From 7f9f3fa0b1d130f207efd2bba049bbcc98cd407d Mon Sep 17 00:00:00 2001
From: Alejandro Colomar <alx@kernel.org>
Date: Sun, 20 Jul 2025 16:51:30 +0200
Subject: [PATCH] lib/string/strcmp/: strneq(), STRNEQ(): Add APIs

Signed-off-by: Alejandro Colomar <alx@kernel.org>
---
 lib/Makefile.am            |  2 ++
 lib/string/README          |  9 +++++++--
 lib/string/strcmp/strneq.c | 13 +++++++++++++
 lib/string/strcmp/strneq.h | 37 +++++++++++++++++++++++++++++++++++++
 4 files changed, 59 insertions(+), 2 deletions(-)
 create mode 100644 lib/string/strcmp/strneq.c
 create mode 100644 lib/string/strcmp/strneq.h

diff --git a/lib/Makefile.am b/lib/Makefile.am
index 31e9c0ee3..dc701148e 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -235,6 +235,8 @@ libshadow_la_SOURCES = \
 	string/strcmp/strcaseprefix.h \
 	string/strcmp/streq.c \
 	string/strcmp/streq.h \
+	string/strcmp/strneq.c \
+	string/strcmp/strneq.h \
 	string/strcmp/strprefix.c \
 	string/strcmp/strprefix.h \
 	string/strcpy/stpecpy.c \
diff --git a/lib/string/README b/lib/string/README
index 13d332110..147b278fd 100644
--- a/lib/string/README
+++ b/lib/string/README
@@ -33,6 +33,11 @@ Don't use some libc functions without Really Good Reasons:
 	The return value of strcmp(3) is confusing.
 	strcmp(3) would be legitimate for sorting strings.
 
+    strncmp(3)
+	Use STRNEQ(), or strpfx(), or else, depending on what you want.
+	The return value of strncmp(3) is confusing,
+	and it is unclear the purpose of its use when you read it.
+
     strcasecmp(3)
 	Use strcaseeq() instead.
 
@@ -131,9 +136,9 @@ strcmp/ - String comparison
 	Like strsfx(), but ignore upper-/lower-case.
 
   n/
-    strneq()  // Unimplemented
+    strneq()
 	Return true if a [[gnu::nonstring]] is equal to a string.
-    STRNEQ()  // Unimplemented
+    STRNEQ()
 	Like strneq(), but takes an array.
 
     strnpfx()  // Unimplemented
diff --git a/lib/string/strcmp/strneq.c b/lib/string/strcmp/strneq.c
new file mode 100644
index 000000000..5791811a9
--- /dev/null
+++ b/lib/string/strcmp/strneq.c
@@ -0,0 +1,13 @@
+// SPDX-FileCopyrightText: 2025, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#include "config.h"
+
+#include "string/strcmp/strneq.h"
+
+#include <stdbool.h>
+#include <stddef.h>
+
+
+extern inline bool strneq(const char *strn, const char *s, size_t size);
diff --git a/lib/string/strcmp/strneq.h b/lib/string/strcmp/strneq.h
new file mode 100644
index 000000000..de8958bae
--- /dev/null
+++ b/lib/string/strcmp/strneq.h
@@ -0,0 +1,37 @@
+// SPDX-FileCopyrightText: 2025, Alejandro Colomar <alx@kernel.org>
+// SPDX-License-Identifier: BSD-3-Clause
+
+
+#ifndef SHADOW_INCLUDE_LIB_STRING_STRCMP_STRNEQ_H_
+#define SHADOW_INCLUDE_LIB_STRING_STRCMP_STRNEQ_H_
+
+
+#include "config.h"
+
+#include <stdbool.h>
+#include <string.h>
+
+#include "attr.h"
+#include "sizeof.h"
+
+
+#define STRNEQ(strn, s)  strneq(strn, s, countof(strn))
+
+
+ATTR_STRING(2)
+inline bool strneq(ATTR_NONSTRING const char *strn, const char *s, size_t size);
+
+
+// nonstring equal
+/* Return true if the nonstring strn and the string s compare equal.  */
+inline bool
+strneq(const char *strn, const char *s, size_t size)
+{
+	if (strlen(s) > size)
+		return false;
+
+	return strncmp(strn, s, size) == 0;
+}
+
+
+#endif  // include guard
-- 
2.47.3