Blimp: add packet-level DEFLATE compression using zlib.

blimp/net/compressed_packet_reader.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BLIMP_NET_COMPRESSED_PACKET_READER_H_
+#define BLIMP_NET_COMPRESSED_PACKET_READER_H_
+
+#include "base/memory/weak_ptr.h"
+#include "blimp/net/blimp_net_export.h"
+#include "blimp/net/packet_reader.h"
+#include "net/base/completion_callback.h"
+#include "net/base/io_buffer.h"
+#include "third_party/zlib/zlib.h"
+
+namespace blimp {
+
+// Filter object which wraps a PacketReader, adding a DEFLATE decompression step
+// to received packets.
+// Details about the encoding format are available in the CompressedPacketWriter
+// header.
+class BLIMP_NET_EXPORT CompressedPacketReader : public PacketReader {
+ public:
+  // |source|: The source which from which compressed packets are read.
+  explicit CompressedPacketReader(scoped_ptr<PacketReader> source);
+
+  ~CompressedPacketReader() override;
+
+  // PacketReader implementation.
+  void ReadPacket(const scoped_refptr<net::GrowableIOBuffer>& decompressed_buf,
+                  const net::CompletionCallback& cb) override;
+
+ private:
+  // Called when source->ReadPacket() has completed.
+  // |buf|: The buffer which will receive decompressed data.
+  // |cb|: Callback which is triggered after decompression has finished.
+  // |result|: The result of the read operation.
+  void ReadCompressedPacketDone(

[Wez, 2016/03/29 00:45:40]

nit: OnCompressedPacketReceived or OnCompressedReadPacketComplete?

There's a general pattern of OnFoo() for callback/handler methods in classes, in
Chromium.

[Kevin M, 2016/03/29 20:36:24]

Done.

+      const scoped_refptr<net::GrowableIOBuffer> decompressed_buf,
+      const net::CompletionCallback& cb,
+      int result);
+
+  // Decompresses the contents of |compressed| to the buffer |decompressed|.
+  // |decompressed_size| is set to the size of the decompressed payload.
+  // On success, returns a >= 0 value indicating the size of the
+  // decompressed payload.
+  // On failure, returns a negative value indicating the error code
+  // (see net_errors.h).
+  int DecompressPacket(
+      char* compressed,
+      int compressed_size,

[Wez, 2016/03/29 00:45:40]

nit: Could you just pass the IOBuffer into which the compressed data was read,
or if that doesn't have the right length then use StringPiece to fold the data
pointer+size into a single parameter?

nit: Since this method already touches |zlib_stream_|, why not let it access
|compressed_buf_| too, rather than pass the buffer in as ptr+size?

[Kevin M, 2016/03/29 20:36:23]

Done.

+      const scoped_refptr<net::GrowableIOBuffer>& decompressed);
+
+  scoped_ptr<PacketReader> source_;
+  scoped_refptr<net::GrowableIOBuffer> compressed_buf_;
+  z_stream zlib_stream_;

[Wez, 2016/03/29 00:45:40]

nit: I'm not familiar with all the C++11 rules, but could this in-line
initialize to zeros w/out memset() by using ... = {0}?

[Kevin M, 2016/03/29 20:36:24]

{} seems to do the trick.

+  base::WeakPtrFactory<CompressedPacketReader> weak_factory_;

[Wez, 2016/03/29 00:45:40]

nit: Suggest a comment preceding |weak_factory_|, e.g. "Used to abandon pending
ReadPacket() calls on teardown.)

[Kevin M, 2016/03/29 20:36:23]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(CompressedPacketReader);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_COMPRESSED_PACKET_READER_H_