lavu: add av_fourcc_make_string() and av_fourcc2str()

doc/APIchanges

@@ -15,6 +15,10 @@ libavutil:     2015-08-28
 
 API changes, most recent first:
 
+2017-03-xx - xxxxxxx - lavu 55.52.100 - avutil.h
+  add av_fourcc_make_string() function and av_fourcc2str() macro to replace
+  av_get_codec_tag_string() from lavc.
+
 2017-03-xx - xxxxxxx - lavf 57.68.100 - avformat.h
   Deprecate that demuxers export the stream rotation angle in AVStream.metadata
   (via an entry named "rotate"). Use av_stream_get_side_data() with

libavutil/avutil.h

@@ -343,6 +343,20 @@ FILE *av_fopen_utf8(const char *path, const char *mode);
  */
 AVRational av_get_time_base_q(void);
 
+#define AV_FOURCC_MAX_STRING_SIZE 32
+
+#define av_fourcc2str(fourcc) av_fourcc_make_string((char[AV_FOURCC_MAX_STRING_SIZE]){0}, fourcc)
+
+/**
+ * Fill the provided buffer with a string containing a FourCC (four-character
+ * code) representation.
+ *
+ * @param buf    a buffer with size in bytes of at least AV_FOURCC_MAX_STRING_SIZE
+ * @param fourcc the fourcc to represent
+ * @return the buffer in input
+ */
+char *av_fourcc_make_string(char *buf, uint32_t fourcc);
+
 /**
  * @}
  * @}

libavutil/utils.c

@@ -121,6 +121,29 @@ unsigned av_int_list_length_for_size(unsigned elsize,
     return i;
 }
 
+char *av_fourcc_make_string(char *buf, uint32_t fourcc)
+{
+    int i;
+    char *orig_buf = buf;
+    size_t buf_size = AV_FOURCC_MAX_STRING_SIZE;
+
+    for (i = 0; i < 4; i++) {
+        const int c = fourcc & 0xff;
+        const int print_chr = (c >= '0' && c <= '9') ||
+                              (c >= 'a' && c <= 'z') ||
+                              (c >= 'A' && c <= 'Z') ||
+                              (c && strchr(". -_", c));
+        const int len = snprintf(buf, buf_size, print_chr ? "%c" : "[%d]", c);
+        if (len < 0)
+            break;
+        buf += len;
+        buf_size = buf_size > len ? buf_size - len : 0;
+        fourcc >>= 8;
+    }
+
+    return orig_buf;
+}
+
 AVRational av_get_time_base_q(void)
 {
     return (AVRational){1, AV_TIME_BASE};

libavutil/version.h

@@ -79,7 +79,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  55
-#define LIBAVUTIL_VERSION_MINOR  51
+#define LIBAVUTIL_VERSION_MINOR  52
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \