lavu/mem: add av_dynarray2_add()

Based on a patch by Clément Bœsch.

See thread:
From: Clément Bœsch <ubitux@gmail.com>
Subject: [FFmpeg-devel] [PATCH 1/5] lavu: add av_dynarray_alloc_elem().
Date: Sun, 14 Apr 2013 03:07:54 +0200

1 files changed, 33 insertions, 0 deletions

diff --git a/libavutil/mem.c b/libavutil/mem.c
index 9b22609d6f..66502eb467 100644
--- a/libavutil/mem.c
+++ b/libavutil/mem.c
@@ -270,6 +270,39 @@ fail:
     *nb_ptr = 0;
 }
 
+void *av_dynarray2_add(void **tab_ptr, int *nb_ptr, size_t elem_size,
+                       const uint8_t *elem_data)
+{
+    int nb = *nb_ptr, nb_alloc;
+    uint8_t *tab = *tab_ptr, *tab_elem_data;
+
+    if ((nb & (nb - 1)) == 0) {
+        if (nb == 0) {
+            nb_alloc = 1;
+        } else {
+            if (nb > INT_MAX / (2 * elem_size))
+                goto fail;
+            nb_alloc = nb * 2;
+        }
+        tab = av_realloc(tab, nb_alloc * elem_size);
+        if (!tab)
+            goto fail;
+        *tab_ptr = tab;
+    }
+    *nb_ptr = nb + 1;
+    tab_elem_data = tab + nb*elem_size;
+    if (elem_data)
+        memcpy(tab_elem_data, elem_data, elem_size);
+    else if (CONFIG_MEMORY_POISONING)
+        memset(tab_elem_data, FF_MEMORY_POISON, elem_size);
+    return tab_elem_data;
+
+fail:
+    av_freep(tab_ptr);
+    *nb_ptr = 0;
+    return NULL;
+}
+
 static void fill16(uint8_t *dst, int len)
 {
     uint32_t v = AV_RN16(dst - 2);