1 files changed, 58 insertions, 0 deletions
diff --git a/lib/string/zustr2stp.h b/lib/string/zustr2stp.h
new file mode 100644
index 0000000..152102b
--- /dev/null
+++ b/lib/string/zustr2stp.h
@@ -0,0 +1,58 @@
+// SPDX-FileCopyrightText: 2022-2024, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#ifndef SHADOW_INCLUDE_LIB_STRING_ZUSTR2STP_H_
+#define SHADOW_INCLUDE_LIB_STRING_ZUSTR2STP_H_
+
+
+#include <config.h>
+
+#include <assert.h>
+#include <string.h>
+
+#include "must_be.h"
+#include "sizeof.h"
+
+
+/*
+ * SYNOPSIS
+ *	char *ZUSTR2STP(char *restrict dst, const char src[restrict]);
+ *
+ * ARGUMENTS
+ *	dst	Destination buffer.
+ *	src	Source null-padded character sequence.
+ *
+ * DESCRIPTION
+ *	This macro copies at most NITEMS(src) non-null bytes from the
+ *	array pointed to by src, followed by a null character, to the
+ *	buffer pointed to by dst.
+ *
+ * RETURN VALUE
+ *	dst + strlen(dst)
+ *		This function returns a pointer to the terminating NUL
+ *		byte.
+ *
+ * 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 `NITEMS(src) + 1`.
+ *
+ * EXAMPLES
+ *	char  hostname[NITEMS(utmp->ut_host) + 1];
+ *
+ *	len = ZUSTR2STP(hostname, utmp->ut_host) - hostname;
+ *	puts(hostname);
+ */
+
+
+#define ZUSTR2STP(dst, src)                                                   \
+({                                                                            \
+	static_assert(!is_array(dst) || sizeof(dst) > SIZEOF_ARRAY(src), ""); \
+                                                                              \
+	stpcpy(mempcpy(dst, src, strnlen(src, NITEMS(src))), "");             \
+})
+
+
+#endif  // include guard