linux-kernel - [PATCH 2/2] lib/string.c: simplify str[c]spn

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Message-Id: <20220328224119.3003834-2-linux@rasmusvillemoes.dk>
Date:   Tue, 29 Mar 2022 00:41:19 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andy@...nel.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] lib/string.c: simplify str[c]spn

Use strchr(), which makes them a lot shorter, and more obviously
symmetric in their treatment of accept/reject. It also saves a little
bit of .text; bloat-o-meter for an arm build says

Function                                     old     new   delta
strcspn                                       92      76     -16
strspn                                       108      76     -32

While here, also remove a stray empty line before EXPORT_SYMBOL().

Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
---
 lib/string.c | 25 ++++++-------------------
 1 file changed, 6 insertions(+), 19 deletions(-)

diff --git a/lib/string.c b/lib/string.c
index 485777c9da83..6f334420f687 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -517,21 +517,13 @@ EXPORT_SYMBOL(strnlen);
 size_t strspn(const char *s, const char *accept)
 {
 	const char *p;
-	const char *a;
-	size_t count = 0;
 
 	for (p = s; *p != '\0'; ++p) {
-		for (a = accept; *a != '\0'; ++a) {
-			if (*p == *a)
-				break;
-		}
-		if (*a == '\0')
-			return count;
-		++count;
+		if (!strchr(accept, *p))
+			break;
 	}
-	return count;
+	return p - s;
 }
-
 EXPORT_SYMBOL(strspn);
 #endif
 
@@ -544,17 +536,12 @@ EXPORT_SYMBOL(strspn);
 size_t strcspn(const char *s, const char *reject)
 {
 	const char *p;
-	const char *r;
-	size_t count = 0;
 
 	for (p = s; *p != '\0'; ++p) {
-		for (r = reject; *r != '\0'; ++r) {
-			if (*p == *r)
-				return count;
-		}
-		++count;
+		if (strchr(reject, *p))
+			break;
 	}
-	return count;
+	return p - s;
 }
 EXPORT_SYMBOL(strcspn);
 #endif
-- 
2.31.1