bdiff: implement cffi version of bdiff

mercurial/pure/bdiff.py

@@ -1,136 +1,169 b''
 # bdiff.py - Python implementation of bdiff.c
 #
 # Copyright 2009 Matt 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.
 
 from __future__ import absolute_import
 
 import array
 import difflib
 import re
 import struct
 
 from . import policy
 policynocffi = policy.policynocffi
 modulepolicy = policy.policy
 
 def splitnewlines(text):
     '''like str.splitlines, but only split on newlines.'''
     lines = [l + '\n' for l in text.split('\n')]
     if lines:
         if lines[-1] == '\n':
             lines.pop()
         else:
             lines[-1] = lines[-1][:-1]
     return lines
 
 def _normalizeblocks(a, b, blocks):
     prev = None
     r = []
     for curr in blocks:
         if prev is None:
             prev = curr
             continue
         shift = 0
 
         a1, b1, l1 = prev
         a1end = a1 + l1
         b1end = b1 + l1
 
         a2, b2, l2 = curr
         a2end = a2 + l2
         b2end = b2 + l2
         if a1end == a2:
             while (a1end + shift < a2end and
                    a[a1end + shift] == b[b1end + shift]):
                 shift += 1
         elif b1end == b2:
             while (b1end + shift < b2end and
                    a[a1end + shift] == b[b1end + shift]):
                 shift += 1
         r.append((a1, b1, l1 + shift))
         prev = a2 + shift, b2 + shift, l2 - shift
     r.append(prev)
     return r
 
 def _tostring(c):
     if type(c) is array.array:
         # this copy overhead isn't ideal
         return c.tostring()
     return str(c)
 
 def bdiff(a, b):
     a = _tostring(a).splitlines(True)
     b = _tostring(b).splitlines(True)
 
     if not a:
         s = "".join(b)
         return s and (struct.pack(">lll", 0, 0, len(s)) + s)
 
     bin = []
     p = [0]
     for i in a: p.append(p[-1] + len(i))
 
     d = difflib.SequenceMatcher(None, a, b).get_matching_blocks()
     d = _normalizeblocks(a, b, d)
     la = 0
     lb = 0
     for am, bm, size in d:
         s = "".join(b[lb:bm])
         if am > la or s:
             bin.append(struct.pack(">lll", p[la], p[am], len(s)) + s)
         la = am + size
         lb = bm + size
 
     return "".join(bin)
 
 def blocks(a, b):
     an = splitnewlines(a)
     bn = splitnewlines(b)
     d = difflib.SequenceMatcher(None, an, bn).get_matching_blocks()
     d = _normalizeblocks(an, bn, d)
     return [(i, i + n, j, j + n) for (i, j, n) in d]
 
 def fixws(text, allws):
     if allws:
         text = re.sub('[ \t\r]+', '', text)
     else:
         text = re.sub('[ \t\r]+', ' ', text)
         text = text.replace(' \n', '\n')
     return text
 
 if modulepolicy not in policynocffi:
     try:
         from _bdiff_cffi import ffi, lib
     except ImportError:
         if modulepolicy == 'cffi': # strict cffi import
             raise
     else:
         def blocks(sa, sb):
             a = ffi.new("struct bdiff_line**")
             b = ffi.new("struct bdiff_line**")
             ac = ffi.new("char[]", sa)
             bc = ffi.new("char[]", sb)
+            l = ffi.new("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
-                l = ffi.new("struct bdiff_hunk*")
                 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("struct bdiff_line**")
+            b = ffi.new("struct bdiff_line**")
+            ac = ffi.new("char[]", sa)
+            bc = ffi.new("char[]", sb)
+            l = ffi.new("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(">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 "".join(rl)