EncoderZlib/DecoderZlib for chromoting

Encoder and decoder using zlib for chromoting. This implementation has zero
copy out of the decoder and encoder. The consequence is that we have to break
out the zlib stream into rect boundaries which requires the synchronication
flush feature in zlib. This feature will hurt compression ratio but the effect
still need to be measured.

This patch also provides tests for testing the Encoder and Decoder pair with
zlib.

TEST=remoting_unittests

Review URL: http://codereview.chromium.org/2868062

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@53738 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 27 insertions, 5 deletions

diff --git a/remoting/base/compressor_zlib.cc b/remoting/base/compressor_zlib.cc
index ae5b388..6f700731 100644
--- a/remoting/base/compressor_zlib.cc
+++ b/remoting/base/compressor_zlib.cc
@@ -37,7 +37,8 @@ CompressorZlib::~CompressorZlib() {
 
 bool CompressorZlib::Process(const uint8* input_data, int input_size,
                              uint8* output_data, int output_size,
-                             int* consumed, int* written) {
+                             CompressorFlush flush, int* consumed,
+                             int* written) {
   DCHECK_GT(output_size, 0);
 
   // Setup I/O parameters.
@@ -46,7 +47,18 @@ bool CompressorZlib::Process(const uint8* input_data, int input_size,
   stream_->avail_out = output_size;
   stream_->next_out = (Bytef*)output_data;
 
-  int ret = deflate(stream_.get(), input_size ? Z_NO_FLUSH : Z_FINISH);
+  int z_flush = 0;
+  if (flush == CompressorSyncFlush) {
+    z_flush = Z_SYNC_FLUSH;
+  } else if (flush == CompressorFinish) {
+    z_flush = Z_FINISH;
+  } else if (flush == CompressorNoFlush) {
+    z_flush = Z_NO_FLUSH;
+  } else {
+    NOTREACHED() << "Unsupported flush mode";
+  }
+
+  int ret = deflate(stream_.get(), z_flush);
   if (ret == Z_STREAM_ERROR) {
     NOTREACHED() << "zlib compression failed";
   }
@@ -54,9 +66,19 @@ bool CompressorZlib::Process(const uint8* input_data, int input_size,
   *consumed = input_size - stream_->avail_in;
   *written = output_size - stream_->avail_out;
 
-  // Return true when we get Z_BUF_ERROR, this way we can feed more data
-  // to zlib.
-  return ret == Z_OK || ret == Z_BUF_ERROR;
+  // If |ret| equals Z_STREAM_END we have reached the end of stream.
+  // If |ret| equals Z_BUF_ERROR we have the end of the synchronication point.
+  // For these two cases we need to stop compressing.
+  if (ret == Z_OK) {
+    return true;
+  } else if (ret == Z_STREAM_END) {
+    return false;
+  } else if (ret == Z_BUF_ERROR) {
+    return stream_->avail_out == 0;
+  } else {
+    NOTREACHED() << "Unexpected zlib error: " << ret;
+    return false;
+  }
 }
 
 }  // namespace remoting