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114 lines
2.5 KiB
C++
114 lines
2.5 KiB
C++
#pragma once
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#include <algorithm>
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#include <array>
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#include <vector>
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// Fast memory storage on the stack when possible or in std::vector
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namespace c11log
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{
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namespace details
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{
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template<unsigned short STACK_SIZE>
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class stack_buf
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{
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public:
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using bufpair_t = std::pair<const char*, std::size_t>;
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using iterator = char const*;
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static constexpr unsigned short stack_size = STACK_SIZE;
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stack_buf() :_v(), _stack_size(0) {}
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~stack_buf() = default;
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stack_buf& operator=(const stack_buf& other) = delete;
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stack_buf(const stack_buf& other):stack_buf(other, delegate_copy_move{})
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{}
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stack_buf(stack_buf&& other):stack_buf(other, delegate_copy_move{})
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{
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other.clear();
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}
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void append(const char* buf, std::size_t buf_size)
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{
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//If we are aleady using _v, forget about the stack
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if (vector_used())
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{
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_v.insert(_v.end(), buf, buf + buf_size);
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}
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//Try use the stack
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else
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{
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if (_stack_size + buf_size <= STACK_SIZE)
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{
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std::memcpy(&_stack_array[_stack_size], buf, buf_size);
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_stack_size += buf_size;
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}
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//Not enough stack space. Copy all to _v
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else
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{
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_v.reserve(_stack_size + buf_size);
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_v.insert(_v.end(), _stack_array.begin(), _stack_array.begin() + _stack_size);
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_v.insert(_v.end(), buf, buf + buf_size);
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}
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}
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}
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void clear()
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{
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_stack_size = 0;
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_v.clear();
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}
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bufpair_t get() const
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{
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if (vector_used())
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return bufpair_t(_v.data(), _v.size());
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else
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return bufpair_t(_stack_array.data(), _stack_size);
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}
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iterator begin() const
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{
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return get().first;
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}
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iterator end() const
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{
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bufpair_t bpair = get();
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return bpair.first + bpair.second;
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}
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std::size_t size() const
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{
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return get().second;
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}
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private:
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struct delegate_copy_move {};
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template<class T1>
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stack_buf(T1&& other, delegate_copy_move)
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{
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_stack_size = other._stack_size;
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if (other.vector_used())
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_v = std::forward<T1>(other)._v;
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else
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std::copy_n(other._stack_array.begin(), other._stack_size, _stack_array.begin());
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}
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inline bool vector_used() const
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{
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return !(_v.empty());
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}
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std::vector<char> _v;
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std::array<char, STACK_SIZE> _stack_array;
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std::size_t _stack_size;
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};
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}
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} //namespace c11log { namespace details {
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