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Added CRC calculation method and check of header using CRC to

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return a positive identification.
This commit is contained in:
Natalia Portillo
2014-04-21 17:23:35 +01:00
parent 76b91a16f9
commit b9e78615e2
2 changed files with 59 additions and 4 deletions
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6
FileSystemIDandChk/ChangeLog
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@@ -1,3 +1,9 @@
2014-04-21 Natalia Portillo <claunia@claunia.com>
* ImagePlugins/TeleDisk.cs:
Added CRC calculation method and check of header using CRC
to return a positive identification.
2014-04-19 Natalia Portillo <claunia@claunia.com>
* ImagePlugins/TeleDisk.cs:

57
FileSystemIDandChk/ImagePlugins/TeleDisk.cs
View File

@@ -187,7 +187,10 @@ namespace FileSystemIDandChk.ImagePlugins
#endregion
#region Internal variables
TD0Header header;
TDCommentBlockHeader commentHeader;
byte[] commentBlock;
string comment;
#endregion
@@ -196,10 +199,10 @@ namespace FileSystemIDandChk.ImagePlugins
Name = "Sydex TeleDisk";
PluginUUID = new Guid("0240B7B1-E959-4CDC-B0BD-386D6E467B88");
}
public override bool IdentifyImage(string imagePath)
{
TD0Header header = new TD0Header();
header = new TD0Header();
byte[] headerBytes = new byte[12];
FileStream stream = new FileStream(imagePath, FileMode.Open, FileAccess.Read);
@@ -220,6 +223,10 @@ namespace FileSystemIDandChk.ImagePlugins
header.sides = headerBytes[9];
header.crc = BitConverter.ToUInt16(headerBytes, 10);
byte[] headerBytesForCRC = new byte[10];
Array.Copy(headerBytes, headerBytesForCRC, 10);
UInt16 calculatedHeaderCRC = TeleDiskCRC(0x0000, headerBytesForCRC);
if (MainClass.isDebug)
{
Console.WriteLine("DEBUG (TeleDisk plugin): header.signature = 0x{0:X4}", header.signature);
@@ -232,8 +239,26 @@ namespace FileSystemIDandChk.ImagePlugins
Console.WriteLine("DEBUG (TeleDisk plugin): header.dosAllocation = 0x{0:X2}", header.dosAllocation);
Console.WriteLine("DEBUG (TeleDisk plugin): header.sides = 0x{0:X2}", header.sides);
Console.WriteLine("DEBUG (TeleDisk plugin): header.crc = 0x{0:X4}", header.crc);
Console.WriteLine("DEBUG (TeleDisk plugin): calculated header crc = 0x{0:X4}", calculatedHeaderCRC);
}
// We need more checks as the magic is too simply.
// This may deny legal images
// That would be much of a coincidence
if (header.crc == calculatedHeaderCRC)
return true;
if (header.sequence != 0x00)
return false;
if (header.dataRate != DataRate250kbps && header.dataRate != DataRate300kbps && header.dataRate != DataRate500kbps)
return false;
if (header.driveType != DriveType35DD && header.driveType != DriveType35ED && header.driveType != DriveType35HD && header.driveType != DriveType525DD &&
header.driveType != DriveType525HD && header.driveType != DriveType525HD_DDDisk && header.driveType != DriveType8inch)
return false;
return true;
}
@@ -321,7 +346,31 @@ namespace FileSystemIDandChk.ImagePlugins
{
throw new NotImplementedException("Not yet implemented.");
}
#region Private methods
static UInt16 TeleDiskCRC(UInt16 crc, byte[] buffer)
{
int counter = 0;
while (counter < buffer.Length)
{
crc ^= (UInt16)((buffer[counter] & 0xFF) << 8);
for (int i = 0; i < 8; i++)
{
if ((crc & 0x8000) > 0)
crc = (UInt16)((crc << 1) ^ TeleDiskCRCPoly);
else
crc = (UInt16)(crc << 1);
}
counter++;
}
return crc;
}
#endregion
#region Unsupported features
public override byte[] ReadSectorTag(UInt64 sectorAddress, SectorTagType tag)