mercurial/cffi/bdiff.py

rhg: Add support for `rhg status --copies`

Copy sources are collected during `status()` rather than after the fact like
in Python, because `status()` takes a `&mut` exclusive reference to the dirstate map
(in order to potentially mutate it for directory mtimes) and returns `Cow<'_, HgPath>`
that borrow the dirstate map.

Even though with `Cow` only some shared borrows remain, the still extend the same
lifetime of the initial `&mut` so the dirstate map cannot be borrowed again
to access copy sources after the fact:

https://doc.rust-lang.org/nomicon/lifetime-mismatch.html#limits-of-lifetimes

Additionally, collecting copy sources during the dirstate tree traversal that
`status()` already does avoids the cost of another traversal or other lookups
(though I haven’t benchmarked that cost).

Differential Revision: https://phab.mercurial-scm.org/D11899

# 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.

from __future__ import absolute_import

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)