typing: add type hints to mpatch implementations

Again, using `merge-pyi` to apply the stubs in cext and then manually type the
private methods.  The generated stub without these hints inferred very little,
and the stuff it did was wrong.

mercurial/cffi/mpatch.py

@@ -1,48 +1,50 b''
 # 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 typing import List
+
 from ..pure.mpatch import *
 from ..pure.mpatch import mpatchError  # silence pyflakes
 from . import _mpatch  # pytype: disable=import-error
 
 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(b"struct mpatch_flist*[1]")
     to_pass = ffi.new(b"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):
+def patches(text: bytes, bins: List[bytes]) -> bytes:
     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(b"cannot decode chunk")
     outlen = lib.mpatch_calcsize(len(text), patch)
     if outlen < 0:
         lib.mpatch_lfree(patch)
         raise mpatchError(b"inconsistency detected")
     buf = ffi.new(b"char[]", outlen)
     if lib.mpatch_apply(buf, text, len(text), patch) < 0:
         lib.mpatch_lfree(patch)
         raise mpatchError(b"error applying patches")
     res = ffi.buffer(buf, outlen)[:]
     lib.mpatch_lfree(patch)
     return res

mercurial/pure/mpatch.py

@@ -1,134 +1,143 b''
 # mpatch.py - Python implementation of mpatch.c
 #
 # Copyright 2009 Olivia Mackall <[e-mail]> and others
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 
 import io
 import struct
 
+from typing import (
+    List,
+    Tuple,
+)
+
 
 stringio = io.BytesIO
 
 
 class mpatchError(Exception):
     """error raised when a delta cannot be decoded"""
 
 
 # This attempts to apply a series of patches in time proportional to
 # the total size of the patches, rather than patches * len(text). This
 # means rather than shuffling strings around, we shuffle around
 # pointers to fragments with fragment lists.
 #
 # When the fragment lists get too long, we collapse them. To do this
 # efficiently, we do all our operations inside a buffer created by
 # mmap and simply use memmove. This avoids creating a bunch of large
 # temporary string buffers.
 
 
-def _pull(dst, src, l):  # pull l bytes from src
+def _pull(
+    dst: List[Tuple[int, int]], src: List[Tuple[int, int]], l: int
+) -> None:  # pull l bytes from src
     while l:
         f = src.pop()
         if f[0] > l:  # do we need to split?
             src.append((f[0] - l, f[1] + l))
             dst.append((l, f[1]))
             return
         dst.append(f)
         l -= f[0]
 
 
-def _move(m, dest, src, count):
+def _move(m: stringio, dest: int, src: int, count: int) -> None:
     """move count bytes from src to dest
 
     The file pointer is left at the end of dest.
     """
     m.seek(src)
     buf = m.read(count)
     m.seek(dest)
     m.write(buf)
 
 
-def _collect(m, buf, list):
+def _collect(
+    m: stringio, buf: int, list: List[Tuple[int, int]]
+) -> Tuple[int, int]:
     start = buf
     for l, p in reversed(list):
         _move(m, buf, p, l)
         buf += l
     return (buf - start, start)
 
 
-def patches(a, bins):
+def patches(a: bytes, bins: List[bytes]) -> bytes:
     if not bins:
         return a
 
     plens = [len(x) for x in bins]
     pl = sum(plens)
     bl = len(a) + pl
     tl = bl + bl + pl  # enough for the patches and two working texts
     b1, b2 = 0, bl
 
     if not tl:
         return a
 
     m = stringio()
 
     # load our original text
     m.write(a)
     frags = [(len(a), b1)]
 
     # copy all the patches into our segment so we can memmove from them
     pos = b2 + bl
     m.seek(pos)
     for p in bins:
         m.write(p)
 
     for plen in plens:
         # if our list gets too long, execute it
         if len(frags) > 128:
             b2, b1 = b1, b2
             frags = [_collect(m, b1, frags)]
 
         new = []
         end = pos + plen
         last = 0
         while pos < end:
             m.seek(pos)
             try:
                 p1, p2, l = struct.unpack(b">lll", m.read(12))
             except struct.error:
                 raise mpatchError(b"patch cannot be decoded")
             _pull(new, frags, p1 - last)  # what didn't change
             _pull([], frags, p2 - p1)  # what got deleted
             new.append((l, pos + 12))  # what got added
             pos += l + 12
             last = p2
         frags.extend(reversed(new))  # what was left at the end
 
     t = _collect(m, b2, frags)
 
     m.seek(t[1])
     return m.read(t[0])
 
 
-def patchedsize(orig, delta):
+def patchedsize(orig: int, delta: bytes) -> int:
     outlen, last, bin = 0, 0, 0
     binend = len(delta)
     data = 12
 
     while data <= binend:
         decode = delta[bin : bin + 12]
         start, end, length = struct.unpack(b">lll", decode)
         if start > end:
             break
         bin = data + length
         data = bin + 12
         outlen += start - last
         last = end
         outlen += length
 
     if bin != binend:
         raise mpatchError(b"patch cannot be decoded")
 
     outlen += orig - last
     return outlen