[FFmpeg-cvslog] fifo: Make writes atomic.

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Fri Dec 23 00:18:36 2011 +0100| [9eb0d8bab1c475edf73c36146d1c3d31ea47f997] | committer: Michael Niedermayer

fifo: Make writes atomic.
Prior to this a X bytes write could be seen as less than X bytes being
available if the check was done at an unfortunate moment.

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=9eb0d8bab1c475edf73c36146d1c3d31ea47f997
---

 libavutil/fifo.c |   19 ++++++++++++-------
 1 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/libavutil/fifo.c b/libavutil/fifo.c
index 3ebd5f9..d1d9ba8 100644
--- a/libavutil/fifo.c
+++ b/libavutil/fifo.c
@@ -83,22 +83,27 @@ int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
 int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size, int (*func)(void*, void*, int))
 {
     int total = size;
+    uint32_t wndx= f->wndx;
+    uint8_t *wptr= f->wptr;
+
     do {
-        int len = FFMIN(f->end - f->wptr, size);
+        int len = FFMIN(f->end - wptr, size);
         if (func) {
-            if (func(src, f->wptr, len) <= 0)
+            if (func(src, wptr, len) <= 0)
                 break;
         } else {
-            memcpy(f->wptr, src, len);
+            memcpy(wptr, src, len);
             src = (uint8_t*)src + len;
         }
 // Write memory barrier needed for SMP here in theory
-        f->wptr += len;
-        if (f->wptr >= f->end)
-            f->wptr = f->buffer;
-        f->wndx += len;
+        wptr += len;
+        if (wptr >= f->end)
+            wptr = f->buffer;
+        wndx += len;
         size -= len;
     } while (size > 0);
+    f->wndx= wndx;
+    f->wptr= wptr;
     return total - size;
 }