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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 // Maintains a per-v8thread stack area that can be used by irregexp
     35 // implementation for its backtracking stack.
     36 // Since there is only one stack area, the Irregexp implementation is not
     37 // re-entrant. I.e., no regular expressions may be executed in the same thread
     38 // during a preempted Irregexp execution.
     39 class RegExpStack {
     40  public:
     41   // Number of allocated locations on the stack below the limit.
     42   // No sequence of pushes must be longer that this without doing a stack-limit
     43   // check.
     44   static const int kStackLimitSlack = 32;
     45 
     46   // Create and delete an instance to control the life-time of a growing stack.
     47   RegExpStack();  // Initializes the stack memory area if necessary.
     48   ~RegExpStack();  // Releases the stack if it has grown.
     49 
     50   // Gives the top of the memory used as stack.
     51   static Address stack_base() {
     52     ASSERT(thread_local_.memory_size_ != 0);
     53     return thread_local_.memory_ + thread_local_.memory_size_;
     54   }
     55 
     56   // The total size of the memory allocated for the stack.
     57   static size_t stack_capacity() { return thread_local_.memory_size_; }
     58 
     59   // If the stack pointer gets below the limit, we should react and
     60   // either grow the stack or report an out-of-stack exception.
     61   // There is only a limited number of locations below the stack limit,
     62   // so users of the stack should check the stack limit during any
     63   // sequence of pushes longer that this.
     64   static Address* limit_address() { return &(thread_local_.limit_); }
     65 
     66   // Ensures that there is a memory area with at least the specified size.
     67   // If passing zero, the default/minimum size buffer is allocated.
     68   static Address EnsureCapacity(size_t size);
     69 
     70   // Thread local archiving.
     71   static int ArchiveSpacePerThread() {
     72     return static_cast<int>(sizeof(thread_local_));
     73   }
     74   static char* ArchiveStack(char* to);
     75   static char* RestoreStack(char* from);
     76   static void FreeThreadResources() { thread_local_.Free(); }
     77 
     78  private:
     79   // Artificial limit used when no memory has been allocated.
     80   static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
     81 
     82   // Minimal size of allocated stack area.
     83   static const size_t kMinimumStackSize = 1 * KB;
     84 
     85   // Maximal size of allocated stack area.
     86   static const size_t kMaximumStackSize = 64 * MB;
     87 
     88   // Structure holding the allocated memory, size and limit.
     89   struct ThreadLocal {
     90     ThreadLocal()
     91         : memory_(NULL),
     92           memory_size_(0),
     93           limit_(reinterpret_cast<Address>(kMemoryTop)) {}
     94     // If memory_size_ > 0 then memory_ must be non-NULL.
     95     Address memory_;
     96     size_t memory_size_;
     97     Address limit_;
     98     void Free();
     99   };
    100 
    101   // Address of allocated memory.
    102   static Address memory_address() {
    103     return reinterpret_cast<Address>(&thread_local_.memory_);
    104   }
    105 
    106   // Address of size of allocated memory.
    107   static Address memory_size_address() {
    108     return reinterpret_cast<Address>(&thread_local_.memory_size_);
    109   }
    110 
    111   // Resets the buffer if it has grown beyond the default/minimum size.
    112   // After this, the buffer is either the default size, or it is empty, so
    113   // you have to call EnsureCapacity before using it again.
    114   static void Reset();
    115 
    116   static ThreadLocal thread_local_;
    117 
    118   friend class ExternalReference;
    119 };
    120 
    121 }}  // namespace v8::internal
    122 
    123 #endif  // V8_REGEXP_STACK_H_
    124