avutil/log: added av_log_format_line2 which returns buffer length

The new function behaves the same as av_log_format_line, but also forwards
the return value from the underlying snprintf call. This will allow
callers to accurately determine the size requirements for the line buffer.

Signed-off-by: Andreas Weis <github@ghulbus-inc.de>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 10 insertions, 1 deletions

diff --git a/libavutil/log.c b/libavutil/log.c
index 45835195e1..0efba7ada4 100644
--- a/libavutil/log.c
+++ b/libavutil/log.c
@@ -284,10 +284,19 @@ static void format_line(void *avcl, int level, const char *fmt, va_list vl,
 void av_log_format_line(void *ptr, int level, const char *fmt, va_list vl,
                         char *line, int line_size, int *print_prefix)
 {
+    av_log_format_line2(ptr, level, fmt, vl, line, line_size, print_prefix);
+}
+
+int av_log_format_line2(void *ptr, int level, const char *fmt, va_list vl,
+                        char *line, int line_size, int *print_prefix)
+{
     AVBPrint part[4];
+    int ret;
+
     format_line(ptr, level, fmt, vl, part, print_prefix, NULL);
-    snprintf(line, line_size, "%s%s%s%s", part[0].str, part[1].str, part[2].str, part[3].str);
+    ret = snprintf(line, line_size, "%s%s%s%s", part[0].str, part[1].str, part[2].str, part[3].str);
     av_bprint_finalize(part+3, NULL);
+    return ret;
 }
 
 void av_log_default_callback(void* ptr, int level, const char* fmt, va_list vl)