Commit 4008ec0e authored by David Gibson's avatar David Gibson

bytestring: Add bytestring_slice function

Add a bytestring_slice() function to take a sub(byte)string of a
bytestring.
Signed-off-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
parent c06054cd
......@@ -95,4 +95,31 @@ static inline char bytestring_byte(struct bytestring s, size_t n)
return s.ptr[n];
}
/**
* bytestring_slice - extract a substring from a bytestring
* @s: bytestring
* @start, @end: indexes
*
* Return a sub-bytestring of @s, starting at byte index @start, and
* running to, but not including byte @end. If @end is before start,
* returns a zero-length bytestring. If @start is out of range,
* return a zero length bytestring at the end of @s.
*
* Note that this doesn't copy or allocate anything - the returned
* bytestring occupies (some of) the same memory as the given
* bytestring.
*/
static inline struct bytestring bytestring_slice(struct bytestring s,
size_t start, size_t end)
{
if (start > s.len)
start = s.len;
if (end > s.len)
end = s.len;
if (end < start)
end = start;
return bytestring(s.ptr + start, end - start);
}
#endif /* CCAN_BYTESTRING_H_ */
......@@ -12,7 +12,7 @@ int main(void)
struct bytestring bs, bs1, bs2, bs3, bs4, bs5;
/* This is how many tests you plan to run */
plan_tests(16);
plan_tests(22);
bs = bytestring(str1, sizeof(str1) - 1);
ok1(bs.ptr == str1);
......@@ -43,6 +43,13 @@ int main(void)
ok1(bytestring_byte(bs2, 5) == 'e');
ok1(bytestring_byte(bs2, 6) == 'f');
ok1(bytestring_eq(bytestring_slice(bs, 0, 4), BYTESTRING("test")));
ok1(bytestring_eq(bytestring_slice(bs, 5, 8), BYTESTRING("str")));
ok1(bytestring_eq(bytestring_slice(bs2, 2, 5), BYTESTRING("c\0d")));
ok1(bytestring_eq(bytestring_slice(bs2, 0, -1U), bs2));
ok1(bytestring_eq(bytestring_slice(bs2, 10, 20), bytestring_NULL));
ok1(bytestring_eq(bytestring_slice(bs2, 2, 1), bytestring_NULL));
/* This exits depending on whether all tests passed */
return exit_status();
}
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