lib/string/: Move string-related files to string/ subdir

Signed-off-by: Alejandro Colomar <alx@kernel.org>

lib/string/zustr2stp.h

@@ -0,0 +1,84 @@
+/*
+ * SPDX-FileCopyrightText: 2022-2023, Alejandro Colomar <alx@kernel.org>
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+
+#ifndef SHADOW_INCLUDE_LIBMISC_ZUSTR2STP_H_
+#define SHADOW_INCLUDE_LIBMISC_ZUSTR2STP_H_
+
+
+#include <config.h>
+
+#include <assert.h>
+#include <stddef.h>
+#include <string.h>
+
+#include "must_be.h"
+#include "sizeof.h"
+
+
+#define ZUSTR2STP(dst, src)                                                   \
+({                                                                            \
+	static_assert(!is_array(dst) || sizeof(dst) > SIZEOF_ARRAY(src), ""); \
+                                                                              \
+	zustr2stp(dst, src, NITEMS(src));                                     \
+})
+
+
+inline char *zustr2stp(char *restrict dst, const char *restrict src, size_t sz);
+
+
+/*
+ * SYNOPSIS
+ *	char *zustr2stp(char *restrict dst,
+ *	                const char src[restrict .sz], size_t sz);
+ *
+ * ARGUMENTS
+ *	dst	Destination buffer where to copy a string.
+ *
+ *	src	Source null-padded character sequence to be copied into
+ *	        dst.
+ *
+ *	sz	Size of the *source* buffer.
+ *
+ * DESCRIPTION
+ *	This function copies the null-padded character sequence pointed
+ *	to by src, into a string at the buffer pointed to by dst.
+ *
+ * RETURN VALUE
+ *	dst + strlen(dst)
+ *		This function returns a pointer to the terminating NUL
+ *		byte.
+ *
+ * ERRORS
+ *	This function doesn't set errno.
+ *
+ * CAVEATS
+ *	This function doesn't know the size of the destination buffer.
+ *	It assumes it will always be large enough.  Since the size of
+ *	the source buffer is known to the caller, it should make sure to
+ *	allocate a destination buffer of at least `sz + 1`.
+ *
+ * EXAMPLES
+ *	char  src[13] = "Hello, world!"  // No '\0' in this buffer!
+ *	char  dst[NITEMS(src) + 1];
+ *
+ *	zustr2stp(dst, src, NITEMS(src));
+ *	puts(dst);
+ */
+
+
+inline char *
+zustr2stp(char *restrict dst, const char *restrict src, size_t sz)
+{
+	char  *p;
+
+	p = mempcpy(dst, src, strnlen(src, sz));
+	*p = '\0';
+
+	return p;
+}
+
+
+#endif  // include guard