mercurial/cffi/mpatch.py

rust-discovery: takefullsample() core implementation

take_full_sample() browses the undecided set in both directions: from
its roots as well as from its heads.

Following what's done on the Python side, we alter update_sample()
signature to take a closure returning an iterator: either ParentsIterator
or an iterator over the children found in `children_cache`. These constructs
should probably be split off in a separate module.

This is a first concrete example where a more abstract graph notion (probably
 a trait) would be useful, as this is nothing but an operation on the reversed
DAG.

A similar motivation in the context of the discovery
process would be to replace the call to dagops::range in
`add_missing_revisions()` with a simple iteration over descendents, again an
operation on the reversed graph.

Differential Revision: https://phab.mercurial-scm.org/D6424

# mpatch.py - CFFI implementation of mpatch.c
#
# Copyright 2016 Maciej Fijalkowski <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

from ..pure.mpatch import *
from ..pure.mpatch import mpatchError  # silence pyflakes
from . import _mpatch

ffi = _mpatch.ffi
lib = _mpatch.lib

@ffi.def_extern()
def cffi_get_next_item(arg, pos):
    all, bins = ffi.from_handle(arg)
    container = ffi.new("struct mpatch_flist*[1]")
    to_pass = ffi.new("char[]", str(bins[pos]))
    all.append(to_pass)
    r = lib.mpatch_decode(to_pass, len(to_pass) - 1, container)
    if r < 0:
        return ffi.NULL
    return container[0]

def patches(text, bins):
    lgt = len(bins)
    all = []
    if not lgt:
        return text
    arg = (all, bins)
    patch = lib.mpatch_fold(ffi.new_handle(arg),
                            lib.cffi_get_next_item, 0, lgt)
    if not patch:
        raise mpatchError("cannot decode chunk")
    outlen = lib.mpatch_calcsize(len(text), patch)
    if outlen < 0:
        lib.mpatch_lfree(patch)
        raise mpatchError("inconsistency detected")
    buf = ffi.new("char[]", outlen)
    if lib.mpatch_apply(buf, text, len(text), patch) < 0:
        lib.mpatch_lfree(patch)
        raise mpatchError("error applying patches")
    res = ffi.buffer(buf, outlen)[:]
    lib.mpatch_lfree(patch)
    return res