1 // Copyright 2009 the V8 project authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef V8_REGEXP_REGEXP_STACK_H_ 6 #define V8_REGEXP_REGEXP_STACK_H_ 7 8 #include "src/base/logging.h" 9 #include "src/base/macros.h" 10 #include "src/globals.h" 11 12 namespace v8 { 13 namespace internal { 14 15 class RegExpStack; 16 17 // Maintains a per-v8thread stack area that can be used by irregexp 18 // implementation for its backtracking stack. 19 // Since there is only one stack area, the Irregexp implementation is not 20 // re-entrant. I.e., no regular expressions may be executed in the same thread 21 // during a preempted Irregexp execution. 22 class RegExpStackScope { 23 public: 24 // Create and delete an instance to control the life-time of a growing stack. 25 26 // Initializes the stack memory area if necessary. 27 explicit RegExpStackScope(Isolate* isolate); 28 ~RegExpStackScope(); // Releases the stack if it has grown. 29 stack()30 RegExpStack* stack() const { return regexp_stack_; } 31 32 private: 33 RegExpStack* regexp_stack_; 34 35 DISALLOW_COPY_AND_ASSIGN(RegExpStackScope); 36 }; 37 38 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 // Gives the top of the memory used as stack. stack_base()47 Address stack_base() { 48 DCHECK(thread_local_.memory_size_ != 0); 49 return thread_local_.memory_ + thread_local_.memory_size_; 50 } 51 52 // The total size of the memory allocated for the stack. stack_capacity()53 size_t stack_capacity() { return thread_local_.memory_size_; } 54 55 // If the stack pointer gets below the limit, we should react and 56 // either grow the stack or report an out-of-stack exception. 57 // There is only a limited number of locations below the stack limit, 58 // so users of the stack should check the stack limit during any 59 // sequence of pushes longer that this. limit_address()60 Address* limit_address() { return &(thread_local_.limit_); } 61 62 // Ensures that there is a memory area with at least the specified size. 63 // If passing zero, the default/minimum size buffer is allocated. 64 Address EnsureCapacity(size_t size); 65 66 // Thread local archiving. ArchiveSpacePerThread()67 static int ArchiveSpacePerThread() { 68 return static_cast<int>(sizeof(ThreadLocal)); 69 } 70 char* ArchiveStack(char* to); 71 char* RestoreStack(char* from); FreeThreadResources()72 void FreeThreadResources() { thread_local_.Free(); } 73 74 private: 75 RegExpStack(); 76 ~RegExpStack(); 77 78 // Artificial limit used when no memory has been allocated. 79 static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1); 80 81 // Minimal size of allocated stack area. 82 static const size_t kMinimumStackSize = 1 * KB; 83 84 // Maximal size of allocated stack area. 85 static const size_t kMaximumStackSize = 64 * MB; 86 87 // Structure holding the allocated memory, size and limit. 88 struct ThreadLocal { ThreadLocalThreadLocal89 ThreadLocal() { Clear(); } 90 // If memory_size_ > 0 then memory_ must be non-NULL. 91 Address memory_; 92 size_t memory_size_; 93 Address limit_; ClearThreadLocal94 void Clear() { 95 memory_ = NULL; 96 memory_size_ = 0; 97 limit_ = reinterpret_cast<Address>(kMemoryTop); 98 } 99 void Free(); 100 }; 101 102 // Address of allocated memory. memory_address()103 Address memory_address() { 104 return reinterpret_cast<Address>(&thread_local_.memory_); 105 } 106 107 // Address of size of allocated memory. memory_size_address()108 Address memory_size_address() { 109 return reinterpret_cast<Address>(&thread_local_.memory_size_); 110 } 111 112 // Resets the buffer if it has grown beyond the default/minimum size. 113 // After this, the buffer is either the default size, or it is empty, so 114 // you have to call EnsureCapacity before using it again. 115 void Reset(); 116 117 ThreadLocal thread_local_; 118 Isolate* isolate_; 119 120 friend class ExternalReference; 121 friend class Isolate; 122 friend class RegExpStackScope; 123 124 DISALLOW_COPY_AND_ASSIGN(RegExpStack); 125 }; 126 127 } // namespace internal 128 } // namespace v8 129 130 #endif // V8_REGEXP_REGEXP_STACK_H_ 131