notwa/crc32
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rewrite out some weirdness

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This commit is contained in:
Connor Olding 2017-04-24 18:11:42 +00:00
parent c3921c69e4
commit accb4a3e26
1 changed files with 9 additions and 11 deletions
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20
crc32.c
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@ -4,7 +4,7 @@ static inline uint32_t
crc_reflect(uint32_t input)
{
uint32_t reflected = 0;
for (int i = 0; i < 4 * 8; i++) {
for (int i = 0; i < 32; i++) {
reflected <<= 1;
reflected |= input & 1;
input >>= 1;
@ -18,7 +18,7 @@ crc_be_fill_table(uint32_t *table, uint32_t polynomial)
const uint32_t lsb = 1 << 31;
uint32_t poly = polynomial;
for (int c = 0; c < CRC_TABLE_SIZE; c++, table++) {
for (int c = 0; c < CRC_TABLE_SIZE; c++) {
uint32_t v = c << 24;
for (int i = 0; i < 8; i++) {
if (v & lsb) {
@ -28,7 +28,7 @@ crc_be_fill_table(uint32_t *table, uint32_t polynomial)
v <<= 1;
}
}
*table = v;
*table++ = v;
}
}
@ -38,7 +38,7 @@ crc_le_fill_table(uint32_t *table, uint32_t polynomial)
const uint32_t lsb = 1;
uint32_t poly = crc_reflect(polynomial);
for (int c = 0; c < CRC_TABLE_SIZE; c++, table++) {
for (int c = 0; c < CRC_TABLE_SIZE; c++) {
uint32_t v = c;
for (int i = 0; i < 8; i++) {
if (v & lsb) {
@ -48,22 +48,20 @@ crc_le_fill_table(uint32_t *table, uint32_t polynomial)
v >>= 1;
}
}
*table = v;
*table++ = v;
}
}
static inline void
crc_be_cycle(uint32_t *table, uint32_t *remainder, uint8_t c)
{
const uint8_t i = ((*remainder) >> 24) ^ c;
const uint32_t next = table[i];
*remainder = ((*remainder) << 8) ^ next;
const uint8_t i = (*remainder >> 24) ^ c;
*remainder = (*remainder << 8) ^ table[i];
}
static inline void
crc_le_cycle(uint32_t *table, uint32_t *remainder, uint8_t c)
{
const uint8_t i = (*remainder) ^ c;
const uint32_t next = table[i];
*remainder = ((*remainder) >> 8) ^ next;
const uint8_t i = (*remainder & 0xFF) ^ c;
*remainder = (*remainder >> 8) ^ table[i];
}