net/spdy/hpack/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/hpack_entry.h"
  16
  17 // All section references below are to http://tools.ietf.org/html/rfc7541.
  18
  19 namespace net {
  20
  21 using base::StringPiece;
  22
  23 namespace test {
  24 class HpackHeaderTablePeer;
  25 }  // namespace test
  26
  27 // A data structure for the static table (2.3.1) and the dynamic table (2.3.2).
  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     bool operator()(const HpackEntry* lhs, const HpackEntry* rhs) const;
  46   };
  47   typedef std::set<HpackEntry*, EntryComparator> OrderedEntrySet;
  48
  49   HpackHeaderTable();
  50
  51   ~HpackHeaderTable();
  52
  53   // Last-acknowledged value of SETTINGS_HEADER_TABLE_SIZE.
  54   size_t settings_size_bound() { return settings_size_bound_; }
  55
  56   // Current and maximum estimated byte size of the table, as described in
  57   // 4.1. Notably, this is /not/ the number of entries in the table.
  58   size_t size() const { return size_; }
  59   size_t max_size() const { return max_size_; }
  60
  61   // Returns the entry matching the index, or NULL.
  62   const HpackEntry* GetByIndex(size_t index);
  63
  64   // Returns the lowest-value entry having |name|, or NULL.
  65   const HpackEntry* GetByName(StringPiece name);
  66
  67   // Returns the lowest-index matching entry, or NULL.
  68   const HpackEntry* GetByNameAndValue(StringPiece name, StringPiece value);
  69
  70   // Returns the index of an entry within this header table.
  71   size_t IndexOf(const HpackEntry* entry) const;
  72
  73   // Sets the maximum size of the header table, evicting entries if
  74   // necessary as described in 5.2.
  75   void SetMaxSize(size_t max_size);
  76
  77   // Sets the SETTINGS_HEADER_TABLE_SIZE bound of the table. Will call
  78   // SetMaxSize() as needed to preserve max_size() <= settings_size_bound().
  79   void SetSettingsHeaderTableSize(size_t settings_size);
  80
  81   // Determine the set of entries which would be evicted by the insertion
  82   // of |name| & |value| into the table, as per section 4.4. No eviction
  83   // actually occurs. The set is returned via range [begin_out, end_out).
  84   void EvictionSet(StringPiece name,
  85                    StringPiece value,
  86                    EntryTable::iterator* begin_out,
  87                    EntryTable::iterator* end_out);
  88
  89   // Adds an entry for the representation, evicting entries as needed. |name|
  90   // and |value| must not be owned by an entry which could be evicted. The
  91   // added HpackEntry is returned, or NULL is returned if all entries were
  92   // evicted and the empty table is of insufficent size for the representation.
  93   const HpackEntry* TryAddEntry(StringPiece name, StringPiece value);
  94
  95   void DebugLogTableState() const;
  96
  97  private:
  98   // Returns number of evictions required to enter |name| & |value|.
  99   size_t EvictionCountForEntry(StringPiece name, StringPiece value) const;
 100
 101   // Returns number of evictions required to reclaim |reclaim_size| table size.
 102   size_t EvictionCountToReclaim(size_t reclaim_size) const;
 103
 104   // Evicts |count| oldest entries from the table.
 105   void Evict(size_t count);
 106
 107   // |static_entries_| and |static_index_| are owned by HpackStaticTable
 108   // singleton.
 109   const EntryTable& static_entries_;
 110   EntryTable dynamic_entries_;
 111
 112   const OrderedEntrySet& static_index_;
 113   OrderedEntrySet dynamic_index_;
 114
 115   // Last acknowledged value for SETTINGS_HEADER_TABLE_SIZE.
 116   size_t settings_size_bound_;
 117
 118   // Estimated current and maximum byte size of the table.
 119   // |max_size_| <= |settings_size_bound_|
 120   size_t size_;
 121   size_t max_size_;
 122
 123   // Total number of table insertions which have occurred. Referenced by
 124   // IndexOf() for determination of an HpackEntry's table index.
 125   size_t total_insertions_;
 126
 127   DISALLOW_COPY_AND_ASSIGN(HpackHeaderTable);
 128 };
 129
 130 }  // namespace net
 131
 132 #endif  // NET_SPDY_HPACK_HEADER_TABLE_H_