1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef NET_SPDY_HPACK_HEADER_TABLE_H_
6#define NET_SPDY_HPACK_HEADER_TABLE_H_
7
8#include <cstddef>
9#include <deque>
10#include <set>
11
12#include "base/basictypes.h"
13#include "base/macros.h"
14#include "net/base/net_export.h"
15#include "net/spdy/hpack_entry.h"
16
17// All section references below are to
18// http://tools.ietf.org/html/draft-ietf-httpbis-header-compression-07
19
20namespace net {
21
22namespace test {
23class HpackHeaderTablePeer;
24}  // namespace test
25
26// A data structure for both the header table (described in 3.1.2) and
27// the reference set (3.1.3).
28class NET_EXPORT_PRIVATE HpackHeaderTable {
29 public:
30  friend class test::HpackHeaderTablePeer;
31
32  // HpackHeaderTable takes advantage of the deque property that references
33  // remain valid, so long as insertions & deletions are at the head & tail.
34  // If this changes (eg we start to drop entries from the middle of the table),
35  // this needs to be a std::list, in which case |index_| can be trivially
36  // extended to map to list iterators.
37  typedef std::deque<HpackEntry> EntryTable;
38
39  // Implements a total ordering of HpackEntry on name(), value(), then index
40  // ascending. Note that index may change over the lifetime of an HpackEntry,
41  // but the relative index order of two entries will not. This comparator is
42  // composed with the 'lookup' HpackEntry constructor to allow for efficient
43  // lower-bounding of matching entries.
44  struct NET_EXPORT_PRIVATE EntryComparator {
45    explicit EntryComparator(HpackHeaderTable* table) : table_(table) {}
46
47    bool operator() (const HpackEntry* lhs, const HpackEntry* rhs) const;
48
49   private:
50    HpackHeaderTable* table_;
51  };
52  typedef std::set<HpackEntry*, EntryComparator> OrderedEntrySet;
53
54  HpackHeaderTable();
55
56  ~HpackHeaderTable();
57
58  // Last-aknowledged value of SETTINGS_HEADER_TABLE_SIZE.
59  size_t settings_size_bound() { return settings_size_bound_; }
60
61  // Current and maximum estimated byte size of the table, as described in
62  // 3.3.1. Notably, this is /not/ the number of entries in the table.
63  size_t size() const { return size_; }
64  size_t max_size() const { return max_size_; }
65
66  const OrderedEntrySet& reference_set() {
67    return reference_set_;
68  }
69
70  // Returns the entry matching the index, or NULL.
71  HpackEntry* GetByIndex(size_t index);
72
73  // Returns the lowest-value entry having |name|, or NULL.
74  HpackEntry* GetByName(base::StringPiece name);
75
76  // Returns the lowest-index matching entry, or NULL.
77  HpackEntry* GetByNameAndValue(base::StringPiece name,
78                                base::StringPiece value);
79
80  // Returns the index of an entry within this header table.
81  size_t IndexOf(const HpackEntry* entry) const;
82
83  // Sets the maximum size of the header table, evicting entries if
84  // necessary as described in 3.3.2.
85  void SetMaxSize(size_t max_size);
86
87  // Sets the SETTINGS_HEADER_TABLE_SIZE bound of the table. Will call
88  // SetMaxSize() as needed to preserve max_size() <= settings_size_bound().
89  void SetSettingsHeaderTableSize(size_t settings_size);
90
91  // Determine the set of entries which would be evicted by the insertion
92  // of |name| & |value| into the table, as per section 3.3.3. No eviction
93  // actually occurs. The set is returned via range [begin_out, end_out).
94  void EvictionSet(base::StringPiece name, base::StringPiece value,
95                   EntryTable::iterator* begin_out,
96                   EntryTable::iterator* end_out);
97
98  // Adds an entry for the representation, evicting entries as needed. |name|
99  // and |value| must not be owned by an entry which could be evicted. The
100  // added HpackEntry is returned, or NULL is returned if all entries were
101  // evicted and the empty table is of insufficent size for the representation.
102  HpackEntry* TryAddEntry(base::StringPiece name, base::StringPiece value);
103
104  // Toggles the presence of a dynamic entry in the reference set. Returns
105  // true if the entry was added, or false if removed. It is an error to
106  // Toggle(entry) if |entry->state()| != 0.
107  bool Toggle(HpackEntry* entry);
108
109  // Removes all entries from the reference set. Sets the state of each removed
110  // entry to zero.
111  void ClearReferenceSet();
112
113  void DebugLogTableState() const;
114
115 private:
116  // Returns number of evictions required to enter |name| & |value|.
117  size_t EvictionCountForEntry(base::StringPiece name,
118                               base::StringPiece value) const;
119
120  // Returns number of evictions required to reclaim |reclaim_size| table size.
121  size_t EvictionCountToReclaim(size_t reclaim_size) const;
122
123  // Evicts |count| oldest entries from the table.
124  void Evict(size_t count);
125
126  EntryTable dynamic_entries_;
127  EntryTable static_entries_;
128
129  // Full table index, over |dynamic_entries_| and |static_entries_|.
130  OrderedEntrySet index_;
131  // The reference set is strictly a subset of |dynamic_entries_|.
132  OrderedEntrySet reference_set_;
133
134  // Last acknowledged value for SETTINGS_HEADER_TABLE_SIZE.
135  size_t settings_size_bound_;
136
137  // Estimated current and maximum byte size of the table.
138  // |max_size_| <= |settings_header_table_size_|
139  size_t size_;
140  size_t max_size_;
141
142  // Total number of table insertions which have occurred. Referenced by
143  // IndexOf() for determination of an HpackEntry's table index.
144  size_t total_insertions_;
145
146  DISALLOW_COPY_AND_ASSIGN(HpackHeaderTable);
147};
148
149}  // namespace net
150
151#endif  // NET_SPDY_HPACK_HEADER_TABLE_H_
152