DEBUG DIGEST refactoring: extract function to digest a value.

src/debug.c

@@ -74,7 +74,7 @@ void xorDigest(unsigned char *digest, void *ptr, size_t len) {
         digest[j] ^= hash[j];
 }
 
-void xorObjectDigest(unsigned char *digest, robj *o) {
+void xorStringObjectDigest(unsigned char *digest, robj *o) {
     o = getDecodedObject(o);
     xorDigest(digest,o->ptr,sdslen(o->ptr));
     decrRefCount(o);
@@ -104,66 +104,35 @@ void mixDigest(unsigned char *digest, void *ptr, size_t len) {
     SHA1Final(digest,&ctx);
 }
 
-void mixObjectDigest(unsigned char *digest, robj *o) {
+void mixStringObjectDigest(unsigned char *digest, robj *o) {
     o = getDecodedObject(o);
     mixDigest(digest,o->ptr,sdslen(o->ptr));
     decrRefCount(o);
 }
 
-/* Compute the dataset digest. Since keys, sets elements, hashes elements
- * are not ordered, we use a trick: every aggregate digest is the xor
- * of the digests of their elements. This way the order will not change
- * the result. For list instead we use a feedback entering the output digest
- * as input in order to ensure that a different ordered list will result in
- * a different digest. */
-void computeDatasetDigest(unsigned char *final) {
-    unsigned char digest[20];
-    char buf[128];
-    dictIterator *di = NULL;
-    dictEntry *de;
-    int j;
-    uint32_t aux;
-
-    memset(final,0,20); /* Start with a clean result */
-
-    for (j = 0; j < server.dbnum; j++) {
-        redisDb *db = server.db+j;
-
-        if (dictSize(db->dict) == 0) continue;
-        di = dictGetSafeIterator(db->dict);
-
-        /* hash the DB id, so the same dataset moved in a different
-         * DB will lead to a different digest */
-        aux = htonl(j);
-        mixDigest(final,&aux,sizeof(aux));
-
-        /* Iterate this DB writing every entry */
-        while((de = dictNext(di)) != NULL) {
-            sds key;
-            robj *keyobj, *o;
-            long long expiretime;
-
-            memset(digest,0,20); /* This key-val digest */
-            key = dictGetKey(de);
-            keyobj = createStringObject(key,sdslen(key));
-
-            mixDigest(digest,key,sdslen(key));
-
-            o = dictGetVal(de);
-
-            aux = htonl(o->type);
+/* This function computes the digest of a data structure stored in the
+ * object 'o'. It is the core of the DEBUG DIGEST command: when taking the
+ * digest of a whole dataset, we take the digest of the key and the value
+ * pair, and xor all those together.
+ *
+ * Note that this function does not reset the initial 'digest' passed, it
+ * will continue mixing this object digest to anything that was already
+ * present. */
+void xorObjectDigest(redisDb *db, robj *keyobj, unsigned char *digest, robj *o) {
+    uint32_t aux = htonl(o->type);
     mixDigest(digest,&aux,sizeof(aux));
-            expiretime = getExpire(db,keyobj);
+    long long expiretime = getExpire(db,keyobj);
+    char buf[128];
 
     /* Save the key and associated value */
     if (o->type == OBJ_STRING) {
-                mixObjectDigest(digest,o);
+        mixStringObjectDigest(digest,o);
     } else if (o->type == OBJ_LIST) {
         listTypeIterator *li = listTypeInitIterator(o,0,LIST_TAIL);
         listTypeEntry entry;
         while(listTypeNext(li,&entry)) {
             robj *eleobj = listTypeGet(&entry);
-                    mixObjectDigest(digest,eleobj);
+            mixStringObjectDigest(digest,eleobj);
             decrRefCount(eleobj);
         }
         listTypeReleaseIterator(li);
@@ -278,6 +247,48 @@ void computeDatasetDigest(unsigned char *final) {
     }
     /* If the key has an expire, add it to the mix */
     if (expiretime != -1) xorDigest(digest,"!!expire!!",10);
+}
+
+/* Compute the dataset digest. Since keys, sets elements, hashes elements
+ * are not ordered, we use a trick: every aggregate digest is the xor
+ * of the digests of their elements. This way the order will not change
+ * the result. For list instead we use a feedback entering the output digest
+ * as input in order to ensure that a different ordered list will result in
+ * a different digest. */
+void computeDatasetDigest(unsigned char *final) {
+    unsigned char digest[20];
+    dictIterator *di = NULL;
+    dictEntry *de;
+    int j;
+    uint32_t aux;
+
+    memset(final,0,20); /* Start with a clean result */
+
+    for (j = 0; j < server.dbnum; j++) {
+        redisDb *db = server.db+j;
+
+        if (dictSize(db->dict) == 0) continue;
+        di = dictGetSafeIterator(db->dict);
+
+        /* hash the DB id, so the same dataset moved in a different
+         * DB will lead to a different digest */
+        aux = htonl(j);
+        mixDigest(final,&aux,sizeof(aux));
+
+        /* Iterate this DB writing every entry */
+        while((de = dictNext(di)) != NULL) {
+            sds key;
+            robj *keyobj, *o;
+
+            memset(digest,0,20); /* This key-val digest */
+            key = dictGetKey(de);
+            keyobj = createStringObject(key,sdslen(key));
+
+            mixDigest(digest,key,sdslen(key));
+
+            o = dictGetVal(de);
+            xorObjectDigest(db,keyobj,digest,o);
+
             /* We can finally xor the key-val digest to the final digest */
             xorDigest(final,digest,20);
             decrRefCount(keyobj);