[github-731] Fix the mini-stream size in the root property. This closes #731

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1922094 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 21 insertions, 8 deletions

diff --git a/poi/src/main/java/org/apache/poi/poifs/filesystem/POIFSMiniStore.java b/poi/src/main/java/org/apache/poi/poifs/filesystem/POIFSMiniStore.java
index 18cdfd58f7..cb1929d0d6 100644
--- a/poi/src/main/java/org/apache/poi/poifs/filesystem/POIFSMiniStore.java
+++ b/poi/src/main/java/org/apache/poi/poifs/filesystem/POIFSMiniStore.java
@@ -247,20 +247,33 @@ public class POIFSMiniStore extends BlockStore {
      * based on full blocks used, not the data within the streams
      */
     void syncWithDataSource() throws IOException {
-        int blocksUsed = 0;
         for (BATBlock sbat : _sbat_blocks) {
             ByteBuffer block = _filesystem.getBlockAt(sbat.getOurBlockIndex());
             sbat.writeData(block);
-
-            if (!sbat.hasFreeSectors()) {
-                blocksUsed += _filesystem.getBigBlockSizeDetails().getBATEntriesPerBlock();
-            } else {
-                blocksUsed += sbat.getOccupiedSize();
-            }
         }
+
         // Set the size on the root in terms of the number of SBAT blocks
         // RootProperty.setSize does the sbat -> bytes conversion for us
-        _filesystem._get_property_table().getRoot().setSize(blocksUsed);
+        _filesystem._get_property_table().getRoot().setSize(computeSize());
+    }
+
+    /**
+     * Computes the size of the mini-stream (in number of mini blocks). The trailing
+     * unallocated mini blocks are ignored, the others are counted as allocated. This
+     * behaviour was checked with MSI files signed with signtool.
+     */
+    private int computeSize() {
+        int entriesPerBlock = _filesystem.getBigBlockSizeDetails().getBATEntriesPerBlock();
+        for (int sbatIndex = _sbat_blocks.size() - 1; sbatIndex >= 0; sbatIndex--) {
+            BATBlock sbat = _sbat_blocks.get(sbatIndex);
+            for (int miniBlockIndex = entriesPerBlock - 1; miniBlockIndex >= 0; miniBlockIndex--) {
+                if (sbat.getValueAt(miniBlockIndex) != POIFSConstants.UNUSED_BLOCK) {
+                    return (sbatIndex * entriesPerBlock) + miniBlockIndex + 1;
+                }
+            }
+        }
+
+        return 0;
     }
 
     @Override