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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef NET_SPDY_SPDY_FRAME_BUILDER_H_
      6 #define NET_SPDY_SPDY_FRAME_BUILDER_H_
      7 
      8 #include <string>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/memory/scoped_ptr.h"
     12 #include "base/strings/string_piece.h"
     13 #include "base/sys_byteorder.h"
     14 #include "net/base/net_export.h"
     15 #include "net/spdy/spdy_protocol.h"
     16 
     17 namespace net {
     18 
     19 class SpdyFramer;
     20 
     21 // This class provides facilities for basic binary value packing
     22 // into Spdy frames.
     23 //
     24 // The SpdyFrameBuilder supports appending primitive values (int, string, etc)
     25 // to a frame instance.  The SpdyFrameBuilder grows its internal memory buffer
     26 // dynamically to hold the sequence of primitive values.   The internal memory
     27 // buffer is exposed as the "data" of the SpdyFrameBuilder.
     28 class NET_EXPORT_PRIVATE SpdyFrameBuilder {
     29  public:
     30   // Initializes a SpdyFrameBuilder with a buffer of given size
     31   explicit SpdyFrameBuilder(size_t size);
     32 
     33   ~SpdyFrameBuilder();
     34 
     35   // Returns the size of the SpdyFrameBuilder's data.
     36   size_t length() const { return length_; }
     37 
     38   // Returns a writeable buffer of given size in bytes, to be appended to the
     39   // currently written frame. Does bounds checking on length but does not
     40   // increment the underlying iterator. To do so, consumers should subsequently
     41   // call Seek().
     42   // In general, consumers should use Write*() calls instead of this.
     43   // Returns NULL on failure.
     44   char* GetWritableBuffer(size_t length);
     45 
     46   // Seeks forward by the given number of bytes. Useful in conjunction with
     47   // GetWriteableBuffer() above.
     48   bool Seek(size_t length);
     49 
     50   // Populates this frame with a SPDY control frame header using
     51   // version-specific information from the |framer| and length information from
     52   // capacity_. The given type must be a control frame type.
     53   // Used only for SPDY versions <4.
     54   bool WriteControlFrameHeader(const SpdyFramer& framer,
     55                                SpdyFrameType type,
     56                                uint8 flags);
     57 
     58   // Populates this frame with a SPDY data frame header using version-specific
     59   // information from the |framer| and length information from capacity_.
     60   bool WriteDataFrameHeader(const SpdyFramer& framer,
     61                             SpdyStreamId stream_id,
     62                             SpdyDataFlags flags);
     63 
     64   // Populates this frame with a SPDY4/HTTP2 frame prefix using
     65   // version-specific information from the |framer| and length information from
     66   // capacity_. The given type must be a control frame type.
     67   // Used only for SPDY versions >=4.
     68   bool WriteFramePrefix(const SpdyFramer& framer,
     69                         SpdyFrameType type,
     70                         uint8 flags,
     71                         SpdyStreamId stream_id);
     72 
     73   // Takes the buffer from the SpdyFrameBuilder.
     74   SpdyFrame* take() {
     75     SpdyFrame* rv = new SpdyFrame(buffer_.release(), length_, true);
     76     capacity_ = 0;
     77     length_ = 0;
     78     return rv;
     79   }
     80 
     81   // Methods for adding to the payload.  These values are appended to the end
     82   // of the SpdyFrameBuilder payload. Note - binary integers are converted from
     83   // host to network form.
     84   bool WriteUInt8(uint8 value) {
     85     return WriteBytes(&value, sizeof(value));
     86   }
     87   bool WriteUInt16(uint16 value) {
     88     value = htons(value);
     89     return WriteBytes(&value, sizeof(value));
     90   }
     91   bool WriteUInt32(uint32 value) {
     92     value = htonl(value);
     93     return WriteBytes(&value, sizeof(value));
     94   }
     95   // TODO(hkhalil) Rename to WriteStringPiece16().
     96   bool WriteString(const std::string& value);
     97   bool WriteStringPiece32(const base::StringPiece& value);
     98   bool WriteBytes(const void* data, uint32 data_len);
     99 
    100   // Update (in-place) the length field in the frame being built to reflect the
    101   // current actual length of bytes written to said frame through this builder.
    102   // The framer parameter is used to determine version-specific location and
    103   // size information of the length field to be written, and must be initialized
    104   // with the correct version for the frame being written.
    105   bool RewriteLength(const SpdyFramer& framer);
    106 
    107   // Update (in-place) the length field in the frame being built to reflect the
    108   // given length.
    109   // The framer parameter is used to determine version-specific location and
    110   // size information of the length field to be written, and must be initialized
    111   // with the correct version for the frame being written.
    112   bool OverwriteLength(const SpdyFramer& framer, size_t length);
    113 
    114  protected:
    115   const char* end_of_payload() const { return buffer_.get() + length_; }
    116 
    117  private:
    118   // Checks to make sure that there is an appropriate amount of space for a
    119   // write of given size, in bytes.
    120   bool CanWrite(size_t length) const;
    121 
    122   scoped_ptr<char[]> buffer_;
    123   size_t capacity_;  // Allocation size of payload, set by constructor.
    124   size_t length_;    // Current length of the buffer.
    125 };
    126 
    127 }  // namespace net
    128 
    129 #endif  // NET_SPDY_SPDY_FRAME_BUILDER_H_
    130