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 
8 namespace v8 {
9 namespace internal {
10 
11 class 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.
18 class 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 
stack()26   RegExpStack* stack() const { return regexp_stack_; }
27 
28  private:
29   RegExpStack* regexp_stack_;
30 
31   DISALLOW_COPY_AND_ASSIGN(RegExpStackScope);
32 };
33 
34 
35 class 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.
stack_base()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.
stack_capacity()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.
limit_address()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.
ArchiveSpacePerThread()63   static int ArchiveSpacePerThread() {
64     return static_cast<int>(sizeof(ThreadLocal));
65   }
66   char* ArchiveStack(char* to);
67   char* RestoreStack(char* from);
FreeThreadResources()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 {
ThreadLocalThreadLocal85     ThreadLocal() { Clear(); }
86     // If memory_size_ > 0 then memory_ must be non-NULL.
87     Address memory_;
88     size_t memory_size_;
89     Address limit_;
ClearThreadLocal90     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.
memory_address()99   Address memory_address() {
100     return reinterpret_cast<Address>(&thread_local_.memory_);
101   }
102 
103   // Address of size of allocated memory.
memory_size_address()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