[FFmpeg-devel] [PATCH 1/2] lavu/fifo: fix a corner case in av_fifo_grow2()

[FFmpeg-devel] [PATCH 1/2] lavu/fifo: fix a corner case in av_fifo_grow2()

[Anton Khirnov]

When the fifo is grown by exactly the current write offset, it would end
up with offset_w = nb_elems. If av_fifo_write_from_cb() is called in
such a state, the user callback would get callled with *nb_elems=0,
which will then cause the write to return without writing anything.
---
 libavutil/fifo.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavutil/fifo.c b/libavutil/fifo.c
index 0af0154945..2af8842cc5 100644
--- a/libavutil/fifo.c
+++ b/libavutil/fifo.c
@@ -115,7 +115,7 @@ int av_fifo_grow2(AVFifo *f, size_t inc)
                     (f->offset_w - copy) * f->elem_size);
             f->offset_w -= copy;
         } else
-            f->offset_w = f->nb_elems + copy;
+            f->offset_w = copy == inc ? 0 : f->nb_elems + copy;
     }
 
     f->nb_elems += inc;
-- 
2.34.1

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[FFmpeg-devel] [PATCH 2/2] lavu/fifo: add a test for _cb functions

[Anton Khirnov]

Makes an auto-growing FIFO and performs a sequence of randomly-sized
writes/peeks/reads.
---
 libavutil/tests/fifo.c | 101 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)

diff --git a/libavutil/tests/fifo.c b/libavutil/tests/fifo.c
index 579602ccf3..bfcdfeebfb 100644
--- a/libavutil/tests/fifo.c
+++ b/libavutil/tests/fifo.c
@@ -18,7 +18,53 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include "libavutil/common.h"
 #include "libavutil/fifo.h"
+#include "libavutil/lfg.h"
+#include "libavutil/random_seed.h"
+
+typedef struct CBState {
+    unsigned int read_idx;
+    unsigned int write_idx;
+    unsigned int to_process;
+    unsigned int offset;
+} CBState;
+
+static int read_cb(void *opaque, void *buf, size_t *nb_elems)
+{
+    CBState  *s = opaque;
+    unsigned *b = buf;
+
+    *nb_elems = FFMIN(*nb_elems, s->to_process);
+
+    for (unsigned i = 0; i < *nb_elems; i++)
+        if (b[i] != s->read_idx + s->offset + i) {
+            printf("Mismatch at idx %u offset %u i %u\n",
+                   s->read_idx, s->offset, i);
+            return AVERROR_BUG;
+        }
+
+    s->offset     += *nb_elems;
+    s->to_process -= *nb_elems;
+
+    return 0;
+}
+
+static int write_cb(void *opaque, void *buf, size_t *nb_elems)
+{
+    CBState  *s = opaque;
+    unsigned *b = buf;
+
+    *nb_elems = FFMIN(*nb_elems, s->to_process);
+
+    for (unsigned i = 0; i < *nb_elems; i++)
+        b[i] = s->write_idx + i;
+
+    s->write_idx  += *nb_elems;
+    s->to_process -= *nb_elems;
+
+    return 0;
+}
 
 int main(void)
 {
@@ -89,6 +135,61 @@ int main(void)
         printf("%d: %d\n", i, j);
     }
 
+    av_fifo_freep2(&fifo);
+
+    /* test randomly-sized write/read/peek with a callback */
+    {
+        CBState        s = { 0 };
+        uint32_t    seed = av_get_random_seed();
+
+        AVLFG lfg;
+        int ret;
+
+        av_lfg_init(&lfg, seed);
+
+        fifo = av_fifo_alloc2(1, sizeof(unsigned), AV_FIFO_FLAG_AUTO_GROW);
+
+        for (i = 0; i < 32; i++) {
+            size_t       nb_elems = 16;
+            unsigned   to_process = av_lfg_get(&lfg) % nb_elems;
+
+            s.to_process = to_process;
+
+            ret = av_fifo_write_from_cb(fifo, write_cb, &s, &nb_elems);
+            if (ret < 0 || s.to_process || nb_elems != to_process) {
+                printf("FIFO write fail; seed %"PRIu32"\n", seed);
+                return 1;
+            }
+
+            nb_elems = av_fifo_can_read(fifo);
+            if (nb_elems > 1) {
+                s.offset     = av_lfg_get(&lfg) % (nb_elems - 1);
+                nb_elems    -= s.offset;
+
+                s.to_process = av_lfg_get(&lfg) % nb_elems;
+                to_process   = s.to_process;
+
+                ret = av_fifo_peek_to_cb(fifo, read_cb, &s, &nb_elems, s.offset);
+                if (ret < 0 || s.to_process || nb_elems != to_process) {
+                    printf("FIFO peek fail; seed %"PRIu32"\n", seed);
+                    return 1;
+                }
+            }
+
+            nb_elems     = av_fifo_can_read(fifo);
+            to_process   = nb_elems ? av_lfg_get(&lfg) % nb_elems : 0;
+            s.to_process = to_process;
+            s.offset     = 0;
+
+            ret = av_fifo_read_to_cb(fifo, read_cb, &s, &nb_elems);
+            if (ret < 0 || s.to_process || to_process != nb_elems) {
+                printf("FIFO peek fail; seed %"PRIu32"\n", seed);
+                return 1;
+            }
+            s.read_idx += s.offset;
+        }
+    }
+
     av_fifo_freep2(&fifo);
     free(p);
 
-- 
2.34.1

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