From dd21676086a97e0789a2de71f806ebf9952a55a8 Mon Sep 17 00:00:00 2001
From: Nick Burch <nick@apache.org>
Date: Mon, 4 Feb 2013 12:52:12 +0000
Subject: [PATCH] An XBAT may not be fully used, and remaining entries may be 0
 not POIFSConstants.UNUSED_BLOCK, so avoid trying to process any that we know
 aren't used. Fixes bug #53810

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1442095 13f79535-47bb-0310-9956-ffa450edef68
---
 .../org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/java/org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java b/src/java/org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java
index def2af198..d2e399794 100644
--- a/src/java/org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java
+++ b/src/java/org/apache/poi/poifs/filesystem/NPOIFSFileSystem.java
@@ -356,6 +356,9 @@ public class NPOIFSFileSystem extends BlockStore
           readBAT(fatAt, loopDetector);
        }
        
+       // Work out how many FAT blocks remain in the XFATs
+       int remainingFATs = _header.getBATCount() - _header.getBATArray().length;
+       
        // Now read the XFAT blocks, and the FATs within them
        BATBlock xfat; 
        int nextAt = _header.getXBATIndex();
@@ -367,11 +370,14 @@ public class NPOIFSFileSystem extends BlockStore
           nextAt = xfat.getValueAt(bigBlockSize.getXBATEntriesPerBlock());
           _xbat_blocks.add(xfat);
           
-          for(int j=0; j<bigBlockSize.getXBATEntriesPerBlock(); j++) {
+          // Process all the (used) FATs from this XFAT
+          int xbatFATs = Math.min(remainingFATs, bigBlockSize.getXBATEntriesPerBlock());
+          for(int j=0; j<xbatFATs; j++) {
              int fatAt = xfat.getValueAt(j);
              if(fatAt == POIFSConstants.UNUSED_BLOCK || fatAt == POIFSConstants.END_OF_CHAIN) break;
              readBAT(fatAt, loopDetector);
           }
+          remainingFATs -= xbatFATs;
        }
        
        // We're now able to load steams