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[FFmpeg-devel,7/8] avutil/fifo: Simplify growing FIFO

Message ID DB6PR0101MB2214FFF1DE9C12BE5A5467618F819@DB6PR0101MB2214.eurprd01.prod.exchangelabs.com
State New
Headers show
Series [FFmpeg-devel,1/8] avutil/mem: Handle fast allocations near UINT_MAX properly | expand

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Commit Message

Andreas Rheinhardt July 5, 2022, 8:26 p.m. UTC 
In case the data in the FIFO currently wraps around,
move the data from the end of the old buffer to the end
of the new buffer instead of moving the data from the start
of the old buffer partially to the end of the new buffer
and partially to the start of the new buffer.
This simplifies the code.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavutil/fifo.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)
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Patch

diff --git a/libavutil/fifo.c b/libavutil/fifo.c
index 51a5af6f39..53359a2112 100644
--- a/libavutil/fifo.c
+++ b/libavutil/fifo.c
@@ -108,17 +108,12 @@  int av_fifo_grow2(AVFifo *f, size_t inc)
         return AVERROR(ENOMEM);
     f->buffer = tmp;
 
-    // move the data from the beginning of the ring buffer
-    // to the newly allocated space
+    // move the data from the end of the ring buffer
+    // to the end of the newly allocated space
     if (f->offset_w <= f->offset_r && !f->is_empty) {
-        const size_t copy = FFMIN(inc, f->offset_w);
-        memcpy(tmp + f->nb_elems * f->elem_size, tmp, copy * f->elem_size);
-        if (copy < f->offset_w) {
-            memmove(tmp, tmp + copy * f->elem_size,
-                    (f->offset_w - copy) * f->elem_size);
-            f->offset_w -= copy;
-        } else
-            f->offset_w = copy == inc ? 0 : f->nb_elems + copy;
+        memmove(tmp + (f->offset_r + inc) * f->elem_size, tmp + f->offset_r * f->elem_size,
+                (f->nb_elems - f->offset_r) * f->elem_size);
+        f->offset_r += inc;
     }
 
     f->nb_elems += inc;