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Improve the pb_decode_varint implementations.

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Results for ARM: -4% execution time, +1% code size
This commit is contained in:
Petteri Aimonen
2013-02-06 22:11:02 +02:00
parent d23939d688
commit 4f379364b3
1 changed files with 40 additions and 18 deletions
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58
pb_decode.c
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@@ -107,37 +107,59 @@ pb_istream_t pb_istream_from_buffer(uint8_t *buf, size_t bufsize)
static bool checkreturn pb_decode_varint32(pb_istream_t *stream, uint32_t *dest)
{
uint8_t byte;
int bitpos = 0;
*dest = 0;
uint32_t result;
while (bitpos < 32 && pb_read(stream, &byte, 1))
if (!pb_read(stream, &byte, 1))
return false;
if (!(byte & 0x80))
{
*dest |= (uint32_t)(byte & 0x7F) << bitpos;
bitpos += 7;
if (!(byte & 0x80))
return true;
/* Quick case, 1 byte value */
result = byte;
}
PB_RETURN_ERROR(stream, "varint overflow");
else
{
/* Multibyte case */
int bitpos = 7;
result = byte & 0x7F;
do
{
if (bitpos >= 32)
PB_RETURN_ERROR(stream, "varint overflow");
if (!pb_read(stream, &byte, 1))
return false;
result |= (uint32_t)(byte & 0x7F) << bitpos;
bitpos += 7;
} while (byte & 0x80);
}
*dest = result;
return true;
}
bool checkreturn pb_decode_varint(pb_istream_t *stream, uint64_t *dest)
{
uint8_t byte;
int bitpos = 0;
*dest = 0;
uint64_t result = 0;
while (bitpos < 64 && pb_read(stream, &byte, 1))
do
{
*dest |= (uint64_t)(byte & 0x7F) << bitpos;
bitpos += 7;
if (bitpos >= 64)
PB_RETURN_ERROR(stream, "varint overflow");
if (!(byte & 0x80))
return true;
}
if (!pb_read(stream, &byte, 1))
return false;
result |= (uint64_t)(byte & 0x7F) << bitpos;
bitpos += 7;
} while (byte & 0x80);
PB_RETURN_ERROR(stream, "varint overflow");
*dest = result;
return true;
}
bool checkreturn pb_skip_varint(pb_istream_t *stream)