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varint.h
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varint.h
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#ifndef _VARINT_H_
#define _VARINT_H_
#include <stdint.h>
// read unsigned varint32 from buffer. assumes the buffer will have enough size
inline const uint8_t *read_uvint32_slow(const uint8_t *buf, uint32_t *value) {
const uint8_t *p;
uint32_t b, result;
p = buf;
b = *p++;
result = (b & 0x7F);
if (likely(b < 0x80)) goto done;
b = *p++;
result |= (b & 0x7F) << 7;
if (likely(b < 0x80)) goto done;
b = *p++;
result |= (b & 0x7F) << 14;
if (likely(b < 0x80)) goto done;
b = *p++;
result |= (b & 0x7F) << 21;
if (likely(b < 0x80)) goto done;
b = *p++;
result |= b << 28;
if (likely(b < 0x80)) goto done;
ALWAYS_ASSERT(false); // should not reach here (improper encoding)
done:
*value = result;
return p;
}
/**
* Read a uvint32 from buf into value, returning the
* next position in buf after the value has been read.
*
* Assumes buf points to a well encoded varint
*/
ALWAYS_INLINE const uint8_t *read_uvint32(const uint8_t *buf,
uint32_t *value) {
if (likely(*buf < 0x80)) {
*value = *buf;
return buf + 1;
}
return read_uvint32_slow(buf, value);
}
inline const uint8_t *failsafe_read_uvint32_slow(const uint8_t *buf,
size_t nbytes,
uint32_t *value) {
const uint8_t *p;
uint32_t b, result;
p = buf;
if (unlikely(!nbytes--)) return nullptr;
b = *p++;
result = (b & 0x7F);
if (likely(b < 0x80)) goto done;
if (unlikely(!nbytes--)) return nullptr;
b = *p++;
result |= (b & 0x7F) << 7;
if (likely(b < 0x80)) goto done;
if (unlikely(!nbytes--)) return nullptr;
b = *p++;
result |= (b & 0x7F) << 14;
if (likely(b < 0x80)) goto done;
if (unlikely(!nbytes--)) return nullptr;
b = *p++;
result |= (b & 0x7F) << 21;
if (likely(b < 0x80)) goto done;
if (unlikely(!nbytes--)) return nullptr;
b = *p++;
result |= b << 28;
if (likely(b < 0x80)) goto done;
done:
*value = result;
return p;
}
ALWAYS_INLINE const uint8_t *failsafe_read_uvint32(const uint8_t *stream,
size_t nbytes,
uint32_t *value) {
if (unlikely(!nbytes)) return nullptr;
const uint8_t ch = *stream;
if (likely(ch < 0x80)) {
*value = ch;
return stream + 1;
}
return failsafe_read_uvint32_slow(stream, nbytes, value);
}
ALWAYS_INLINE size_t skip_uvint32(const uint8_t *stream, uint8_t *rawv) {
if (rawv) {
if (likely((rawv[0] = stream[0]) < 0x80)) return 1;
if (likely((rawv[1] = stream[1]) < 0x80)) return 2;
if (likely((rawv[2] = stream[2]) < 0x80)) return 3;
if (likely((rawv[3] = stream[3]) < 0x80)) return 4;
if (likely((rawv[4] = stream[4]) < 0x80)) return 5;
} else {
if (likely(stream[0] < 0x80)) return 1;
if (likely(stream[1] < 0x80)) return 2;
if (likely(stream[2] < 0x80)) return 3;
if (likely(stream[3] < 0x80)) return 4;
if (likely(stream[4] < 0x80)) return 5;
}
ALWAYS_ASSERT(false);
return 0;
}
ALWAYS_INLINE size_t
failsafe_skip_uvint32(const uint8_t *stream, size_t nbytes, uint8_t *rawv) {
if (rawv) {
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[0] = stream[0]) < 0x80)) return 1;
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[1] = stream[1]) < 0x80)) return 2;
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[2] = stream[2]) < 0x80)) return 3;
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[3] = stream[3]) < 0x80)) return 4;
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[4] = stream[4]) < 0x80)) return 5;
} else {
if (unlikely(!nbytes--)) return 0;
if (likely(stream[0] < 0x80)) return 1;
if (unlikely(!nbytes--)) return 0;
if (likely(stream[1] < 0x80)) return 2;
if (unlikely(!nbytes--)) return 0;
if (likely(stream[2] < 0x80)) return 3;
if (unlikely(!nbytes--)) return 0;
if (likely(stream[3] < 0x80)) return 4;
if (unlikely(!nbytes--)) return 0;
if (likely(stream[4] < 0x80)) return 5;
}
ALWAYS_ASSERT(false);
return 0;
}
/**
* write uint32_t as unsigned varint32 to buffer. assumes the buffer will have
* enough size. returns the position in buf after the value has been written
*/
inline uint8_t *write_uvint32(uint8_t *buf, uint32_t value) {
while (value > 0x7F) {
*buf++ = (((uint8_t)value) & 0x7F) | 0x80;
value >>= 7;
}
*buf++ = ((uint8_t)value) & 0x7F;
return buf;
}
inline size_t size_uvint32(uint32_t value) {
if (likely(value <= 0x7F)) return 1;
if (likely(value <= ((0x7F << 7) | 0x7F))) return 2;
if (likely(value <= ((0x7F << 14) | (0x7F << 7) | 0x7F))) return 3;
if (likely(value <= ((0x7F << 21) | (0x7F << 14) | (0x7F << 7) | 0x7F)))
return 4;
return 5;
}
class varint {
public:
static void Test();
};
#endif /* _VARINT_H_ */