text: // Copyright 2014 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 QUICHE_SPDY_CORE_HPACK_HPACK_OUTPUT_STREAM_H_
  #define QUICHE_SPDY_CORE_HPACK_HPACK_OUTPUT_STREAM_H_
  
  #include <cstdint>
  #include <map>
  #include <string>
  
  #include "absl/strings/string_view.h"
  #include "quiche/common/platform/api/quiche_export.h"
  #include "quiche/spdy/core/hpack/hpack_constants.h"
  
  // All section references below are to
  // http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-08
  
  namespace spdy {
  
  // An HpackOutputStream handles all the low-level details of encoding
  // header fields.
  class QUICHE_EXPORT_PRIVATE HpackOutputStream {
   public:
    HpackOutputStream();
    HpackOutputStream(const HpackOutputStream&) = delete;
    HpackOutputStream& operator=(const HpackOutputStream&) = delete;
    ~HpackOutputStream();
  
    // Appends the lower |bit_size| bits of |bits| to the internal buffer.
    //
    // |bit_size| must be > 0 and <= 8. |bits| must not have any bits
    // set other than the lower |bit_size| bits.
    void AppendBits(uint8_t bits, size_t bit_size);
  
    // Simply forwards to AppendBits(prefix.bits, prefix.bit-size).
    void AppendPrefix(HpackPrefix prefix);
  
    // Directly appends |buffer|.
    void AppendBytes(absl::string_view buffer);
  
    // Appends the given integer using the representation described in
    // 6.1. If the internal buffer ends on a byte boundary, the prefix
    // length N is taken to be 8; otherwise, it is taken to be the
    // number of bits to the next byte boundary.
    //
    // It is guaranteed that the internal buffer will end on a byte
    // boundary after this function is called.
    void AppendUint32(uint32_t I);
  
    // Return pointer to internal buffer.  |bit_offset_| needs to be zero.
    std::string* MutableString();
  
    // Returns the internal buffer as a string, then resets state.
    std::string TakeString();
  
    // Returns up to |max_size| bytes of the internal buffer. Resets
    // internal state with the overflow.
    std::string BoundedTakeString(size_t max_size);
  
    // Size in bytes of stream's internal buffer.
    size_t size() const { return buffer_.size(); }
  
   private:
    // The internal bit buffer.
    std::string buffer_;
  
    // If 0, the buffer ends on a byte boundary. If non-zero, the buffer
    // ends on the nth most significant bit. Guaranteed to be < 8.
    size_t bit_offset_;
  };
  
  }  // namespace spdy
  
  #endif  // QUICHE_SPDY_CORE_HPACK_HPACK_OUTPUT_STREAM_H_
  