text: // Copyright (c) 2012 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_SPDY_SPDY_FRAME_READER_H_
  #define NET_SPDY_SPDY_FRAME_READER_H_
  #pragma once
  
  #include "base/basictypes.h"
  #include "base/string_piece.h"
  #include "net/base/net_export.h"
  
  namespace net {
  
  // Used for reading SPDY frames. Though there isn't really anything terribly
  // SPDY-specific here, it's a helper class that's useful when doing SPDY
  // framing.
  //
  // To use, simply construct a SpdyFramerReader using the underlying buffer that
  // you'd like to read fields from, then call one of the Read*() methods to
  // actually do some reading.
  //
  // This class keeps an internal iterator to keep track of what's already been
  // read and each successive Read*() call automatically increments said iterator
  // on success. On failure, internal state of the SpdyFrameReader should not be
  // trusted and it is up to the caller to throw away the failed instance and
  // handle the error as appropriate. None of the Read*() methods should ever be
  // called after failure, as they will also fail immediately.
  class NET_EXPORT_PRIVATE SpdyFrameReader {
   public:
    // Caller must provide an underlying buffer to work on.
    SpdyFrameReader(const char* data, const size_t len);
  
    // Empty destructor.
    ~SpdyFrameReader() {}
  
    // Reads a 16-bit unsigned integer into the given output parameter.
    // Forwards the internal iterater on success.
    // Returns true on success, false otherwise.
    bool ReadUInt16(uint16* result);
  
    // Reads a 32-bit unsigned integer into the given output parameter.
    // Forwards the internal iterater on success.
    // Returns true on success, false otherwise.
    bool ReadUInt32(uint32* result);
  
    // Reads a string prefixed with 16-bit length into the given output parameter.
    //
    // NOTE: Does not copy but rather references strings in the underlying buffer.
    // This should be kept in mind when handling memory management!
    //
    // Forwards the internal iterater on success.
    // Returns true on success, false otherwise.
    bool ReadStringPiece16(base::StringPiece* result);
  
    // Reads a string prefixed with 32-bit length into the given output parameter.
    //
    // NOTE: Does not copy but rather references strings in the underlying buffer.
    // This should be kept in mind when handling memory management!
    //
    // Forwards the internal iterater on success.
    // Returns true on success, false otherwise.
    bool ReadStringPiece32(base::StringPiece* result);
  
    // Reads a given number of bytes into the given buffer. The buffer
    // must be of adequate size.
    // Forwards the internal iterater on success.
    // Returns true on success, false otherwise.
    bool ReadBytes(void* result, size_t size);
  
    // Returns true if the entirety of the underlying buffer has been read via
    // Read*() calls.
    bool IsDoneReading() const;
  
   private:
    // Returns true if the underlying buffer has enough room to read the given
    // amount of bytes.
    bool CanRead(size_t bytes) const;
  
    // To be called when a read fails for any reason.
    void OnFailure();
  
    // The data buffer that we're reading from.
    const char* data_;
  
    // The length of the data buffer that we're reading from.
    const size_t len_;
  
    // The location of the next read from our data buffer.
    size_t ofs_;
  };
  
  }  // namespace net
  
  #endif  // NET_SPDY_SPDY_FRAME_READER_H_
  