/// <summary>
/// Determines whether the stream starts with the given string.
/// </summary>
/// <returns>
/// 1: when starts with the given string, 0: when valid HTTP method, -1: otherwise
/// </returns>
private static async ValueTask <int> startsWith(IPeekStream httpReader, IBufferPool bufferPool, string expectedStart, CancellationToken cancellationToken = default)
{
const int lengthToCheck = 10;
if (bufferPool.BufferSize < lengthToCheck)
{
throw new Exception($"Buffer is too small. Minimum size is {lengthToCheck} bytes");
}
byte[] buffer = bufferPool.GetBuffer(bufferPool.BufferSize);
try
{
bool isExpected = true;
int i = 0;
while (i < lengthToCheck)
{
int peeked = await httpReader.PeekBytesAsync(buffer, i, i, lengthToCheck - i, cancellationToken);
if (peeked <= 0)
{
return(-1);
}
peeked += i;
while (i < peeked)
{
int b = buffer[i];
if (b == ' ' && i > 2)
{
return(isExpected ? 1 : 0);
}
else
{
char ch = (char)b;
if (ch < 'A' || ch > 'z' || (ch > 'Z' && ch < 'a')) // ASCII letter
{
return(-1);
}
else if (i >= expectedStart.Length || ch != expectedStart[i])
{
isExpected = false;
}
}
i++;
}
}
// only letters
return(0);
}
finally
{
bufferPool.ReturnBuffer(buffer);
}
}
/// <summary>
/// Gets the HTTP method from the stream.
/// </summary>
public static async ValueTask <KnownMethod> GetMethod(IPeekStream httpReader, IBufferPool bufferPool, CancellationToken cancellationToken = default)
{
const int lengthToCheck = 20;
if (bufferPool.BufferSize < lengthToCheck)
{
throw new Exception($"Buffer is too small. Minimum size is {lengthToCheck} bytes");
}
byte[] buffer = bufferPool.GetBuffer(bufferPool.BufferSize);
try
{
int i = 0;
while (i < lengthToCheck)
{
int peeked = await httpReader.PeekBytesAsync(buffer, i, i, lengthToCheck - i, cancellationToken);
if (peeked <= 0)
{
return(KnownMethod.Invalid);
}
peeked += i;
while (i < peeked)
{
int b = buffer[i];
if (b == ' ' && i > 2)
{
return(getKnownMethod(buffer.AsSpan(0, i)));
}
char ch = (char)b;
if ((ch < 'A' || ch > 'z' || (ch > 'Z' && ch < 'a')) && (ch != '-')) // ASCII letter
{
return(KnownMethod.Invalid);
}
i++;
}
}
// only letters, but no space (or shorter than 3 characters)
return(KnownMethod.Invalid);
}
finally
{
bufferPool.ReturnBuffer(buffer);
}
}
