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27
28#ifndef V8_REGEXP_STACK_H_
29#define V8_REGEXP_STACK_H_
30
31namespace v8 {
32namespace internal {
33
34class 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.
41class 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
58class 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
93 private:
94  RegExpStack();
95  ~RegExpStack();
96
97  // Artificial limit used when no memory has been allocated.
98  static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
99
100  // Minimal size of allocated stack area.
101  static const size_t kMinimumStackSize = 1 * KB;
102
103  // Maximal size of allocated stack area.
104  static const size_t kMaximumStackSize = 64 * MB;
105
106  // Structure holding the allocated memory, size and limit.
107  struct ThreadLocal {
108    ThreadLocal() { Clear(); }
109    // If memory_size_ > 0 then memory_ must be non-NULL.
110    Address memory_;
111    size_t memory_size_;
112    Address limit_;
113    void Clear() {
114      memory_ = NULL;
115      memory_size_ = 0;
116      limit_ = reinterpret_cast<Address>(kMemoryTop);
117    }
118    void Free();
119  };
120
121  // Address of allocated memory.
122  Address memory_address() {
123    return reinterpret_cast<Address>(&thread_local_.memory_);
124  }
125
126  // Address of size of allocated memory.
127  Address memory_size_address() {
128    return reinterpret_cast<Address>(&thread_local_.memory_size_);
129  }
130
131  // Resets the buffer if it has grown beyond the default/minimum size.
132  // After this, the buffer is either the default size, or it is empty, so
133  // you have to call EnsureCapacity before using it again.
134  void Reset();
135
136  ThreadLocal thread_local_;
137  Isolate* isolate_;
138
139  friend class ExternalReference;
140  friend class Isolate;
141  friend class RegExpStackScope;
142
143  DISALLOW_COPY_AND_ASSIGN(RegExpStack);
144};
145
146}}  // namespace v8::internal
147
148#endif  // V8_REGEXP_STACK_H_
149