int IndexOfRest(byte value, int firstLength)
{
if (_rest == null)
{
return(-1);
}
var index = _rest.IndexOf(value);
if (index != -1)
{
return(firstLength + index);
}
return(-1);
}
// TODO (pri 3): I am pretty sure this whole routine can be written much better
// searches values that potentially straddle between first and rest
internal static int IndexOfStraddling(this ReadOnlySpan <byte> first, IReadOnlyBufferList <byte> rest, ReadOnlySpan <byte> value)
{
Debug.Assert(first.IndexOf(value) == -1);
if (rest == null)
{
return(-1);
}
// we only need to search the end of the first buffer. More precisely, only up to value.Length - 1 bytes in the first buffer
// The other bytes in first, were already search and presumably did not match
int bytesToSkipFromFirst = 0;
if (first.Length > value.Length - 1)
{
bytesToSkipFromFirst = first.Length - value.Length - 1;
}
// now that we know how many bytes we need to skip, create slice of first buffer with bytes that need to be searched.
ReadOnlySpan <byte> bytesToSearchAgain;
if (bytesToSkipFromFirst > 0)
{
bytesToSearchAgain = first.Slice(bytesToSkipFromFirst);
}
else
{
bytesToSearchAgain = first;
}
int index;
// now combine the bytes from the end of the first buffer with bytes in the rest, and serarch the combined buffer
// this check is a small optimization: if the first byte from the value does not exist in the bytesToSearchAgain, there is no reason to combine
if (bytesToSearchAgain.IndexOf(value[0]) != -1)
{
var combinedBufferLength = value.Length << 1;
var combined = combinedBufferLength < 128 ?
stackalloc byte[combinedBufferLength] :
// TODO (pri 3): I think this could be eliminated by chunking values
new byte[combinedBufferLength];
bytesToSearchAgain.CopyTo(combined);
int combinedLength = bytesToSearchAgain.Length + rest.CopyTo(combined.Slice(bytesToSearchAgain.Length));
combined = combined.Slice(0, combinedLength);
if (combined.Length < value.Length)
{
return(-1);
}
index = combined.IndexOf(value);
if (index != -1)
{
return(index + bytesToSkipFromFirst);
}
}
// try to find the bytes in _rest
index = rest.IndexOf(value);
if (index != -1)
{
return(first.Length + index);
}
return(-1);
}
