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#pragma once
#include <util/system/yassert.h>
#include "output.h"
/**
* @addtogroup Streams
* @{
*/
/**
* Output stream with direct access to the output buffer.
*
* Derived classes must implement `DoNext` and `DoUndo` methods.
*/
class IZeroCopyOutput: public IOutputStream {
public:
IZeroCopyOutput() noexcept = default;
~IZeroCopyOutput() override = default;
IZeroCopyOutput(IZeroCopyOutput&&) noexcept = default;
IZeroCopyOutput& operator=(IZeroCopyOutput&&) noexcept = default;
/**
* Returns the next buffer to write to from this output stream.
*
* @param ptr[out] Pointer to the start of the buffer.
* @returns Size of the returned buffer, in bytes.
* Return value is always nonzero.
*/
template <class T>
inline size_t Next(T** ptr) {
Y_ASSERT(ptr);
return DoNext((void**)ptr);
}
/**
* Tells the stream that `len` bytes at the end of the buffer returned previously
* by Next were actually not written so the current position in stream must be moved backwards.
* `len` must not be greater than the size of the buffer previously returned by `Next`.
*
* @param len[in] Number of bytes at the end to move the position by.
*
*/
inline void Undo(size_t len) {
return DoUndo(len);
}
protected:
void DoWrite(const void* buf, size_t len) override;
virtual size_t DoNext(void** ptr) = 0;
virtual void DoUndo(size_t len) = 0;
};
/** @} */
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