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#pragma once
#include <util/generic/bitops.h>
#include <util/system/unaligned_mem.h>
namespace NBitIO {
class TBitInputImpl {
i64 RealStart;
i64 Start;
ui64 Length;
ui64 BOffset;
const ui32 FakeStart;
char Fake[16];
const i64 FStart;
public:
TBitInputImpl(const char* start, const char* end)
: RealStart((i64)start)
, Start((i64)start)
, Length((end - start) << 3)
, BOffset(0)
, FakeStart(Length > 64 ? Length - 64 : 0)
, FStart((i64)Fake - (FakeStart >> 3))
{
memcpy(Fake, (const char*)(RealStart + (FakeStart >> 3)), (Length - FakeStart) >> 3);
Start = FakeStart ? RealStart : FStart;
}
ui64 GetBitLength() const {
return Length;
}
protected:
template <ui32 bits>
Y_FORCE_INLINE bool ReadKImpl(ui64& result) {
result = (ReadUnaligned<ui64>((const void*)(Start + (BOffset >> 3))) >> (BOffset & 7)) & Mask64(bits);
BOffset += bits;
if (BOffset < FakeStart)
return true;
if (BOffset > Length) {
result = 0;
BOffset -= bits;
return false;
}
Start = FStart;
return true;
}
Y_FORCE_INLINE bool ReadImpl(ui64& result, ui32 bits) {
result = (ReadUnaligned<ui64>((const void*)(Start + (BOffset >> 3))) >> (BOffset & 7)) & MaskLowerBits(bits);
BOffset += bits;
if (BOffset < FakeStart)
return true;
if (Y_UNLIKELY(BOffset > Length)) {
result = 0;
BOffset -= bits;
return false;
}
Start = FStart;
return true;
}
Y_FORCE_INLINE bool EofImpl() const {
return BOffset >= Length;
}
Y_FORCE_INLINE ui64 BitOffset() const {
return BOffset;
}
Y_FORCE_INLINE bool Seek(i64 offset) {
if (offset < 0 || offset > (i64)Length)
return false;
BOffset = offset;
Start = BOffset < FakeStart ? RealStart : FStart;
return true;
}
protected:
template <ui64 bits, typename T>
Y_FORCE_INLINE static void CopyToResultK(T& result, ui64 r64, ui64 skipbits) {
result = (result & ~(Mask64(bits) << skipbits)) | (r64 << skipbits);
}
template <typename T>
Y_FORCE_INLINE static void CopyToResult(T& result, ui64 r64, ui64 bits, ui64 skipbits) {
result = (result & InverseMaskLowerBits(bits, skipbits)) | (r64 << skipbits);
}
public:
template <ui64 bits>
Y_FORCE_INLINE bool ReadWordsImpl(ui64& data) {
data = 0;
const ui64 haveMore = NthBit64(bits);
const ui64 mask = Mask64(bits);
ui64 current = 0;
ui64 byteNo = 0;
do {
if (!ReadKImpl<bits + 1>(current))
return false;
data |= (current & mask) << (byteNo++ * bits);
} while (current & haveMore);
return true;
}
};
}
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