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improve buf_cmp and buf_cmp_mask helpers 

Rewrite buf_cmp to use memcpy for bulk of comparison.  Add static
helper to perform comparison of trailing byte, which uses another
static helper to perform a maksed comparison.  The masked comparison
helper is used by the buf_cmp_mask to simplify its loop.
Improve types to use void *, unsigned, and return bool.
This commit is contained in:
Zachary T Welch 2009-11-14 10:27:34 -08:00
parent d50caa97d1
commit e4ee891759
2 changed files with 43 additions and 42 deletions
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79
src/helper/binarybuffer.c
View File

@ -65,52 +65,53 @@ uint8_t* buf_cpy(const uint8_t *from, uint8_t *to, int size)
return to;
}
int buf_cmp(const uint8_t *buf1, const uint8_t *buf2, int size)
static bool buf_cmp_masked(uint8_t a, uint8_t b, uint8_t m)
{
if (!buf1 || !buf2)
return 1;
for (unsigned i = 0, num_bytes = CEIL(size, 8); i < num_bytes; i++)
{
/* last byte */
/* mask out bits that don't really belong to the buffer if size isn't a multiple of 8 bits */
if ((size % 8) && (i == num_bytes -1))
{
if ((buf1[i] & ((1 << (size % 8)) - 1)) != (buf2[i] & ((1 << (size % 8)) - 1)))
return 1;
}
else
{
if (buf1[i] != buf2[i])
return 1;
}
}
return 0;
return (a & m) != (b & m);
}
static bool buf_cmp_trailing(uint8_t a, uint8_t b, uint8_t m, unsigned trailing)
{
uint8_t mask = (1 << trailing) - 1;
return buf_cmp_masked(a, b, mask & m);
}
int buf_cmp_mask(const uint8_t *buf1, const uint8_t *buf2, const uint8_t *mask, int size)
bool buf_cmp(const void *_buf1, const void *_buf2, unsigned size)
{
for (unsigned i = 0, num_bytes = CEIL(size, 8); i < num_bytes; i++)
{
/* last byte */
/* mask out bits that don't really belong to the buffer if size isn't a multiple of 8 bits */
if ((size % 8) && (i == num_bytes -1))
{
if ((buf1[i] & ((1 << (size % 8)) - 1) & mask[i]) !=
(buf2[i] & ((1 << (size % 8)) - 1) & mask[i]))
return 1;
}
else
{
if ((buf1[i] & mask[i]) != (buf2[i] & mask[i]))
return 1;
}
}
if (!_buf1 || !_buf2)
return _buf1 != _buf2;
return 0;
unsigned last = size / 8;
if (memcmp(_buf1, _buf2, last) != 0)
return false;
unsigned trailing = size % 8;
if (!trailing)
return false;
const uint8_t *buf1 = _buf1, *buf2 = _buf2;
return buf_cmp_trailing(buf1[last], buf2[last], 0xff, trailing);
}
bool buf_cmp_mask(const void *_buf1, const void *_buf2,
const void *_mask, unsigned size)
{
if (!_buf1 || !_buf2)
return _buf1 != _buf2 || _buf1 != _mask;
const uint8_t *buf1 = _buf1, *buf2 = _buf2, *mask = _mask;
unsigned last = size / 8;
for (unsigned i = 0; i < last; i++)
{
if (buf_cmp_masked(buf1[i], buf2[i], mask[i]))
return true;
}
unsigned trailing = size % 8;
if (!trailing)
return false;
return buf_cmp_trailing(buf1[last], buf2[last], mask[last], trailing);
}
uint8_t* buf_set_ones(uint8_t *buf, int count)
{
for (unsigned i = 0, num_bytes = CEIL(count, 8); i < num_bytes; i++)

6
src/helper/binarybuffer.h
View File

@ -70,9 +70,9 @@ static inline uint32_t buf_get_u32(const uint8_t* buffer,
/// flip_u32 inverts the bit order inside a 32-bit word (31..0 -> 0..31)
uint32_t flip_u32(uint32_t value, unsigned int num);
int buf_cmp(const uint8_t *buf1, const uint8_t *buf2, int size);
int buf_cmp_mask(const uint8_t *buf1, const uint8_t *buf2,
const uint8_t *mask, int size);
bool buf_cmp(const void *buf1, const void *buf2, unsigned size);
bool buf_cmp_mask(const void *buf1, const void *buf2,
const void *mask, unsigned size);
uint8_t* buf_cpy(const uint8_t *from, uint8_t *to, int size);
uint8_t* buf_set_ones(uint8_t *buf, int count);