X-Git-Url: https://git.saurik.com/redis.git/blobdiff_plain/c03206fdf1dc0241d97204aba813c13b82f40d6e..a6dd455b09cb67e18799c0b2ed720d213608e13d:/ziplist.c

diff --git a/ziplist.c b/ziplist.c
index b29c630b..71d965a8 100644
--- a/ziplist.c
+++ b/ziplist.c
@@ -340,7 +340,7 @@ static unsigned char *__ziplistInsert(unsigned char *zl, unsigned char *p, char
     /* When the insert position is not equal to the tail, we need to
      * make sure that the next entry can hold this entry's length in
      * its prevlen field. */
-    nextdiff = p[0] != ZIP_END ? zipPrevLenByteDiff(p,reqlen) : 0;
+    nextdiff = (p[0] != ZIP_END) ? zipPrevLenByteDiff(p,reqlen) : 0;
 
     /* Store offset because a realloc may change the address of zl. */
     offset = p-zl;
@@ -424,12 +424,18 @@ unsigned char *ziplistIndex(unsigned char *zl, int index) {
             p += zipRawEntryLength(p);
         }
     }
-    return p[0] == ZIP_END || index > 0 ? NULL : p;
+    return (p[0] == ZIP_END || index > 0) ? NULL : p;
 }
 
 /* Return pointer to next entry in ziplist. */
 unsigned char *ziplistNext(unsigned char *p) {
-    return *p == ZIP_END ? p : p+zipRawEntryLength(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
@@ -455,31 +461,42 @@ 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.
  * Also update *p in place, to be able to iterate over the
  * ziplist, while deleting entries. */
-unsigned char *ziplistDelete(unsigned char *zl, unsigned char **p) {
+unsigned char *ziplistDelete(unsigned char *zl, unsigned char **p, int direction) {
     unsigned int offset = *p-zl;
     zl = __ziplistDelete(zl,*p,1);
 
     /* Store pointer to current element in p, because ziplistDelete will
-     * do a realloc which might result in a different "zl"-pointer. */
-    *p = zl+offset;
+     * do a realloc which might result in a different "zl"-pointer.
+     * When the delete direction is back to front, we might delete the last
+     * entry and end up with "p" pointing to ZIP_END, so check this. */
+    if (*(zl+offset) == ZIP_END && direction == ZIPLIST_HEAD) {
+        *p = ZIPLIST_ENTRY_TAIL(zl);
+    } else {
+        *p = zl+offset;
+    }
     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;
     char sencoding;
     long long val, sval;
-    if (*p == ZIP_END) return 0;
+    if (p[0] == ZIP_END) return 0;
 
     entry = zipEntry(p);
     if (entry.encoding == ZIP_ENC_RAW) {
@@ -744,6 +761,40 @@ int main(int argc, char **argv) {
         printf("\n");
     }
 
+    printf("Iterate from back to front:\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, -1);
+        while (ziplistGet(p, &entry, &elen, &value)) {
+            printf("Entry: ");
+            if (entry) {
+                fwrite(entry,elen,1,stdout);
+            } else {
+                printf("%lld", value);
+            }
+            p = ziplistPrev(p);
+            printf("\n");
+        }
+        printf("\n");
+    }
+
+    printf("Iterate from back to front, deleting all items:\n");
+    {
+        zl = createList();
+        p = ziplistIndex(zl, -1);
+        while (ziplistGet(p, &entry, &elen, &value)) {
+            printf("Entry: ");
+            if (entry) {
+                fwrite(entry,elen,1,stdout);
+            } else {
+                printf("%lld", value);
+            }
+            zl = ziplistDelete(zl, &p, ZIPLIST_HEAD);
+            printf("\n");
+        }
+        printf("\n");
+    }
+
     printf("Delete inclusive range 0,0:\n");
     {
         zl = createList();
@@ -786,7 +837,7 @@ int main(int argc, char **argv) {
         while (ziplistGet(p, &entry, &elen, &value)) {
             if (entry && strncmp("foo", entry, elen) == 0) {
                 printf("Delete foo\n");
-                zl = ziplistDelete(zl, &p);
+                zl = ziplistDelete(zl, &p, ZIPLIST_TAIL);
             } else {
                 printf("Entry: ");
                 if (entry) {