OpenSSL.jl/src/flow_control.jl

function queue_encrypted_bytes(client, buf)
    # println("Adding $(length(buf)) for a total of $(length(buf) + length(client.write_buf))")
    append!(client.write_buf, buf)
end

function do_ssl_handshake(client)
    n = SSL_handshake(client)
    status = ssl_status(client, n)
    if status in (SSL_WANT_READ, SSL_WANT_WRITE)
        while true
            (n, buf) = bio_read(client)
            # println("bio_read: $(n)")
            if n > 0
                queue_encrypted_bytes(client, buf)
            elseif !bio_should_retry(client.wbio)
                return -1
            end
            if n <= 0
                break
            end
        end
    end
    # println("End of ssl handshake")
    return status
end

function send_unencrypted_bytes(client, buf)
    append!(client.encrypt_buf, buf)
end

function do_encrypt(client)
    ssl_init_finished(client) || return 0

    while length(client.encrypt_buf) > 0
        n = ssl_write(client, client.encrypt_buf)
        status = ccall((:SSL_get_error, libssl), SSL_ERRORS, (Ptr{Cvoid}, Cint),
	               client.ssl, n)
        if n > 0
            splice!(client.encrypt_buf, 1:n)
            while true
                (n, buf) = bio_read(client)
                if n > 0
                    queue_encrypted_bytes(client, buf)
                elseif !bio_should_retry(client.wbio)
                    return -1
                end
                n > 0 || break
            end
        end
        if status in (SSL_ERROR, SSL_SYSCALL)
            @warn "SSL ERROR"
            return -1
        end
        if n == 0
            break
        end
    end
    return 0
end


function on_read_cb(client, buffer)
    idx = 1
    len = length(buffer)
    while len > 0
        n = bio_write!(client, buffer[idx:end])
        if n <= 0
            return -1
        end
        idx += n
        len -= n
        
        if ! ssl_init_finished(client)
            # println("SSL not finished yet")
            if (do_ssl_handshake(client) == -1)
                return -1
            end
            if !ssl_init_finished(client)
                return 0
            end
        end
        # println("NOW IT FINISHED\n")
        while true
            (n, buf) = read(client)
            if n > 0
                client.io_on_read(buf[1:n])
            else
                break
            end
        end
        status = ssl_status(client, n)
        if status in (SSL_WANT_READ, SSL_WANT_WRITE)
            while true
                (n, buf) = bio_read(client)
                if n > 0
                    queue_encrypted_bytes(client, buf)
                elseif !bio_should_retry(client.wbio)
                    return -1
                end
                n < 0 && break
            end
        end
        if status in (SSL_ERROR, SSL_SYSCALL)
            return -1
        end
    end
    return 0
end

function do_sock_read(client::SSLClient)
    buf = readavailable(client.sock)
    if length(buf) > 0
        return on_read_cb(client, buf)
    else
        return -1
    end
end

function do_sock_write(client::SSLClient)
    n = write(client.sock, client.write_buf)
    # println("Written to the client: $n")
    if n > 0
        splice!(client.write_buf, 1:n)
        return 0
    else
        return -1
    end
end