public override void Erase(Stream strm, long erasureLength, Prng prng,
ErasureMethodProgressFunction callback)
{
if (method == null || method.Guid == Guid)
throw new InvalidOperationException(S._("The First/last 16KB erasure method " +
"requires another erasure method to erase the file.\n\nThis must " +
"be set in the Plugin Settings dialog."));
if (erasureLength != long.MaxValue)
throw new ArgumentException(S._("The amount of data erased should not be " +
"limited, since this is a self-limiting erasure method."));
if (strm.Length < dataSize)
{
method.Erase(strm, erasureLength, prng, callback);
return;
}
strm.Seek(0, SeekOrigin.Begin);
method.Erase(strm, dataSize, prng, callback);
strm.Seek(-dataSize, SeekOrigin.End);
method.Erase(strm, long.MaxValue, prng, callback);
}
public static void Register(Prng prng)
{
lock (ManagerLibrary.Instance.PRNGManager.prngs)
ManagerLibrary.Instance.PRNGManager.prngs.Add(prng.Guid, prng);
}
public abstract void Erase(Stream stream, long erasureLength, Prng prng, ErasureMethodProgressFunction callback);
public virtual void EraseUnusedSpace(Stream stream, Prng prng, ErasureMethodProgressFunction callback)
{
Erase(stream, long.MaxValue, prng, callback);
}
public override void Erase(Stream stream, long erasureLength, Prng prng,
ErasureMethodProgressFunction callback)
{
ErasureMethodPass[] randomizedPasses = PassesSet;
if (RandomizePasses)
randomizedPasses = ShufflePasses(randomizedPasses);
long strmStart = stream.Position;
long strmLength = Math.Min(stream.Length - strmStart, erasureLength);
long totalData = CalculateEraseDataSize(null, strmLength);
byte[] buffer = new byte[Math.Min(DiskOperationUnit, strmLength)];
for (int pass = 0; pass < Passes; ++pass)
{
if (callback != null)
callback(0, totalData, pass + 1);
stream.Seek(strmStart, SeekOrigin.Begin);
long toWrite = strmLength;
int dataStopped = buffer.Length;
while (toWrite > 0)
{
int amount = (int)Math.Min(toWrite, buffer.Length - dataStopped);
if (amount == 0)
{
randomizedPasses[pass].Execute(buffer, prng);
dataStopped = 0;
continue;
}
stream.Write(buffer, dataStopped, amount);
stream.Flush();
toWrite -= amount;
if (callback != null)
callback(amount, totalData, pass + 1);
}
}
}
public void Execute(byte[] buffer, Prng prng)
{
Function(buffer, OpaqueValue == null ? prng : OpaqueValue);
}
public override void Erase(Stream strm, long erasureLength, Prng prng,
ErasureMethodProgressFunction callback)
{
throw new InvalidOperationException(S._("The DefaultMethod class should never " +
"be used and should instead be replaced before execution!"));
}