#include "crc.h"
uint64_t
crc_reverse_init(crcInfoPtr crc)
{
cc_dispatch_once(&crc->table_init, crc, gen_std_crc_table);
return crc->descriptor->def.parms.initial_value;
}
static inline uint8_t
crc_table_value8(uint8_t *table, uint8_t p, uint8_t crc) {
return table[(crc ^ p) & 0xff] ^ (crc >> 8);
}
static inline uint16_t
crc_table_value16(uint16_t *table, uint8_t p, uint16_t crc) {
return table[(crc ^ p) & 0xff] ^ (crc >> 8);
}
static inline uint32_t
crc_table_value32(uint32_t *table, uint8_t p, uint32_t crc) {
return table[(crc ^ p) & 0xff] ^ (crc >> 8);
}
static inline uint64_t
crc_table_value64(uint64_t *table, uint8_t p, uint64_t crc) {
return table[(crc ^ p) & 0xffLL] ^ (crc >> 8);
}
uint64_t
crc_reverse_update(crcInfoPtr crc, uint8_t *p, size_t len, uint64_t current)
{
while (len--) {
switch (crc->descriptor->def.parms.width) {
case 1: current = crc_table_value8(crc->table.bytes, *p, (uint8_t) current); break;
case 2: current = crc_table_value16(crc->table.b16, *p, (uint16_t) current); break;
case 4: current = crc_table_value32(crc->table.b32, *p, (uint32_t) current); break;
case 8: current = crc_table_value64(crc->table.b64, *p, current); break;
}
p++;
}
return current;
}
uint64_t
crc_reverse_final(crcInfoPtr crc, uint64_t current)
{
return current ^ crc->descriptor->def.parms.final_xor;
}
uint64_t
crc_reverse_oneshot(crcInfoPtr crc, uint8_t *p, size_t len)
{
uint64_t current = crc_reverse_init(crc);
current = crc_reverse_update(crc, p, len, current);
return crc_reverse_final(crc, current);
}