[patch 7/7] Optimize manifest.add.addlistdelta

[Chris Mason]

# HG changeset patch
# User mason at suse.com
Optimize manifest.add.addlistdelta

This optimizes addlistdelta to run on larger regions of the addlist
at a time.  gendelta already had these optimizations to compress
the delta found in the main manifest.add loop, this patch just pulls
the compression out into a helper function, and the result of the 
compression is sent to both addlistdelta and gendelta.

This patch turns:
addlist[1] = "new line 1"
addlist[2] = "new line 2"
addlist[3] = "new line 3"

Into

addlist[1:4] = ["new line1", "new line2", "new line3"]

Performance gain is only 3-4% in the common case, but it is much cleaner.

Index: mine/mercurial/hg.py
===================================================================
--- mine.orig/mercurial/hg.py	2005-08-22 13:18:24.000000000 -0400
+++ mine/mercurial/hg.py	2005-08-22 13:19:41.000000000 -0400
@@ -145,23 +145,34 @@ class manifest(revlog):
             changed=None):
         # directly generate the mdiff delta from the data collected during
         # the bisect loop below
-        def gendelta(delta):
+        def gendelta(addlist, delta):
+            result = []
+            for x in delta:
+                if x[2]:
+                    s = "".join(x[2])
+                else:
+                    s = ""
+                start = addlist.offset(x[0])
+                end = addlist.offset(x[1])
+                result.append(struct.pack(">lll", start, end, len(s)) + s)
+            return result
+        def compressdelta(delta):
             i = 0
             result = []
             while i < len(delta):
-                start = delta[i][2]
-                end = delta[i][3]
-                l = delta[i][4]
-                if l == None:
-                    l = ""
-                while i < len(delta) - 1 and start <= delta[i+1][2] \
-                          and end >= delta[i+1][2]:
-                    if delta[i+1][3] > end:
-                        end = delta[i+1][3]
-                    if delta[i+1][4]:
-                        l += delta[i+1][4]
+                start = delta[i][0]
+                end = delta[i][1]
+                l = []
+                if delta[i][2]:
+                    l.append(delta[i][2])
+                while i < (len(delta) - 1) and start <= delta[i+1][0] \
+                          and end >= delta[i+1][0]:
+                    if delta[i+1][1] > end:
+                        end = delta[i+1][1]
+                    if delta[i+1][2]:
+                        l.append(delta[i+1][2])
                     i += 1
-                result.append(struct.pack(">lll", start, end, len(l)) +  l)
+                result.append([start, end, l])
                 i += 1
             return result
 
@@ -174,8 +185,8 @@ class manifest(revlog):
                 i -= 1
                 start = delta[i][0]
                 end = delta[i][1]
-                if delta[i][4]:
-                    addlist[start:end] = [delta[i][4]]
+                if delta[i][2]:
+                    addlist[start:end] = delta[i][2]
                 else:
                     del addlist[start:end]
             return addlist
@@ -229,13 +240,14 @@ class manifest(revlog):
                     # item is found, replace/delete the existing line
                     start = bs - 1
                     end = bs
-                delta.append((start, end, addlist.offset(start), addlist.offset(end), l))
+                delta.append([start, end, l])
 
-            self.addlist = addlistdelta(addlist, delta)
+            cdelta = compressdelta(delta)
             if self.mapcache[0] == self.tip():
-                cachedelta = "".join(gendelta(delta))
+                cachedelta = "".join(gendelta(addlist, cdelta))
             else:
                 cachedelta = None
+            self.addlist = addlistdelta(addlist, cdelta)
 
         text = self.addlist.text()
         n = self.addrevision(text, transaction, link, p1, p2, cachedelta)

--