This series improves the following function:
libavformat/protocols.c: avio_enum_protocols()
There are really only 3 logical commits:
[1] Add const-correctness (fixes a compile-time warning)
{2} Refactoring (cleanup)
[3] Add functions to the API (use them too)
However, {2} is presented as a bunch of tiny little transformations
that are intended to aid comprehension; they can be squashed into
one commit as the maintainer sees fit (indeed, as shown below, the
squashed diff is already quite comprehensible):
{2} Refactoring
[2.0] Add more const-correctness
[2.1] Split declaration and initialization
[2.2] Convert recursion to iteration
[2.3] Move 'iterate' label
[2.4] Consolidate initialization of 'p'
[2.5] Add block curly braces to 'if' statement
[2.6] Move assignment to '*opaque'
[2.7] Indent code
[2.8] Make the 'else' logic explicit
[2.9] Reverse the conditional
[2.a] Move branch to bottom of function
[2.b] Convert the 'goto' loop to a 'for(;;)' block
[2.c] Move the loop variables
[2.d] Move loop initialization
[2.e] Create a macro for generating different loops
For your convenience, this email itself provides an example squashing
of those commits; to apply it, do something like the following:
$ git am /path/to/patch-1.eml # Patch [1]
$ git am --scissors /path/to/this-email # This email's Patch {2}
$ git am /path/to/patch-3.eml # Patch [3]
Alternatively, you can have the best of both worlds by means of a merge:
$ git am /path/to/patch-1.eml # Patch [1]
$ patch_1=$(git rev-parse HEAD)
$ git am /path/to/patch-2.*.eml # Patches [2.*]
$ git reset --hard "$patch_1"
$ git merge --no-ff -m \
'libavformat/protocols.c: avio_enum_protocols(): Refactor' \
ORIG_HEAD
$ git am /path/to/patch-3.eml # Patch [3]
That will produce a very nice history:
$ git log --oneline --graph
Here is the overall change for the entire series:
fftools/cmdutils.c | 4 ++--
libavformat/avio.h | 24 +++++++++++++++++++++++-
libavformat/protocols.c | 36 +++++++++++++++++++++++++-----------
3 files changed, 50 insertions(+), 14 deletions(-)
Sincerely,
Michael Witten
--8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<----8<--
Subject: libavformat/protocols.c: avio_enum_protocols(): Refactor
Date: Wed, 11 Aug 2021 19:00:09 -0000
This commit is the result of squashing a series of very tiny
transformations; it refactors 'avio_enum_protocols()' into
2 functions:
* avio_enum_protocols_for_input()
* avio_enum_protocols_for_output()
Those functions are in turn mostly implemented by this macro:
* AVIO_ENUM_PROTOCOLS()
The goal of this refactoring was the following:
* To make the code more immediately understandable.
* To reduce the potential for redundant computation.
diff --git a/libavformat/avio.h b/libavformat/avio.h
index 0b35409787..3b92cf742a 100644
--- a/libavformat/avio.h
+++ b/libavformat/avio.h
@@ -786,7 +786,7 @@ int avio_close_dyn_buf(AVIOContext *s, uint8_t **pbuffer);
*
* @return A static string containing the name of current protocol or NULL
*/
-const char *avio_enum_protocols(void **opaque, int output);
+const char *avio_enum_protocols(void **const opaque, const int output);
/**
* Get AVClass by names of available protocols.
diff --git a/libavformat/protocols.c b/libavformat/protocols.c
index e0b3405ab8..4cb8ae0b63 100644
--- a/libavformat/protocols.c
+++ b/libavformat/protocols.c
@@ -91,19 +91,35 @@ const AVClass *ff_urlcontext_child_class_iterate(void
**iter)
return ret;
}
-const char *avio_enum_protocols(void **opaque, int output)
+#define AVIO_ENUM_PROTOCOLS(METHOD) \
+ typedef const URLProtocol *const *Iterator; \
+ for(Iterator p = *opaque ? (Iterator)(*opaque) + 1 : url_protocols; *p;
++p) { \
+ if ((*p)->METHOD) { \
+ *opaque = (void *)p; \
+ return (*p)->name; \
+ } \
+ } \
+ *opaque = NULL; \
+ return NULL;
+
+static inline
+const char *avio_enum_protocols_for_output(void **const opaque)
{
- const URLProtocol *const *p = *opaque;
+ AVIO_ENUM_PROTOCOLS(url_write);
+}
- p = p ? p + 1 : url_protocols;
- *opaque = (void *)p;
- if (!*p) {
- *opaque = NULL;
- return NULL;
- }
- if ((output && (*p)->url_write) || (!output && (*p)->url_read))
- return (*p)->name;
- return avio_enum_protocols(opaque, output);
+static inline
+const char *avio_enum_protocols_for_input(void **const opaque)
+{
+ AVIO_ENUM_PROTOCOLS(url_read);
+}
+
+const char *avio_enum_protocols(void **const opaque, const int output)
+{
+ if (output)
+ return avio_enum_protocols_for_output(opaque);
+ else
+ return avio_enum_protocols_for_input(opaque);
}
const AVClass *avio_protocol_get_class(const char *name)
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