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#pragma once
#include <util/system/yassert.h>
#include <util/system/defaults.h>
#include <util/generic/ylimits.h>
#include "input.h"
class IOutputStream;
/**
* @addtogroup Streams
* @{
*/
/**
* Input stream with direct access to the input buffer.
*
* Derived classes must implement `DoNext` method.
*/
class IZeroCopyInput: public IInputStream {
public:
IZeroCopyInput() noexcept = default;
~IZeroCopyInput() override;
IZeroCopyInput(IZeroCopyInput&&) noexcept = default;
IZeroCopyInput& operator=(IZeroCopyInput&&) noexcept = default;
/**
* Returns the next data chunk from this input stream.
*
* Note that this function is not guaranteed to return the requested number
* of bytes, even if they are in fact available in the stream.
*
* @param ptr[out] Pointer to the start of the data chunk.
* @param len[in] Maximal size of the data chunk to be returned, in bytes.
* @returns Size of the returned data chunk, in bytes.
* Return value of zero signals end of stream.
*/
template <class T>
inline size_t Next(T** ptr, size_t len) {
Y_ASSERT(ptr);
return DoNext((const void**)ptr, len);
}
template <class T>
inline size_t Next(T** ptr) {
return Next(ptr, Max<size_t>());
}
protected:
size_t DoRead(void* buf, size_t len) override;
size_t DoSkip(size_t len) override;
ui64 DoReadAll(IOutputStream& out) override;
virtual size_t DoNext(const void** ptr, size_t len) = 0;
};
/**
* Input stream with direct access to the input buffer and ability to undo read
*
* Derived classes must implement `DoUndo` method.
*/
class IZeroCopyInputFastReadTo: public IZeroCopyInput {
public:
IZeroCopyInputFastReadTo() noexcept = default;
~IZeroCopyInputFastReadTo() override;
IZeroCopyInputFastReadTo(IZeroCopyInputFastReadTo&&) noexcept = default;
IZeroCopyInputFastReadTo& operator=(IZeroCopyInputFastReadTo&&) noexcept = default;
protected:
size_t DoReadTo(TString& st, char ch) override;
private:
/**
* Undo read.
*
* Note that this function not check if you try undo more that read. In fact Undo used for undo read in last chunk.
*
* @param len[in] Bytes to undo.
*/
inline void Undo(size_t len) {
if (len) {
DoUndo(len);
}
}
virtual void DoUndo(size_t len) = 0;
};
/** @} */
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