296 lines
9.0 KiB
V
296 lines
9.0 KiB
V
module websocket
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import encoding.utf8
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const (
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header_len_offset = 2 // offset for lengthpart of websocket header
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buffer_size = 256 // default buffer size
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extended_payload16_end_byte = 4 // header length with 16-bit extended payload
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extended_payload64_end_byte = 10 // header length with 64-bit extended payload
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)
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// Fragment represents a websocket data fragment
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struct Fragment {
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data []byte // included data payload data in a fragment
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opcode OPCode // interpretation of the payload data
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}
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// Frame represents a data frame header
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struct Frame {
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mut:
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// length of the websocket header part
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header_len int = 2
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// size of total frame
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frame_size int = 2
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fin bool // true if final fragment of message
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rsv1 bool // reserved for future use in websocket RFC
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rsv2 bool // reserved for future use in websocket RFC
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rsv3 bool // reserved for future use in websocket RFC
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opcode OPCode // interpretation of the payload data
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has_mask bool // true if the payload data is masked
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payload_len int // payload length
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masking_key [4]byte // all frames from client to server is masked with this key
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}
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const (
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invalid_close_codes = [999, 1004, 1005, 1006, 1014, 1015, 1016, 1100, 2000, 2999, 5000, 65536]
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)
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// validate_client validates client frame rules from RFC6455
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pub fn (mut ws Client) validate_frame(frame &Frame) ? {
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if frame.rsv1 || frame.rsv2 || frame.rsv3 {
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ws.close(1002, 'rsv cannot be other than 0, not negotiated') ?
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return error('rsv cannot be other than 0, not negotiated')
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}
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if (int(frame.opcode) >= 3 && int(frame.opcode) <= 7)
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|| (int(frame.opcode) >= 11 && int(frame.opcode) <= 15) {
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ws.close(1002, 'use of reserved opcode') ?
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return error('use of reserved opcode')
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}
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if frame.has_mask && !ws.is_server {
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// server should never send masked frames
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// to client, close connection
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ws.close(1002, 'client got masked frame') ?
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return error('client sent masked frame')
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}
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if is_control_frame(frame.opcode) {
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if !frame.fin {
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ws.close(1002, 'control message must not be fragmented') ?
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return error('unexpected control frame with no fin')
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}
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if frame.payload_len > 125 {
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ws.close(1002, 'control frames must not exceed 125 bytes') ?
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return error('unexpected control frame payload length')
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}
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}
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if frame.fin == false && ws.fragments.len == 0 && frame.opcode == .continuation {
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err_msg := 'unexecpected continuation, there are no frames to continue, $frame'
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ws.close(1002, err_msg) ?
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return error(err_msg)
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}
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}
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// is_control_frame returns true if the frame is a control frame
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fn is_control_frame(opcode OPCode) bool {
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return opcode !in [.text_frame, .binary_frame, .continuation]
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}
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// is_data_frame returns true if the frame is a control frame
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fn is_data_frame(opcode OPCode) bool {
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return opcode in [.text_frame, .binary_frame]
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}
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// read_payload reads the message payload from the socket
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fn (mut ws Client) read_payload(frame &Frame) ?[]byte {
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if frame.payload_len == 0 {
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return []byte{}
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}
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mut buffer := []byte{cap: frame.payload_len}
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mut read_buf := [1]byte{}
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mut bytes_read := 0
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for bytes_read < frame.payload_len {
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len := ws.socket_read_ptr(&read_buf[0], 1) ?
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if len != 1 {
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return error('expected read all message, got zero')
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}
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bytes_read += len
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buffer << read_buf[0]
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}
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if bytes_read != frame.payload_len {
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return error('failed to read payload')
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}
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if frame.has_mask {
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for i in 0 .. frame.payload_len {
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buffer[i] ^= frame.masking_key[i % 4] & 0xff
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}
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}
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return buffer
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}
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// validate_utf_8 validates payload for valid utf8 encoding
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// - Future implementation needs to support fail fast utf errors for strict autobahn conformance
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fn (mut ws Client) validate_utf_8(opcode OPCode, payload []byte) ? {
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if opcode in [.text_frame, .close] && !utf8.validate(payload.data, payload.len) {
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ws.logger.error('malformed utf8 payload, payload len: ($payload.len)')
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ws.send_error_event('Recieved malformed utf8.')
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ws.close(1007, 'malformed utf8 payload') ?
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return error('malformed utf8 payload')
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}
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}
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// read_next_message reads 1 to n frames to compose a message
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pub fn (mut ws Client) read_next_message() ?Message {
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for {
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frame := ws.parse_frame_header() ?
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ws.validate_frame(&frame) ?
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frame_payload := ws.read_payload(&frame) ?
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if is_control_frame(frame.opcode) {
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// Control frames can interject other frames
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// and need to be returned immediately
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msg := Message{
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opcode: OPCode(frame.opcode)
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payload: frame_payload.clone()
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}
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unsafe { frame_payload.free() }
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return msg
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}
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// if the message is fragmented we just put it on fragments
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// a fragment is allowed to have zero size payload
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if !frame.fin {
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ws.fragments << &Fragment{
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data: frame_payload.clone()
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opcode: frame.opcode
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}
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unsafe { frame_payload.free() }
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continue
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}
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if ws.fragments.len == 0 {
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ws.validate_utf_8(frame.opcode, frame_payload) or {
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ws.logger.error('UTF8 validation error: $err, len of payload($frame_payload.len)')
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ws.send_error_event('UTF8 validation error: $err, len of payload($frame_payload.len)')
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return err
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}
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msg := Message{
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opcode: OPCode(frame.opcode)
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payload: frame_payload.clone()
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}
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unsafe { frame_payload.free() }
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return msg
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}
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defer {
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ws.fragments = []
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}
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if is_data_frame(frame.opcode) {
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ws.close(0, '') ?
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return error('Unexpected frame opcode')
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}
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payload := ws.payload_from_fragments(frame_payload) ?
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opcode := ws.opcode_from_fragments()
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ws.validate_utf_8(opcode, payload) ?
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msg := Message{
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opcode: opcode
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payload: payload.clone()
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}
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unsafe {
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frame_payload.free()
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payload.free()
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}
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return msg
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}
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return none
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}
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// payload_from_fragments returs the whole paylaod from fragmented message
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fn (ws Client) payload_from_fragments(fin_payload []byte) ?[]byte {
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mut total_size := 0
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for f in ws.fragments {
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if f.data.len > 0 {
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total_size += f.data.len
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}
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}
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total_size += fin_payload.len
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if total_size == 0 {
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return []byte{}
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}
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mut total_buffer := []byte{cap: total_size}
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for f in ws.fragments {
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if f.data.len > 0 {
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total_buffer << f.data
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}
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}
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total_buffer << fin_payload
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return total_buffer
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}
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// opcode_from_fragments returns the opcode for message from the first fragment sent
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fn (ws Client) opcode_from_fragments() OPCode {
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return OPCode(ws.fragments[0].opcode)
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}
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// parse_frame_header parses next message by decoding the incoming frames
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pub fn (mut ws Client) parse_frame_header() ?Frame {
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mut buffer := [256]byte{}
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mut bytes_read := 0
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mut frame := Frame{}
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mut rbuff := [1]byte{}
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mut mask_end_byte := 0
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for ws.state == .open {
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read_bytes := ws.socket_read_ptr(&rbuff[0], 1) ?
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if read_bytes == 0 {
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// this is probably a timeout or close
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continue
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}
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buffer[bytes_read] = rbuff[0]
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bytes_read++
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// parses the first two header bytes to get basic frame information
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if bytes_read == u64(websocket.header_len_offset) {
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frame.fin = (buffer[0] & 0x80) == 0x80
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frame.rsv1 = (buffer[0] & 0x40) == 0x40
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frame.rsv2 = (buffer[0] & 0x20) == 0x20
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frame.rsv3 = (buffer[0] & 0x10) == 0x10
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frame.opcode = OPCode(int(buffer[0] & 0x7F))
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frame.has_mask = (buffer[1] & 0x80) == 0x80
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frame.payload_len = buffer[1] & 0x7F
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// if has mask set the byte postition where mask ends
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if frame.has_mask {
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mask_end_byte = if frame.payload_len < 126 {
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websocket.header_len_offset + 4
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} else if frame.payload_len == 126 {
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websocket.header_len_offset + 6
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} else if frame.payload_len == 127 {
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websocket.header_len_offset + 12
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} else {
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0
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} // impossible
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}
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frame.payload_len = frame.payload_len
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frame.frame_size = frame.header_len + frame.payload_len
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if !frame.has_mask && frame.payload_len < 126 {
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break
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}
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}
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if frame.payload_len == 126 && bytes_read == u64(websocket.extended_payload16_end_byte) {
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frame.header_len += 2
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frame.payload_len = 0
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frame.payload_len |= buffer[2] << 8
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frame.payload_len |= buffer[3]
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frame.frame_size = frame.header_len + frame.payload_len
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if !frame.has_mask {
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break
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}
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}
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if frame.payload_len == 127 && bytes_read == u64(websocket.extended_payload64_end_byte) {
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frame.header_len += 8
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// these shift operators needs 64 bit on clang with -prod flag
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mut payload_len := u64(0)
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payload_len |= u64(buffer[2]) << 56
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payload_len |= u64(buffer[3]) << 48
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payload_len |= u64(buffer[4]) << 40
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payload_len |= u64(buffer[5]) << 32
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payload_len |= u64(buffer[6]) << 24
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payload_len |= u64(buffer[7]) << 16
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payload_len |= u64(buffer[8]) << 8
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payload_len |= u64(buffer[9])
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frame.payload_len = int(payload_len)
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if !frame.has_mask {
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break
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}
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}
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if frame.has_mask && bytes_read == mask_end_byte {
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frame.masking_key[0] = buffer[mask_end_byte - 4]
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frame.masking_key[1] = buffer[mask_end_byte - 3]
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frame.masking_key[2] = buffer[mask_end_byte - 2]
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frame.masking_key[3] = buffer[mask_end_byte - 1]
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break
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}
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}
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return frame
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}
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// unmask_sequence unmask any given sequence
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fn (f Frame) unmask_sequence(mut buffer []byte) {
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for i in 0 .. buffer.len {
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buffer[i] ^= f.masking_key[i % 4] & 0xff
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}
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}
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