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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#pragma once
#include <cstddef>
namespace search {
/**
* Abstract class to write to a buffer with an abstract backing store
* and abstract backing buffer. Each time backing buffer is full,
* flush() is called to resize it or drain it to the backing store.
*/
class BufferWriter
{
char *_cur;
char *_end;
char *_start;
protected:
void rewind() { _cur = _start; }
void setup(void *start, size_t len) {
_start = static_cast<char *>(start);
_end = _start + len;
rewind();
}
size_t freeLen() const { return _end - _cur; }
size_t usedLen() const { return _cur - _start; }
void writeFast(const void *src, size_t len)
{
__builtin_memcpy(_cur, src, len);
_cur += len;
}
void writeSlow(const void *src, size_t len);
public:
BufferWriter();
virtual ~BufferWriter();
virtual void flush() = 0;
void write(const void *src, size_t len)
{
if (__builtin_expect(len <= freeLen(), true)) {
writeFast(src, len);
return;
}
writeSlow(src, len);
}
};
} // namespace search
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