From 4cb848582e6677e32ade16575f3b75c1efac405a Mon Sep 17 00:00:00 2001
From: Eric House <eehouse@trand>
Date: Tue, 28 Aug 2012 07:35:11 -0700
Subject: [PATCH] fix edge cases in prefix matching

---
 xwords4/common/dictiter.c | 19 +++++++++++++++----
 xwords4/linux/linuxmain.c |  4 ++--
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/xwords4/common/dictiter.c b/xwords4/common/dictiter.c
index 9315fa0a4..fa0598abc 100644
--- a/xwords4/common/dictiter.c
+++ b/xwords4/common/dictiter.c
@@ -194,13 +194,18 @@ findStartsWithChars( DictIter* iter, const XP_UCHAR* chars, XP_U16 charsOffset,
                      array_edge* edge, XP_U16 nTilesUsed )
 {
     XP_S16 result = -1;
-    if ( NULL == edge || ( '\0' == chars[charsOffset] ) ) {
+    XP_U16 charsLen = XP_STRLEN( &chars[charsOffset] );
+    if ( NULL == edge ) {
+        if ( 0 == charsLen ) {
+            iter->nEdges = nTilesUsed;
+            result = charsOffset;
+        } 
+    } else if ( 0 == charsLen ) {
         iter->nEdges = nTilesUsed;
         result = charsOffset;
     } else {
         const DictionaryCtxt* dict = iter->dict;
         XP_U16 nodeSize = dict->nodeSize;
-        XP_U16 charsLen = XP_STRLEN( &chars[charsOffset] );
         for ( ; ; ) {
             Tile tile = EDGETILE( dict, edge );
             const XP_UCHAR* facep = dict_getTileString( dict, tile );
@@ -650,8 +655,14 @@ dict_findStartsWith( DictIter* iter, const XP_UCHAR* prefix )
     ASSERT_INITED( iter );
     array_edge* edge = dict_getTopEdge( iter->dict );
     XP_S16 offset = findStartsWithChars( iter, prefix, 0, edge, 0 );
-    if ( 0 < offset ) {
-        if ( nextWord( iter ) ) {
+    if ( 0 > offset ) {
+        /* not found; do nothing */
+    } else if ( 0 == offset ) {
+        if ( !firstWord( iter ) ) {
+            offset = -1;
+        }
+    } else {
+        if ( ACCEPT_ITER( iter, iter->nEdges ) || nextWord( iter ) ) {
             DictPosition result = figurePosition( iter );
             iter->position = result;
         } else {
diff --git a/xwords4/linux/linuxmain.c b/xwords4/linux/linuxmain.c
index a831f0bf3..6eafff375 100644
--- a/xwords4/linux/linuxmain.c
+++ b/xwords4/linux/linuxmain.c
@@ -1306,7 +1306,7 @@ walk_dict_test( const LaunchParams* XP_UNUSED_DBG(params),
             for ( ii = 0; ii < count; ++ii ) {
                 gchar* prefix = (gchar*)g_slist_nth_data( testPrefixes, ii );
                 XP_S16 lenMatched = dict_findStartsWith( &iter, prefix );
-                if ( 0 < lenMatched ) {
+                if ( 0 <= lenMatched ) {
                     XP_UCHAR buf[32];
                     XP_UCHAR bufPrev[32] = {0};
                     dict_wordToString( &iter, buf, VSIZE(buf) );
@@ -1314,7 +1314,7 @@ walk_dict_test( const LaunchParams* XP_UNUSED_DBG(params),
                     XP_ASSERT( 0 == strncmp( buf, prefix, lenMatched ) );
 
                     DictPosition pos = dict_getPosition( &iter );
-                    XP_ASSERT( 0 == strncmp( buf, words[pos], lenMatched ) );
+                    XP_ASSERT( 0 == strcmp( buf, words[pos] ) );
                     if ( pos > 0 ) {
                         if ( !dict_getNthWord( &iter, pos-1, depth, &data ) ) {
                             XP_ASSERT( 0 );