expose extra functionality from ziplist.c

ziplist.c

@@ -432,6 +432,12 @@ unsigned char *ziplistNext(unsigned char *p) {
     return (p[0] == ZIP_END) ? NULL : p+zipRawEntryLength(p);
 }
 
+/* Return pointer to previous entry in ziplist. */
+unsigned char *ziplistPrev(unsigned char *p) {
+    zlentry entry = zipEntry(p);
+    return (entry.prevrawlen == 0) ? NULL : p-entry.prevrawlen;
+}
+
 /* Get entry pointer to by 'p' and store in either 'e' or 'v' depending
  * on the encoding of the entry. 'e' is always set to NULL to be able
  * to find out whether the string pointer or the integer value was set.
@@ -455,10 +461,9 @@ unsigned int ziplistGet(unsigned char *p, char **sstr, unsigned int *slen, long
     return 1;
 }
 
-/* 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 p == NULL ? zl : __ziplistDelete(zl,p,num);
+/* Insert an entry at "p". */
+unsigned char *ziplistInsert(unsigned char *zl, unsigned char *p, char *s, unsigned int slen) {
+    return __ziplistInsert(zl,p,s,slen);
 }
 
 /* Delete a single entry from the ziplist, pointed to by *p.
@@ -474,6 +479,12 @@ unsigned char *ziplistDelete(unsigned char *zl, unsigned char **p) {
     return zl;
 }
 
+/* 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 (p == NULL) ? zl : __ziplistDelete(zl,p,num);
+}
+
 /* Compare entry pointer to by 'p' with 'entry'. Return 1 if equal. */
 unsigned int ziplistCompare(unsigned char *p, char *sstr, unsigned int slen) {
     zlentry entry;

ziplist.h

@@ -6,8 +6,10 @@ unsigned char *ziplistPush(unsigned char *zl, char *s, unsigned int slen, int wh
 unsigned char *ziplistPop(unsigned char *zl, sds *target, int where);
 unsigned char *ziplistIndex(unsigned char *zl, int index);
 unsigned char *ziplistNext(unsigned char *p);
+unsigned char *ziplistPrev(unsigned char *p);
 unsigned int ziplistGet(unsigned char *p, char **sstr, unsigned int *slen, long long *sval);
 unsigned char *ziplistDelete(unsigned char *zl, unsigned char **p);
+unsigned char *ziplistInsert(unsigned char *zl, unsigned char *p, char *s, unsigned int slen);
 unsigned char *ziplistDeleteRange(unsigned char *zl, unsigned int index, unsigned int num);
 unsigned int ziplistCompare(unsigned char *p, char *entry, unsigned int elen);
 unsigned int ziplistLen(unsigned char *zl);