/// <summary>
/// Create a new SgaFileReader. Will immediately read the header information
/// for the file and throw <see cref="InvalidSgaException"/> if stream is not a valid SGA.
/// </summary>
/// <param name="stream">A SGA file stream</param>
/// <exception cref="IOException" />
public SgaFileReader(string filePath)
{
this.reader = new BinaryReader(File.OpenRead(filePath));
try
{
this.header = ReadFileHeader();
byte[] dataHeaderBuffer = ReadDataHeader(header);
SgaDataHeaderInfo dataHeaderInfo = ReadDataHeaderInfo(dataHeaderBuffer);
SgaFileEntry[] files = ReadFiles(header, dataHeaderInfo, dataHeaderBuffer);
SgaDirectory[] directories = ReadDirs(files, dataHeaderInfo, dataHeaderBuffer);
var tocs = ReadTocs(directories, dataHeaderInfo, dataHeaderBuffer);
if (tocs.Length != 1)
{
throw new IOException($"SGA file does not have exactly 1 TOC {filePath}");
}
this.directories = new Dictionary <string, SgaDirectory>(directories.Length);
foreach (var directory in directories)
{
this.directories.Add(directory.Name, directory);
}
}
catch (IOException ex)
{
Dispose();
throw ex;
}
}
/// <summary>
/// Read file header data using Binary Reader. Assumes binary reader is located at beginning
/// of header info.
/// </summary>
/// <exception cref="IOException"/>
private SgaFileHeader ReadFileHeader()
{
string identifier = Encoding.ASCII.GetString(this.reader.ReadBytes(8));
if (!"_ARCHIVE".Equals(identifier))
{
throw new InvalidSgaException($"File Identifier '{identifier}' should be '_ARCHIVE'");
}
var header = new SgaFileHeader
{
Identifier = identifier,
Version = this.reader.ReadUInt32(),
ToolMD5 = this.reader.ReadBytes(16),
ArchiveType = Encoding.Unicode.GetString(this.reader.ReadBytes(128)).TrimEnd('\0'),
MD5 = this.reader.ReadBytes(16),
DataHeaderSize = this.reader.ReadUInt32(),
DataOffset = this.reader.ReadUInt32()
};
if (header.Version != 2 && header.Version != 4)
{
throw new InvalidSgaException("SGA Version is not supported");
}
if (header.Version == 4)
{
header.Platform = this.reader.ReadUInt32();
// Value of 1 means Win32, x86 or Little Endian.
// It is unknown what a value not of 1 is so we should throw an error.
if (header.Platform != 1)
{
throw new InvalidSgaException($"Unknown Platform '{header.Platform}'");
}
}
return(header);
}
/// <summary>
/// Reads the Data header into buffer and verifies the checksum.
/// </summary>
private byte[] ReadDataHeader(SgaFileHeader header)
{
var data = this.reader.ReadBytes(Convert.ToInt32(header.DataHeaderSize));
// Here we validate that the checksum matches. If this step passes there is good odds that we are
// indeed reading an SGA file.
using MD5 md5 = MD5.Create();
byte[] key = Encoding.ASCII.GetBytes("DFC9AF62-FC1B-4180-BC27-11CCE87D3EFF");
var buf = new byte[key.Length + data.Length];
key.CopyTo(buf, 0);
data.CopyTo(buf, key.Length);
byte[] md5Main = md5.ComputeHash(buf);
if (!md5Main.SequenceEqual(header.MD5))
{
throw new InvalidSgaException("Header MD5 does not match");
}
return(data);
}
