michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: package org.mozilla.gecko.background.bagheera;
michael@0: 
michael@0: import java.io.UnsupportedEncodingException;
michael@0: import java.util.zip.Deflater;
michael@0: 
michael@0: import ch.boye.httpclientandroidlib.HttpEntity;
michael@0: 
michael@0: public class DeflateHelper {
michael@0:   /**
michael@0:    * Conservative upper bound for zlib size, equivalent to the first few lines
michael@0:    * in zlib's deflateBound function.
michael@0:    *
michael@0:    * Includes zlib header.
michael@0:    *
michael@0:    * @param sourceLen
michael@0:    *          the number of bytes to compress.
michael@0:    * @return the number of bytes to allocate for the compressed output.
michael@0:    */
michael@0:   public static int deflateBound(final int sourceLen) {
michael@0:     return sourceLen + ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5 + 6;
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Deflate the input into the output array, returning the number of bytes
michael@0:    * written to output.
michael@0:    */
michael@0:   public static int deflate(byte[] input, byte[] output) {
michael@0:     final Deflater deflater = new Deflater();
michael@0:     deflater.setInput(input);
michael@0:     deflater.finish();
michael@0: 
michael@0:     final int length = deflater.deflate(output);
michael@0:     deflater.end();
michael@0:     return length;
michael@0:   }
michael@0: 
michael@0:   /**
michael@0:    * Deflate the input, returning an HttpEntity that offers an accurate window
michael@0:    * on the output.
michael@0:    *
michael@0:    * Note that this method does not trim the output array. (Test code can use
michael@0:    * TestDeflation#deflateTrimmed(byte[]).)
michael@0:    *
michael@0:    * Trimming would be more efficient for long-term space use, but we expect this
michael@0:    * entity to be transient.
michael@0:    *
michael@0:    * Note also that deflate can require <b>more</b> space than the input.
michael@0:    * {@link #deflateBound(int)} tells us the most it will use.
michael@0:    *
michael@0:    * @param bytes the input to deflate.
michael@0:    * @return the deflated input as an entity.
michael@0:    */
michael@0:   public static HttpEntity deflateBytes(final byte[] bytes) {
michael@0:     // We would like to use DeflaterInputStream here, but it's minSDK=9, and we
michael@0:     // still target 8. It would also force us to use chunked Transfer-Encoding,
michael@0:     // so perhaps it's for the best!
michael@0: 
michael@0:     final byte[] out = new byte[deflateBound(bytes.length)];
michael@0:     final int outLength = deflate(bytes, out);
michael@0:     return new BoundedByteArrayEntity(out, 0, outLength);
michael@0:   }
michael@0: 
michael@0:   public static HttpEntity deflateBody(final String payload) {
michael@0:     final byte[] bytes;
michael@0:     try {
michael@0:       bytes = payload.getBytes("UTF-8");
michael@0:     } catch (UnsupportedEncodingException ex) {
michael@0:       // This will never happen. Thanks, Java!
michael@0:       throw new RuntimeException(ex);
michael@0:     }
michael@0:     return deflateBytes(bytes);
michael@0:   }
michael@0: }