Ben Murdoch | 4a90d5f | 2016-03-22 12:00:34 +0000 | [diff] [blame] | 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 | |
| 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(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. |
| 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. |
| 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. |
| 67 | static int ArchiveSpacePerThread() { |
| 68 | return static_cast<int>(sizeof(ThreadLocal)); |
| 69 | } |
| 70 | char* ArchiveStack(char* to); |
| 71 | char* RestoreStack(char* from); |
| 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 { |
| 89 | ThreadLocal() { Clear(); } |
| 90 | // If memory_size_ > 0 then memory_ must be non-NULL. |
| 91 | Address memory_; |
| 92 | size_t memory_size_; |
| 93 | Address limit_; |
| 94 | 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. |
| 103 | Address memory_address() { |
| 104 | return reinterpret_cast<Address>(&thread_local_.memory_); |
| 105 | } |
| 106 | |
| 107 | // Address of size of allocated memory. |
| 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_ |