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Rewrite encoding functions #1358

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merged 2 commits into from
Mar 27, 2023
Merged

Rewrite encoding functions #1358

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dca4082
Rewrite encoding functions
PragmaTwice Mar 27, 2023
7961273
Merge branch 'unstable' into encoding
PragmaTwice Mar 27, 2023
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87 changes: 33 additions & 54 deletions src/common/encoding.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -99,44 +99,30 @@
void EncodeFixed8(char *buf, uint8_t value) { buf[0] = static_cast<char>(value & 0xff); }

void EncodeFixed16(char *buf, uint16_t value) {
if (BYTE_ORDER == BIG_ENDIAN) {
memcpy(buf, &value, sizeof(value));
} else {
buf[0] = static_cast<char>((value >> 8) & 0xff);
buf[1] = static_cast<char>(value & 0xff);
if constexpr (BYTE_ORDER == LITTLE_ENDIAN) {
value = __builtin_bswap16(value);
}
__builtin_memcpy(buf, &value, sizeof(value));
}

void EncodeFixed32(char *buf, uint32_t value) {
if (BYTE_ORDER == BIG_ENDIAN) {
memcpy(buf, &value, sizeof(value));
} else {
buf[0] = static_cast<char>((value >> 24) & 0xff);
buf[1] = static_cast<char>((value >> 16) & 0xff);
buf[2] = static_cast<char>((value >> 8) & 0xff);
buf[3] = static_cast<char>(value & 0xff);
if constexpr (BYTE_ORDER == LITTLE_ENDIAN) {
value = __builtin_bswap32(value);
}
__builtin_memcpy(buf, &value, sizeof(value));
}

void EncodeFixed64(char *buf, uint64_t value) {
if (BYTE_ORDER == BIG_ENDIAN) {
memcpy(buf, &value, sizeof(value));
} else {
buf[0] = static_cast<char>((value >> 56) & 0xff);
buf[1] = static_cast<char>((value >> 48) & 0xff);
buf[2] = static_cast<char>((value >> 40) & 0xff);
buf[3] = static_cast<char>((value >> 32) & 0xff);
buf[4] = static_cast<char>((value >> 24) & 0xff);
buf[5] = static_cast<char>((value >> 16) & 0xff);
buf[6] = static_cast<char>((value >> 8) & 0xff);
buf[7] = static_cast<char>(value & 0xff);
if constexpr (BYTE_ORDER == LITTLE_ENDIAN) {
value = __builtin_bswap64(value);
}
__builtin_memcpy(buf, &value, sizeof(value));
}

void PutFixed8(std::string *dst, uint8_t value) {
char buf[1];
buf[0] = static_cast<char>(value & 0xff);
dst->append(buf, 1);
EncodeFixed8(buf, value);
dst->append(buf, sizeof(buf));
}

void PutFixed16(std::string *dst, uint16_t value) {
Expand All @@ -159,7 +145,9 @@ void PutFixed64(std::string *dst, uint64_t value) {

void PutDouble(std::string *dst, double value) {
uint64_t u64 = 0;
memcpy(&u64, &value, sizeof(value));

__builtin_memcpy(&u64, &value, sizeof(value));

auto ptr = &u64;
if ((*ptr >> 63) == 1) {
// signed bit would be zero
Expand All @@ -168,6 +156,7 @@ void PutDouble(std::string *dst, double value) {
// signed bit would be one
*ptr |= 0x8000000000000000;
}

PutFixed64(dst, *ptr);
}

Expand Down Expand Up @@ -217,50 +206,40 @@ bool GetDouble(rocksdb::Slice *input, double *value) {
}

uint16_t DecodeFixed16(const char *ptr) {
if (BYTE_ORDER == BIG_ENDIAN) {
uint16_t value = 0;
memcpy(&value, ptr, sizeof(value));
return value;
} else {
return ((static_cast<uint16_t>(static_cast<uint8_t>(ptr[1]))) |
(static_cast<uint16_t>(static_cast<uint8_t>(ptr[0])) << 8));
}
uint16_t value = 0;

__builtin_memcpy(&value, ptr, sizeof(value));

return BYTE_ORDER == LITTLE_ENDIAN ? __builtin_bswap16(value) : value;
}

uint32_t DecodeFixed32(const char *ptr) {
if (BYTE_ORDER == BIG_ENDIAN) {
uint32_t value = 0;
memcpy(&value, ptr, sizeof(value));
return value;
} else {
return ((static_cast<uint32_t>(static_cast<uint8_t>(ptr[3]))) |
(static_cast<uint32_t>(static_cast<uint8_t>(ptr[2])) << 8) |
(static_cast<uint32_t>(static_cast<uint8_t>(ptr[1])) << 16) |
(static_cast<uint32_t>(static_cast<uint8_t>(ptr[0])) << 24));
}
uint32_t value = 0;

__builtin_memcpy(&value, ptr, sizeof(value));

return BYTE_ORDER == LITTLE_ENDIAN ? __builtin_bswap32(value) : value;
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@PragmaTwice Is there a possibility to use if constexpr here with the condition? Or it wouldn't change anything?

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Yes, if constexpr is just a constraint in this case. Compiler will eliminate constant conditions.

}

uint64_t DecodeFixed64(const char *ptr) {
if (BYTE_ORDER == BIG_ENDIAN) {
uint64_t value = 0;
memcpy(&value, ptr, sizeof(value));
return value;
} else {
uint64_t hi = DecodeFixed32(ptr);
uint64_t lo = DecodeFixed32(ptr + 4);
return (hi << 32) | lo;
}
uint64_t value = 0;

__builtin_memcpy(&value, ptr, sizeof(value));

return BYTE_ORDER == LITTLE_ENDIAN ? __builtin_bswap64(value) : value;
}

double DecodeDouble(const char *ptr) {
uint64_t decoded = DecodeFixed64(ptr);

if ((decoded >> 63) == 0) {
decoded ^= 0xffffffffffffffff;
} else {
decoded &= 0x7fffffffffffffff;
}

double value = 0;
memcpy(&value, &decoded, sizeof(value));
__builtin_memcpy(&value, &decoded, sizeof(value));
return value;
}

Expand Down
2 changes: 0 additions & 2 deletions src/common/encoding.h
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,4 @@ uint64_t DecodeFixed64(const char *ptr);
double DecodeDouble(const char *ptr);
char *EncodeVarint32(char *dst, uint32_t v);
void PutVarint32(std::string *dst, uint32_t v);
const char *GetVarint32PtrFallback(const char *p, const char *limit, uint32_t *value);
const char *GetVarint32Ptr(const char *p, const char *limit, uint32_t *value);
bool GetVarint32(rocksdb::Slice *input, uint32_t *value);