From f5b95f4e28488292231bc3184ff49d0de343b317 Mon Sep 17 00:00:00 2001
From: Jaifroid <egk10@cam.ac.uk>
Date: Mon, 26 Nov 2018 17:34:26 +0000
Subject: [PATCH] Fix incomplete searches in some ZIM files

Former-commit-id: cb0cd14bd44a005d0a1fa784847ac7fe41bfca37 [formerly 17a97e25963e921a257b4de53b2e5c8df90e63ad]
Former-commit-id: f4666707e53b4478de6f0efeb0d8eba1e0e18da1
---
 www/js/lib/util.js       | 11 ++++++++---
 www/js/lib/zimArchive.js | 19 ++++++++++++++-----
 2 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/www/js/lib/util.js b/www/js/lib/util.js
index 3154dd60..3e2ddb4e 100644
--- a/www/js/lib/util.js
+++ b/www/js/lib/util.js
@@ -236,11 +236,16 @@ define(['q'], function (q) {
         if (end <= begin)
             return lowerBound ? begin : null;
         var mid = Math.floor((begin + end) / 2);
-        return query(mid).then(function (decision) {
-            if (decision < 0)
+        return query(mid).then(function(decision)
+        {
+            if (decision == -1)
                 return binarySearch(begin, mid, query, lowerBound);
-            else if (decision > 0)
+            else if (decision == 1)
                 return binarySearch(mid + 1, end, query, lowerBound);
+            else if (decision == -2)
+                return binarySearch(begin, end - 1, query, lowerBound)
+            else if (decision == 2)
+                return binarySearch(begin + 1, end, query, lowerBound)
             else
                 return mid;
         });
diff --git a/www/js/lib/zimArchive.js b/www/js/lib/zimArchive.js
index ed9d613a..74bd9836 100644
--- a/www/js/lib/zimArchive.js
+++ b/www/js/lib/zimArchive.js
@@ -180,13 +180,22 @@ define(['zimfile', 'zimDirEntry', 'util', 'utf8'],
      */
     ZIMArchive.prototype.findDirEntriesWithPrefixCaseSensitive = function(prefix, resultSize, callback) {
         var that = this;
+        // Vector is used to remember the search direction if we encounter a dirEntry with an empty title
+        var vector = -1;
         util.binarySearch(0, this._file.articleCount, function(i) {
             return that._file.dirEntryByTitleIndex(i).then(function(dirEntry) {
-                if (dirEntry.namespace < "A")
-                    return 1;
-                else if (dirEntry.namespace > "A")
-                    return -1;
-                return prefix <= dirEntry.title ? -1 : 1;
+                if (dirEntry.namespace < "A") vector = 1;
+                if (dirEntry.namespace > "A") vector = -1;
+                if (dirEntry.namespace !== "A") return vector;
+                // We should now be in namespace A
+                if (dirEntry.title) { 
+                    vector = prefix <= dirEntry.title ? -1 : 1;
+                    return vector;
+                } else {
+                    // Since there is no title, we must nudge the search algorith up or down
+                    // We signal this to util.binarySearch by returning -2 or +2 instead of -1 or +1
+                    return vector + vector;
+                }
             });
         }, true).then(function(firstIndex) {
             var dirEntries = [];