mercurial/cffi/mpatchbuild.py

copies: avoid instancing more changectx to access parent revisions

We just need to know the revision numbers of the parents, creating full context
is needlessly expensive.

This provide a small, but noticeable performance boost.

revision: large amount; added files: large amount; rename small amount; c3b14617fbd7 9ba6ab77fd29
before: ! wall 2.885636 comb 2.900000 user 2.870000 sys 0.030000 (median of 10)
after:  ! wall 2.702270 comb 2.710000 user 2.690000 sys 0.020000 (median of 10)
revision: large amount; added files: small amount; rename small amount; c3b14617fbd7 f650a9b140d2
before: ! wall 4.298271 comb 4.290000 user 4.240000 sys 0.050000 (median of 10)
after:  ! wall 3.976610 comb 3.970000 user 3.920000 sys 0.050000 (median of 10)
revision: large amount; added files: large amount; rename large amount; 08ea3258278e d9fa043f30c0
before: ! wall 0.773397 comb 0.770000 user 0.770000 sys 0.000000 (median of 11)
after:  ! wall 0.701634 comb 0.700000 user 0.700000 sys 0.000000 (median of 13)
revision: small amount; added files: large amount; rename large amount; df6f7a526b60 a83dc6a2d56f
before: ! wall 0.013585 comb 0.010000 user 0.010000 sys 0.000000 (median of 217)
after:  ! wall 0.013550 comb 0.010000 user 0.010000 sys 0.000000 (median of 218)
revision: small amount; added files: large amount; rename small amount; 4aa4e1f8e19a 169138063d63
before: ! wall 0.003202 comb 0.000000 user 0.000000 sys 0.000000 (median of 929)
after:  ! wall 0.002993 comb 0.010000 user 0.010000 sys 0.000000 (median of 992)
revision: small amount; added files: small amount; rename small amount; 4bc173b045a6 964879152e2e
before: ! wall 0.000077 comb 0.000000 user 0.000000 sys 0.000000 (median of 12060)
after:  ! wall 0.000072 comb 0.000000 user 0.000000 sys 0.000000 (median of 12804)
revision: medium amount; added files: large amount; rename medium amount; c95f1ced15f2 2c68e87c3efe
before: ! wall 0.510614 comb 0.500000 user 0.500000 sys 0.000000 (median of 18)
after:  ! wall 0.473681 comb 0.470000 user 0.470000 sys 0.000000 (median of 20)
revision: medium amount; added files: medium amount; rename small amount; d343da0c55a8 d7746d32bf9d
before: ! wall 0.126552 comb 0.130000 user 0.130000 sys 0.000000 (median of 77)
after:  ! wall 0.115240 comb 0.110000 user 0.110000 sys 0.000000 (median of 85)

Differential Revision: https://phab.mercurial-scm.org/D7122

from __future__ import absolute_import

import cffi
import os

ffi = cffi.FFI()
mpatch_c = os.path.join(
    os.path.join(os.path.dirname(__file__), b'..', b'mpatch.c')
)
with open(mpatch_c) as f:
    ffi.set_source(
        b"mercurial.cffi._mpatch", f.read(), include_dirs=[b"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()