Add c_ustr2stpe()

This allows copying with truncation from a measured character sequence
to a string.

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

2 files changed, 62 insertions, 0 deletions

diff --git a/include/c/str/cpy/stp/stpe/ustr2stpe.h b/include/c/str/cpy/stp/stpe/ustr2stpe.h
new file mode 100644
index 0000000..a4424b8
--- /dev/null
+++ b/include/c/str/cpy/stp/stpe/ustr2stpe.h
@@ -0,0 +1,49 @@
+// Copyright 2023 Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier:  LGPL-3.0-or-later WITH LGPL-3.0-linking-exception
+
+
+#ifndef INCLUDE_C_STR_CPY_STP_STPE_USTR2STPE_H_
+#define INCLUDE_C_STR_CPY_STP_STPE_USTR2STPE_H_
+
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <sys/param.h>
+
+#include <c/branch/likely.h>
+#include <c/branch/unreachable.h>
+#include <c/mem/cpy/mempcpy.h>
+#include <c/qual/nullable/nullable.h>
+#include <c/str/len/strlen.h>
+
+
+#pragma clang assume_nonnull begin
+inline char *c_nullable c_ustr2stpe(char *c_nullable dst, char *end,
+    const char *restrict src, size_t slen);
+
+
+inline char *c_nullable
+c_ustr2stpe(char *c_nullable dst, char *end, const char *restrict src,
+    size_t slen)
+{
+	bool    trunc;
+	size_t  dsize, dlen;
+
+	if (dst == end)
+		return end;
+	if (c_unlikely(dst == NULL))  // Allow chaining with stpeprintf().
+		return NULL;
+	c_impossible(dst > end);
+
+	dsize = end - dst;
+	slen = MIN(slen, dsize);
+	trunc = (slen == dsize);
+	dlen = slen - trunc;
+	dst[dlen] = '\0';
+
+	return c_mempcpy(dst, src, dlen) + trunc;
+}
+#pragma clang assume_nonnull end
+
+
+#endif  // Header guard
diff --git a/src/c/str/cpy/stp/stpe/ustr2stpe.c b/src/c/str/cpy/stp/stpe/ustr2stpe.c
new file mode 100644
index 0000000..a7df817
--- /dev/null
+++ b/src/c/str/cpy/stp/stpe/ustr2stpe.c
@@ -0,0 +1,13 @@
+// Copyright 2023 Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier:  LGPL-3.0-or-later WITH LGPL-3.0-linking-exception
+
+
+#include <c/str/cpy/stp/stpe/ustr2stpe.h>
+
+#include <c/qual/nullable/nullable.h>
+
+
+#pragma clang assume_nonnull begin
+extern inline char *c_nullable c_ustr2stpe(char *c_nullable dst, char end[0],
+    const char *restrict src, size_t slen);
+#pragma clang assume_nonnull end