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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
       2             :  * vim: set ts=8 sts=4 et sw=4 tw=99: */
       3             : 
       4             : // Copyright 2009 the V8 project authors. All rights reserved.
       5             : // Redistribution and use in source and binary forms, with or without
       6             : // modification, are permitted provided that the following conditions are
       7             : // met:
       8             : //
       9             : //     * Redistributions of source code must retain the above copyright
      10             : //       notice, this list of conditions and the following disclaimer.
      11             : //     * Redistributions in binary form must reproduce the above
      12             : //       copyright notice, this list of conditions and the following
      13             : //       disclaimer in the documentation and/or other materials provided
      14             : //       with the distribution.
      15             : //     * Neither the name of Google Inc. nor the names of its
      16             : //       contributors may be used to endorse or promote products derived
      17             : //       from this software without specific prior written permission.
      18             : //
      19             : // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
      20             : // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
      21             : // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
      22             : // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
      23             : // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
      24             : // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
      25             : // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
      26             : // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
      27             : // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
      28             : // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
      29             : // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
      30             : 
      31             : #ifndef V8_REGEXP_STACK_H_
      32             : #define V8_REGEXP_STACK_H_
      33             : 
      34             : #include "jspubtd.h"
      35             : #include "js/Utility.h"
      36             : 
      37             : namespace js {
      38             : namespace irregexp {
      39             : 
      40             : class RegExpStack;
      41             : 
      42             : // Maintains a per-thread stack area that can be used by irregexp
      43             : // implementation for its backtracking stack.
      44             : //
      45             : // Since there is only one stack area, the Irregexp implementation is not
      46             : // re-entrant. I.e., no regular expressions may be executed in the same thread
      47             : // during a preempted Irregexp execution.
      48             : class RegExpStackScope
      49             : {
      50             :   public:
      51             :     // Create and delete an instance to control the life-time of a growing stack.
      52             : 
      53             :     // Initializes the stack memory area if necessary.
      54             :     explicit RegExpStackScope(JSContext* cx);
      55             : 
      56             :     // Releases the stack if it has grown.
      57             :     ~RegExpStackScope();
      58             : 
      59             :   private:
      60             :     RegExpStack* regexp_stack;
      61             : };
      62             : 
      63             : class RegExpStack
      64             : {
      65             :   public:
      66             :     // Number of allocated locations on the stack above the limit.
      67             :     // No sequence of pushes must be longer that this without doing a stack-limit
      68             :     // check.
      69             :     static const int kStackLimitSlack = 32;
      70             : 
      71             :     RegExpStack();
      72             :     ~RegExpStack();
      73             :     bool init();
      74             : 
      75             :     // Resets the buffer if it has grown beyond the default/minimum size.
      76             :     void reset();
      77             : 
      78             :     // Attempts to grow the stack by at least kStackLimitSlack entries.
      79             :     bool grow();
      80             : 
      81             :     // Address of allocated memory.
      82          80 :     static size_t offsetOfBase() { return offsetof(RegExpStack, base_); }
      83         206 :     static size_t offsetOfLimit() { return offsetof(RegExpStack, limit_); }
      84             : 
      85           8 :     void* base() { return base_; }
      86           0 :     void* limit() { return limit_; }
      87             : 
      88             :   private:
      89             :     // Artificial limit used when no memory has been allocated.
      90             :     static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
      91             : 
      92             :     // Minimal size of allocated stack area, in bytes.
      93             :     static const size_t kMinimumStackSize = 1 * 1024;
      94             : 
      95             :     // Maximal size of allocated stack area, in bytes.
      96             :     static const size_t kMaximumStackSize = 64 * 1024 * 1024;
      97             : 
      98             :     // If size > 0 then base must be non-nullptr.
      99             :     void* base_;
     100             : 
     101             :     // Length in bytes of base.
     102             :     size_t size;
     103             : 
     104             :     // If the stack pointer gets above the limit, we should react and
     105             :     // either grow the stack or report an out-of-stack exception.
     106             :     // There is only a limited number of locations above the stack limit,
     107             :     // so users of the stack should check the stack limit during any
     108             :     // sequence of pushes longer than this.
     109             :     void* limit_;
     110             : 
     111           8 :     void updateLimit() {
     112           8 :         MOZ_ASSERT(size >= kStackLimitSlack * sizeof(void*));
     113           8 :         limit_ = static_cast<uint8_t*>(base()) + size - (kStackLimitSlack * sizeof(void*));
     114           8 :     }
     115             : };
     116             : 
     117             : int
     118             : GrowBacktrackStack(JSRuntime* rt);
     119             : 
     120             : }}  // namespace js::irregexp
     121             : 
     122             : #endif  // V8_REGEXP_STACK_H_