Previously, we operated on smartlists of NUL-terminated strings,
which required us to copy both inputs to produce the NUL-terminated
strings. Then we copied parts of _those_ inputs to produce an
output smartlist of NUL-terminated strings. And finally, we
concatenated everything into a final resulting string.
This implementation, instead, uses a pointer-and-extent pattern to
represent each line as a pointer into the original inputs and a
length. These line objects are then added by reference into the
output. No actual bytes are copied from the original strings until
we finally concatenate the final result together.
Bookkeeping structures and newly allocated strings (like ed
commands) are allocated inside a memarea, to avoid needless mallocs
or complicated should-I-free-this-or-not bookkeeping.
In my measurements, this improves CPU performance by something like
18%. The memory savings should be much, much higher.
This takes two fuzzers: one which generates a diff and makes sure it
works, and one which applies a diff.
So far, they won't crash, but there's a bug in my
string-manipulation code someplace that I'm having to work around,
related to the case where you have a blank line at the end of a
file, or where you diff a file with itself.
Also, add very strict split/join functions, and totally forbid
nonempty files that end with somethig besides a newline. This
change is necessary to ensure that diff/apply are actually reliable
inverse operations.
The 2-line diff changs is needed to make the unit tests actually
test the cases that they thought they were testing.
The bogus free was found while testing those cases
(This commit was extracted by nickm based on the final outcome of
the project, taking only the changes in the files touched by this
commit from the consdiff_rebased branch. The directory-system
changes are going to get worked on separately.)
Windows doesn't let you check the socket error for a socket with
WSAGetLastError() and getsockopt(SO_ERROR). But
getsockopt(SO_ERROR) clears the error on the socket, so you can't
call it more than once per error.
When we introduced recv_ni to help drain alert sockets, back in
0.2.6.3-alpha, we had the failure path for recv_ni call getsockopt()
twice, though: once to check for EINTR and one to check for EAGAIN.
Of course, we never got the eagain, so we treated it as an error,
and warned about: "No error".
The fix here is to have these functions return -errno on failure.
Fixes bug 21540; bugfix on 0.2.6.3-alpha.
The 64-bit load and store code was generating pretty bad output with
my compiler, so I extracted the code from csiphash and used that instead.
Close ticket 21737
