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      1 // Copyright 2009 the V8 project authors. All rights reserved.
      2 // Redistribution and use in source and binary forms, with or without
      3 // modification, are permitted provided that the following conditions are
      4 // met:
      5 //
      6 //     * Redistributions of source code must retain the above copyright
      7 //       notice, this list of conditions and the following disclaimer.
      8 //     * Redistributions in binary form must reproduce the above
      9 //       copyright notice, this list of conditions and the following
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27 
     28 #ifndef V8_REGEXP_STACK_H_
     29 #define V8_REGEXP_STACK_H_
     30 
     31 namespace v8 {
     32 namespace internal {
     33 
     34 class RegExpStack;
     35 
     36 // Maintains a per-v8thread stack area that can be used by irregexp
     37 // implementation for its backtracking stack.
     38 // Since there is only one stack area, the Irregexp implementation is not
     39 // re-entrant. I.e., no regular expressions may be executed in the same thread
     40 // during a preempted Irregexp execution.
     41 class RegExpStackScope {
     42  public:
     43   // Create and delete an instance to control the life-time of a growing stack.
     44 
     45   // Initializes the stack memory area if necessary.
     46   explicit RegExpStackScope(Isolate* isolate);
     47   ~RegExpStackScope();  // Releases the stack if it has grown.
     48 
     49   RegExpStack* stack() const { return regexp_stack_; }
     50 
     51  private:
     52   RegExpStack* regexp_stack_;
     53 
     54   DISALLOW_COPY_AND_ASSIGN(RegExpStackScope);
     55 };
     56 
     57 
     58 class RegExpStack {
     59  public:
     60   // Number of allocated locations on the stack below the limit.
     61   // No sequence of pushes must be longer that this without doing a stack-limit
     62   // check.
     63   static const int kStackLimitSlack = 32;
     64 
     65   // Gives the top of the memory used as stack.
     66   Address stack_base() {
     67     ASSERT(thread_local_.memory_size_ != 0);
     68     return thread_local_.memory_ + thread_local_.memory_size_;
     69   }
     70 
     71   // The total size of the memory allocated for the stack.
     72   size_t stack_capacity() { return thread_local_.memory_size_; }
     73 
     74   // If the stack pointer gets below the limit, we should react and
     75   // either grow the stack or report an out-of-stack exception.
     76   // There is only a limited number of locations below the stack limit,
     77   // so users of the stack should check the stack limit during any
     78   // sequence of pushes longer that this.
     79   Address* limit_address() { return &(thread_local_.limit_); }
     80 
     81   // Ensures that there is a memory area with at least the specified size.
     82   // If passing zero, the default/minimum size buffer is allocated.
     83   Address EnsureCapacity(size_t size);
     84 
     85   // Thread local archiving.
     86   static int ArchiveSpacePerThread() {
     87     return static_cast<int>(sizeof(ThreadLocal));
     88   }
     89   char* ArchiveStack(char* to);
     90   char* RestoreStack(char* from);
     91   void FreeThreadResources() { thread_local_.Free(); }
     92  private:
     93   RegExpStack();
     94   ~RegExpStack();
     95 
     96   // Artificial limit used when no memory has been allocated.
     97   static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
     98 
     99   // Minimal size of allocated stack area.
    100   static const size_t kMinimumStackSize = 1 * KB;
    101 
    102   // Maximal size of allocated stack area.
    103   static const size_t kMaximumStackSize = 64 * MB;
    104 
    105   // Structure holding the allocated memory, size and limit.
    106   struct ThreadLocal {
    107     ThreadLocal() { Clear(); }
    108     // If memory_size_ > 0 then memory_ must be non-NULL.
    109     Address memory_;
    110     size_t memory_size_;
    111     Address limit_;
    112     void Clear() {
    113       memory_ = NULL;
    114       memory_size_ = 0;
    115       limit_ = reinterpret_cast<Address>(kMemoryTop);
    116     }
    117     void Free();
    118   };
    119 
    120   // Address of allocated memory.
    121   Address memory_address() {
    122     return reinterpret_cast<Address>(&thread_local_.memory_);
    123   }
    124 
    125   // Address of size of allocated memory.
    126   Address memory_size_address() {
    127     return reinterpret_cast<Address>(&thread_local_.memory_size_);
    128   }
    129 
    130   // Resets the buffer if it has grown beyond the default/minimum size.
    131   // After this, the buffer is either the default size, or it is empty, so
    132   // you have to call EnsureCapacity before using it again.
    133   void Reset();
    134 
    135   ThreadLocal thread_local_;
    136   Isolate* isolate_;
    137 
    138   friend class ExternalReference;
    139   friend class Isolate;
    140   friend class RegExpStackScope;
    141 
    142   DISALLOW_COPY_AND_ASSIGN(RegExpStack);
    143 };
    144 
    145 }}  // namespace v8::internal
    146 
    147 #endif  // V8_REGEXP_STACK_H_
    148