[FFmpeg-devel] [PR] avutil/mem: Add av_malloc_with_paddingz() (PR #21509)

[michaelni via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

PR #21509 opened by michaelni
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21509
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21509.patch

Add a av_malloc() that adds padding like AV_INPUT_BUFFER_PADDING_SIZE
and clears it.

This is a operation we commonly use so this function should simplify
many cases

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>


>From cc424b2a5568ee35a3435ff58a84d2a18c1c6843 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michael@niedermayer.cc>
Date: Mon, 19 Jan 2026 05:15:23 +0100
Subject: [PATCH] avutil/mem: Add av_malloc_with_paddingz()

Add a av_malloc() that adds padding like AV_INPUT_BUFFER_PADDING_SIZE
and clears it.

This is a operation we commonly use so this function should simplify
many cases

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavutil/mem.c | 10 ++++++++++
 libavutil/mem.h | 13 +++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/libavutil/mem.c b/libavutil/mem.c
index b205d3fb25..aac7ef4d12 100644
--- a/libavutil/mem.c
+++ b/libavutil/mem.c
@@ -261,6 +261,16 @@ void *av_mallocz(size_t size)
     return ptr;
 }
 
+void *av_malloc_with_paddingz(size_t size, size_t padding)
+{
+    if (size > SIZE_MAX - padding)
+        return NULL;
+    uint8_t *p = av_malloc(size + padding);
+    if(p)
+        memset(p + size, 0, padding);
+    return p;
+}
+
 void *av_calloc(size_t nmemb, size_t size)
 {
     size_t result;
diff --git a/libavutil/mem.h b/libavutil/mem.h
index ab7648ac57..6a4c144f18 100644
--- a/libavutil/mem.h
+++ b/libavutil/mem.h
@@ -129,6 +129,19 @@ void *av_malloc(size_t size) av_malloc_attrib av_alloc_size(1);
  */
 void *av_mallocz(size_t size) av_malloc_attrib av_alloc_size(1);
 
+/**
+ * Allocate a memory block with alignment suitable for all memory accesses
+ * (including vectors if available on the CPU)
+ *
+ * An additional padding will be allocated and cleared.
+ *
+ * @param size Size in bytes for the memory block to be allocated
+ * @param padding Size in bytes of padding allocated and zeroed after size.
+ * @return Pointer to the allocated block, or `NULL` if it cannot be allocated
+ * @see av_malloc()
+ */
+void *av_malloc_with_paddingz(size_t size, size_t padding) av_malloc_attrib av_alloc_size(1);
+
 /**
  * Allocate a memory block for an array with av_malloc().
  *
-- 
2.52.0

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