util: split out memcmp()/memset() related calls into memory-util.[ch]

Just some source rearranging.

src/basic/memory-util.h

@@ -0,0 +1,53 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+#pragma once
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <string.h>
+#include <sys/types.h>
+
+#include "macro.h"
+
+size_t page_size(void) _pure_;
+#define PAGE_ALIGN(l) ALIGN_TO((l), page_size())
+
+/* Normal memcpy requires src to be nonnull. We do nothing if n is 0. */
+static inline void memcpy_safe(void *dst, const void *src, size_t n) {
+        if (n == 0)
+                return;
+        assert(src);
+        memcpy(dst, src, n);
+}
+
+/* Normal memcmp requires s1 and s2 to be nonnull. We do nothing if n is 0. */
+static inline int memcmp_safe(const void *s1, const void *s2, size_t n) {
+        if (n == 0)
+                return 0;
+        assert(s1);
+        assert(s2);
+        return memcmp(s1, s2, n);
+}
+
+/* Compare s1 (length n1) with s2 (length n2) in lexicographic order. */
+static inline int memcmp_nn(const void *s1, size_t n1, const void *s2, size_t n2) {
+        return memcmp_safe(s1, s2, MIN(n1, n2))
+            ?: CMP(n1, n2);
+}
+
+#define memzero(x,l)                                            \
+        ({                                                      \
+                size_t _l_ = (l);                               \
+                void *_x_ = (x);                                \
+                _l_ == 0 ? _x_ : memset(_x_, 0, _l_);           \
+        })
+
+#define zero(x) (memzero(&(x), sizeof(x)))
+
+bool memeqzero(const void *data, size_t length);
+
+#define eqzero(x) memeqzero(x, sizeof(x))
+
+static inline void *mempset(void *s, int c, size_t n) {
+        memset(s, c, n);
+        return (uint8_t*)s + n;
+}