[FFmpeg-devel] [PATCH 1/2] avcodec/libx265: Don't use AVBPrint unnecessarily

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

This code uses the AVBPrint API for exactly one av_bprintf()
in a scenario in which a good upper bound for the needed
size of the buffer is available (with said upper bound being
much smaller than sizeof(AVBPrint)). So one can simply use
snprintf() instead. This also avoids the (always-false due to
the current size of the internal AVBPrint buffer) check for
whether the AVBPrint is complete.

Furthermore, the old code used AV_BPRINT_SIZE_AUTOMATIC
which implies that the AVBPrint buffer will never be
(re)allocated and yet it used av_bprint_finalize().
This has of course also been removed.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
This has actually been mentioned in my review of v3
of this patchset:
https://patchwork.ffmpeg.org/project/ffmpeg/patch/20230817214858.184010-13-jeebjp@gmail.com/

 libavcodec/libx265.c | 31 ++++++-------------------------
 1 file changed, 6 insertions(+), 25 deletions(-)

diff --git a/libavcodec/libx265.c b/libavcodec/libx265.c
index 70ec6d3539..d7620878b8 100644
--- a/libavcodec/libx265.c
+++ b/libavcodec/libx265.c
@@ -28,17 +28,14 @@
 #include <float.h>
 
 #include "libavutil/avassert.h"
-#include "libavutil/bprint.h"
 #include "libavutil/buffer.h"
 #include "libavutil/internal.h"
-#include "libavutil/common.h"
 #include "libavutil/mastering_display_metadata.h"
 #include "libavutil/opt.h"
 #include "libavutil/pixdesc.h"
 #include "avcodec.h"
 #include "codec_internal.h"
 #include "encode.h"
-#include "internal.h"
 #include "packet_internal.h"
 #include "atsc_a53.h"
 #include "sei.h"
@@ -182,13 +179,10 @@ static int handle_mdcv(const AVClass **avcl, const x265_api *api,
                        x265_param *params,
                        const AVMasteringDisplayMetadata *mdcv)
 {
-    int ret = AVERROR_BUG;
-    AVBPrint buf;
-    av_bprint_init(&buf, 0, AV_BPRINT_SIZE_AUTOMATIC);
+    char buf[10 /* # of PRId64s */ * 20 /* max strlen for %PRId64 */ + sizeof("G(,)B(,)R(,)WP(,)L(,)")];
 
     // G(%hu,%hu)B(%hu,%hu)R(%hu,%hu)WP(%hu,%hu)L(%u,%u)
-    av_bprintf(
-        &buf,
+    snprintf(buf, sizeof(buf),
         "G(%"PRId64",%"PRId64")B(%"PRId64",%"PRId64")R(%"PRId64",%"PRId64")"
         "WP(%"PRId64",%"PRId64")L(%"PRId64",%"PRId64")",
         av_rescale_q(1, mdcv->display_primaries[1][0], (AVRational){ 1, 50000 }),
@@ -202,28 +196,15 @@ static int handle_mdcv(const AVClass **avcl, const x265_api *api,
         av_rescale_q(1, mdcv->max_luminance,  (AVRational){ 1, 10000 }),
         av_rescale_q(1, mdcv->min_luminance,  (AVRational){ 1, 10000 }));
 
-    if (!av_bprint_is_complete(&buf)) {
-        av_log(avcl, AV_LOG_ERROR,
-          "MDCV string too long for its available space!\n");
-        ret = AVERROR(ENOMEM);
-        goto end;
-    }
-
-    if (api->param_parse(params, "master-display", buf.str) ==
+    if (api->param_parse(params, "master-display", buf) ==
             X265_PARAM_BAD_VALUE) {
         av_log(avcl, AV_LOG_ERROR,
                "Invalid value \"%s\" for param \"master-display\".\n",
-               buf.str);
-        ret = AVERROR(EINVAL);
-        goto end;
+               buf);
+        return AVERROR(EINVAL);
     }
 
-    ret = 0;
-
-end:
-    av_bprint_finalize(&buf, NULL);
-
-    return ret;
+    return 0;
 }
 
 static int handle_side_data(AVCodecContext *avctx, const x265_api *api,
-- 
2.40.1

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