The Tor Browser: mobile/android/base/background/bagheera/DeflateHelper.java@fc2d59ddac77

     1 /* This Source Code Form is subject to the terms of the Mozilla Public

     2  * License, v. 2.0. If a copy of the MPL was not distributed with this

     3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

     5 package org.mozilla.gecko.background.bagheera;

     7 import java.io.UnsupportedEncodingException;

     8 import java.util.zip.Deflater;

    10 import ch.boye.httpclientandroidlib.HttpEntity;

    12 public class DeflateHelper {

    13   /**

    14    * Conservative upper bound for zlib size, equivalent to the first few lines

    15    * in zlib's deflateBound function.

    16    *

    17    * Includes zlib header.

    18    *

    19    * @param sourceLen

    20    *          the number of bytes to compress.

    21    * @return the number of bytes to allocate for the compressed output.

    22    */

    23   public static int deflateBound(final int sourceLen) {

    24     return sourceLen + ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5 + 6;

    25   }

    27   /**

    28    * Deflate the input into the output array, returning the number of bytes

    29    * written to output.

    30    */

    31   public static int deflate(byte[] input, byte[] output) {

    32     final Deflater deflater = new Deflater();

    33     deflater.setInput(input);

    34     deflater.finish();

    36     final int length = deflater.deflate(output);

    37     deflater.end();

    38     return length;

    39   }

    41   /**

    42    * Deflate the input, returning an HttpEntity that offers an accurate window

    43    * on the output.

    44    *

    45    * Note that this method does not trim the output array. (Test code can use

    46    * TestDeflation#deflateTrimmed(byte[]).)

    47    *

    48    * Trimming would be more efficient for long-term space use, but we expect this

    49    * entity to be transient.

    50    *

    51    * Note also that deflate can require <b>more</b> space than the input.

    52    * {@link #deflateBound(int)} tells us the most it will use.

    53    *

    54    * @param bytes the input to deflate.

    55    * @return the deflated input as an entity.

    56    */

    57   public static HttpEntity deflateBytes(final byte[] bytes) {

    58     // We would like to use DeflaterInputStream here, but it's minSDK=9, and we

    59     // still target 8. It would also force us to use chunked Transfer-Encoding,

    60     // so perhaps it's for the best!

    62     final byte[] out = new byte[deflateBound(bytes.length)];

    63     final int outLength = deflate(bytes, out);

    64     return new BoundedByteArrayEntity(out, 0, outLength);

    65   }

    67   public static HttpEntity deflateBody(final String payload) {

    68     final byte[] bytes;

    69     try {

    70       bytes = payload.getBytes("UTF-8");

    71     } catch (UnsupportedEncodingException ex) {

    72       // This will never happen. Thanks, Java!

    73       throw new RuntimeException(ex);

    74     }

    75     return deflateBytes(bytes);

    76   }

    77 }

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