[FFmpeg-devel] [PATCH 22/22] avfilter/formats: Avoid allocations when merging channel layouts

[Andreas Rheinhardt]

When one merges two AVFilterChannelLayouts structs, there is no need to
allocate a new one. Instead one can reuse one of the two given ones.
If one does this, one also doesn't need to update the references of the
AVFilterChannelLayouts that is reused. Therefore this commit reuses the
structure with the higher refcount.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
This can of course be applied independently of 7-21.

 libavfilter/formats.c | 48 +++++++++++++++++++------------------------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/libavfilter/formats.c b/libavfilter/formats.c
index 00d050e439..2d33dd7afe 100644
--- a/libavfilter/formats.c
+++ b/libavfilter/formats.c
@@ -48,13 +48,13 @@ do {                                                                       \
     av_freep(&a);                                                          \
 } while (0)
 
-#define MERGE_REF(ret, a, fmts, type, fail)                                \
+#define MERGE_REF(ret, a, fmts, type, fail_statement)                      \
 do {                                                                       \
     type ***tmp;                                                           \
                                                                            \
     if (!(tmp = av_realloc_array(ret->refs, ret->refcount + a->refcount,   \
                                  sizeof(*tmp))))                           \
-        goto fail;                                                         \
+        { fail_statement }                                                 \
     ret->refs = tmp;                                                       \
     MERGE_REF_NO_ALLOC(ret, a, fmts);                                      \
 } while (0)
@@ -157,10 +157,10 @@ AVFilterFormats *ff_merge_samplerates(AVFilterFormats *a,
     if (a->nb_formats && b->nb_formats) {
         MERGE_FORMATS(ret, a, b, formats, nb_formats, AVFilterFormats, fail);
     } else if (a->nb_formats) {
-        MERGE_REF(a, b, formats, AVFilterFormats, fail);
+        MERGE_REF(a, b, formats, AVFilterFormats, return NULL;);
         ret = a;
     } else {
-        MERGE_REF(b, a, formats, AVFilterFormats, fail);
+        MERGE_REF(b, a, formats, AVFilterFormats, return NULL;);
         ret = b;
     }
 
@@ -177,7 +177,7 @@ fail:
 AVFilterChannelLayouts *ff_merge_channel_layouts(AVFilterChannelLayouts *a,
                                                  AVFilterChannelLayouts *b)
 {
-    AVFilterChannelLayouts *ret = NULL;
+    uint64_t *channel_layouts;
     unsigned a_all = a->all_layouts + a->all_counts;
     unsigned b_all = b->all_layouts + b->all_counts;
     int ret_max, ret_nb = 0, i, j, round;
@@ -201,15 +201,13 @@ AVFilterChannelLayouts *ff_merge_channel_layouts(AVFilterChannelLayouts *a,
                 return NULL;
             b->nb_channel_layouts = j;
         }
-        MERGE_REF(b, a, channel_layouts, AVFilterChannelLayouts, fail);
+        MERGE_REF(b, a, channel_layouts, AVFilterChannelLayouts, return NULL;);
         return b;
     }
 
     ret_max = a->nb_channel_layouts + b->nb_channel_layouts;
-    if (!(ret = av_mallocz(sizeof(*ret))) ||
-        !(ret->channel_layouts = av_malloc_array(ret_max,
-                                                 sizeof(*ret->channel_layouts))))
-        goto fail;
+    if (!(channel_layouts = av_malloc_array(ret_max, sizeof(channel_layouts))))
+        return NULL;
 
     /* a[known] intersect b[known] */
     for (i = 0; i < a->nb_channel_layouts; i++) {
@@ -217,7 +215,7 @@ AVFilterChannelLayouts *ff_merge_channel_layouts(AVFilterChannelLayouts *a,
             continue;
         for (j = 0; j < b->nb_channel_layouts; j++) {
             if (a->channel_layouts[i] == b->channel_layouts[j]) {
-                ret->channel_layouts[ret_nb++] = a->channel_layouts[i];
+                channel_layouts[ret_nb++] = a->channel_layouts[i];
                 a->channel_layouts[i] = b->channel_layouts[j] = 0;
             }
         }
@@ -232,7 +230,7 @@ AVFilterChannelLayouts *ff_merge_channel_layouts(AVFilterChannelLayouts *a,
             bfmt = FF_COUNT2LAYOUT(av_get_channel_layout_nb_channels(fmt));
             for (j = 0; j < b->nb_channel_layouts; j++)
                 if (b->channel_layouts[j] == bfmt)
-                    ret->channel_layouts[ret_nb++] = a->channel_layouts[i];
+                    channel_layouts[ret_nb++] = a->channel_layouts[i];
         }
         /* 1st round: swap to prepare 2nd round; 2nd round: put it back */
         FFSWAP(AVFilterChannelLayouts *, a, b);
@@ -243,27 +241,23 @@ AVFilterChannelLayouts *ff_merge_channel_layouts(AVFilterChannelLayouts *a,
             continue;
         for (j = 0; j < b->nb_channel_layouts; j++)
             if (a->channel_layouts[i] == b->channel_layouts[j])
-                ret->channel_layouts[ret_nb++] = a->channel_layouts[i];
+                channel_layouts[ret_nb++] = a->channel_layouts[i];
     }
 
-    ret->nb_channel_layouts = ret_nb;
-    if (!ret->nb_channel_layouts)
+    if (!ret_nb)
         goto fail;
 
-    ret->refs = av_realloc_array(NULL, a->refcount + b->refcount,
-                                 sizeof(*ret->refs));
-    if (!ret->refs)
-        goto fail;
-    MERGE_REF_NO_ALLOC(ret, a, channel_layouts);
-    MERGE_REF_NO_ALLOC(ret, b, channel_layouts);
-    return ret;
+    if (a->refcount > b->refcount)
+        FFSWAP(AVFilterChannelLayouts *, a, b);
+
+    MERGE_REF(b, a, channel_layouts, AVFilterChannelLayouts, goto fail;);
+    av_freep(&b->channel_layouts);
+    b->channel_layouts    = channel_layouts;
+    b->nb_channel_layouts = ret_nb;
+    return b;
 
 fail:
-    if (ret) {
-        av_assert1(!ret->refs);
-        av_freep(&ret->channel_layouts);
-        av_freep(&ret);
-    }
+    av_free(channel_layouts);
     return NULL;
 }
 
-- 
2.20.1