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 #include <wtf/PassOwnPtr.h>
  33
  34 namespace JSC {
  35
  36 StructureIDTable::StructureIDTable()
  37     : m_firstFreeOffset(0)
  38     , m_table(adoptPtr(new StructureOrOffset[s_initialSize]))
  39     , m_size(0)
  40     , m_capacity(s_initialSize)
  41 {
  42     // We pre-allocate the first offset so that the null Structure
  43     // can still be represented as the StructureID '0'.
  44     allocateID(0);
  45 }
  46
  47 void StructureIDTable::resize(size_t newCapacity)
  48 {
  49     // Create the new table.
  50     OwnPtr<StructureOrOffset> newTable = adoptPtr(new StructureOrOffset[newCapacity]);
  51
  52     // Copy the contents of the old table to the new table.
  53     memcpy(newTable.get(), table(), m_capacity * sizeof(StructureOrOffset));
  54
  55     // Store fence to make sure we've copied everything before doing the swap.
  56     WTF::storeStoreFence();
  57
  58     // Swap the old and new tables.
  59     swap(m_table, newTable);
  60
  61     // Put the old table (now labeled as new) into the list of old tables.
  62     m_oldTables.append(newTable.release());
  63
  64     // Update the capacity.
  65     m_capacity = newCapacity;
  66 }
  67
  68 void StructureIDTable::flushOldTables()
  69 {
  70     m_oldTables.clear();
  71 }
  72
  73 StructureID StructureIDTable::allocateID(Structure* structure)
  74 {
  75 #if USE(JSVALUE64)
  76     if (!m_firstFreeOffset) {
  77         RELEASE_ASSERT(m_capacity <= UINT_MAX);
  78         if (m_size == m_capacity)
  79             resize(m_capacity * 2);
  80         ASSERT(m_size < m_capacity);
  81
  82         StructureOrOffset newEntry;
  83         newEntry.structure = structure;
  84
  85         if (m_size == s_unusedID) {
  86             m_size++;
  87             return allocateID(structure);
  88         }
  89
  90         StructureID result = m_size;
  91         table()[result] = newEntry;
  92         m_size++;
  93         return result;
  94     }
  95
  96     ASSERT(m_firstFreeOffset != s_unusedID);
  97
  98     StructureID result = m_firstFreeOffset;
  99     m_firstFreeOffset = table()[m_firstFreeOffset].offset;
 100     table()[result].structure = structure;
 101     return result;
 102 #else
 103     return structure;
 104 #endif
 105 }
 106
 107 void StructureIDTable::deallocateID(Structure* structure, StructureID structureID)
 108 {
 109 #if USE(JSVALUE64)
 110     ASSERT(structureID != s_unusedID);
 111     RELEASE_ASSERT(table()[structureID].structure == structure);
 112     table()[structureID].offset = m_firstFreeOffset;
 113     m_firstFreeOffset = structureID;
 114 #else
 115     UNUSED_PARAM(structure);
 116     UNUSED_PARAM(structureID);
 117 #endif
 118 }
 119
 120 } // namespace JSC