Ensure backward compatibility

Author: flanglet

src/io/CompressedInputStream.cpp

@@ -351,11 +351,14 @@ void CompressedInputStream::readHeader()
     const int crcSize = bsVersion <= 5 ? 16 : 24;
     const uint32 cksum1 = uint32(_ibs->readBits(crcSize));
 
-    uint32 seed = (bsVersion <= 5 ? 1 : 0x01030507) * uint32(bsVersion);
+    uint32 seed = (bsVersion >= 6 ? 0x01030507 : 1) * uint32(bsVersion);
     const uint32 HASH = 0x1E35A7BD;
 
     uint32 cksum2 = HASH * seed;
-    cksum2 ^= (HASH * uint32(~ckSize));
+
+    if (bsVersion >= 6)
+        cksum2 ^= (HASH * uint32(~ckSize));
+
     cksum2 ^= (HASH * uint32(~_entropyType));
     cksum2 ^= (HASH * uint32((~_transformType) >> 32));
     cksum2 ^= (HASH * uint32(~_transformType));