From 7ab7081aeddb23aed98c0f0308d48b8062368e09 Mon Sep 17 00:00:00 2001
From: Jules Villard <jvillard@eecs.qmul.ac.uk>
Date: Tue, 25 Oct 2011 22:22:30 +0100
Subject: [PATCH 1/4] initialise changeLog of new users

applyConcurrentDiff crashes when accessing changeLog[df.uid].length
otherwise.
---
 server.js | 1 +
 1 file changed, 1 insertion(+)

diff --git a/server.js b/server.js
index 5212ef4..a163fb1 100644
--- a/server.js
+++ b/server.js
@@ -20,6 +20,7 @@ var handleReq = function(req, res) {
         } else if(req.url.match(/^\/getDoc/)) {
                 res.writeHead(200, {'Content-Type': 'text/json'});
                 res.end(JSON.stringify([doc,++lastUser]));
+                changeLog[lastUser] = [];
         } else if(df = req.url.match(/^\/getDiff\?(.*)/)) {
                 var uid = unescape(df[1]);
                 var mydiffs = changeLog[uid];

From 783b04a87cb2cf3be647021fce0170c5d82cd8c6 Mon Sep 17 00:00:00 2001
From: Jules Villard <jvillard@eecs.qmul.ac.uk>
Date: Tue, 25 Oct 2011 22:47:30 +0100
Subject: [PATCH 2/4] changed Content-type of the answer to putDiff to
 text/json

seems appropriate.
---
 server.js | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/server.js b/server.js
index a163fb1..1b2a05d 100644
--- a/server.js
+++ b/server.js
@@ -24,7 +24,7 @@ var handleReq = function(req, res) {
         } else if(df = req.url.match(/^\/getDiff\?(.*)/)) {
                 var uid = unescape(df[1]);
                 var mydiffs = changeLog[uid];
-                res.writeHead(200, {'Content-Type': 'text/plain'});
+                res.writeHead(200, {'Content-Type': 'text/json'});
                 res.end(JSON.stringify(mydiffs));
                 changeLog[uid] = [];
         } else if(df = req.url.match(/^\/putDiff\?(.*)/)) {
@@ -64,5 +64,3 @@ var applyConcurrentDiff = function(df) {
 }
 
 http.createServer(handleReq).listen(4242,"127.0.0.1")
-
-

From 75da69fcb9e7d91c42c345696ff5d739c1793e55 Mon Sep 17 00:00:00 2001
From: Jules Villard <jvillard@eecs.qmul.ac.uk>
Date: Tue, 25 Oct 2011 22:49:27 +0100
Subject: [PATCH 3/4] remove unused functions from the diff library

namely makeDiff, makeDel, and makeInsert
---
 diffLib.js | 31 -------------------------------
 1 file changed, 31 deletions(-)

diff --git a/diffLib.js b/diffLib.js
index e60f060..ab967ce 100644
--- a/diffLib.js
+++ b/diffLib.js
@@ -6,11 +6,6 @@ var applyDiff = function(oldStr, diff) {
         }
 }
 
-var makeDiff = function(oldStr, newStr) {
-        if (oldStr.length > newStr.length) return makeDel(oldStr,newStr);
-        else return makeInsert(oldStr,newStr);
-}
-
 var makeDiffList = function(oldStr, newStr) {
         if (oldStr === newStr) return [];
         res = [];
@@ -29,29 +24,6 @@ var makeDiffList = function(oldStr, newStr) {
         return res;
 }
 
-// Requires that oldStr be the same as newStr, but missing a single contiguous block.
-// \exists s1,s2,s3 st oldStr === s1+s3 ^ newStr === s1+s2+s3
-var makeInsert = function(oldStr, newStr) {
-        var res = {type:"insert", content:""};
-        for(var i = 0 ; oldStr[i]===newStr[i] && i<newStr.length ; i++) { }
-        res.point = i;
-        for( ; oldStr[res.point]!==newStr[i] && i<newStr.length ; i++) {
-                res.content+=newStr[i];
-        }
-        // Assert: newStr.length - oldStr.length === i - res.point
-        return res;
-}
-
-// Requires that oldStr be the same as newStr, but with one extra char.
-// \exists s1,s2,s3 st oldStr === s1+s2+s3 ^ newStr === s1+s3 ^ len(s2)===1
-var makeDel = function(oldStr, newStr) {
-        var res = {type:"delete", length:1}
-        for(var i = 0 ; oldStr[i]===newStr[i] && i<newStr.length ; i++) { }
-        res.point = i;
-        // Assert: newStr.length - oldStr.length === i - res.point
-        return res;
-}
-
 // Tells you if two diffs clash footprints
 var isClash = function(d1,d2) {
         var d1fp = {start:d1.point, end:d1.point};
@@ -71,9 +43,6 @@ var updateAafterB = function(d1,d2) {
 
 if(typeof(exports)!=='undefined') {
         exports.applyDiff = applyDiff;
-        exports.makeDiff = makeDiff;
-        exports.makeInsert = makeInsert;
-        exports.makeDel = makeDel;
         exports.isClash = isClash;
         exports.updateAafterB = updateAafterB;
         exports.makeDiffList = makeDiffList;

From e2825604b7bca41da70c9caead2ecf7f1986f533 Mon Sep 17 00:00:00 2001
From: Jules Villard <jvillard@eecs.qmul.ac.uk>
Date: Tue, 25 Oct 2011 23:08:10 +0100
Subject: [PATCH 4/4] fixed bug in the diff algorithm

The previous algo could fail as i + j could be > oldStr.length. This
results in a negative delete (urgh). For instance:

oldStr = "aaa"
newStr = "aabaaa"

gives i = 2 and j = 3.
---
 diffLib.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/diffLib.js b/diffLib.js
index ab967ce..69d4f49 100644
--- a/diffLib.js
+++ b/diffLib.js
@@ -12,7 +12,7 @@ var makeDiffList = function(oldStr, newStr) {
         // i := the number of equal chars at the beginning of the strings
         for(var i = 0 ; i< oldStr.length && i< newStr.length && oldStr[i]===newStr[i] ; i++) {}
         // j := the number of equal chars at the end of the strings
-        for(var j = 0 ; j< oldStr.length && j< newStr.length && oldStr[oldStr.length-j-1]===newStr[newStr.length-j-1] ; j++) {}
+        for(var j = 0 ; j< oldStr.length - i && j< newStr.length - i && oldStr[oldStr.length-j-1]===newStr[newStr.length-j-1] ; j++) {}
         if(i+j!==oldStr.length) {
                 // Some stuff was deleted from oldStr
                 res.push({type:"delete",point:i,length:(oldStr.length-i-j)});