From cf34397d9e064cc07b4dd65f95beb12c1e11be65 Mon Sep 17 00:00:00 2001
From: Dan Stillman <dstillman@zotero.org>
Date: Mon, 23 Jun 2008 20:28:42 +0000
Subject: [PATCH] Implements levenshtein as SQLite UDF

Function from Ben
---
 chrome/content/zotero/xpcom/db.js | 46 ++++++++++++++++++++++++++++++-
 1 file changed, 45 insertions(+), 1 deletion(-)

diff --git a/chrome/content/zotero/xpcom/db.js b/chrome/content/zotero/xpcom/db.js
index 0e0fa2676..c19f38732 100644
--- a/chrome/content/zotero/xpcom/db.js
+++ b/chrome/content/zotero/xpcom/db.js
@@ -59,7 +59,7 @@ Zotero.DBConnection = function(dbName) {
 	this._dbIsCorrupt = null
 	this._self = this;
 }
-	
+
 /////////////////////////////////////////////////////////////////
 //
 // Public methods
@@ -951,6 +951,50 @@ Zotero.DBConnection.prototype._getDBConnection = function () {
 	observerService.addObserver(this, "xpcom-shutdown", false);
 	observerService = null;
 	
+	// Levenshtein distance UDF
+	//
+	// Implements mozIStorageFunction
+	// TODO: move somewhere else
+	var lev = {
+		min3: function (a, b, c) {
+			var min;
+			min = a;
+			if (b < min)
+				min = b;
+			if (c < min)
+				min = c;
+			return min;
+		},
+		
+		onFunctionCall: function (arg) {
+			var a = arg.getUTF8String(0);
+			var b = arg.getUTF8String(1);
+			
+			var arr = new Array(a.length+1);
+			var i, j, cost;
+		
+			for(i=0; i<=a.length; i++)
+				arr[i] = new Array(b.length);
+		
+			for (i = 0; i <= a.length; i++) {
+				arr[i][0] = i;
+			}
+			for (j = 0; j <= b.length; j++) {
+				arr[0][j] = j;
+			}
+		
+			for (i = 1; i <= a.length; i++) {
+				for (j = 1; j <= b.length; j++) {
+					cost = (a[i-1] == b[j-1])? 0 : 1;
+					arr[i][j] = this.min3(arr[i-1][j] + 1, arr[i][j-1] + 1, arr[i-1][j-1] + cost);
+				}
+			}
+			return arr[a.length][b.length];
+		}
+	};
+	
+	this._connection.createFunction('levenshtein', 2, lev);
+	
 	return this._connection;
 }