public static RollingSignature CreateRollingSignature(byte[] byteBlock, int length)
{
decimal s1 = 0;
decimal s2 = 0;
for (var i = 0; i < length; i++)
{
s1 += byteBlock[i];
}
for (int i = 0; i < length; i++)
{
s2 += (uint)(length - i) * byteBlock[i];
}
var signature = new RollingSignature() { Sig1 = s1, Sig2 = s2 };
return signature;
}
// very manual writer... but want to see how small I can get the data.
public static CompleteSignature ReadBinaryCompleteSignature(Stream s)
{
var sig = new CompleteSignature();
var l = new List<BlockSignature>();
var reader = new BinaryReader(s);
int numberOfEntries = reader.ReadInt32();
for (var i = 0; i < numberOfEntries; i++)
{
var entry = new BlockSignature();
// 8 bytes. offset
long offset = reader.ReadInt64();
// 4 bytes. size
int size = reader.ReadInt32();
// 4 bytes. Block Number;
int blockNumber = reader.ReadInt32();
// 4 bytes. Rolling Signature.
decimal sig1 = reader.ReadDecimal();
decimal sig2 = reader.ReadDecimal();
RollingSignature rollingSig = new RollingSignature() { Sig1 = sig1, Sig2 = sig2 };
// should be 16 bytes.
byte[] md5 = reader.ReadBytes(16);
entry.BlockNumber = (UInt32)blockNumber;
entry.RollingSig = (RollingSignature)rollingSig;
entry.MD5Signature = md5;
entry.Offset = offset;
entry.Size = (uint)size;
l.Add(entry);
}
sig.SignatureList = l.ToArray<BlockSignature>();
return sig;
}
internal static RollingSignature RollSignature(int length, byte previousByte, byte nextByte, RollingSignature existingSignature)
{
decimal s1 = 0;
decimal s2 = 0;
s1 = existingSignature.Sig1;
s2 = existingSignature.Sig2;
s1 = s1 - previousByte + nextByte;
s2 = s2 - (previousByte * length) + s1;
var res = new RollingSignature() { Sig1 = s1, Sig2 = s2 };
return res;
}
