mercurial/cffi/bdiff.py

util: implement `writelines()` on atomictempfile

With typehints on the vfs objects, pytype will flag this:

    FAILED: /mnt/c/Users/Matt/hg/.pytype/pyi/mercurial/patch.pyi
    /usr/bin/python3.8 -m pytype.single
        --imports_info /mnt/c/Users/Matt/hg/.pytype/imports/mercurial.patch.imports
        --module-name mercurial.patch -V 3.7
        -o /mnt/c/Users/Matt/hg/.pytype/pyi/mercurial/patch.pyi
        --analyze-annotated --nofail --quick
        /mnt/c/Users/Matt/hg/mercurial/patch.py
    File "/mnt/c/Users/Matt/hg/mercurial/patch.py", line 535, in writerej:
        No attribute 'writelines' on mercurial.util.atomictempfile [attribute-error]
      In Union[
          mercurial.util.atomictempfile,
          mercurial.vfs.checkambigatclosing,
          mercurial.vfs.delayclosedfile,
          mercurial.windows.fdproxy,
          mercurial.windows.mixedfilemodewrapper
      ]

It's not a real problem there (atomictempfile is only created by passing
different args), but it's reasonable for this to implement the function and
behave like a normal file.  There are other functions missing that can be added
if/when needed.

# bdiff.py - CFFI implementation of bdiff.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.


import struct

from ..pure.bdiff import *
from . import _bdiff  # pytype: disable=import-error

ffi = _bdiff.ffi
lib = _bdiff.lib


def blocks(sa, sb):
    a = ffi.new(b"struct bdiff_line**")
    b = ffi.new(b"struct bdiff_line**")
    ac = ffi.new(b"char[]", str(sa))
    bc = ffi.new(b"char[]", str(sb))
    l = ffi.new(b"struct bdiff_hunk*")
    try:
        an = lib.bdiff_splitlines(ac, len(sa), a)
        bn = lib.bdiff_splitlines(bc, len(sb), b)
        if not a[0] or not b[0]:
            raise MemoryError
        count = lib.bdiff_diff(a[0], an, b[0], bn, l)
        if count < 0:
            raise MemoryError
        rl = [None] * count
        h = l.next
        i = 0
        while h:
            rl[i] = (h.a1, h.a2, h.b1, h.b2)
            h = h.next
            i += 1
    finally:
        lib.free(a[0])
        lib.free(b[0])
        lib.bdiff_freehunks(l.next)
    return rl


def bdiff(sa, sb):
    a = ffi.new(b"struct bdiff_line**")
    b = ffi.new(b"struct bdiff_line**")
    ac = ffi.new(b"char[]", str(sa))
    bc = ffi.new(b"char[]", str(sb))
    l = ffi.new(b"struct bdiff_hunk*")
    try:
        an = lib.bdiff_splitlines(ac, len(sa), a)
        bn = lib.bdiff_splitlines(bc, len(sb), b)
        if not a[0] or not b[0]:
            raise MemoryError
        count = lib.bdiff_diff(a[0], an, b[0], bn, l)
        if count < 0:
            raise MemoryError
        rl = []
        h = l.next
        la = lb = 0
        while h:
            if h.a1 != la or h.b1 != lb:
                lgt = (b[0] + h.b1).l - (b[0] + lb).l
                rl.append(
                    struct.pack(
                        b">lll",
                        (a[0] + la).l - a[0].l,
                        (a[0] + h.a1).l - a[0].l,
                        lgt,
                    )
                )
                rl.append(str(ffi.buffer((b[0] + lb).l, lgt)))
            la = h.a2
            lb = h.b2
            h = h.next

    finally:
        lib.free(a[0])
        lib.free(b[0])
        lib.bdiff_freehunks(l.next)
    return b"".join(rl)