setup_mpatch_cffi.py

annotate: calculate line count correctly

Before this patch, the "lines" function inside "annotate" returns 1 for
empty text (''). This patch makes it 0. Because the function should match
mdiff.splitnewlines (used by mdiff.allblocks), or s.splitlines (used at the
end of the "annotate" method). Both len(mdiff.splitnewlines('')) and
len(''.splitlines(True)) are 0.

This issue was discovered while testing fastannotate [1].

I could not find a test case to reveal this issue. However in theory this
could reduce memory usage a little bit, and avoids surprises when people
are touching this area in the future.

[1]: https://bitbucket.org/facebook/hg-experimental/commits/525b3b98e93a

from __future__ import absolute_import

import cffi
import os

ffi = cffi.FFI()
mpatch_c = os.path.join(os.path.join(os.path.dirname(__file__), 'mercurial',
                                     'mpatch.c'))
ffi.set_source("_mpatch_cffi", open(mpatch_c).read(),
               include_dirs=["mercurial"])
ffi.cdef("""

struct mpatch_frag {
       int start, end, len;
       const char *data;
};

struct mpatch_flist {
       struct mpatch_frag *base, *head, *tail;
};

extern "Python" struct mpatch_flist* cffi_get_next_item(void*, ssize_t);

int mpatch_decode(const char *bin, ssize_t len, struct mpatch_flist** res);
ssize_t mpatch_calcsize(size_t len, struct mpatch_flist *l);
void mpatch_lfree(struct mpatch_flist *a);
static int mpatch_apply(char *buf, const char *orig, size_t len,
                        struct mpatch_flist *l);
struct mpatch_flist *mpatch_fold(void *bins,
                       struct mpatch_flist* (*get_next_item)(void*, ssize_t),
                       ssize_t start, ssize_t end);
""")

if __name__ == '__main__':
    ffi.compile()