Add ziplistMerge()

This started out as #2158 by sunheehnus, but I kept rewriting it
until I could understand things more easily and get a few more
correctness guarantees out of the readability flow.

The original commit created and returned a new ziplist with the contents of
both input ziplists, but I prefer to grow one of the input ziplists
and destroy the other one.

So, instead of malloc+copy as in #2158, the merge now reallocs one of
the existing ziplists and copies the other ziplist into the new space.

Also added merge test cases to ziplistTest()

1 files changed, 1 insertions, 0 deletions

diff --git a/src/ziplist.h b/src/ziplist.h
index ef0e27140..e92b5e783 100644
--- a/src/ziplist.h
+++ b/src/ziplist.h
@@ -32,6 +32,7 @@
 #define ZIPLIST_TAIL 1
 
 unsigned char *ziplistNew(void);
+unsigned char *ziplistMerge(unsigned char **first, unsigned char **second);
 unsigned char *ziplistPush(unsigned char *zl, unsigned char *s, unsigned int slen, int where);
 unsigned char *ziplistIndex(unsigned char *zl, int index);
 unsigned char *ziplistNext(unsigned char *zl, unsigned char *p);