2022-03-28 23:23:55

by Rasmus Villemoes

Subject: [PATCH 1/2] lib/test_string.c: add strspn and strcspn tests

Before refactoring strspn() and strcspn(), add some simple test cases.

Signed-off-by: Rasmus Villemoes <[email protected]>
---
lib/test_string.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)

diff --git a/lib/test_string.c b/lib/test_string.c
index 9dfd6f52de92..c5cb92fb710e 100644
--- a/lib/test_string.c
+++ b/lib/test_string.c
@@ -179,6 +179,34 @@ static __init int strnchr_selftest(void)
return 0;
}

+static __init int strspn_selftest(void)
+{
+ static const struct strspn_test {
+ const char str[16];
+ const char accept[16];
+ const char reject[16];
+ unsigned a;
+ unsigned r;
+ } tests[] __initconst = {
+ { "foobar", "", "", 0, 6 },
+ { "abba", "abc", "ABBA", 4, 4 },
+ { "abba", "a", "b", 1, 1 },
+ { "", "abc", "abc", 0, 0},
+ };
+ const struct strspn_test *s = tests;
+ size_t i, res;
+
+ for (i = 0; i < ARRAY_SIZE(tests); ++i, ++s) {
+ res = strspn(s->str, s->accept);
+ if (res != s->a)
+ return 0x100 + 2*i;
+ res = strcspn(s->str, s->reject);
+ if (res != s->r)
+ return 0x100 + 2*i + 1;
+ }
+ return 0;
+}
+
static __exit void string_selftest_remove(void)
{
}
@@ -212,6 +240,11 @@ static __init int string_selftest_init(void)
if (subtest)
goto fail;

+ test = 6;
+ subtest = strspn_selftest();
+ if (subtest)
+ goto fail;
+
pr_info("String selftests succeeded\n");
return 0;
fail:
--
2.31.1

2022-03-28 23:24:07

by Rasmus Villemoes

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 <[email protected]>
---
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