1 files changed, 90 insertions, 0 deletions
diff --git a/lib/string/stpecpy.h b/lib/string/stpecpy.h
new file mode 100644
index 0000000..2324baa
--- /dev/null
+++ b/lib/string/stpecpy.h
@@ -0,0 +1,90 @@
+/*
+ * SPDX-FileCopyrightText:  2022 - 2023, Alejandro Colomar <alx@kernel.org>
+ *
+ * SPDX-License-Identifier:  BSD-3-Clause
+ */
+
+
+#ifndef SHADOW_INCLUDE_LIB_STPECPY_H_
+#define SHADOW_INCLUDE_LIB_STPECPY_H_
+
+
+#include <config.h>
+
+#if !defined(HAVE_STPECPY)
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <string.h>
+
+#include "attr.h"
+
+
+ATTR_STRING(3)
+inline char *stpecpy(char *dst, char *end, const char *restrict src);
+
+
+/*
+ * SYNOPSIS
+ *	[[gnu::null_terminated_string_arg(3)]]
+ *	char *_Nullable stpecpy(char *_Nullable dst, char end[0],
+ *	                        const char *restrict src);
+ *
+ * ARGUMENTS
+ *	dst	Destination buffer where to copy a string.
+ *
+ *	end	Pointer to one after the last element of the buffer
+ *		pointed to by `dst`.  Usually, it should be calculated
+ *		as `dst + NITEMS(dst)`.
+ *
+ *	src	Source string to be copied into dst.
+ *
+ * DESCRIPTION
+ *	This function copies the string pointed to by src, into a string
+ *	at the buffer pointed to by dst.  If the destination buffer,
+ *	limited by a pointer to its end --one after its last element--,
+ *	isn't large enough to hold the copy, the resulting string is
+ *	truncated.
+ *
+ *	This function can be chained with calls to [v]stpeprintf().
+ *
+ * RETURN VALUE
+ *	dst + strlen(dst)
+ *		•  On success, this function returns a pointer to the
+ *		   terminating NUL byte.
+ *
+ *	end
+ *		•  If this call truncated the resulting string.
+ *		•  If `dst == end` (a previous chained call to these
+ *		   functions truncated).
+ *	NULL
+ *		•  If `dst == NULL` (a previous chained call to
+ *		   [v]stpeprintf() failed).
+ *
+ * ERRORS
+ *	This function doesn't set errno.
+ */
+
+
+inline char *
+stpecpy(char *dst, char *end, const char *restrict src)
+{
+	bool    trunc;
+	size_t  dsize, dlen, slen;
+
+	if (dst == end)
+		return end;
+	if (dst == NULL)
+		return NULL;
+
+	dsize = end - dst;
+	slen = strnlen(src, dsize);
+	trunc = (slen == dsize);
+	dlen = slen - trunc;
+
+	return stpcpy(mempcpy(dst, src, dlen), "") + trunc;
+}
+
+
+#endif  // !HAVE_STPECPY
+#endif  // include guard