public static IEnumerable <OutputCommand> ComputeCommands(
BinaryReader inputStream,
SignatureFile signatures)
{
OutputCommand currentCommand = new OutputCommand {
Kind = CommandKind.Reserved
};
Rollsum currentSum;
Queue <byte> currentBlock;
// Read the first block to initialize
ReadNewBlock(inputStream, signatures.BlockLength, out currentBlock, out currentSum);
while (currentBlock.Count > 0)
{
// if the block has a matching rolling sum to any contained in the signature, those are candidates
var matchCandidates = signatures.BlockLookup[currentSum.Digest];
bool wasMatch = false;
if (matchCandidates.Any())
{
// now compute the strong sum and see if any of the signature blocks match it
byte[] currentStrongSum = signatures.StrongSumMethod(currentBlock.ToArray()).Take(signatures.StrongSumLength).ToArray();
var matchingBlock = matchCandidates.FirstOrDefault(s => s.StrongSum.SequenceEqual(currentStrongSum));
// if one of the signature blocks was a match, we can generate a Copy command
if (matchingBlock != null)
{
if (currentCommand.Kind == CommandKind.Copy &&
currentCommand.Position + currentCommand.Length == matchingBlock.StartPos)
{
// in this case, we can just add this copy onto the previous one
currentCommand.Length = currentCommand.Length + (ulong)currentBlock.Count;
}
else
{
// if we can't append to the current command, then return the current command and start a new one
if (currentCommand.Kind != CommandKind.Reserved)
{
yield return(currentCommand);
}
currentCommand = new OutputCommand
{
Kind = CommandKind.Copy,
Position = matchingBlock.StartPos,
Length = (ulong)currentBlock.Count
};
}
// if we found a match, then we read a whole new block and reset the sum to it's hash
wasMatch = true;
ReadNewBlock(inputStream, signatures.BlockLength, out currentBlock, out currentSum);
}
}
// if there was no match for the current block, the we have to output it's first byte (at least)
// as a literal value, and try again starting at the next byte
if (!wasMatch)
{
// pull out the oldest byte
byte oldestByte = currentBlock.Dequeue();
// if we're not at the end of the file
if (inputStream.BaseStream.Position != inputStream.BaseStream.Length)
{
// read a byte and add it in, hoping to find a match at the next spot
byte nextByte = inputStream.ReadByte();
currentBlock.Enqueue(nextByte);
currentSum.Rotate(byteOut: oldestByte, byteIn: nextByte);
}
else
{
// if we are at the end of the file, then just rollout the oldestByte and see if we have a match for the partial block
// (this could happen if we match the last block in the original file)
currentSum.Rollout(byteOut: oldestByte);
}
if (currentCommand.Kind == CommandKind.Literal && currentCommand.Literal.Count < MaxLiteralLength)
{
// if we already have a literal command, just append a new byte on
currentCommand.Literal.Add(oldestByte);
}
else
{
// otherwise we have to emit the current command and start a new literal command
if (currentCommand.Kind != CommandKind.Reserved)
{
yield return(currentCommand);
}
currentCommand = new OutputCommand
{
Kind = CommandKind.Literal,
Literal = new List <byte> {
oldestByte
},
};
}
}
}
yield return(currentCommand);
yield return(new OutputCommand
{
Kind = CommandKind.End,
});
}
public static IEnumerable<OutputCommand> ComputeCommands(
BinaryReader inputStream,
SignatureFile signatures)
{
OutputCommand currentCommand = new OutputCommand { Kind = CommandKind.Reserved };
Rollsum currentSum;
Queue<byte> currentBlock;
// Read the first block to initialize
ReadNewBlock(inputStream, signatures.BlockLength, out currentBlock, out currentSum);
while (currentBlock.Count > 0)
{
// if the block has a matching rolling sum to any contained in the signature, those are candidates
var matchCandidates = signatures.BlockLookup[currentSum.Digest];
bool wasMatch = false;
if (matchCandidates.Any())
{
// now compute the strong sum and see if any of the signature blocks match it
byte[] currentStrongSum = signatures.StrongSumMethod(currentBlock.ToArray()).Take(signatures.StrongSumLength).ToArray();
var matchingBlock = matchCandidates.FirstOrDefault(s => s.StrongSum.SequenceEqual(currentStrongSum));
// if one of the signature blocks was a match, we can generate a Copy command
if (matchingBlock != null)
{
if (currentCommand.Kind == CommandKind.Copy &&
currentCommand.Position + currentCommand.Length == matchingBlock.StartPos)
{
// in this case, we can just add this copy onto the previous one
currentCommand.Length = currentCommand.Length + (ulong)currentBlock.Count;
}
else
{
// if we can't append to the current command, then return the current command and start a new one
if (currentCommand.Kind != CommandKind.Reserved)
{
yield return currentCommand;
}
currentCommand = new OutputCommand
{
Kind = CommandKind.Copy,
Position = matchingBlock.StartPos,
Length = (ulong)currentBlock.Count
};
}
// if we found a match, then we read a whole new block and reset the sum to it's hash
wasMatch = true;
ReadNewBlock(inputStream, signatures.BlockLength, out currentBlock, out currentSum);
}
}
// if there was no match for the current block, the we have to output it's first byte (at least)
// as a literal value, and try again starting at the next byte
if (!wasMatch)
{
// pull out the oldest byte
byte oldestByte = currentBlock.Dequeue();
// if we're not at the end of the file
if (inputStream.BaseStream.Position != inputStream.BaseStream.Length)
{
// read a byte and add it in, hoping to find a match at the next spot
byte nextByte = inputStream.ReadByte();
currentBlock.Enqueue(nextByte);
currentSum.Rotate(byteOut: oldestByte, byteIn: nextByte);
}
else
{
// if we are at the end of the file, then just rollout the oldestByte and see if we have a match for the partial block
// (this could happen if we match the last block in the original file)
currentSum.Rollout(byteOut: oldestByte);
}
if (currentCommand.Kind == CommandKind.Literal && currentCommand.Literal.Count < MaxLiteralLength)
{
// if we already have a literal command, just append a new byte on
currentCommand.Literal.Add(oldestByte);
}
else
{
// otherwise we have to emit the current command and start a new literal command
if (currentCommand.Kind != CommandKind.Reserved)
{
yield return currentCommand;
}
currentCommand = new OutputCommand
{
Kind = CommandKind.Literal,
Literal = new List<byte> { oldestByte },
};
}
}
}
yield return currentCommand;
yield return new OutputCommand
{
Kind = CommandKind.End,
};
}
public static IEnumerable <OutputCommand> ComputeCommands(BinaryReader inputStream, SignatureFile signatures)
{
OutputCommand outputCommand = default(OutputCommand);
outputCommand.Kind = CommandKind.Reserved;
OutputCommand outputCommand2 = outputCommand;
long inputLength = inputStream.BaseStream.Length;
ReadNewBlock(inputStream, signatures.BlockLength, out Queue <byte> currentBlock, out Rollsum currentSum);
while (currentBlock.Count > 0)
{
List <BlockSignature> value = null;
bool flag = false;
if (signatures.BlockLookup.TryGetValue(currentSum.Digest, out value))
{
byte[] currentStrongSum = signatures.StrongSumMethod(currentBlock.ToArray());
BlockSignature matchingBlock = FindBlockSignatureByStrongSum(value, currentStrongSum);
if (matchingBlock != null)
{
if (outputCommand2.Kind == CommandKind.Copy && outputCommand2.Position + outputCommand2.Length == matchingBlock.StartPos)
{
outputCommand2.Length = (ulong)((long)outputCommand2.Length + (long)currentBlock.Count);
}
else
{
if (outputCommand2.Kind != CommandKind.Reserved)
{
yield return(outputCommand2);
}
outputCommand = default(OutputCommand);
outputCommand.Kind = CommandKind.Copy;
outputCommand.Position = matchingBlock.StartPos;
outputCommand.Length = (ulong)currentBlock.Count;
outputCommand2 = outputCommand;
}
flag = true;
ReadNewBlock(inputStream, signatures.BlockLength, out currentBlock, out currentSum);
}
}
if (!flag)
{
byte oldestByte = currentBlock.Dequeue();
if (inputStream.BaseStream.Position != inputLength)
{
byte b = inputStream.ReadByte();
currentBlock.Enqueue(b);
currentSum.Rotate(oldestByte, b);
}
else
{
currentSum.Rollout(oldestByte);
}
if (outputCommand2.Kind == CommandKind.Literal && outputCommand2.Literal.Count < 4194304)
{
outputCommand2.Literal.Add(oldestByte);
}
else
{
if (outputCommand2.Kind != CommandKind.Reserved)
{
yield return(outputCommand2);
}
outputCommand = default(OutputCommand);
outputCommand.Kind = CommandKind.Literal;
outputCommand.Literal = new List <byte>
{
oldestByte
};
outputCommand2 = outputCommand;
}
}
}
yield return(outputCommand2);
outputCommand = new OutputCommand
{
Kind = CommandKind.End
};
yield return(outputCommand);
}
