the current read state of this body
remaining indicates the bytes left in the current chunk. initial state is zero.
total indicates the size of the current chunk or zero to indicate that we expect to read a chunk size at the start of the next bytes. initial state is zero.
read state for a chunked-encoded body. the number of bytes that have been read from the current chunk is the difference between remaining and total.
current index represents the bytes that have already been read. initial state is zero
total length indicates the claimed length, usually determined by the content-length header
read state for a fixed-length body.
the terminal read state
Returns the argument unchanged.