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