runtime/StructureIDTable.cpp

   1 /*
   2  * Copyright (C) 2013 Apple Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions
   6  * are met:
   7  * 1. Redistributions of source code must retain the above copyright
   8  *    notice, this list of conditions and the following disclaimer.
   9  * 2. Redistributions in binary form must reproduce the above copyright
  10  *    notice, this list of conditions and the following disclaimer in the
  11  *    documentation and/or other materials provided with the distribution.
  12  *
  13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
  14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
  17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
  23  * THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "config.h"
  27 #include "StructureIDTable.h"
  28
  29 #include <limits.h>
  30 #include <wtf/Atomics.h>
  31 #include <wtf/DataLog.h>
  32
  33 namespace JSC {
  34
  35 StructureIDTable::StructureIDTable()
  36     : m_firstFreeOffset(0)
  37     , m_table(std::make_unique<StructureOrOffset[]>(s_initialSize))
  38     , m_size(0)
  39     , m_capacity(s_initialSize)
  40 {
  41     // We pre-allocate the first offset so that the null Structure
  42     // can still be represented as the StructureID '0'.
  43     allocateID(0);
  44 }
  45
  46 void StructureIDTable::resize(size_t newCapacity)
  47 {
  48     // Create the new table.
  49     auto newTable = std::make_unique<StructureOrOffset[]>(newCapacity);
  50
  51     // Copy the contents of the old table to the new table.
  52     memcpy(newTable.get(), table(), m_capacity * sizeof(StructureOrOffset));
  53
  54     // Store fence to make sure we've copied everything before doing the swap.
  55     WTF::storeStoreFence();
  56
  57     // Swap the old and new tables.
  58     swap(m_table, newTable);
  59
  60     // Put the old table (now labeled as new) into the list of old tables.
  61     m_oldTables.append(WTF::move(newTable));
  62
  63     // Update the capacity.
  64     m_capacity = newCapacity;
  65 }
  66
  67 void StructureIDTable::flushOldTables()
  68 {
  69     m_oldTables.clear();
  70 }
  71
  72 StructureID StructureIDTable::allocateID(Structure* structure)
  73 {
  74 #if USE(JSVALUE64)
  75     if (!m_firstFreeOffset) {
  76         RELEASE_ASSERT(m_capacity <= UINT_MAX);
  77         if (m_size == m_capacity)
  78             resize(m_capacity * 2);
  79         ASSERT(m_size < m_capacity);
  80
  81         StructureOrOffset newEntry;
  82         newEntry.structure = structure;
  83
  84         if (m_size == s_unusedID) {
  85             m_size++;
  86             return allocateID(structure);
  87         }
  88
  89         StructureID result = m_size;
  90         table()[result] = newEntry;
  91         m_size++;
  92         return result;
  93     }
  94
  95     ASSERT(m_firstFreeOffset != s_unusedID);
  96
  97     StructureID result = m_firstFreeOffset;
  98     m_firstFreeOffset = table()[m_firstFreeOffset].offset;
  99     table()[result].structure = structure;
 100     return result;
 101 #else
 102     return structure;
 103 #endif
 104 }
 105
 106 void StructureIDTable::deallocateID(Structure* structure, StructureID structureID)
 107 {
 108 #if USE(JSVALUE64)
 109     ASSERT(structureID != s_unusedID);
 110     RELEASE_ASSERT(table()[structureID].structure == structure);
 111     table()[structureID].offset = m_firstFreeOffset;
 112     m_firstFreeOffset = structureID;
 113 #else
 114     UNUSED_PARAM(structure);
 115     UNUSED_PARAM(structureID);
 116 #endif
 117 }
 118
 119 } // namespace JSC