lavf/avio: add avio_vprintf()

This new function makes it possible to use avio_printf() functionality from
a function taking a variable list of arguments.

Signed-off-by: Marton Balint <cus@passwd.hu>

doc/APIchanges

@@ -14,6 +14,10 @@ libavutil:     2021-04-27
 
 API changes, most recent first:
 
+2022-06-12 - xxxxxxxxxx - lavf 59.25.100 - avio.h
+  Add avio_vprintf(), similar to avio_printf() but allow to use it
+  from within a function taking a variable argument list as input.
+
 2022-05-23 - xxxxxxxxx - lavu 57.25.100 - avutil.h
   Deprecate av_fopen_utf8() without replacement.
 

libavformat/avio.h

@@ -519,6 +519,12 @@ int64_t avio_size(AVIOContext *s);
  */
 int avio_feof(AVIOContext *s);
 
+/**
+ * Writes a formatted string to the context taking a va_list.
+ * @return number of bytes written, < 0 on error.
+ */
+int avio_vprintf(AVIOContext *s, const char *fmt, va_list ap);
+
 /**
  * Writes a formatted string to the context.
  * @return number of bytes written, < 0 on error.

libavformat/aviobuf.c

@@ -1292,15 +1292,12 @@ int avio_closep(AVIOContext **s)
     return ret;
 }
 
-int avio_printf(AVIOContext *s, const char *fmt, ...)
+int avio_vprintf(AVIOContext *s, const char *fmt, va_list ap)
 {
-    va_list ap;
     AVBPrint bp;
 
     av_bprint_init(&bp, 0, INT_MAX);
-    va_start(ap, fmt);
     av_vbprintf(&bp, fmt, ap);
-    va_end(ap);
     if (!av_bprint_is_complete(&bp)) {
         av_bprint_finalize(&bp, NULL);
         s->error = AVERROR(ENOMEM);
@@ -1311,6 +1308,18 @@ int avio_printf(AVIOContext *s, const char *fmt, ...)
     return bp.len;
 }
 
+int avio_printf(AVIOContext *s, const char *fmt, ...)
+{
+    va_list ap;
+    int ret;
+
+    va_start(ap, fmt);
+    ret = avio_vprintf(s, fmt, ap);
+    va_end(ap);
+
+    return ret;
+}
+
 void avio_print_string_array(AVIOContext *s, const char *strings[])
 {
     for(; *strings; strings++)

libavformat/version.h

@@ -31,7 +31,7 @@
 
 #include "version_major.h"
 
-#define LIBAVFORMAT_VERSION_MINOR  24
+#define LIBAVFORMAT_VERSION_MINOR  25
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \