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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.
#ifndef QUICHE_SPDY_CORE_HPACK_HPACK_HEADER_TABLE_H_
#define QUICHE_SPDY_CORE_HPACK_HPACK_HEADER_TABLE_H_
#include <cstddef>
#include <memory>
#include <vector>
#include "absl/container/flat_hash_map.h"
#include "absl/strings/string_view.h"
#include "quiche/common/platform/api/quiche_export.h"
#include "quiche/common/quiche_circular_deque.h"
#include "quiche/spdy/core/hpack/hpack_entry.h"
// All section references below are to http://tools.ietf.org/html/rfc7541.
namespace spdy {
namespace test {
class HpackHeaderTablePeer;
} // namespace test
// Return value of GetByName() and GetByNameAndValue() if matching entry is not
// found. This value is never used in HPACK for indexing entries, see
// https://httpwg.org/specs/rfc7541.html#index.address.space.
inline constexpr size_t kHpackEntryNotFound = 0;
// A data structure for the static table (2.3.1) and the dynamic table (2.3.2).
class QUICHE_EXPORT HpackHeaderTable {
public:
friend class test::HpackHeaderTablePeer;
// Use a lightweight, memory efficient container for the static table, which
// is initialized once and never changed after.
using StaticEntryTable = std::vector<HpackEntry>;
// HpackHeaderTable takes advantage of the deque property that references
// remain valid, so long as insertions & deletions are at the head & tail.
using DynamicEntryTable =
quiche::QuicheCircularDeque<std::unique_ptr<HpackEntry>>;
using NameValueToEntryMap = absl::flat_hash_map<HpackLookupEntry, size_t>;
using NameToEntryMap = absl::flat_hash_map<absl::string_view, size_t>;
HpackHeaderTable();
HpackHeaderTable(const HpackHeaderTable&) = delete;
HpackHeaderTable& operator=(const HpackHeaderTable&) = delete;
~HpackHeaderTable();
// Last-acknowledged value of SETTINGS_HEADER_TABLE_SIZE.
size_t settings_size_bound() const { return settings_size_bound_; }
// Current and maximum estimated byte size of the table, as described in
// 4.1. Notably, this is /not/ the number of entries in the table.
size_t size() const { return size_; }
size_t max_size() const { return max_size_; }
// The HPACK indexing scheme used by GetByName() and GetByNameAndValue() is
// defined at https://httpwg.org/specs/rfc7541.html#index.address.space.
// Returns the index of the lowest-index entry matching |name|,
// or kHpackEntryNotFound if no matching entry is found.
size_t GetByName(absl::string_view name);
// Returns the index of the lowest-index entry matching |name| and |value|,
// or kHpackEntryNotFound if no matching entry is found.
size_t GetByNameAndValue(absl::string_view name, absl::string_view value);
// Sets the maximum size of the header table, evicting entries if
// necessary as described in 5.2.
void SetMaxSize(size_t max_size);
// Sets the SETTINGS_HEADER_TABLE_SIZE bound of the table. Will call
// SetMaxSize() as needed to preserve max_size() <= settings_size_bound().
void SetSettingsHeaderTableSize(size_t settings_size);
// Determine the set of entries which would be evicted by the insertion
// of |name| & |value| into the table, as per section 4.4. No eviction
// actually occurs. The set is returned via range [begin_out, end_out).
void EvictionSet(absl::string_view name, absl::string_view value,
DynamicEntryTable::iterator* begin_out,
DynamicEntryTable::iterator* end_out);
// Adds an entry for the representation, evicting entries as needed. |name|
// and |value| must not point to an entry in |dynamic_entries_| which is about
// to be evicted, but they may point to an entry which is not.
// The added HpackEntry is returned, or NULL is returned if all entries were
// evicted and the empty table is of insufficent size for the representation.
const HpackEntry* TryAddEntry(absl::string_view name,
absl::string_view value);
private:
// Returns number of evictions required to enter |name| & |value|.
size_t EvictionCountForEntry(absl::string_view name,
absl::string_view value) const;
// Returns number of evictions required to reclaim |reclaim_size| table size.
size_t EvictionCountToReclaim(size_t reclaim_size) const;
// Evicts |count| oldest entries from the table.
void Evict(size_t count);
// |static_entries_|, |static_index_|, and |static_name_index_| are owned by
// HpackStaticTable singleton.
// Stores HpackEntries.
const StaticEntryTable& static_entries_;
DynamicEntryTable dynamic_entries_;
// Tracks the index of the unique HpackEntry for a given header name and
// value. Keys consist of string_views that point to strings stored in
// |static_entries_|.
const NameValueToEntryMap& static_index_;
// Tracks the index of the first static entry for each name in the static
// table. Each key is a string_view that points to a name string stored in
// |static_entries_|.
const NameToEntryMap& static_name_index_;
// Tracks the index of the most recently inserted HpackEntry for a given
// header name and value. Keys consist of string_views that point to strings
// stored in |dynamic_entries_|.
NameValueToEntryMap dynamic_index_;
// Tracks the index of the most recently inserted HpackEntry for a given
// header name. Each key is a string_view that points to a name string stored
// in |dynamic_entries_|.
NameToEntryMap dynamic_name_index_;
// Last acknowledged value for SETTINGS_HEADER_TABLE_SIZE.
size_t settings_size_bound_;
// Estimated current and maximum byte size of the table.
// |max_size_| <= |settings_size_bound_|
size_t size_;
size_t max_size_;
// Total number of dynamic table insertions so far
// (including entries that have been evicted).
size_t dynamic_table_insertions_;
};
} // namespace spdy
#endif // QUICHE_SPDY_CORE_HPACK_HPACK_HEADER_TABLE_H_