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// Copyright (c) 2019 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 "quic/core/qpack/qpack_blocking_manager.h"
#include <limits>
#include <utility>
namespace quic {
QpackBlockingManager::QpackBlockingManager() : known_received_count_(0) {}
bool QpackBlockingManager::OnHeaderAcknowledgement(QuicStreamId stream_id) {
auto it = header_blocks_.find(stream_id);
if (it == header_blocks_.end()) {
return false;
}
QUICHE_DCHECK(!it->second.empty());
const IndexSet& indices = it->second.front();
QUICHE_DCHECK(!indices.empty());
const uint64_t required_index_count = RequiredInsertCount(indices);
if (known_received_count_ < required_index_count) {
known_received_count_ = required_index_count;
}
DecreaseReferenceCounts(indices);
it->second.pop_front();
if (it->second.empty()) {
header_blocks_.erase(it);
}
return true;
}
void QpackBlockingManager::OnStreamCancellation(QuicStreamId stream_id) {
auto it = header_blocks_.find(stream_id);
if (it == header_blocks_.end()) {
return;
}
for (const IndexSet& indices : it->second) {
DecreaseReferenceCounts(indices);
}
header_blocks_.erase(it);
}
bool QpackBlockingManager::OnInsertCountIncrement(uint64_t increment) {
if (increment >
std::numeric_limits<uint64_t>::max() - known_received_count_) {
return false;
}
known_received_count_ += increment;
return true;
}
void QpackBlockingManager::OnHeaderBlockSent(QuicStreamId stream_id,
IndexSet indices) {
QUICHE_DCHECK(!indices.empty());
IncreaseReferenceCounts(indices);
header_blocks_[stream_id].push_back(std::move(indices));
}
bool QpackBlockingManager::blocking_allowed_on_stream(
QuicStreamId stream_id,
uint64_t maximum_blocked_streams) const {
// This should be the most common case: the limit is larger than the number of
// streams that have unacknowledged header blocks (regardless of whether they
// are blocked or not) plus one for stream |stream_id|.
if (header_blocks_.size() + 1 <= maximum_blocked_streams) {
return true;
}
// This should be another common case: no blocked stream allowed.
if (maximum_blocked_streams == 0) {
return false;
}
uint64_t blocked_stream_count = 0;
for (const auto& header_blocks_for_stream : header_blocks_) {
for (const IndexSet& indices : header_blocks_for_stream.second) {
if (RequiredInsertCount(indices) > known_received_count_) {
if (header_blocks_for_stream.first == stream_id) {
// Sending blocking references is allowed if stream |stream_id| is
// already blocked.
return true;
}
++blocked_stream_count;
// If stream |stream_id| is already blocked, then it is not counted yet,
// therefore the number of blocked streams is at least
// |blocked_stream_count + 1|, which cannot be more than
// |maximum_blocked_streams| by API contract.
// If stream |stream_id| is not blocked, then blocking will increase the
// blocked stream count to at least |blocked_stream_count + 1|. If that
// is larger than |maximum_blocked_streams|, then blocking is not
// allowed on stream |stream_id|.
if (blocked_stream_count + 1 > maximum_blocked_streams) {
return false;
}
break;
}
}
}
// Stream |stream_id| is not blocked.
// If there are no blocked streams, then
// |blocked_stream_count + 1 <= maximum_blocked_streams| because
// |maximum_blocked_streams| is larger than zero.
// If there are are blocked streams, then
// |blocked_stream_count + 1 <= maximum_blocked_streams| otherwise the method
// would have returned false when |blocked_stream_count| was incremented.
// Therefore blocking on |stream_id| is allowed.
return true;
}
uint64_t QpackBlockingManager::smallest_blocking_index() const {
return entry_reference_counts_.empty()
? std::numeric_limits<uint64_t>::max()
: entry_reference_counts_.begin()->first;
}
// static
uint64_t QpackBlockingManager::RequiredInsertCount(const IndexSet& indices) {
return *indices.rbegin() + 1;
}
void QpackBlockingManager::IncreaseReferenceCounts(const IndexSet& indices) {
for (const uint64_t index : indices) {
auto it = entry_reference_counts_.lower_bound(index);
if (it != entry_reference_counts_.end() && it->first == index) {
++it->second;
} else {
entry_reference_counts_.insert(it, {index, 1});
}
}
}
void QpackBlockingManager::DecreaseReferenceCounts(const IndexSet& indices) {
for (const uint64_t index : indices) {
auto it = entry_reference_counts_.find(index);
QUICHE_DCHECK(it != entry_reference_counts_.end());
QUICHE_DCHECK_NE(0u, it->second);
if (it->second == 1) {
entry_reference_counts_.erase(it);
} else {
--it->second;
}
}
}
} // namespace quic
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