[FFmpeg-devel] [PATCH 05/35] lavu/fifo: add a new FIFO grow function

[Anton Khirnov <anton@khirnov.net>]

Consistently use size_t for sizes.

Unlike av_fifo_grow(), which addds to the currently used size, this
function adds to the allocated size.

No new function is provided for a generic realloc, since the current code
only supports increasing the FIFO size.
---
 doc/APIchanges   |  3 ++-
 libavutil/fifo.c | 61 +++++++++++++++++++++++++++---------------------
 libavutil/fifo.h | 14 +++++++++++
 3 files changed, 50 insertions(+), 28 deletions(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index 9400c5147a..98eae55719 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -18,7 +18,8 @@ API changes, most recent first:
   Add av_fifo_alloc2(), which allows setting a FIFO element size.
   Operations on FIFOs created with this function on these elements
   rather than bytes.
-  Add av_fifo_elem_size(), av_fifo_can_read(), av_fifo_can_write().
+  Add av_fifo_elem_size(), av_fifo_can_read(), av_fifo_can_write(),
+  av_fifo_grow2().
 
 2022-01-xx - xxxxxxxxxx - lavu fifo.h
   Access to all AVFifoBuffer members is deprecated. The struct will
diff --git a/libavutil/fifo.c b/libavutil/fifo.c
index 8cde2c20e1..28d6d1b2e6 100644
--- a/libavutil/fifo.c
+++ b/libavutil/fifo.c
@@ -150,41 +150,48 @@ int av_fifo_space(const AVFifoBuffer *f)
     return av_fifo_can_write(f);
 }
 
-int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
+int av_fifo_grow2(AVFifoBuffer *f, size_t inc)
 {
     FifoBuffer *fb = (FifoBuffer*)f;
+    uint8_t *tmp;
 
-    if (new_size > FIFO_SIZE_MAX)
+    if (inc > FIFO_SIZE_MAX - fb->nb_elems)
         return AVERROR(EINVAL);
 
-    if (fb->nb_elems < new_size) {
-        uint8_t *tmp;
-
-        tmp = av_realloc_array(f->buffer, new_size, fb->elem_size);
-        if (!tmp)
-            return AVERROR(ENOMEM);
-
-        // move the data from the beginning of the ring buffer
-        // to the newly allocated space
-        if (fb->offset_w <= fb->offset_r && !fb->is_empty) {
-            const size_t copy = FFMIN(new_size - fb->nb_elems, fb->offset_w);
-            memcpy(tmp + fb->nb_elems * fb->elem_size, tmp, copy * fb->elem_size);
-            if (copy < fb->offset_w) {
-                memmove(tmp, tmp + copy * fb->elem_size,
-                        (fb->offset_w - copy) * fb->elem_size);
-                fb->offset_w -= copy;
-            } else
-                fb->offset_w = fb->nb_elems + copy;
-        }
+    tmp = av_realloc_array(f->buffer, fb->nb_elems + inc, fb->elem_size);
+    if (!tmp)
+        return AVERROR(ENOMEM);
+
+    // move the data from the beginning of the ring buffer
+    // to the newly allocated space
+    if (fb->offset_w <= fb->offset_r && !fb->is_empty) {
+        const size_t copy = FFMIN(inc, fb->offset_w);
+        memcpy(tmp + fb->nb_elems * fb->elem_size, tmp, copy * fb->elem_size);
+        if (copy < fb->offset_w) {
+            memmove(tmp, tmp + copy * fb->elem_size,
+                    (fb->offset_w - copy) * fb->elem_size);
+            fb->offset_w -= copy;
+        } else
+            fb->offset_w = fb->nb_elems + copy;
+    }
+
+    f->buffer     = tmp;
+    fb->nb_elems += inc;
 
-        f->buffer = tmp;
 #if FF_API_FIFO_PUBLIC
-        f->end    = f->buffer + new_size;
-        f->rptr   = f->buffer + fb->offset_r * fb->elem_size;
-        f->wptr   = f->buffer + fb->offset_w * fb->elem_size;
+    f->end    = f->buffer + fb->nb_elems * fb->elem_size;
+    f->rptr   = f->buffer + fb->offset_r * fb->elem_size;
+    f->wptr   = f->buffer + fb->offset_w * fb->elem_size;
 #endif
-        fb->nb_elems = new_size;
-    }
+
+    return 0;
+}
+
+int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
+{
+    FifoBuffer *fb = (FifoBuffer*)f;
+    if (fb->nb_elems < new_size)
+        return av_fifo_grow2(f, new_size - fb->nb_elems);
     return 0;
 }
 
diff --git a/libavutil/fifo.h b/libavutil/fifo.h
index 9e78082b3b..375d0d133b 100644
--- a/libavutil/fifo.h
+++ b/libavutil/fifo.h
@@ -129,6 +129,20 @@ size_t av_fifo_can_read(const AVFifoBuffer *f);
  */
 size_t av_fifo_can_write(const AVFifoBuffer *f);
 
+/**
+ * Enlarge an AVFifoBuffer.
+ *
+ * On success, the FIFO will be large enough to hold exactly
+ * inc + av_fifo_can_read() + av_fifo_can_write()
+ * elements. In case of failure, the old FIFO is kept unchanged.
+ *
+ * @param f AVFifoBuffer to resize
+ * @param inc number of elements to allocate for, in addition to the current
+ *            allocated size
+ * @return a non-negative number on success, a negative error code on failure
+ */
+int av_fifo_grow2(AVFifoBuffer *f, size_t inc);
+
 /**
  * Feed data at specific position from an AVFifoBuffer to a user-supplied callback.
  * Similar as av_fifo_gereric_read but without discarding data.
-- 
2.33.0

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