r2903: a considerably more efficient (both in terms of CPU and memory)

convert_string_talloc() implementation.

the previous version used a minimum of 512 bytes, which is way above the average
of what is needed.
(This used to be commit abcd841a8530ba3273d56c9001ea277611507be3)

diff --git a/source4/lib/charcnv.c b/source4/lib/charcnv.c
index 392ad3cc72761062bf944b7ceb24f77fa887e518..e5331b973ee25e75cae8d5ab49f468c418cccaff 100644 (file)
--- a/source4/lib/charcnv.c
+++ b/source4/lib/charcnv.c
@@ -168,7 +168,7 @@ ssize_t convert_string(charset_t from, charset_t to,
  **/
 
 ssize_t convert_string_talloc(TALLOC_CTX *ctx, charset_t from, charset_t to,
-                               void const *src, size_t srclen, void **dest)
+                             void const *src, size_t srclen, void **dest)
 {
        size_t i_len, o_len, destlen;
        size_t retval;
@@ -189,20 +189,25 @@ ssize_t convert_string_talloc(TALLOC_CTX *ctx, charset_t from, charset_t to,
                return -1;
        }
 
-       destlen = MAX(srclen, 512);
+       /* it is _very_ rare that a conversion increases the size by
+          more than 3x */
+       destlen = srclen;
        outbuf = NULL;
 convert:
-       destlen = destlen * 2;
+       destlen = 2 + (destlen*3);
        ob = (char *)talloc_realloc(ctx, outbuf, destlen);
        if (!ob) {
                DEBUG(0, ("convert_string_talloc: realloc failed!\n"));
                talloc_free(outbuf);
                return (size_t)-1;
-       }
-       else
+       } else {
                outbuf = ob;
+       }
+
+       /* we give iconv 2 less bytes to allow us to terminate at the
+          end */
        i_len = srclen;
-       o_len = destlen;
+       o_len = destlen-2;
        retval = smb_iconv(descriptor,
                           &inbuf, &i_len,
                           &outbuf, &o_len);
@@ -220,20 +225,15 @@ convert:
                }
                DEBUG(0,("Conversion error: %s(%s)\n",reason,inbuf));
                talloc_free(ob);
-               /* smb_panic(reason); */
                return (size_t)-1;
        }
        
-       destlen = destlen - o_len;
-       /* +2 for mandetory null termination, UTF8 or UTF16 */
-       *dest = (char *)talloc_realloc(ctx, ob, destlen+2);
-       if (!*dest) {
-               DEBUG(0, ("convert_string_talloc: out of memory!\n"));
-               talloc_free(ob);
-               return (size_t)-1;
-       }
-       ((char *)*dest)[destlen] = '\0';
-       ((char *)*dest)[destlen+1] = '\0';
+       destlen = (destlen-2) - o_len;
+
+       /* guarantee null termination in all charsets */
+       SSVAL(ob, destlen, 0);
+
+       *dest = ob;
 
        return destlen;
 }