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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 "base/basictypes.h"
#include "base/logging.h"
namespace net {
using base::StringPiece;
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);
uint8 next_octet = 0;
if (!PeekNextOctet(&next_octet))
return false;
if ((next_octet >> (8 - prefix.bit_size)) == prefix.bits) {
bit_offset_ = 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;
}
// TODO(akalin): Figure out how to handle the storage for
// Huffman-encoded sequences.
bool HpackInputStream::DecodeNextStringLiteral(StringPiece* str) {
if (MatchPrefixAndConsume(kStringLiteralIdentityEncoded)) {
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;
}
// TODO(akalin): Handle Huffman-encoded sequences.
return false;
}
} // namespace net
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