Add net::GzipSourceStream

net/filter/gzip_source_stream.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 NET_FILTER_GZIP_SOURCE_STREAM_H_
+#define NET_FILTER_GZIP_SOURCE_STREAM_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "net/base/io_buffer.h"
+#include "net/base/net_export.h"
+#include "net/filter/filter_source_stream.h"
+#include "net/filter/gzip_header.h"
+
+typedef struct z_stream_s z_stream;
+
+namespace net {
+
+class IOBuffer;
+
+// GZipSourceStream applies gzip and deflate content encoding/decoding to a data
+// stream. As specified by HTTP 1.1, with gzip encoding the content is
+// wrapped with a gzip header, and with deflate encoding the content is in
+// a raw, headerless DEFLATE stream.
+//
+// Internally GZipSourceStream uses zlib inflate to do decoding.
+//
+class NET_EXPORT_PRIVATE GzipSourceStream : public FilterSourceStream {
+ public:
+  ~GzipSourceStream() override;
+
+  // Creates a GzipSourceStream. Return nullptr if initialization fails.
+  static std::unique_ptr<GzipSourceStream> Create(
+      std::unique_ptr<SourceStream> previous,
+      SourceStream::SourceType type);
+
+ private:
+  enum InputState {
+    // Starts processing the input stream. Checks whether the stream is valid
+    // and whether a fallback to plain data is needed.
+    STATE_START,
+    // Gzip header of the input stream is being processed.
+    STATE_GZIP_HEADER,
+    // The input stream is being decoded.
+    STATE_COMPRESSED_BODY,
+    // The input stream is being passed through undecoded.
+    STATE_UNCOMPRESSED_BODY,
+  };
+
+  GzipSourceStream(std::unique_ptr<SourceStream> previous,
+                   SourceStream::SourceType type);
+
+  // Returns true if initialization is successful, false otherwise.
+  // For instance, this method returns false if there is not enough memory or
+  // if there is a version mismatch.
+  bool Init();
+
+  // SourceStream implementation
+  std::string GetTypeAsString() const override;
+  int FilterData(IOBuffer* output_buffer,
+                 int output_buffer_size,
+                 IOBuffer* input_buffer,
+                 int input_buffer_size,
+                 int* consumed_bytes,
+                 bool upstream_end_reached) override;
+
+  // Synchronous decompressor. This function consumes bytes from |input_buffer|
+  // and decompresses them into |output_buffer| until it consumes all of
+  // |input_buffer|. This decompressor will decompress a zlib stream (either

[Randy Smith (Not in Mondays), 2016/09/21 20:57:06]

Presumably it will also stop when it's filled |*output_buffer|?

[xunjieli, 2016/09/22 17:20:49]

Done. Added to the doc.

+  // gzip or deflate) until the zlib reaches EOF, then will pass any further
+  // input through untouched.
+  int Decompress(IOBuffer* output_buffer,
+                 int output_buffer_size,
+                 char* input_buffer,
+                 int input_buffer_size,
+                 int* consumed_bytes);
+
+  // Passes through as many bytes as possible from from |input_buffer| to
+  // |output_buffer|. It might additionally drains footer bytes from the
+  // |input_buffer| without writing the footer bytes to |output_buffer|. The

[Randy Smith (Not in Mondays), 2016/09/21 20:57:06]

I don't find this documentation complete; can this happen anywhere in the
stream, or only at the beginning?  (

[xunjieli, 2016/09/22 17:20:49]

Done. I have inlined this method. After applying your suggestion on the footer,
this method is only two lines.

+  // total number of consumed bytes from |input_buffer| will be written to
+  // |consumed_bytes|.
+  size_t Passthrough(char* output_buffer,
+                     int output_buffer_size,
+                     char* input_buffer,
+                     int input_buffer_size,
+                     int* consumed_bytes);
+
+  // Inserts a zlib header to the data stream before calling zlib inflate.
+  // This is used to work around server bugs.
+  // The function returns true on success and false otherwise.

[Randy Smith (Not in Mondays), 2016/09/21 20:57:06]

nit, suggestion: I don't think the comments needs to say both true on success
and false otherwise; if you specify that it returns true on success (or false on
failure) the other is implicit.  Also, it's more useful if the comment describes
what can lead to failure (like the Init() comment now does).

[xunjieli, 2016/09/22 17:20:49]

Done.

+  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 can be called multiple times with
+  // multiple |input_buffer|. The number of consumed bytes will be written to
+  // |consumed_bytes|.
+  bool IsGzipHeaderInvalid(char* input_buffer,
+                           int input_buffer_size,
+                           int* consumed_bytes);

[Randy Smith (Not in Mondays), 2016/09/21 20:57:06]

I don't see this function in the source file anymore?

[xunjieli, 2016/09/22 17:20:49]

Done.

+
+  // 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 first byte of the stream.
+  bool ShouldFallbackToPlain(char first_byte);
+
+  // Returns number of footer bytes to skip.
+  size_t NumGzipFooterBytesToSkip(int input_buffer_size);
+
+  // The control block of zlib which actually does the decoding.
+  // This data structure is initialized by Init and updated only by
+  // Decompress, with InsertZlibHeader being the exception as a workaround.
+  std::unique_ptr<z_stream> zlib_stream_;
+
+  // A flag used by Decompress to record whether we've successfully added
+  // a zlib header to this stream.
+  bool zlib_header_added_;
+
+  // Used to parse the gzip header in gzip stream.
+  // It is used when the decoding mode is GZIP_SOURCE_STREAM_GZIP.
+  GZipHeader gzip_header_;
+
+  // Tracks how many bytes of gzip footer are yet to be filtered.
+  size_t gzip_footer_bytes_left_;
+
+  // Tracks the state of the input stream.
+  InputState input_state_;
+
+  DISALLOW_COPY_AND_ASSIGN(GzipSourceStream);
+};
+
+}  // namespace net
+
+#endif  // NET_FILTER_GZIP_SOURCE_STREAM_H__