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_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. stack_capacity()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. limit_address()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. ArchiveSpacePerThread()68 static int ArchiveSpacePerThread() { 69 return static_cast<int>(sizeof(ThreadLocal)); 70 } 71 char* ArchiveStack(char* to); 72 char* RestoreStack(char* from); FreeThreadResources()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 { ThreadLocalThreadLocal91 ThreadLocal() { Clear(); } 92 // If memory_size_ > 0 then memory_ must be non-nullptr. 93 byte* memory_; 94 size_t memory_size_; 95 Address limit_; ClearThreadLocal96 void Clear() { 97 memory_ = nullptr; 98 memory_size_ = 0; 99 limit_ = kMemoryTop; 100 } 101 void Free(); 102 }; 103 104 // Address of allocated memory. memory_address()105 Address memory_address() { 106 return reinterpret_cast<Address>(&thread_local_.memory_); 107 } 108 109 // Address of size of allocated memory. memory_size_address()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_ 133