D88: Use the data length field to seek past any extra data.

This will effectively ignore the field length if it is shorter
than the sector size (or 0).

Author: tdaede

lib/imagereader/d88imagereader.cc

@@ -117,6 +117,10 @@ class D88ImageReader : public ImageReader
                 int ddam = sectorHeaderReader.seek(7).read_8();
                 int fddStatusCode = sectorHeaderReader.seek(8).read_8();
                 int rpm = sectorHeaderReader.seek(13).read_8();
+                int dataLength = sectorHeaderReader.seek(14).read_le16();
+                if (dataLength < sectorSize) {
+                    dataLength = sectorSize;
+                }
                 // D88 provides much more sector information that is currently
                 // ignored
                 if (ddam != 0)
@@ -188,6 +192,7 @@ class D88ImageReader : public ImageReader
                 }
                 Bytes data(sectorSize);
                 inputFile.read((char*)data.begin(), data.size());
+                inputFile.seekg(dataLength-sectorSize, std::ios_base::cur);
                 const auto& sector = image->put(track, head, sectorId);
                 sector->status = Sector::OK;
                 sector->logicalTrack = track;