view mercurial/cffi/bdiffbuild.py @ 50317:af776c3d5c3e stable

debugdeltachain: stop summing the same chain over and over

Before this patch, delta chain size was computed from scratch for each chain,
disregarding the fact very likely already computed the same of length-1 prefix
for another revisions.

We not cache delta chain size and shortcut the computation when we see them.

Just for my mercurial-devel clone, this move the computation from about 17.5
second to about 4.8 seconds.

import cffi
import os

ffi = cffi.FFI()
with open(
    os.path.join(os.path.join(os.path.dirname(__file__), '..'), 'bdiff.c')
) as f:
    ffi.set_source(
        "mercurial.cffi._bdiff", f.read(), include_dirs=['mercurial']
    )
ffi.cdef(
    """
struct bdiff_line {
    int hash, n, e;
    ssize_t len;
    const char *l;
};

struct bdiff_hunk;
struct bdiff_hunk {
    int a1, a2, b1, b2;
    struct bdiff_hunk *next;
};

int bdiff_splitlines(const char *a, ssize_t len, struct bdiff_line **lr);
int bdiff_diff(struct bdiff_line *a, int an, struct bdiff_line *b, int bn,
    struct bdiff_hunk *base);
void bdiff_freehunks(struct bdiff_hunk *l);
void free(void*);
"""
)

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