Improved binary diff from Christopher Li

This is more intelligent/efficient by combining neighboring inserts,
replaces and deletes. Passes test of converting kernel repo, but
doesn't appear to substantially affect compression or performance.

mercurial/mdiff.py

@@ -1,71 +1,71 b''
 #!/usr/bin/python
 import difflib, struct, mmap
 from mercurial.mpatch import *
 
 def unidiff(a, ad, b, bd, fn):
     if not a and not b: return ""
     a = a.splitlines(1)
     b = b.splitlines(1)
     l = list(difflib.unified_diff(a, b, "a/" + fn, "b/" + fn, ad, bd))
 
     for ln in xrange(len(l)):
         if l[ln][-1] != '\n':
             l[ln] += "\n\ No newline at end of file\n"
 
     return "".join(l)
 
 def textdiff(a, b):
     return diff(a.splitlines(1), b.splitlines(1))
 
 def sortdiff(a, b):
     la = lb = 0
-
+    lena = len(a)
+    lenb = len(b)
     while 1:
-        if la >= len(a) or lb >= len(b): break
-        if b[lb] < a[la]:
-            si = lb
-            while lb < len(b) and b[lb] < a[la] : lb += 1
-            yield "insert", la, la, si, lb
-        elif a[la] < b[lb]:
-            si = la
-            while la < len(a) and a[la] < b[lb]: la += 1
-            yield "delete", si, la, lb, lb
-        else:
+        am, bm, = la, lb
+        while lb < lenb and la < len and a[la] == b[lb] :
             la += 1
             lb += 1
-
-    if lb < len(b):
-        yield "insert", la, la, lb, len(b)
-
-    if la < len(a):
-        yield "delete", la, len(a), lb, lb
+        if la>am: yield (am, bm, la-am)
+        while lb < lenb and b[lb] < a[la]: lb += 1
+        if lb>=lenb: break
+        while la < lena and b[lb] > a[la]: la += 1
+        if la>=lena: break
+    yield (lena, lenb, 0)
 
 def diff(a, b, sorted=0):
+    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))
 
     if sorted:
         d = sortdiff(a, b)
     else:
-        d = difflib.SequenceMatcher(None, a, b).get_opcodes()
-
-    for o, m, n, s, t in d:
-        if o == 'equal': continue
-        s = "".join(b[s:t])
-        bin.append(struct.pack(">lll", p[m], p[n], len(s)) + s)
-
+        d = difflib.SequenceMatcher(None, a, b).get_matching_blocks()
+    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 patchtext(bin):
     pos = 0
     t = []
     while pos < len(bin):
         p1, p2, l = struct.unpack(">lll", bin[pos:pos + 12])
         pos += 12
         t.append(bin[pos:pos + l])
         pos += l
     return "".join(t)
 
 def patch(a, bin):
     return patches(a, [bin])