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_STACK_H_
6#define V8_REGEXP_STACK_H_
7
8namespace v8 {
9namespace internal {
10
11class RegExpStack;
12
13// Maintains a per-v8thread stack area that can be used by irregexp
14// implementation for its backtracking stack.
15// Since there is only one stack area, the Irregexp implementation is not
16// re-entrant. I.e., no regular expressions may be executed in the same thread
17// during a preempted Irregexp execution.
18class RegExpStackScope {
19 public:
20  // Create and delete an instance to control the life-time of a growing stack.
21
22  // Initializes the stack memory area if necessary.
23  explicit RegExpStackScope(Isolate* isolate);
24  ~RegExpStackScope();  // Releases the stack if it has grown.
25
26  RegExpStack* stack() const { return regexp_stack_; }
27
28 private:
29  RegExpStack* regexp_stack_;
30
31  DISALLOW_COPY_AND_ASSIGN(RegExpStackScope);
32};
33
34
35class RegExpStack {
36 public:
37  // Number of allocated locations on the stack below the limit.
38  // No sequence of pushes must be longer that this without doing a stack-limit
39  // check.
40  static const int kStackLimitSlack = 32;
41
42  // Gives the top of the memory used as stack.
43  Address stack_base() {
44    DCHECK(thread_local_.memory_size_ != 0);
45    return thread_local_.memory_ + thread_local_.memory_size_;
46  }
47
48  // The total size of the memory allocated for the stack.
49  size_t stack_capacity() { return thread_local_.memory_size_; }
50
51  // If the stack pointer gets below the limit, we should react and
52  // either grow the stack or report an out-of-stack exception.
53  // There is only a limited number of locations below the stack limit,
54  // so users of the stack should check the stack limit during any
55  // sequence of pushes longer that this.
56  Address* limit_address() { return &(thread_local_.limit_); }
57
58  // Ensures that there is a memory area with at least the specified size.
59  // If passing zero, the default/minimum size buffer is allocated.
60  Address EnsureCapacity(size_t size);
61
62  // Thread local archiving.
63  static int ArchiveSpacePerThread() {
64    return static_cast<int>(sizeof(ThreadLocal));
65  }
66  char* ArchiveStack(char* to);
67  char* RestoreStack(char* from);
68  void FreeThreadResources() { thread_local_.Free(); }
69
70 private:
71  RegExpStack();
72  ~RegExpStack();
73
74  // Artificial limit used when no memory has been allocated.
75  static const uintptr_t kMemoryTop = static_cast<uintptr_t>(-1);
76
77  // Minimal size of allocated stack area.
78  static const size_t kMinimumStackSize = 1 * KB;
79
80  // Maximal size of allocated stack area.
81  static const size_t kMaximumStackSize = 64 * MB;
82
83  // Structure holding the allocated memory, size and limit.
84  struct ThreadLocal {
85    ThreadLocal() { Clear(); }
86    // If memory_size_ > 0 then memory_ must be non-NULL.
87    Address memory_;
88    size_t memory_size_;
89    Address limit_;
90    void Clear() {
91      memory_ = NULL;
92      memory_size_ = 0;
93      limit_ = reinterpret_cast<Address>(kMemoryTop);
94    }
95    void Free();
96  };
97
98  // Address of allocated memory.
99  Address memory_address() {
100    return reinterpret_cast<Address>(&thread_local_.memory_);
101  }
102
103  // Address of size of allocated memory.
104  Address memory_size_address() {
105    return reinterpret_cast<Address>(&thread_local_.memory_size_);
106  }
107
108  // Resets the buffer if it has grown beyond the default/minimum size.
109  // After this, the buffer is either the default size, or it is empty, so
110  // you have to call EnsureCapacity before using it again.
111  void Reset();
112
113  ThreadLocal thread_local_;
114  Isolate* isolate_;
115
116  friend class ExternalReference;
117  friend class Isolate;
118  friend class RegExpStackScope;
119
120  DISALLOW_COPY_AND_ASSIGN(RegExpStack);
121};
122
123}}  // namespace v8::internal
124
125#endif  // V8_REGEXP_STACK_H_
126