public uint GetAddress(uint hereAddress, byte mode, VcdReader addressSection)
{
uint address = 0;
switch (GetMode(mode))
{
case AddressMode.Self:
address = addressSection.ReadInteger();
break;
case AddressMode.Here:
address = hereAddress - addressSection.ReadInteger();
break;
case AddressMode.Near:
address = near[mode - 2] + addressSection.ReadInteger();
break;
case AddressMode.Same:
int index = mode - (2 + NearSlots);
address = same[index * 256 + addressSection.ReadByte()];
break;
}
Update(address);
return(address);
}
private Header ReadHeader()
{
var header = new Header();
var fields = (HeaderFields)vcdReader.ReadByte();
if (fields.Contains(HeaderFields.NotSupported))
{
throw new FormatException("unrecognized header indicator bits set");
}
header.SecondaryCompressor = SecondaryCompressor.None;
if (fields.Contains(HeaderFields.SecondaryCompression))
{
throw new NotSupportedException("unavailable secondary compressor");
}
if (fields.Contains(HeaderFields.CodeTable))
{
throw new NotSupportedException("compressed code table not implemented");
}
if (fields.Contains(HeaderFields.ApplicationData))
{
header.ApplicationData = ReadApplicationData();
}
return(header);
}
public uint GetAddress(uint hereAddress, byte mode, VcdReader addressSection)
{
uint address = 0;
switch (GetMode(mode)) {
case AddressMode.Self:
address = addressSection.ReadInteger();
break;
case AddressMode.Here:
address = hereAddress - addressSection.ReadInteger();
break;
case AddressMode.Near:
address = near[mode - 2] + addressSection.ReadInteger();
break;
case AddressMode.Same:
int index = mode - (2 + NearSlots);
address = same[index * 256 + addressSection.ReadByte()];
break;
}
Update(address);
return address;
}
private Window ReadWindow()
{
var window = new Window();
// Get window indicator
window.Source = (WindowFields)vcdReader.ReadByte();
if (window.Source.Contains(WindowFields.NotSupported))
{
throw new FormatException("unrecognized window indicator bits set");
}
if (window.Source.Contains(WindowFields.Source | WindowFields.Target))
{
window.SourceSegmentLength = vcdReader.ReadInteger();
window.SourceSegmentOffset = vcdReader.ReadInteger();
}
// Copy offset and copy length may not overflow
if (window.SourceSegmentOffset.CheckOverflow(window.SourceSegmentLength))
{
throw new FormatException("decoder copy window overflows a file offset");
}
// Check copy window bounds
if (window.Source.Contains(WindowFields.Target) &&
window.SourceSegmentOffset + window.SourceSegmentLength > lastWindowOffset)
{
throw new FormatException("VCD_TARGET window out of bounds");
}
// Start of Delta Encoding Data
vcdReader.ReadInteger(); // Length of the delta encoding (following data)
// Get the length of target window
window.TargetWindowLength = vcdReader.ReadInteger();
lastWindowLength = window.TargetWindowLength;
// Set the maximum decoder position, beyond which we should not
// decode any data. This may not exceed the size of a UInt32.
if (window.SourceSegmentLength.CheckOverflow(window.TargetWindowLength))
{
throw new FormatException("decoder target window overflows a UInt32");
}
// Check for malicious files
if (window.TargetWindowLength > HardMaxWindowSize)
{
throw new FormatException("Hard window size exceeded");
}
// Get compressed / delta fields
window.CompressedFields = (WindowCompressedFields)vcdReader.ReadByte();
if (window.CompressedFields.Contains(WindowCompressedFields.Invalid))
{
throw new FormatException("unrecognized delta indicator bits set");
}
// Compressed fields is only used with secondary compression
if (window.CompressedFields != WindowCompressedFields.None &&
header.SecondaryCompressor == SecondaryCompressor.None)
{
throw new FormatException("invalid delta indicator bits set");
}
// Read section lengths
var dataLength = vcdReader.ReadInteger();
var instructionsLength = vcdReader.ReadInteger();
var addressesLength = vcdReader.ReadInteger();
// Read checksum if so (it's in big-endian-non-integer)
if (window.Source.Contains(WindowFields.Adler32))
{
var checksum = vcdReader.ReadBytes(4);
window.Checksum = (uint)((checksum[0] << 24) | (checksum[1] << 16) |
(checksum[2] << 8) | checksum[3]);
}
// Read sections
var data = new MemoryStream(vcdReader.ReadBytes(dataLength));
var instructions = new MemoryStream(vcdReader.ReadBytes(instructionsLength));
var addresses = new MemoryStream(vcdReader.ReadBytes(addressesLength));
window.Data = new VcdReader(data);
window.Instructions = new VcdReader(instructions);
window.Addresses = new VcdReader(addresses);
return(window);
}
