From http://www.jwz.org/xscreensaver/xscreensaver-5.27.tar.gz

[xscreensaver] / utils / aligned_malloc.c

diff --git a/utils/aligned_malloc.c b/utils/aligned_malloc.c
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+++ b/utils/aligned_malloc.c
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+/* -*- mode: c; tab-width: 4; fill-column: 128 -*- */
+/* vi: set ts=4 tw=128: */
+
+/*
+aligned_malloc.c, Copyright (c) 2014 Dave Odell <dmo2118@gmail.com>
+
+Permission to use, copy, modify, distribute, and sell this software and its
+documentation for any purpose is hereby granted without fee, provided that
+the above copyright notice appear in all copies and that both that
+copyright notice and this permission notice appear in supporting
+documentation.  No representations are made about the suitability of this
+software for any purpose.  It is provided "as is" without express or
+implied warranty.
+*/
+
+#include "aligned_malloc.h"
+
+#include <stddef.h>
+#include <stdlib.h>
+
+#if !(_POSIX_VERSION >= 200112L || _XOPEN_VERSION >= 600)
+
+#include <assert.h>
+#include <errno.h>
+
+int aligned_malloc(void **ptr, unsigned alignment, size_t size)
+{
+       void *block_start;
+       ptrdiff_t align1 = alignment - 1;
+
+       assert(alignment && !(alignment & (alignment - 1))); /* alignment must be a power of two. */
+
+       size += sizeof(void *) + align1;
+       block_start = malloc(size);
+       if(!block_start)
+               return ENOMEM;
+       *ptr = (void *)(((ptrdiff_t)block_start + sizeof(void *) + align1) & ~align1);
+       ((void **)(*ptr))[-1] = block_start;
+       return 0;
+}
+
+void aligned_free(void *ptr)
+{
+       free(((void **)(ptr))[-1]);
+}
+
+#endif