Function xorDigest

app/redis-6.2.6/src/debug.c:79–90

Compute the sha1 of string at 's' with 'len' bytes long. * The SHA1 is then xored against the string pointed by digest. * Since xor is commutative, this operation is used in order to * "add" digests relative to unordered elements. * * So digest(a,b,c,d) will be the same of digest(b,a,c,d) */

 *
 * So digest(a,b,c,d) will be the same of digest(b,a,c,d) */
void xorDigest(unsigned char *digest, void *ptr, size_t len) {
    SHA1_CTX ctx;
    unsigned char hash[20], *s = ptr;
    int j;

    SHA1Init(&ctx);
    SHA1Update(&ctx,s,len);
    SHA1Final(hash,&ctx);

    for (j = 0; j < 20; j++)
        digest[j] ^= hash[j];
}

void xorStringObjectDigest(unsigned char *digest, robj *o) {
    o = getDecodedObject(o);