return zl;
}
-/* Returns an offset to use for iterating with ziplistNext. */
-unsigned char *ziplistIndex(unsigned char *zl, unsigned int index) {
- unsigned char *p = zl+ZIPLIST_HEADER_SIZE;
- unsigned int i = 0;
- for (; i < index; i++) {
- if (*p == ZIP_END) break;
- p += zipRawEntryLength(p);
+/* Returns an offset to use for iterating with ziplistNext. When the given
+ * index is negative, the list is traversed back to front. When the list
+ * doesn't contain an element at the provided index, NULL is returned. */
+unsigned char *ziplistIndex(unsigned char *zl, int index) {
+ unsigned char *p;
+ zlentry entry;
+ if (index < 0) {
+ index = (-index)-1;
+ p = ZIPLIST_ENTRY_TAIL(zl);
+ if (p[0] != ZIP_END) {
+ entry = zipEntry(p);
+ while (entry.prevrawlen > 0 && index--) {
+ p -= entry.prevrawlen;
+ entry = zipEntry(p);
+ }
+ }
+ } else {
+ p = ZIPLIST_ENTRY_HEAD(zl);
+ while (p[0] != ZIP_END && index--) {
+ p += zipRawEntryLength(p);
+ }
}
- return p;
+ return p[0] == ZIP_END || index > 0 ? NULL : p;
}
/* Return pointer to next entry in ziplist. */
* Return 0 if 'p' points to the end of the zipmap, 1 otherwise. */
unsigned int ziplistGet(unsigned char *p, char **sstr, unsigned int *slen, long long *sval) {
zlentry entry;
- if (*p == ZIP_END) return 0;
+ if (p == NULL || p[0] == ZIP_END) return 0;
if (sstr) *sstr = NULL;
entry = zipEntry(p);
/* Delete a range of entries from the ziplist. */
unsigned char *ziplistDeleteRange(unsigned char *zl, unsigned int index, unsigned int num) {
unsigned char *p = ziplistIndex(zl,index);
- return __ziplistDelete(zl,p,num);
+ return p == NULL ? zl : __ziplistDelete(zl,p,num);
}
/* Delete a single entry from the ziplist, pointed to by *p.
printf("Pop tail: %s (length %ld)\n", s, sdslen(s));
ziplistRepr(zl);
+ printf("Get element at index 3:\n");
+ {
+ zl = createList();
+ p = ziplistIndex(zl, 3);
+ if (!ziplistGet(p, &entry, &elen, &value)) {
+ printf("ERROR: Could not access index 3\n");
+ return 1;
+ }
+ if (entry) {
+ fwrite(entry,elen,1,stdout);
+ printf("\n");
+ } else {
+ printf("%lld\n", value);
+ }
+ printf("\n");
+ }
+
+ printf("Get element at index 4 (out of range):\n");
+ {
+ zl = createList();
+ p = ziplistIndex(zl, 4);
+ if (p == NULL) {
+ printf("No entry\n");
+ } else {
+ printf("ERROR: Out of range index should return NULL, returned offset: %ld\n", p-zl);
+ return 1;
+ }
+ printf("\n");
+ }
+
+ printf("Get element at index -1 (last element):\n");
+ {
+ zl = createList();
+ p = ziplistIndex(zl, -1);
+ if (!ziplistGet(p, &entry, &elen, &value)) {
+ printf("ERROR: Could not access index -1\n");
+ return 1;
+ }
+ if (entry) {
+ fwrite(entry,elen,1,stdout);
+ printf("\n");
+ } else {
+ printf("%lld\n", value);
+ }
+ printf("\n");
+ }
+
+ printf("Get element at index -4 (first element):\n");
+ {
+ zl = createList();
+ p = ziplistIndex(zl, -4);
+ if (!ziplistGet(p, &entry, &elen, &value)) {
+ printf("ERROR: Could not access index -4\n");
+ return 1;
+ }
+ if (entry) {
+ fwrite(entry,elen,1,stdout);
+ printf("\n");
+ } else {
+ printf("%lld\n", value);
+ }
+ printf("\n");
+ }
+
+ printf("Get element at index -5 (reverse out of range):\n");
+ {
+ zl = createList();
+ p = ziplistIndex(zl, -5);
+ if (p == NULL) {
+ printf("No entry\n");
+ } else {
+ printf("ERROR: Out of range index should return NULL, returned offset: %ld\n", p-zl);
+ return 1;
+ }
+ printf("\n");
+ }
+
printf("Iterate list from 0 to end:\n");
{
zl = createList();