Fix sdsAllocSize for SDS_TYPE_5

sdsalloc returns sds's length for SDS_TYPE_5. It's not correct for
SDS_TYPE_5.

This patch makes sdsAllocSize call zmalloc_size for
SDS_TYPE_5. sdsalloc is a lower level function that continues to
return length for SDS_TYPE_5.

Signed-off-by: Vadym Khoptynets <vadymkh@amazon.com>

src/sds.c

@@ -39,6 +39,7 @@
 #include "sds.h"
 #include "sdsalloc.h"
 #include "util.h"
+#include "zmalloc.h"
 
 const char *SDS_NOINIT = "SDS_NOINIT";
 
@@ -178,13 +179,7 @@ sds sdsdup(const sds s) {
 /* Free an sds string. No operation is performed if 's' is NULL. */
 void sdsfree(sds s) {
     if (s == NULL) return;
-
-    /* SDS_TYPE_5 header doesn't contain the size of the allocation */
-    if ((s[-1] & SDS_TYPE_MASK) == SDS_TYPE_5) {
-        s_free(sdsAllocPtr(s));
-    } else {
-        s_free_with_size(sdsAllocPtr(s), sdsAllocSize(s));
-    }
+    s_free_with_size(sdsAllocPtr(s), sdsAllocSize(s));
 }
 
 /* Set the sds string length to the length as obtained with strlen(), so
@@ -337,7 +332,7 @@ sds sdsResize(sds s, size_t size, int would_regrow) {
      * type. */
     int use_realloc = (oldtype==type || (type < oldtype && type > SDS_TYPE_8));
     size_t newlen = use_realloc ? oldhdrlen+size+1 : hdrlen+size+1;
-    size_t usable = sdsalloc(s);
+    size_t usable = sdsAllocSize(s);
 
     if (use_realloc) {
         int alloc_already_optimal = 0;
@@ -346,18 +341,18 @@ sds sdsResize(sds s, size_t size, int would_regrow) {
              * We aim to avoid calling realloc() when using Jemalloc if there is no
              * change in the allocation size, as it incurs a cost even if the
              * allocation size stays the same. */
-            alloc_already_optimal = (je_nallocx(newlen, 0) == zmalloc_size(sh));
+            alloc_already_optimal = (je_nallocx(newlen, 0) == usable);
         #endif
         if (!alloc_already_optimal) {
             newsh = s_realloc_usable(sh, newlen, &usable);
             if (newsh == NULL) return NULL;
-            usable = usable - oldhdrlen - 1;
             s = (char*)newsh+oldhdrlen;
         }
+        usable -= (oldhdrlen + 1);
     } else {
         newsh = s_malloc_usable(newlen, &usable);
         if (newsh == NULL) return NULL;
-        usable = usable - hdrlen - 1;
+        usable -= (hdrlen + 1);
         memcpy((char*)newsh+hdrlen, s, len);
         s_free(sh);
         s = (char*)newsh+hdrlen;
@@ -377,8 +372,13 @@ sds sdsResize(sds s, size_t size, int would_regrow) {
  * 4) The implicit null term.
  */
 size_t sdsAllocSize(sds s) {
-    size_t alloc = sdsalloc(s);
-    return sdsHdrSize(s[-1])+alloc+1;
+    char header = s[-1];
+    /* SDS_TYPE_5 header doesn't contain the size of the allocation */
+    if ((header & SDS_TYPE_MASK) == SDS_TYPE_5) {
+        return zmalloc_size(sdsAllocPtr(s));
+    } else {
+        return sdsHdrSize(header) + sdsalloc(s) + 1;
+    }
 }
 
 /* Return the pointer of the actual SDS allocation (normally SDS strings