use more efficient code to produce non-codec-capability list (bug #3960)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@5421 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/rtp.c b/rtp.c
index d4989db..41f37b3 100755 (executable)
--- a/rtp.c
+++ b/rtp.c
@@ -853,21 +853,35 @@ char* ast_rtp_lookup_mime_subtype(const int isAstFormat, const int code) {
 char *ast_rtp_lookup_mime_multiple(char *buf, int size, const int capability, const int isAstFormat)
 {
        int format;
+       unsigned len;
+       char *end = buf;
+       char *start = buf;
 
        if (!buf || !size)
                return NULL;
 
-       snprintf(buf, size, "0x%x (", capability);
+       snprintf(end, size, "0x%x (", capability);
+
+       len = strlen(end);
+       end += len;
+       size -= len;
+       start = end;
 
        for (format = 1; format < AST_RTP_MAX; format <<= 1) {
                if (capability & format) {
                        const char *name = ast_rtp_lookup_mime_subtype(isAstFormat, format);
-                       snprintf(buf + strlen(buf), size - strlen(buf), "%s|", name);
+                       snprintf(end, size, "%s|", name);
+                       len = strlen(end);
+                       end += len;
+                       size -= len;
                }
        }
-       if (!ast_strlen_zero(buf))
-               buf[strlen(buf)] = ')';
 
+       if (start == end)
+               snprintf(start, size, "nothing)"); 
+       else if (size > 1)
+               *(end -1) = ')';
+       
        return buf;
 }