utils: add osmo_strnchr()

When finding a char in a string, I want to be able to limit the search area by
size, not only by nul terminator.

Change-Id: I48f8ace9f51f8a06796648883afcabe3b4e8b537
This commit is contained in:
Neels Hofmeyr 2019-11-19 01:38:10 +01:00
parent ff65d24ec4
commit 06356fd9c3
4 changed files with 65 additions and 0 deletions

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@ -139,6 +139,7 @@ uint64_t osmo_decode_big_endian(const uint8_t *data, size_t data_len);
uint8_t *osmo_encode_big_endian(uint64_t value, size_t data_len);
size_t osmo_strlcpy(char *dst, const char *src, size_t siz);
const char *osmo_strnchr(const char *str, size_t str_size, char c);
bool osmo_is_hexstr(const char *str, int min_digits, int max_digits,
bool require_even);

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@ -525,6 +525,28 @@ size_t osmo_strlcpy(char *dst, const char *src, size_t siz)
return ret;
}
/*! Find first occurence of a char in a size limited string.
* Like strchr() but with a buffer size limit.
* \param[in] str String buffer to examine.
* \param[in] str_size sizeof(str).
* \param[in] c Character to look for.
* \return Pointer to the matched char, or NULL if not found.
*/
const char *osmo_strnchr(const char *str, size_t str_size, char c)
{
const char *end = str + str_size;
const char *pos;
if (!str)
return NULL;
for (pos = str; pos < end; pos++) {
if (c == *pos)
return pos;
if (!*pos)
return NULL;
}
return NULL;
}
/*! Validate that a given string is a hex string within given size limits.
* Note that each hex digit amounts to a nibble, so if checking for a hex
* string to result in N bytes, pass amount of digits as 2*N.

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@ -1191,6 +1191,39 @@ static void osmo_print_n_test(void)
}
}
static void osmo_strnchr_test(void)
{
struct test {
const char *haystack;
size_t haystack_len;
const char *needle;
int expect_offset;
};
struct test tests[] = {
{ "foo=bar", 8, "=", 3 },
{ "foo=bar", 4, "=", 3 },
{ "foo=bar", 3, "=", -1 },
{ "foo=bar", 0, "=", -1 },
{ "foo\0=bar", 9, "=", -1 },
{ "foo\0=bar", 9, "\0", 3 },
};
struct test *t;
printf("\n%s()\n", __func__);
for (t = tests; t - tests < ARRAY_SIZE(tests); t++) {
const char *r = osmo_strnchr(t->haystack, t->haystack_len, t->needle[0]);
int offset = -1;
if (r)
offset = r - t->haystack;
printf("osmo_strnchr(%s, %zu, ",
osmo_quote_str(t->haystack, -1), t->haystack_len);
printf("'%s') -> %d",
osmo_escape_str(t->needle, 1), offset);
if (offset != t->expect_offset)
printf(" ERROR expected %d", t->expect_offset);
printf("\n");
}
}
int main(int argc, char **argv)
{
static const struct log_info log_info = {};
@ -1213,5 +1246,6 @@ int main(int argc, char **argv)
startswith_test();
name_c_impl_test();
osmo_print_n_test();
osmo_strnchr_test();
return 0;
}

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@ -403,3 +403,11 @@ NULL token_len=10 buf_size=1 -> token="" rc=0
NULL token_len=10 buf_size=0 -> token="unchanged" rc=0
"" token_len=10 buf_size=0 -> token="unchanged" rc=0
"foo=bar" token_len=0 buf_size=0 -> token="unchanged" rc=0
osmo_strnchr_test()
osmo_strnchr("foo=bar", 8, '=') -> 3
osmo_strnchr("foo=bar", 4, '=') -> 3
osmo_strnchr("foo=bar", 3, '=') -> -1
osmo_strnchr("foo=bar", 0, '=') -> -1
osmo_strnchr("foo", 9, '=') -> -1
osmo_strnchr("foo", 9, '\0') -> 3