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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_input_stream.h"
#include <algorithm>
#include "base/basictypes.h"
#include "base/logging.h"
namespace net {
using base::StringPiece;
using std::string;
HpackInputStream::HpackInputStream(uint32 max_string_literal_size,
StringPiece buffer)
: max_string_literal_size_(max_string_literal_size),
buffer_(buffer),
bit_offset_(0) {}
HpackInputStream::~HpackInputStream() {}
bool HpackInputStream::HasMoreData() const {
return !buffer_.empty();
}
bool HpackInputStream::MatchPrefixAndConsume(HpackPrefix prefix) {
DCHECK_GT(prefix.bit_size, 0u);
DCHECK_LE(prefix.bit_size, 8u);
uint32 peeked = 0;
size_t peeked_count = 0;
if (!PeekBits(&peeked_count, &peeked))
return false;
if ((peeked >> (32 - prefix.bit_size)) == prefix.bits) {
ConsumeBits(prefix.bit_size);
return true;
}
return false;
}
bool HpackInputStream::PeekNextOctet(uint8* next_octet) {
if ((bit_offset_ > 0) || buffer_.empty())
return false;
*next_octet = buffer_[0];
return true;
}
bool HpackInputStream::DecodeNextOctet(uint8* next_octet) {
if (!PeekNextOctet(next_octet))
return false;
buffer_.remove_prefix(1);
return true;
}
bool HpackInputStream::DecodeNextUint32(uint32* I) {
size_t N = 8 - bit_offset_;
DCHECK_GT(N, 0u);
DCHECK_LE(N, 8u);
bit_offset_ = 0;
*I = 0;
uint8 next_marker = (1 << N) - 1;
uint8 next_octet = 0;
if (!DecodeNextOctet(&next_octet))
return false;
*I = next_octet & next_marker;
bool has_more = (*I == next_marker);
size_t shift = 0;
while (has_more && (shift < 32)) {
uint8 next_octet = 0;
if (!DecodeNextOctet(&next_octet))
return false;
has_more = (next_octet & 0x80) != 0;
next_octet &= 0x7f;
uint32 addend = next_octet << shift;
// Check for overflow.
if ((addend >> shift) != next_octet) {
return false;
}
*I += addend;
shift += 7;
}
return !has_more;
}
bool HpackInputStream::DecodeNextIdentityString(StringPiece* str) {
uint32 size = 0;
if (!DecodeNextUint32(&size))
return false;
if (size > max_string_literal_size_)
return false;
if (size > buffer_.size())
return false;
*str = StringPiece(buffer_.data(), size);
buffer_.remove_prefix(size);
return true;
}
bool HpackInputStream::DecodeNextHuffmanString(const HpackHuffmanTable& table,
string* str) {
uint32 encoded_size = 0;
if (!DecodeNextUint32(&encoded_size))
return false;
if (encoded_size > buffer_.size())
return false;
HpackInputStream bounded_reader(
max_string_literal_size_,
StringPiece(buffer_.data(), encoded_size));
buffer_.remove_prefix(encoded_size);
// HpackHuffmanTable will not decode beyond |max_string_literal_size_|.
return table.DecodeString(&bounded_reader, max_string_literal_size_, str);
}
bool HpackInputStream::PeekBits(size_t* peeked_count, uint32* out) {
size_t byte_offset = (bit_offset_ + *peeked_count) / 8;
size_t bit_offset = (bit_offset_ + *peeked_count) % 8;
if (*peeked_count >= 32 || byte_offset >= buffer_.size()) {
return false;
}
// We'll read the minimum of the current byte remainder,
// and the remaining unfilled bits of |out|.
size_t bits_to_read = std::min(32 - *peeked_count, 8 - bit_offset);
uint32 new_bits = static_cast<uint32>(buffer_[byte_offset]);
// Shift byte remainder to most-signifcant bits of |new_bits|.
// This drops the leading |bit_offset| bits of the byte.
new_bits = new_bits << (24 + bit_offset);
// Shift bits to the most-significant open bits of |out|.
new_bits = new_bits >> *peeked_count;
CHECK_EQ(*out & new_bits, 0u);
*out |= new_bits;
*peeked_count += bits_to_read;
return true;
}
void HpackInputStream::ConsumeBits(size_t bit_count) {
size_t byte_count = (bit_offset_ + bit_count) / 8;
bit_offset_ = (bit_offset_ + bit_count) % 8;
CHECK_GE(buffer_.size(), byte_count);
if (bit_offset_ != 0) {
CHECK_GT(buffer_.size(), 0u);
}
buffer_.remove_prefix(byte_count);
}
void HpackInputStream::ConsumeByteRemainder() {
if (bit_offset_ != 0) {
ConsumeBits(8 - bit_offset_);
}
}
} // namespace net
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