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// 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.
#include "net/spdy/hpack/hpack_output_stream.h"
#include "base/logging.h"
namespace net {
using base::StringPiece;
using std::string;
HpackOutputStream::HpackOutputStream() : bit_offset_(0) {}
HpackOutputStream::~HpackOutputStream() {}
void HpackOutputStream::AppendBits(uint8 bits, size_t bit_size) {
DCHECK_GT(bit_size, 0u);
DCHECK_LE(bit_size, 8u);
DCHECK_EQ(bits >> bit_size, 0);
size_t new_bit_offset = bit_offset_ + bit_size;
if (bit_offset_ == 0) {
// Buffer ends on a byte boundary.
DCHECK_LE(bit_size, 8u);
buffer_.append(1, bits << (8 - bit_size));
} else if (new_bit_offset <= 8) {
// Buffer does not end on a byte boundary but the given bits fit
// in the remainder of the last byte.
*buffer_.rbegin() |= bits << (8 - new_bit_offset);
} else {
// Buffer does not end on a byte boundary and the given bits do
// not fit in the remainder of the last byte.
*buffer_.rbegin() |= bits >> (new_bit_offset - 8);
buffer_.append(1, bits << (16 - new_bit_offset));
}
bit_offset_ = new_bit_offset % 8;
}
void HpackOutputStream::AppendPrefix(HpackPrefix prefix) {
AppendBits(prefix.bits, prefix.bit_size);
}
void HpackOutputStream::AppendBytes(StringPiece buffer) {
DCHECK_EQ(bit_offset_, 0u);
buffer_.append(buffer.data(), buffer.size());
}
void HpackOutputStream::AppendUint32(uint32 I) {
// The algorithm below is adapted from the pseudocode in 6.1.
size_t N = 8 - bit_offset_;
uint8 max_first_byte = static_cast<uint8>((1 << N) - 1);
if (I < max_first_byte) {
AppendBits(static_cast<uint8>(I), N);
} else {
AppendBits(max_first_byte, N);
I -= max_first_byte;
while ((I & ~0x7f) != 0) {
buffer_.append(1, (I & 0x7f) | 0x80);
I >>= 7;
}
AppendBits(static_cast<uint8>(I), 8);
}
}
void HpackOutputStream::TakeString(string* output) {
// This must hold, since all public functions cause the buffer to
// end on a byte boundary.
DCHECK_EQ(bit_offset_, 0u);
buffer_.swap(*output);
buffer_.clear();
bit_offset_ = 0;
}
} // namespace net
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