linux-kernel - [PATCH nolibc 30/61] tools/nolibc/string: add strncpy() and strlcpy()

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Date:   Mon, 18 Apr 2022 17:41:54 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     gwml@...r.gnuweeb.org, kernel-team@...com, w@....eu,
        Willy Tarreau <w@....eu>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH nolibc 30/61] tools/nolibc/string: add strncpy() and strlcpy()

From: Willy Tarreau <w@....eu>

These are minimal variants. strncpy() always fills the destination for
<size> chars, while strlcpy() copies no more than <size> including the
zero and returns the source's length. The respective sizes on various
archs are:

  strncpy(): x86:0x1f mips:0x30 arm:0x20
  strlcpy(): x86:0x17 mips:0x34 arm:0x1a

Signed-off-by: Willy Tarreau <w@....eu>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 tools/include/nolibc/string.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/tools/include/nolibc/string.h b/tools/include/nolibc/string.h
index b831a02de83f..7c274efcdfae 100644
--- a/tools/include/nolibc/string.h
+++ b/tools/include/nolibc/string.h
@@ -121,6 +121,34 @@ size_t nolibc_strlen(const char *str)
 		nolibc_strlen((str));           \
 })
 
+static __attribute__((unused))
+size_t strlcpy(char *dst, const char *src, size_t size)
+{
+	size_t len;
+	char c;
+
+	for (len = 0;;) {
+		c = src[len];
+		if (len < size)
+			dst[len] = c;
+		if (!c)
+			break;
+		len++;
+	}
+	return len;
+}
+
+static __attribute__((unused))
+char *strncpy(char *dst, const char *src, size_t size)
+{
+	size_t len;
+
+	for (len = 0; len < size; len++)
+		if ((dst[len] = *src))
+			src++;
+	return dst;
+}
+
 static __attribute__((unused))
 char *strrchr(const char *s, int c)
 {
-- 
2.31.1.189.g2e36527f23