[ON HOLD] Implement pull-based design for content decoding

net/filter/gzip_stream_source.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.
+
+#include "base/memory/scoped_ptr.h"
+#include "net/filter/gzip_header.h"
+#include "net/filter/stream_source.h"
+
+typedef struct z_stream_s z_stream;

[mmenke, 2016/03/04 21:15:56]

I don't think we want this in the global namespace.  Maybe just use zstream_s? 
Or could move it into the private section of GzipStreamSource.

Also, I think the C++0x11 way of doing this is "using z_stream = z_stream_s;"

[xunjieli, 2016/04/20 19:16:09]

I tried this suggestion, but the code failed to compile. Can we tackle this in a
separate CL? This line is copied over from gzip_filter.h

+
+namespace net {
+
+class BlockBuffer;
+
+class GzipStreamSource : public StreamSource {
+ public:
+  enum GzipStreamSourceMode {
+    GZIP_STREAM_SOURCE_DEFLATE,
+    GZIP_STREAM_SOURCE_GZIP,
+  };
+
+  GzipStreamSource(scoped_ptr<StreamSource> previous);

[mmenke, 2016/03/04 21:15:56]

explicit

[xunjieli, 2016/04/20 19:16:09]

Done.

+  ~GzipStreamSource() override;
+
+  bool Init(GzipStreamSourceMode mode, bool gzip_fallback);

[mmenke, 2016/03/04 21:15:56]

These arguments need to be documented.

[xunjieli, 2016/04/20 19:16:09]

Done.

+
+ private:
+  enum GzipStreamState {
+    GZIP_STREAM_ERROR,
+    GZIP_STREAM_MORE_INPUT,
+    GZIP_STREAM_MORE_OUTPUT_SPACE,
+  };
+
+  // StreamSource implementation
+  Error ReadInternal(IOBuffer* dest_buffer,
+                     size_t buffer_size,
+                     size_t* bytes_read) override;
+
+  GzipStreamState Decompress(IOBuffer* dest_buffer,
+                             size_t buffer_size,
+                             size_t* bytes_read);
+
+  GzipStreamState Passthrough(IOBuffer* dest_buffer,
+                              size_t buffer_size,
+                              size_t* bytes_read);
+
+  void OnReadComplete(const OnReadCompleteCallback& callback,
+                      IOBuffer* dest_buffer,
+                      size_t dest_buffer_size,
+                      Error error,
+                      size_t bytes_read);
+
+  bool InsertZlibHeader();
+
+  // Returns whether an invalid GZip header has been observed. This method
+  // returns true as soon as an invalid GZip header is observed; it returns
+  // false if a complete, valid header has been observed, or not enough bytes
+  // have been seen to be sure. This method pulls its input from |buffer_|.
+  bool IsGzipHeaderInvalid();
+
+  // Returns whether this stream looks like it could be plain text (ie, not
+  // actually gzipped). Right now this uses an extremely simple heuristic; see
+  // the source for details. This method checks the input in |buffer_|, but does
+  // not drain from it.
+  bool ShouldFallbackToPlain();
+
+  // Skips gzip footer bytes if necessary. Might drain input from |buffer_| if
+  // there are still footer bytes to read.
+  void SkipGzipFooterIfNeeded();
+
+  scoped_refptr<IOBuffer> pending_read_buffer_;
+
+  scoped_ptr<z_stream> zlib_stream_;
+  bool zlib_eof_;
+  bool zlib_header_added_;
+
+  GZipHeader gzip_header_;
+  bool gzip_header_unchecked_;
+  bool gzip_fallback_unchecked_;

[mmenke, 2016/03/04 21:15:56]

These need to be documented.  Also, "unchecked" is not a great name for a bool -
double negatives are confusing.

[xunjieli, 2016/04/20 19:16:09]

Done.

+  size_t gzip_footer_bytes_left_;
+};
+
+}  // namespace net