[FFmpeg-devel] [PATCH 1/2] lavu: add syntax for loading AV_OPT_TYPE_BINARY from files

[Niklas Haas]

From: Niklas Haas <git at haasn.dev>

I arbitrarily decided to use the syntax 'opt=@filename' to match e.g.
`curl -Ffield=@filename`, and also because @ is not a valid hex
character, nor does it conflict with any other common shell or ffmpeg
syntax.

This is arguably somewhat clunky because it does not round-trip with
av_opt_get - you will get back a hex interpretation of the loaded file,
rather than the filename it was loaded from. It also implies a (perhaps
unnecessary) memcpy from mapped file memory into a allocated memory.
This is unfortunately necessary because there's no way for us to know
whether av_free or av_file_unmap is needed to clean up previous option
values.

The motivating use case was the introduction of several new binary
options for vf_libplacebo, but other filters that currently rely on
manual file-path loading could benefit from it as well.
---
 doc/APIchanges      |  4 ++++
 libavutil/opt.c     | 53 ++++++++++++++++++++++++++++++++++++++++++++-
 libavutil/opt.h     |  5 +++++
 libavutil/version.h |  2 +-
 4 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index ea402f6118..0400b10721 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -14,6 +14,10 @@ libavutil:     2021-04-27
 
 API changes, most recent first:
 
+2022-03-04 - xxxxxxxxxx - lavu 57.23.100 - opt.h
+  Add av_opt_set_filepath() to set a binary option from a file.
+  Support '@filename' syntax in av_opt_set() for binary options.
+
 2022-02-07 - xxxxxxxxxx - lavu 57.21.100 - fifo.h
   Deprecate AVFifoBuffer and the API around it, namely av_fifo_alloc(),
   av_fifo_alloc_array(), av_fifo_free(), av_fifo_freep(), av_fifo_reset(),
diff --git a/libavutil/opt.c b/libavutil/opt.c
index d951edca9d..151536d229 100644
--- a/libavutil/opt.c
+++ b/libavutil/opt.c
@@ -32,6 +32,7 @@
 #include "common.h"
 #include "dict.h"
 #include "eval.h"
+#include "file.h"
 #include "log.h"
 #include "parseutils.h"
 #include "pixdesc.h"
@@ -465,6 +466,33 @@ static int set_string_dict(void *obj, const AVOption *o, const char *val, uint8_
     return 0;
 }
 
+static int set_string_filepath(void *obj, const AVOption *o, const char *path, uint8_t **dst)
+{
+    int *lendst = (int *)(dst + 1);
+    uint8_t *bin;
+    size_t bin_len;
+    int err;
+
+    av_freep(dst);
+    *lendst = 0;
+
+    if (!path || !path[0])
+        return 0;
+
+    err = av_file_map(path, &bin, &bin_len, 0, obj);
+    if (err)
+        return err;
+
+    *dst = av_memdup(bin, bin_len);
+    av_file_unmap(bin, bin_len);
+
+    if (!*dst)
+        return AVERROR(ENOMEM);
+
+    *lendst = bin_len;
+    return 0;
+}
+
 int av_opt_set(void *obj, const char *name, const char *val, int search_flags)
 {
     int ret = 0;
@@ -492,7 +520,11 @@ int av_opt_set(void *obj, const char *name, const char *val, int search_flags)
     case AV_OPT_TYPE_STRING:
         return set_string(obj, o, val, dst);
     case AV_OPT_TYPE_BINARY:
-        return set_string_binary(obj, o, val, dst);
+        if (val && val[0] == '@') {
+            return set_string_filepath(obj, o, &val[1], dst);
+        } else {
+            return set_string_binary(obj, o, val, dst);
+        }
     case AV_OPT_TYPE_FLAGS:
     case AV_OPT_TYPE_INT:
     case AV_OPT_TYPE_INT64:
@@ -631,6 +663,25 @@ int av_opt_set_bin(void *obj, const char *name, const uint8_t *val, int len, int
     return 0;
 }
 
+int av_opt_set_filepath(void *obj, const char *name, const char *path, int search_flags)
+{
+    uint8_t *bin;
+    size_t bin_len;
+    int err;
+
+    if (!path || !path[0])
+        return av_opt_set_bin(obj, name, NULL, 0, search_flags);
+
+    err = av_file_map(path, &bin, &bin_len, 0, obj);
+    if (err)
+        return err;
+
+    err = av_opt_set_bin(obj, name, bin, bin_len, search_flags);
+    av_file_unmap(bin, bin_len);
+
+    return err;
+}
+
 int av_opt_set_image_size(void *obj, const char *name, int w, int h, int search_flags)
 {
     void *target_obj;
diff --git a/libavutil/opt.h b/libavutil/opt.h
index 2820435eec..97d7c69482 100644
--- a/libavutil/opt.h
+++ b/libavutil/opt.h
@@ -699,6 +699,11 @@ int av_opt_set_channel_layout(void *obj, const char *name, int64_t ch_layout, in
  * caller still owns val is and responsible for freeing it.
  */
 int av_opt_set_dict_val(void *obj, const char *name, const AVDictionary *val, int search_flags);
+/**
+ * @note This behaves like av_opt_set_bin() but loads the binary data from a
+ * file. May also return errors related to file I/O.
+ */
+int av_opt_set_filepath(void *obj, const char *name, const char *val, int search_flags);
 
 /**
  * Set a binary option to an integer list.
diff --git a/libavutil/version.h b/libavutil/version.h
index c7004601c8..6c5d90507c 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -79,7 +79,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  57
-#define LIBAVUTIL_VERSION_MINOR  22
+#define LIBAVUTIL_VERSION_MINOR  23
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
-- 
2.35.1