From a5c93e40ac0b478bfe086ff32e1e027f7855fa05 Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Mon, 25 Aug 2003 03:47:22 +0000
Subject: [PATCH] Handle hashes.

---
 shredcompare.py | 69 +++++++++++++++++++++++++++++++++++--------------
 1 file changed, 50 insertions(+), 19 deletions(-)

diff --git a/shredcompare.py b/shredcompare.py
index 6f72054..e4b0c20 100755
--- a/shredcompare.py
+++ b/shredcompare.py
@@ -2,6 +2,8 @@
 #
 # shredcompare -- find similarities in file trees.
 #
+# 1.0 by Eric S. Raymond, 24 Aug 2003.
+#
 # Implements the shred algorithm described at:
 #
 #	http://theinquirer.net/?article=10061
@@ -39,7 +41,15 @@
 #
 # In this implementation, lines are preprocessed to remove whitespace
 # differences.
-import sys, os, os.path, re, md5, getopt, time
+#
+# The -h option supports building a cache containing the shred list
+# for a tree you specify.  This is strictly a speed hack.  If your
+# tree is named `foo', the file will be named `foo.hash'.  On your
+# next comparison run it will be picked up automatically. It is
+# your responsibility to make sure each hash file is newer than
+# the correspobding tree.
+
+import sys, os, os.path, re, md5, getopt, time, cPickle
 
 shredsize = 5
 verbose = False
@@ -90,12 +100,18 @@ def eligible(file):
 def shredtree(tree):
     "Shred an entire file tree; return a dictionary of checksums-to-locations."
     shreds = {}
-    # First, prepare the shred list.
-    for root, dirs, files in os.walk(tree):
-        for file in files:
-            path = os.path.join(root, file)
-            if eligible(path):
-                shreds.update(shredfile(path, tree))
+    if os.path.exists(tree + ".hash"):
+        # There's a precomputed shred list.
+        rfp = open(tree + ".hash")
+        shreds = cPickle.load(rfp)
+        rfp.close()
+    else:
+        # No precomputed hashes.  Prepare a news shred list.
+        for root, dirs, files in os.walk(tree):
+            for file in files:
+                path = os.path.join(root, file)
+                if eligible(path):
+                    shreds.update(shredfile(path, tree))
     return shreds
 
 def shredcompare(tree1, tree2):
@@ -131,26 +147,41 @@ def shredcompare(tree1, tree2):
                 matches = matches[:j] + matches[j+1:]
     return matches
 
+def report_time():
+    "Report time since the last elapsed time"
+    endtime = time.time()
+    if verbose:
+        elapsed = endtime - starttime 
+        hours = elapsed/3600; elapsed %= 3600
+        minutes = elapsed/60; elapsed %= 60
+        seconds = elapsed
+        print "%% Done in %dh, %dm, %ds" % (hours, minutes, seconds)
+
+
 if __name__ == '__main__':
     try:
-        (optlist, args) = getopt.getopt(sys.argv[1:], 's:v')
+        (optlist, args) = getopt.getopt(sys.argv[1:], 'h:s:v')
     except getopt.GetoptError:
-        sys.stderr.write("usage: shredcompare [-s shredsize] [-v] tree1 tree2\n")
+        sys.stderr.write("usage: shredcompare [-s shredsize] [-v] [-h] tree1 tree2\n")
         sys.exit(2)
+    makehash = None
     for (opt, val) in optlist:
         if opt == '-s':
             shredsize = int(val)
         elif opt == '-v':
             verbose = True
+        elif opt == '-h':
+            makehash = val
     starttime = time.time()
-    matches = shredcompare(args[0], args[1])
-    endtime = time.time()
-    if verbose:
-        elapsed = endtime - starttime 
-        hours = elapsed/3600; elapsed %= 3600
-        minutes = elapsed/60; elapsed %= 60
-        seconds = elapsed
-        print "%% Done in %dh, %dm, %ds" % (hours, minutes, seconds)
-    for (source, target) in matches:
-        print source, "->", target
+    if makehash:
+        shreds = shredtree(makehash)
+        report_time()
+        wfp = open(makehash + ".hash")
+        cPickle.dump(shreds, wfp)
+        wfp.close()
+    else:
+        matches = shredcompare(args[0], args[1])
+        report_time()
+        for (source, target) in matches:
+            print source, "->", target
 
-- 
2.43.0