;
} else if (d == EQUALS) {
// Emit the last (partial) output tuple;
// expect no further data or padding characters.
output[op+1] = (byte) (value >> 2);
output[op] = (byte) (value >> 10);
op += 2;
state = 5;
} else if (d != SKIP) {
throw new IllegalArgumentException("bad base-64");
}
break;
case 4:
if (d == EQUALS) {
++state;
} else if (d != SKIP) {
throw new IllegalArgumentException("bad base-64");
}
break;
case 5:
if (d != SKIP) {
throw new IllegalArgumentException("bad base-64");
}
break;
}
}
// Done reading input. Now figure out where we are left in
// the state machine and finish up.
switch (state) {
case 0:
// Output length is a multiple of three. Fine.
break;
case 1:
// Read one extra input byte, which isn't enough to
// make another output byte. Illegal.
throw new IllegalArgumentException("bad base-64");
case 2:
// Read two extra input bytes, enough to emit 1 more
// output byte. Fine.
output[op++] = (byte) (value >> 4);
break;
case 3:
// Read three extra input bytes, enough to emit 2 more
// output bytes. Fine.
output[op+1] = (byte) (value >> 2);
output[op] = (byte) (value >> 10);
op += 2;
break;
case 4:
// Read one padding '=' when we expected 2. Illegal.
throw new IllegalArgumentException("bad base-64");
case 5:
// Read all the padding '='s we expected and no more.
// Fine.
break;
}
// Maybe we got lucky and allocated exactly enough output space.
if (op == output.length) {
return output;
}
// Need to shorten the array, so allocate a new one of the
// right size and copy.
byte[] temp = new byte[op];
System.arraycopy(output, 0, temp, 0, op);
return temp;
}
/**
* Emit a new line every this many output tuples. Corresponds to
* a 76-character line length (the maximum allowable according to
* RFC 2045).
*/
private static final int LINE_GROUPS = 19;
/**
* Lookup table for turning Base64 alphabet positions (6 bits)
* into output bytes.
*/
private static final byte ENCODE[] = {
'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', '+', '/',
};
/**
* Lookup table for turning Base64 alphabet positions (6 bits)
* into output bytes.
*/
private static final byte ENCODE_WEBSAFE[] = {
'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', '-', '_',
};
/**
* Base64-encode the given data and return a newly allocated
* String with the result.
*
* @param input the data to encode
* @param flags controls certain features of the encoded output.
* Passing 0 results in output that adheres to RFC
* 2045.
*/
public static String encodeString(byte[] input, int flags) {
return new String(encode(input, flags));
}
/**
* Base64-encode the given data and return a newly allocated
* String with the result.
*
* @param input the data to encode
* @param offset the position within the input array at which to
* start
* @param len the number of bytes of input to encode
* @param flags controls certain features of the encoded output.
* Passing 0 results in output that adheres to RFC
* 2045.
*/
public static String encodeString(byte[] input, int offset, int len, int flags) {
return new String(encode(input, offset, len, flags));
}
/**
* Base64-encode the given data and return a newly allocated
* byte[] with the result.
*
* @param input the data to encode
* @param flags controls certain features of the encoded output.
* Passing 0 results in output that adheres to RFC
* 2045.
*/
public static byte[] encode(byte[] input, int flags) {
return encode(input, 0, input.length, flags);
}
/**
* Base64-encode the given data and return a newly allocated
* byte[] with the result.
*
* @param input the data to encode
* @param offset the position within the input array at which to
* start
* @param len the number of bytes of input to encode
* @param flags controls certain features of the encoded output.
* Passing 0 results in output that adheres to RFC
* 2045.
*/
public static byte[] encode(byte[] input, int offset, int len, int flags) {
final boolean do_padding = (flags & NO_PADDING) == 0;
final boolean do_newline = (flags & NO_WRAP) == 0;
final boolean do_cr = (flags & CRLF) != 0;
final byte[] encode = ((flags & WEB_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE;
// Compute the exact length of the array we will produce.
int output_len = len / 3 * 4;
// Account for the tail of the data and the padding bytes, if any.
if (do_padding) {
if (len % 3 > 0) {
output_len += 4;
}
} else {
switch (len % 3) {
case 0: break;
case 1: output_len += 2; break;
case 2: output_len += 3; break;
}
}
// Account for the newlines, if any.
if (do_newline && len > 0) {
output_len += (((len-1) / (3 * LINE_GROUPS)) + 1) * (do_cr ? 2 : 1);
}
int op = 0;
byte[] output = new byte[output_len];
// The main loop, turning 3 input bytes into 4 output bytes on
// each iteration.
int count = do_newline ? LINE_GROUPS : -1;
int p = offset;
len += offset;
while (p+3 <= len) {
int v = ((input[p++] & 0xff) << 16) |
((input[p++] & 0xff) << 8) |
(input[p++] & 0xff);
output[op++] = encode[(v >> 18) & 0x3f];
output[op++] = encode[(v >> 12) & 0x3f];
output[op++] = encode[(v >> 6) & 0x3f];
output[op++] = encode[v & 0x3f];
if (--count == 0) {
if (do_cr) output[op++] = '\r';
output[op++] = '\n';
count = LINE_GROUPS;
}
}
// Finish up the tail of the input.
if (p == len-1) {
int v = (input[p] & 0xff) << 4;
output[op++] = encode[(v >> 6) & 0x3f];
output[op++] = encode[v & 0x3f];
if (do_padding) {
output[op++] = '=';
output[op++] = '=';
}
if (do_newline) {
if (do_cr) output[op++] = '\r';
output[op++] = '\n';
}
} else if (p == len-2) {
int v = ((input[p] & 0xff) << 10) | ((input[p+1] & 0xff) << 2);
output[op++] = encode[(v >> 12) & 0x3f];
output[op++] = encode[(v >> 6) & 0x3f];
output[op++] = encode[v & 0x3f];
if (do_padding) {
output[op++] = '=';
}
if (do_newline) {
if (do_cr) output[op++] = '\r';
output[op++] = '\n';
}
} else if (do_newline && op > 0 && count != LINE_GROUPS) {
if (do_cr) output[op++] = '\r';
output[op++] = '\n';
}
assert op == output.length;
return output;
}
}
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