6d1abc5b2c
utils/base64.cc had some strange code with a strange comment in
base64_begins_with().
The code had
base.substr(operand.size() - 4, operand.size())
The comment claims that this is "last 4 bytes of base64-encoded string",
but this comment is misleading - operand is typically shorter than base
(this this whole point of the base64_begins_with()), so the real
intention of the code is not to find the *last* 4 bytes of base, but rather
the *next* four bytes after the (operand.size() - 4) which we already copied.
These four bytes that may need the full power of base64_decode_string()
because they may or may not contain padding.
But, if we really want the next 4 bytes, why pass operand.size() as the
length of the substring? operand.size() is at least 4 (it's a mutiple of
4, and if it's 0 we returned earlier), but it could me more. We don't
need more, we just need 4. It's not really wrong to take more than 4 (so
this patch doesn't *fix* any bug), but can be wasteful. So this code
should be:
base.substr(operand.size() - 4, 4)
We already have in test/boost/alternator_unit_test.cc a test,
test_base64_begins_with that takes encoded base64 strings up to 12
characters in length (corresponding to decoded strings up to 8 chars),
and substrings from length 0 to the base string's length, and check
that test_base64_begins_with succeeds.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closes scylladb/scylladb#25712
5.4 KiB
5.4 KiB