stack.h

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#ifndef RAPIDJSON_INTERNAL_STACK_H_
#define RAPIDJSON_INTERNAL_STACK_H_
 
namespace rapidjson {
namespace internal {
 
// Stack
 
 
template <typename Allocator>
class Stack {
public:
    Stack(Allocator* allocator, size_t stack_capacity) : allocator_(allocator), own_allocator_(0), stack_(0), stack_top_(0), stack_end_(0), stack_capacity_(stack_capacity) {
        RAPIDJSON_ASSERT(stack_capacity_ > 0);
        if (!allocator_)
            own_allocator_ = allocator_ = new Allocator();
        stack_top_ = stack_ = (char*)allocator_->Malloc(stack_capacity_);
        stack_end_ = stack_ + stack_capacity_;
    }
 
    ~Stack() {
        Allocator::Free(stack_);
        delete own_allocator_; // Only delete if it is owned by the stack
    }
 
    void Clear() { /*stack_top_ = 0;*/ stack_top_ = stack_; }
 
    template<typename T>
    T* Push(size_t count = 1) {
         // Expand the stack if needed
        if (stack_top_ + sizeof(T) * count >= stack_end_) {
            size_t new_capacity = stack_capacity_ * 2;
            size_t size = GetSize();
            size_t new_size = GetSize() + sizeof(T) * count;
            if (new_capacity < new_size)
                new_capacity = new_size;
            stack_ = (char*)allocator_->Realloc(stack_, stack_capacity_, new_capacity);
            stack_capacity_ = new_capacity;
            stack_top_ = stack_ + size;
            stack_end_ = stack_ + stack_capacity_;
        }
        T* ret = (T*)stack_top_;
        stack_top_ += sizeof(T) * count;
        return ret;
    }
 
    template<typename T>
    T* Pop(size_t count) {
        RAPIDJSON_ASSERT(GetSize() >= count * sizeof(T));
        stack_top_ -= count * sizeof(T);
        return (T*)stack_top_;
    }
 
    template<typename T>
    T* Top() { 
        RAPIDJSON_ASSERT(GetSize() >= sizeof(T));
        return (T*)(stack_top_ - sizeof(T));
    }
 
    template<typename T>
    T* Bottom() { return (T*)stack_; }
 
    Allocator& GetAllocator() { return *allocator_; }
    size_t GetSize() const { return stack_top_ - stack_; }
    size_t GetCapacity() const { return stack_capacity_; }
 
private:
    Allocator* allocator_;
    Allocator* own_allocator_;
    char *stack_;
    char *stack_top_;
    char *stack_end_;
    size_t stack_capacity_;
};
 
} // namespace internal
} // namespace rapidjson
 
#endif // RAPIDJSON_STACK_H_