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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 "quiche/spdy/core/hpack/hpack_header_table.h"
#include <algorithm>
#include "quiche/common/platform/api/quiche_logging.h"
#include "quiche/spdy/core/hpack/hpack_constants.h"
#include "quiche/spdy/core/hpack/hpack_static_table.h"
namespace spdy {
HpackHeaderTable::HpackHeaderTable()
: static_entries_(ObtainHpackStaticTable().GetStaticEntries()),
static_index_(ObtainHpackStaticTable().GetStaticIndex()),
static_name_index_(ObtainHpackStaticTable().GetStaticNameIndex()),
settings_size_bound_(kDefaultHeaderTableSizeSetting),
size_(0),
max_size_(kDefaultHeaderTableSizeSetting),
dynamic_table_insertions_(0) {}
HpackHeaderTable::~HpackHeaderTable() = default;
size_t HpackHeaderTable::GetByName(absl::string_view name) {
{
auto it = static_name_index_.find(name);
if (it != static_name_index_.end()) {
return 1 + it->second;
}
}
{
NameToEntryMap::const_iterator it = dynamic_name_index_.find(name);
if (it != dynamic_name_index_.end()) {
return dynamic_table_insertions_ - it->second + kStaticTableSize;
}
}
return kHpackEntryNotFound;
}
size_t HpackHeaderTable::GetByNameAndValue(absl::string_view name,
absl::string_view value) {
HpackLookupEntry query{name, value};
{
auto it = static_index_.find(query);
if (it != static_index_.end()) {
return 1 + it->second;
}
}
{
auto it = dynamic_index_.find(query);
if (it != dynamic_index_.end()) {
return dynamic_table_insertions_ - it->second + kStaticTableSize;
}
}
return kHpackEntryNotFound;
}
void HpackHeaderTable::SetMaxSize(size_t max_size) {
QUICHE_CHECK_LE(max_size, settings_size_bound_);
max_size_ = max_size;
if (size_ > max_size_) {
Evict(EvictionCountToReclaim(size_ - max_size_));
QUICHE_CHECK_LE(size_, max_size_);
}
}
void HpackHeaderTable::SetSettingsHeaderTableSize(size_t settings_size) {
settings_size_bound_ = settings_size;
SetMaxSize(settings_size_bound_);
}
void HpackHeaderTable::EvictionSet(absl::string_view name,
absl::string_view value,
DynamicEntryTable::iterator* begin_out,
DynamicEntryTable::iterator* end_out) {
size_t eviction_count = EvictionCountForEntry(name, value);
*begin_out = dynamic_entries_.end() - eviction_count;
*end_out = dynamic_entries_.end();
}
size_t HpackHeaderTable::EvictionCountForEntry(absl::string_view name,
absl::string_view value) const {
size_t available_size = max_size_ - size_;
size_t entry_size = HpackEntry::Size(name, value);
if (entry_size <= available_size) {
// No evictions are required.
return 0;
}
return EvictionCountToReclaim(entry_size - available_size);
}
size_t HpackHeaderTable::EvictionCountToReclaim(size_t reclaim_size) const {
size_t count = 0;
for (auto it = dynamic_entries_.rbegin();
it != dynamic_entries_.rend() && reclaim_size != 0; ++it, ++count) {
reclaim_size -= std::min(reclaim_size, (*it)->Size());
}
return count;
}
void HpackHeaderTable::Evict(size_t count) {
for (size_t i = 0; i != count; ++i) {
QUICHE_CHECK(!dynamic_entries_.empty());
HpackEntry* entry = dynamic_entries_.back().get();
const size_t index = dynamic_table_insertions_ - dynamic_entries_.size();
size_ -= entry->Size();
auto it = dynamic_index_.find({entry->name(), entry->value()});
QUICHE_DCHECK(it != dynamic_index_.end());
// Only remove an entry from the index if its insertion index matches;
// otherwise, the index refers to another entry with the same name and
// value.
if (it->second == index) {
dynamic_index_.erase(it);
}
auto name_it = dynamic_name_index_.find(entry->name());
QUICHE_DCHECK(name_it != dynamic_name_index_.end());
// Only remove an entry from the literal index if its insertion index
/// matches; otherwise, the index refers to another entry with the same
// name.
if (name_it->second == index) {
dynamic_name_index_.erase(name_it);
}
dynamic_entries_.pop_back();
}
}
const HpackEntry* HpackHeaderTable::TryAddEntry(absl::string_view name,
absl::string_view value) {
// Since |dynamic_entries_| has iterator stability, |name| and |value| are
// valid even after evicting other entries and push_front() making room for
// the new one.
Evict(EvictionCountForEntry(name, value));
size_t entry_size = HpackEntry::Size(name, value);
if (entry_size > (max_size_ - size_)) {
// Entire table has been emptied, but there's still insufficient room.
QUICHE_DCHECK(dynamic_entries_.empty());
QUICHE_DCHECK_EQ(0u, size_);
return nullptr;
}
const size_t index = dynamic_table_insertions_;
dynamic_entries_.push_front(
std::make_unique<HpackEntry>(std::string(name), std::string(value)));
HpackEntry* new_entry = dynamic_entries_.front().get();
auto index_result = dynamic_index_.insert(std::make_pair(
HpackLookupEntry{new_entry->name(), new_entry->value()}, index));
if (!index_result.second) {
// An entry with the same name and value already exists in the dynamic
// index. We should replace it with the newly added entry.
QUICHE_DVLOG(1) << "Found existing entry at: " << index_result.first->second
<< " replacing with: " << new_entry->GetDebugString()
<< " at: " << index;
QUICHE_DCHECK_GT(index, index_result.first->second);
dynamic_index_.erase(index_result.first);
auto insert_result = dynamic_index_.insert(std::make_pair(
HpackLookupEntry{new_entry->name(), new_entry->value()}, index));
QUICHE_CHECK(insert_result.second);
}
auto name_result =
dynamic_name_index_.insert(std::make_pair(new_entry->name(), index));
if (!name_result.second) {
// An entry with the same name already exists in the dynamic index. We
// should replace it with the newly added entry.
QUICHE_DVLOG(1) << "Found existing entry at: " << name_result.first->second
<< " replacing with: " << new_entry->GetDebugString()
<< " at: " << index;
QUICHE_DCHECK_GT(index, name_result.first->second);
dynamic_name_index_.erase(name_result.first);
auto insert_result =
dynamic_name_index_.insert(std::make_pair(new_entry->name(), index));
QUICHE_CHECK(insert_result.second);
}
size_ += entry_size;
++dynamic_table_insertions_;
return dynamic_entries_.front().get();
}
} // namespace spdy
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