sds.c: sdsAllocSize() function added.

src/sds.c

@@ -123,6 +123,12 @@ sds sdsRemoveFreeSpace(sds s) {
     return sh->buf;
 }
 
+size_t sdsAllocSize(sds s) {
+    struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
+
+    return sizeof(*sh)+sh->len+sh->free+1;
+}
+
 /* Increment the sds length and decrements the left free space at the
  * end of the string accordingly to 'incr'. Also set the null term
  * in the new end of the string.

src/sds.h

@@ -94,5 +94,7 @@ sds sdsmapchars(sds s, char *from, char *to, size_t setlen);
 /* Low level functions exposed to the user API */
 sds sdsMakeRoomFor(sds s, size_t addlen);
 void sdsIncrLen(sds s, int incr);
+sds sdsRemoveFreeSpace(sds s);
+size_t sdsAllocSize(sds s);
 
 #endif