BLI: add new 'memory_utils' module with func checking a whole memory chunk is filled of zero,

and an helper to ensure all memory of a given structure passed a given member is filled of zero.

source/blender/blenlib/BLI_memory_utils.h

@@ -0,0 +1,34 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+#ifndef __BLI_MEMORY_UTILS_H__
+#define __BLI_MEMORY_UTILS_H__
+
+/** \file BLI_memory_utils.h
+ *  \ingroup bli
+ *  \brief Generic memory manipulation API.
+ */
+
+/* it may be defined already */
+#ifndef __BLI_UTILDEFINES_H__
+bool BLI_memory_is_zero(const void *arr, const size_t size);
+#endif
+
+#endif  /* __BLI_MEMORY_UTILS_H__ */

source/blender/blenlib/BLI_utildefines.h

@@ -513,6 +513,17 @@ extern "C" {
 	       sizeof(*(struct_var)) - OFFSETOF_STRUCT(struct_var, member)); \
 } (void)0
 
+/* defined
+ * in memory_utils.c for now. I do not know where we should put it actually... */
+#ifndef __BLI_MEMORY_UTILS_H__
+extern bool BLI_memory_is_zero(const void *arr, const size_t arr_size);
+#endif
+
+#define MEMCMP_STRUCT_OFS_IS_ZERO(struct_var, member) \
+	(BLI_memory_is_zero( \
+	       (char *)(struct_var)  + OFFSETOF_STRUCT(struct_var, member), \
+	       sizeof(*(struct_var)) - OFFSETOF_STRUCT(struct_var, member)))
+
 /* Warning-free macros for storing ints in pointers. Use these _only_
  * for storing an int in a pointer, not a pointer in an int (64bit)! */
 #define SET_INT_IN_POINTER(i)    ((void *)(intptr_t)(i))

source/blender/blenlib/CMakeLists.txt

@@ -88,6 +88,7 @@ set(SRC
 	intern/math_statistics.c
 	intern/math_vector.c
 	intern/math_vector_inline.c
+	intern/memory_utils.c
 	intern/noise.c
 	intern/path_util.c
 	intern/polyfill2d.c
@@ -169,6 +170,7 @@ set(SRC
 	BLI_math_statistics.h
 	BLI_math_vector.h
 	BLI_memarena.h
+	BLI_memory_utils.h
 	BLI_mempool.h
 	BLI_noise.h
 	BLI_path_util.h

source/blender/blenlib/intern/memory_utils.c

@@ -0,0 +1,50 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/blenlib/intern/memory_utils.c
+ *  \ingroup bli
+ *  \brief Generic memory manipulation API.
+ *
+ * This is to extend on existing functions
+ * such as ``memcpy`` & ``memcmp``.
+ */
+#include <string.h>
+
+#include "BLI_sys_types.h"
+#include "BLI_utildefines.h"
+
+#include "BLI_memory_utils.h"
+
+#include "BLI_strict_flags.h"
+
+/**
+ * Check if memory is zero'd, as with memset(s, 0, nbytes)
+ */
+bool BLI_memory_is_zero(const void *s, const size_t nbytes)
+{
+	const char *s_byte = s;
+	const char *s_end = (const char *)s + nbytes;
+
+	while ((s_byte != s_end) && (*s_byte == 0)) {
+		s_byte++;
+	}
+
+	return (s_byte == s_end);
+}