dsdecmp/CSharp/DSDecmp/Formats/Nitro/NitroCFormat.cs
barubary 4302517e58 C#: Added xml comments to methods that did not have any (in the main DSDecmp project).
The SupportsDecompression-flag is now also used in the main program, and not just in composite formats.
2011-11-14 17:33:30 +00:00

71 lines
2.6 KiB
C#

using System;
using System.Collections.Generic;
using System.Text;
namespace DSDecmp.Formats.Nitro
{
/// <summary>
/// Base class for Nitro-based decompressors. Uses the 1-byte magic and 3-byte decompression
/// size format.
/// </summary>
public abstract class NitroCFormat : CompressionFormat
{
/// <summary>
/// If true, Nitro Decompressors will not decompress files that have a decompressed
/// size (plaintext size) larger than MaxPlaintextSize.
/// </summary>
public static bool SkipLargePlaintexts = true;
/// <summary>
/// The maximum allowed size of the decompressed file (plaintext size) allowed for Nitro
/// Decompressors. Only used when SkipLargePlaintexts = true.
/// </summary>
public static int MaxPlaintextSize = 0x180000;
/// <summary>
/// The first byte of every file compressed with the format for this particular
/// Nitro Dcompressor instance.
/// </summary>
protected byte magicByte;
/// <summary>
/// Creates a new instance of the Nitro Compression Format base class.
/// </summary>
/// <param name="magicByte">The expected first byte of the file for this format.</param>
protected NitroCFormat(byte magicByte)
{
this.magicByte = magicByte;
}
/// <summary>
/// Checks if the first four bytes match the format used in nitro compression formats.
/// </summary>
public override bool Supports(System.IO.Stream stream, long inLength)
{
long startPosition = stream.Position;
try
{
int firstByte = stream.ReadByte();
if (firstByte != this.magicByte)
return false;
// no need to read the size info as well if it's used anyway.
if (!SkipLargePlaintexts)
return true;
byte[] sizeBytes = new byte[3];
stream.Read(sizeBytes, 0, 3);
int outSize = IOUtils.ToNDSu24(sizeBytes, 0);
if (outSize == 0)
{
sizeBytes = new byte[4];
stream.Read(sizeBytes, 0, 4);
outSize = (int)IOUtils.ToNDSu32(sizeBytes, 0);
}
return outSize <= MaxPlaintextSize;
}
finally
{
stream.Position = startPosition;
}
}
}
}