V8 API Reference, 7.2.502.16 (for Deno 0.2.4)
regexp-stack.h
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.
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 
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.
47  Address stack_base() {
48  DCHECK_NE(0, thread_local_.memory_size_);
49  return reinterpret_cast<Address>(thread_local_.memory_) +
50  thread_local_.memory_size_;
51  }
52 
53  // The total size of the memory allocated for the stack.
54  size_t stack_capacity() { return thread_local_.memory_size_; }
55 
56  // If the stack pointer gets below the limit, we should react and
57  // either grow the stack or report an out-of-stack exception.
58  // There is only a limited number of locations below the stack limit,
59  // so users of the stack should check the stack limit during any
60  // sequence of pushes longer that this.
61  Address* limit_address() { return &(thread_local_.limit_); }
62 
63  // Ensures that there is a memory area with at least the specified size.
64  // If passing zero, the default/minimum size buffer is allocated.
65  Address EnsureCapacity(size_t size);
66 
67  // Thread local archiving.
68  static int ArchiveSpacePerThread() {
69  return static_cast<int>(sizeof(ThreadLocal));
70  }
71  char* ArchiveStack(char* to);
72  char* RestoreStack(char* from);
73  void FreeThreadResources() { thread_local_.Free(); }
74 
75  private:
76  RegExpStack();
77  ~RegExpStack();
78 
79  // Artificial limit used when no memory has been allocated.
80  static const Address kMemoryTop =
81  static_cast<Address>(static_cast<uintptr_t>(-1));
82 
83  // Minimal size of allocated stack area.
84  static const size_t kMinimumStackSize = 1 * KB;
85 
86  // Maximal size of allocated stack area.
87  static const size_t kMaximumStackSize = 64 * MB;
88 
89  // Structure holding the allocated memory, size and limit.
90  struct ThreadLocal {
91  ThreadLocal() { Clear(); }
92  // If memory_size_ > 0 then memory_ must be non-nullptr.
93  byte* memory_;
94  size_t memory_size_;
95  Address limit_;
96  void Clear() {
97  memory_ = nullptr;
98  memory_size_ = 0;
99  limit_ = kMemoryTop;
100  }
101  void Free();
102  };
103 
104  // Address of allocated memory.
105  Address memory_address() {
106  return reinterpret_cast<Address>(&thread_local_.memory_);
107  }
108 
109  // Address of size of allocated memory.
110  Address memory_size_address() {
111  return reinterpret_cast<Address>(&thread_local_.memory_size_);
112  }
113 
114  // Resets the buffer if it has grown beyond the default/minimum size.
115  // After this, the buffer is either the default size, or it is empty, so
116  // you have to call EnsureCapacity before using it again.
117  void Reset();
118 
119  ThreadLocal thread_local_;
120  Isolate* isolate_;
121 
122  friend class ExternalReference;
123  friend class Isolate;
124  friend class RegExpStackScope;
125 
126  DISALLOW_COPY_AND_ASSIGN(RegExpStack);
127 };
128 
129 } // namespace internal
130 } // namespace v8
131 
132 #endif // V8_REGEXP_REGEXP_STACK_H_
Definition: libplatform.h:13