78 lines
2.9 KiB
C++
78 lines
2.9 KiB
C++
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// nisps/core/fixed_buffer.hpp — heap-free dynamic-length array with
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// compile-time capacity. Replaces std::vector in hot paths.
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//
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// API mirrors a tiny subset of std::vector: push_back / clear / size / data /
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// operator[] / iterators / front / back. NO reserve, NO resize-with-default,
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// NO insert. If you need those, you're probably reaching for the wrong tool.
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//
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// Bounds checking: push_back returns bool (false ⇒ full, no-op). operator[]
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// is unchecked — match std::vector's behavior.
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#pragma once
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#include <array>
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#include <cstddef>
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#include <type_traits>
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#include <utility>
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namespace nisps {
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template <typename T, std::size_t N>
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class FixedBuffer {
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public:
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using value_type = T;
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using size_type = std::size_t;
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using iterator = T*;
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using const_iterator = const T*;
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constexpr FixedBuffer() noexcept = default;
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// Trivially copyable when T is. Move/copy semantics fine — backing store
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// is std::array, which has correct value-semantics.
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constexpr size_type size() const noexcept { return n_; }
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static constexpr size_type capacity() noexcept { return N; }
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constexpr bool empty() const noexcept { return n_ == 0u; }
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constexpr bool full() const noexcept { return n_ == N; }
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constexpr T* data() noexcept { return buf_.data(); }
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constexpr const T* data() const noexcept { return buf_.data(); }
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constexpr T& operator[](size_type i) noexcept { return buf_[i]; }
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constexpr const T& operator[](size_type i) const noexcept { return buf_[i]; }
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constexpr T& front() noexcept { return buf_[0]; }
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constexpr const T& front() const noexcept { return buf_[0]; }
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constexpr T& back() noexcept { return buf_[n_ - 1u]; }
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constexpr const T& back() const noexcept { return buf_[n_ - 1u]; }
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constexpr iterator begin() noexcept { return buf_.data(); }
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constexpr const_iterator begin() const noexcept { return buf_.data(); }
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constexpr iterator end() noexcept { return buf_.data() + n_; }
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constexpr const_iterator end() const noexcept { return buf_.data() + n_; }
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constexpr void clear() noexcept { n_ = 0u; }
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// Returns true on success. Does NOT throw or assert when full — callers
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// are expected to size the buffer correctly.
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constexpr bool push_back(const T& v) noexcept(std::is_nothrow_copy_assignable_v<T>) {
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if (n_ >= N) return false;
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buf_[n_++] = v;
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return true;
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}
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constexpr bool push_back(T&& v) noexcept(std::is_nothrow_move_assignable_v<T>) {
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if (n_ >= N) return false;
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buf_[n_++] = std::move(v);
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return true;
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}
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// pop_back — trivial decrement; does not destroy (T must be cleanup-free).
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constexpr void pop_back() noexcept { if (n_ > 0u) --n_; }
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private:
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std::array<T, N> buf_{};
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size_type n_ = 0u;
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};
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} // namespace nisps
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