cpp / expert
Snippet
In-place Construction in Raw Array Buffers
This example shows how to manage memory manually using placement new within a pre-allocated stack buffer. This technique avoids dynamic memory allocation overhead and ensures that objects are aligned correctly and constructed only when needed.
snippet.cpp
cpp
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#include <new>#include <memory>template <typename T, std::size_t Capacity>class ManualBuffer {alignas(T) char buffer[Capacity * sizeof(T)];std::size_t count = 0;public:template <typename... Args>void emplace_back(Args&&... args) {if (count >= Capacity) return;new (buffer + (count * sizeof(T))) T(std::forward<Args>(args)...);count++;}~ManualBuffer() {for (std::size_t i = 0; i < count; ++i) {reinterpret_cast<T*>(buffer + (i * sizeof(T)))->~T();}}};
Breakdown
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alignas(T) char buffer[...];
Allocates a raw byte array with the correct alignment requirements for type T.
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new (buffer + ...) T(...);
Uses placement new to construct an object at a specific memory address.
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reinterpret_cast<T*>(...)->~T();
Explicitly calls the destructor for manually constructed objects before the buffer is destroyed.