net/spdy/hpack_header_table.h

   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
  20 namespace net {
  21
  22 namespace test {
  23 class 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).
  28 class 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_