linux-kernel - [PATCH 4/9] strstarts: helper function for !strncmp(str, prefix, strlen(prefix))

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Message-Id: <20090207124638.32FEBDDDDF@ozlabs.org>
Date:	Sat, 07 Feb 2009 23:15:22 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	linux-kernel@...r.kernel.org
Cc:	Tim Abbott <tabbott@....edu>
Subject: [PATCH 4/9] strstarts: helper function for !strncmp(str, prefix, strlen(prefix))


Impact: minor new API

ksplice added a "starts_with" function, which seems like a common need.
When people open-code it they seem to use fixed numbers rather than strlen,
so it's quite a readability win (also, strncmp() almost always wants != 0
on it).

So here's strstarts().

Cc: Anders Kaseorg <andersk@....edu>
Cc: Jeff Arnold <jbarnold@....edu>
Cc: Tim Abbott <tabbott@....edu>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
---
 include/linux/string.h |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -114,5 +114,14 @@ extern ssize_t memory_read_from_buffer(v
 extern ssize_t memory_read_from_buffer(void *to, size_t count, loff_t *ppos,
 			const void *from, size_t available);
 
+/**
+ * strstarts - does @str start with @prefix?
+ * @str: string to examine
+ * @prefix: prefix to look for.
+ */
+static inline bool strstarts(const char *str, const char *prefix)
+{
+	return strncmp(str, prefix, strlen(prefix)) == 0;
+}
 #endif
 #endif /* _LINUX_STRING_H_ */

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