+ Updated for protectors fiddling with too big block table index

1 files changed, 6 insertions, 1 deletions

diff --git a/src/StormLib.h b/src/StormLib.h
index c25a1a8..3621096 100644
--- a/src/StormLib.h
+++ b/src/StormLib.h
@@ -230,7 +230,12 @@ extern "C" {
                                   MPQ_FILE_SIGNATURE     |  \
                                   MPQ_FILE_EXISTS)
 
-#define MPQ_BLOCK_INDEX(bi) ((bi) & 0x0FFFFFFF) // Index mask for block table index
+// We need to mask out the upper 4 bits of the block table index.
+// This is because it gets shifted out when calculating block table offset
+// BlockTableOffset = pHash->dwBlockIndex << 0x04
+// Malformed MPQ maps may contain block indexes like 0x40000001 or 0xF0000023
+#define BLOCK_INDEX_MASK          0x0FFFFFFF
+#define MPQ_BLOCK_INDEX(pHash) (pHash->dwBlockIndex & BLOCK_INDEX_MASK)
 
 // Compression types for multiple compressions
 #define MPQ_COMPRESSION_HUFFMANN          0x01  // Huffmann compression (used on WAVE files only)