size_t http_parser_execute()

in AZ3166/src/cores/arduino/httpclient/http_parser/http_parser.c [634:2091]


size_t http_parser_execute (http_parser *parser,
                            const http_parser_settings *settings,
                            const char *data,
                            size_t len)
{
  char c, ch;
  int8_t unhex_val;
  const char *p = data;
  const char *header_field_mark = 0;
  const char *header_value_mark = 0;
  const char *url_mark = 0;
  const char *body_mark = 0;
  const char *status_mark = 0;
  enum state p_state = (enum state) parser->state;
  const unsigned int lenient = parser->lenient_http_headers;

  /* We're in an error state. Don't bother doing anything. */
  if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {
    return 0;
  }

  if (len == 0) {
    switch (CURRENT_STATE()) {
      case s_body_identity_eof:
        /* Use of CALLBACK_NOTIFY() here would erroneously return 1 byte read if
         * we got paused.
         */
        CALLBACK_NOTIFY_NOADVANCE(message_complete);
        return 0;

      case s_dead:
      case s_start_req_or_res:
      case s_start_res:
      case s_start_req:
        return 0;

      default:
        SET_ERRNO(HPE_INVALID_EOF_STATE);
        return 1;
    }
  }


  if (CURRENT_STATE() == s_header_field)
    header_field_mark = data;
  if (CURRENT_STATE() == s_header_value)
    header_value_mark = data;
  switch (CURRENT_STATE()) {
  case s_req_path:
  case s_req_schema:
  case s_req_schema_slash:
  case s_req_schema_slash_slash:
  case s_req_server_start:
  case s_req_server:
  case s_req_server_with_at:
  case s_req_query_string_start:
  case s_req_query_string:
  case s_req_fragment_start:
  case s_req_fragment:
    url_mark = data;
    break;
  case s_res_status:
    status_mark = data;
    break;
  default:
    break;
  }

  for (p=data; p != data + len; p++) {
    ch = *p;

    if (PARSING_HEADER(CURRENT_STATE()))
      COUNT_HEADER_SIZE(1);

reexecute:
    switch (CURRENT_STATE()) {

      case s_dead:
        /* this state is used after a 'Connection: close' message
         * the parser will error out if it reads another message
         */
        if (LIKELY(ch == CR || ch == LF))
          break;

        SET_ERRNO(HPE_CLOSED_CONNECTION);
        goto error;

      case s_start_req_or_res:
      {
        if (ch == CR || ch == LF)
          break;
        parser->flags = 0;
        parser->content_length = ULLONG_MAX;

        if (ch == 'H') {
          UPDATE_STATE(s_res_or_resp_H);

          CALLBACK_NOTIFY(message_begin);
        } else {
          parser->type = HTTP_REQUEST;
          UPDATE_STATE(s_start_req);
          REEXECUTE();
        }

        break;
      }

      case s_res_or_resp_H:
        if (ch == 'T') {
          parser->type = HTTP_RESPONSE;
          UPDATE_STATE(s_res_HT);
        } else {
          if (UNLIKELY(ch != 'E')) {
            SET_ERRNO(HPE_INVALID_CONSTANT);
            goto error;
          }

          parser->type = HTTP_REQUEST;
          parser->method = HTTP_HEAD;
          parser->index = 2;
          UPDATE_STATE(s_req_method);
        }
        break;

      case s_start_res:
      {
        parser->flags = 0;
        parser->content_length = ULLONG_MAX;

        switch (ch) {
          case 'H':
            UPDATE_STATE(s_res_H);
            break;

          case CR:
          case LF:
            break;

          default:
            SET_ERRNO(HPE_INVALID_CONSTANT);
            goto error;
        }

        CALLBACK_NOTIFY(message_begin);
        break;
      }

      case s_res_H:
        STRICT_CHECK(ch != 'T');
        UPDATE_STATE(s_res_HT);
        break;

      case s_res_HT:
        STRICT_CHECK(ch != 'T');
        UPDATE_STATE(s_res_HTT);
        break;

      case s_res_HTT:
        STRICT_CHECK(ch != 'P');
        UPDATE_STATE(s_res_HTTP);
        break;

      case s_res_HTTP:
        STRICT_CHECK(ch != '/');
        UPDATE_STATE(s_res_first_http_major);
        break;

      case s_res_first_http_major:
        if (UNLIKELY(ch < '0' || ch > '9')) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        parser->http_major = ch - '0';
        UPDATE_STATE(s_res_http_major);
        break;

      /* major HTTP version or dot */
      case s_res_http_major:
      {
        if (ch == '.') {
          UPDATE_STATE(s_res_first_http_minor);
          break;
        }

        if (!IS_NUM(ch)) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        parser->http_major *= 10;
        parser->http_major += ch - '0';

        if (UNLIKELY(parser->http_major > 999)) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        break;
      }

      /* first digit of minor HTTP version */
      case s_res_first_http_minor:
        if (UNLIKELY(!IS_NUM(ch))) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        parser->http_minor = ch - '0';
        UPDATE_STATE(s_res_http_minor);
        break;

      /* minor HTTP version or end of request line */
      case s_res_http_minor:
      {
        if (ch == ' ') {
          UPDATE_STATE(s_res_first_status_code);
          break;
        }

        if (UNLIKELY(!IS_NUM(ch))) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        parser->http_minor *= 10;
        parser->http_minor += ch - '0';

        if (UNLIKELY(parser->http_minor > 999)) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        break;
      }

      case s_res_first_status_code:
      {
        if (!IS_NUM(ch)) {
          if (ch == ' ') {
            break;
          }

          SET_ERRNO(HPE_INVALID_STATUS);
          goto error;
        }
        parser->status_code = ch - '0';
        UPDATE_STATE(s_res_status_code);
        break;
      }

      case s_res_status_code:
      {
        if (!IS_NUM(ch)) {
          switch (ch) {
            case ' ':
              UPDATE_STATE(s_res_status_start);
              break;
            case CR:
              UPDATE_STATE(s_res_line_almost_done);
              break;
            case LF:
              UPDATE_STATE(s_header_field_start);
              break;
            default:
              SET_ERRNO(HPE_INVALID_STATUS);
              goto error;
          }
          break;
        }

        parser->status_code *= 10;
        parser->status_code += ch - '0';

        if (UNLIKELY(parser->status_code > 999)) {
          SET_ERRNO(HPE_INVALID_STATUS);
          goto error;
        }

        break;
      }

      case s_res_status_start:
      {
        if (ch == CR) {
          UPDATE_STATE(s_res_line_almost_done);
          break;
        }

        if (ch == LF) {
          UPDATE_STATE(s_header_field_start);
          break;
        }

        MARK(status);
        UPDATE_STATE(s_res_status);
        parser->index = 0;
        break;
      }

      case s_res_status:
        if (ch == CR) {
          UPDATE_STATE(s_res_line_almost_done);
          CALLBACK_DATA(status);
          break;
        }

        if (ch == LF) {
          UPDATE_STATE(s_header_field_start);
          CALLBACK_DATA(status);
          break;
        }

        break;

      case s_res_line_almost_done:
        STRICT_CHECK(ch != LF);
        UPDATE_STATE(s_header_field_start);
        break;

      case s_start_req:
      {
        if (ch == CR || ch == LF)
          break;
        parser->flags = 0;
        parser->content_length = ULLONG_MAX;

        if (UNLIKELY(!IS_ALPHA(ch))) {
          SET_ERRNO(HPE_INVALID_METHOD);
          goto error;
        }

        parser->method = (enum http_method) 0;
        parser->index = 1;
        switch (ch) {
          case 'A': parser->method = HTTP_ACL; break;
          case 'B': parser->method = HTTP_BIND; break;
          case 'C': parser->method = HTTP_CONNECT; /* or COPY, CHECKOUT */ break;
          case 'D': parser->method = HTTP_DELETE; break;
          case 'G': parser->method = HTTP_GET; break;
          case 'H': parser->method = HTTP_HEAD; break;
          case 'L': parser->method = HTTP_LOCK; /* or LINK */ break;
          case 'M': parser->method = HTTP_MKCOL; /* or MOVE, MKACTIVITY, MERGE, M-SEARCH, MKCALENDAR */ break;
          case 'N': parser->method = HTTP_NOTIFY; break;
          case 'O': parser->method = HTTP_OPTIONS; break;
          case 'P': parser->method = HTTP_POST;
            /* or PROPFIND|PROPPATCH|PUT|PATCH|PURGE */
            break;
          case 'R': parser->method = HTTP_REPORT; /* or REBIND */ break;
          case 'S': parser->method = HTTP_SUBSCRIBE; /* or SEARCH */ break;
          case 'T': parser->method = HTTP_TRACE; break;
          case 'U': parser->method = HTTP_UNLOCK; /* or UNSUBSCRIBE, UNBIND, UNLINK */ break;
          default:
            SET_ERRNO(HPE_INVALID_METHOD);
            goto error;
        }
        UPDATE_STATE(s_req_method);

        CALLBACK_NOTIFY(message_begin);

        break;
      }

      case s_req_method:
      {
        const char *matcher;
        if (UNLIKELY(ch == '\0')) {
          SET_ERRNO(HPE_INVALID_METHOD);
          goto error;
        }

        matcher = method_strings[parser->method];
        if (ch == ' ' && matcher[parser->index] == '\0') {
          UPDATE_STATE(s_req_spaces_before_url);
        } else if (ch == matcher[parser->index]) {
          ; /* nada */
        } else if (IS_ALPHA(ch)) {

          switch (parser->method << 16 | parser->index << 8 | ch) {
#define XX(meth, pos, ch, new_meth) \
            case (HTTP_##meth << 16 | pos << 8 | ch): \
              parser->method = HTTP_##new_meth; break;

            XX(POST,      1, 'U', PUT)
            XX(POST,      1, 'A', PATCH)
            XX(CONNECT,   1, 'H', CHECKOUT)
            XX(CONNECT,   2, 'P', COPY)
            XX(MKCOL,     1, 'O', MOVE)
            XX(MKCOL,     1, 'E', MERGE)
            XX(MKCOL,     2, 'A', MKACTIVITY)
            XX(MKCOL,     3, 'A', MKCALENDAR)
            XX(SUBSCRIBE, 1, 'E', SEARCH)
            XX(REPORT,    2, 'B', REBIND)
            XX(POST,      1, 'R', PROPFIND)
            XX(PROPFIND,  4, 'P', PROPPATCH)
            XX(PUT,       2, 'R', PURGE)
            XX(LOCK,      1, 'I', LINK)
            XX(UNLOCK,    2, 'S', UNSUBSCRIBE)
            XX(UNLOCK,    2, 'B', UNBIND)
            XX(UNLOCK,    3, 'I', UNLINK)
#undef XX

            default:
              SET_ERRNO(HPE_INVALID_METHOD);
              goto error;
          }
        } else if (ch == '-' &&
                   parser->index == 1 &&
                   parser->method == HTTP_MKCOL) {
          parser->method = HTTP_MSEARCH;
        } else {
          SET_ERRNO(HPE_INVALID_METHOD);
          goto error;
        }

        ++parser->index;
        break;
      }

      case s_req_spaces_before_url:
      {
        if (ch == ' ') break;

        MARK(url);
        if (parser->method == HTTP_CONNECT) {
          UPDATE_STATE(s_req_server_start);
        }

        UPDATE_STATE(parse_url_char(CURRENT_STATE(), ch));
        if (UNLIKELY(CURRENT_STATE() == s_dead)) {
          SET_ERRNO(HPE_INVALID_URL);
          goto error;
        }

        break;
      }

      case s_req_schema:
      case s_req_schema_slash:
      case s_req_schema_slash_slash:
      case s_req_server_start:
      {
        switch (ch) {
          /* No whitespace allowed here */
          case ' ':
          case CR:
          case LF:
            SET_ERRNO(HPE_INVALID_URL);
            goto error;
          default:
            UPDATE_STATE(parse_url_char(CURRENT_STATE(), ch));
            if (UNLIKELY(CURRENT_STATE() == s_dead)) {
              SET_ERRNO(HPE_INVALID_URL);
              goto error;
            }
        }

        break;
      }

      case s_req_server:
      case s_req_server_with_at:
      case s_req_path:
      case s_req_query_string_start:
      case s_req_query_string:
      case s_req_fragment_start:
      case s_req_fragment:
      {
        switch (ch) {
          case ' ':
            UPDATE_STATE(s_req_http_start);
            CALLBACK_DATA(url);
            break;
          case CR:
          case LF:
            parser->http_major = 0;
            parser->http_minor = 9;
            UPDATE_STATE((ch == CR) ?
              s_req_line_almost_done :
              s_header_field_start);
            CALLBACK_DATA(url);
            break;
          default:
            UPDATE_STATE(parse_url_char(CURRENT_STATE(), ch));
            if (UNLIKELY(CURRENT_STATE() == s_dead)) {
              SET_ERRNO(HPE_INVALID_URL);
              goto error;
            }
        }
        break;
      }

      case s_req_http_start:
        switch (ch) {
          case 'H':
            UPDATE_STATE(s_req_http_H);
            break;
          case ' ':
            break;
          default:
            SET_ERRNO(HPE_INVALID_CONSTANT);
            goto error;
        }
        break;

      case s_req_http_H:
        STRICT_CHECK(ch != 'T');
        UPDATE_STATE(s_req_http_HT);
        break;

      case s_req_http_HT:
        STRICT_CHECK(ch != 'T');
        UPDATE_STATE(s_req_http_HTT);
        break;

      case s_req_http_HTT:
        STRICT_CHECK(ch != 'P');
        UPDATE_STATE(s_req_http_HTTP);
        break;

      case s_req_http_HTTP:
        STRICT_CHECK(ch != '/');
        UPDATE_STATE(s_req_first_http_major);
        break;

      /* first digit of major HTTP version */
      case s_req_first_http_major:
        if (UNLIKELY(ch < '1' || ch > '9')) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        parser->http_major = ch - '0';
        UPDATE_STATE(s_req_http_major);
        break;

      /* major HTTP version or dot */
      case s_req_http_major:
      {
        if (ch == '.') {
          UPDATE_STATE(s_req_first_http_minor);
          break;
        }

        if (UNLIKELY(!IS_NUM(ch))) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        parser->http_major *= 10;
        parser->http_major += ch - '0';

        if (UNLIKELY(parser->http_major > 999)) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        break;
      }

      /* first digit of minor HTTP version */
      case s_req_first_http_minor:
        if (UNLIKELY(!IS_NUM(ch))) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        parser->http_minor = ch - '0';
        UPDATE_STATE(s_req_http_minor);
        break;

      /* minor HTTP version or end of request line */
      case s_req_http_minor:
      {
        if (ch == CR) {
          UPDATE_STATE(s_req_line_almost_done);
          break;
        }

        if (ch == LF) {
          UPDATE_STATE(s_header_field_start);
          break;
        }

        /* XXX allow spaces after digit? */

        if (UNLIKELY(!IS_NUM(ch))) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        parser->http_minor *= 10;
        parser->http_minor += ch - '0';

        if (UNLIKELY(parser->http_minor > 999)) {
          SET_ERRNO(HPE_INVALID_VERSION);
          goto error;
        }

        break;
      }

      /* end of request line */
      case s_req_line_almost_done:
      {
        if (UNLIKELY(ch != LF)) {
          SET_ERRNO(HPE_LF_EXPECTED);
          goto error;
        }

        UPDATE_STATE(s_header_field_start);
        break;
      }

      case s_header_field_start:
      {
        if (ch == CR) {
          UPDATE_STATE(s_headers_almost_done);
          break;
        }

        if (ch == LF) {
          /* they might be just sending \n instead of \r\n so this would be
           * the second \n to denote the end of headers*/
          UPDATE_STATE(s_headers_almost_done);
          REEXECUTE();
        }

        c = TOKEN(ch);

        if (UNLIKELY(!c)) {
          SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
          goto error;
        }

        MARK(header_field);

        parser->index = 0;
        UPDATE_STATE(s_header_field);

        switch (c) {
          case 'c':
            parser->header_state = h_C;
            break;

          case 'p':
            parser->header_state = h_matching_proxy_connection;
            break;

          case 't':
            parser->header_state = h_matching_transfer_encoding;
            break;

          case 'u':
            parser->header_state = h_matching_upgrade;
            break;

          default:
            parser->header_state = h_general;
            break;
        }
        break;
      }

      case s_header_field:
      {
        const char* start = p;
        for (; p != data + len; p++) {
          ch = *p;
          c = TOKEN(ch);

          if (!c)
            break;

          switch (parser->header_state) {
            case h_general:
              break;

            case h_C:
              parser->index++;
              parser->header_state = (c == 'o' ? h_CO : h_general);
              break;

            case h_CO:
              parser->index++;
              parser->header_state = (c == 'n' ? h_CON : h_general);
              break;

            case h_CON:
              parser->index++;
              switch (c) {
                case 'n':
                  parser->header_state = h_matching_connection;
                  break;
                case 't':
                  parser->header_state = h_matching_content_length;
                  break;
                default:
                  parser->header_state = h_general;
                  break;
              }
              break;

            /* connection */

            case h_matching_connection:
              parser->index++;
              if (parser->index > sizeof(CONNECTION)-1
                  || c != CONNECTION[parser->index]) {
                parser->header_state = h_general;
              } else if (parser->index == sizeof(CONNECTION)-2) {
                parser->header_state = h_connection;
              }
              break;

            /* proxy-connection */

            case h_matching_proxy_connection:
              parser->index++;
              if (parser->index > sizeof(PROXY_CONNECTION)-1
                  || c != PROXY_CONNECTION[parser->index]) {
                parser->header_state = h_general;
              } else if (parser->index == sizeof(PROXY_CONNECTION)-2) {
                parser->header_state = h_connection;
              }
              break;

            /* content-length */

            case h_matching_content_length:
              parser->index++;
              if (parser->index > sizeof(CONTENT_LENGTH)-1
                  || c != CONTENT_LENGTH[parser->index]) {
                parser->header_state = h_general;
              } else if (parser->index == sizeof(CONTENT_LENGTH)-2) {
                parser->header_state = h_content_length;
              }
              break;

            /* transfer-encoding */

            case h_matching_transfer_encoding:
              parser->index++;
              if (parser->index > sizeof(TRANSFER_ENCODING)-1
                  || c != TRANSFER_ENCODING[parser->index]) {
                parser->header_state = h_general;
              } else if (parser->index == sizeof(TRANSFER_ENCODING)-2) {
                parser->header_state = h_transfer_encoding;
              }
              break;

            /* upgrade */

            case h_matching_upgrade:
              parser->index++;
              if (parser->index > sizeof(UPGRADE)-1
                  || c != UPGRADE[parser->index]) {
                parser->header_state = h_general;
              } else if (parser->index == sizeof(UPGRADE)-2) {
                parser->header_state = h_upgrade;
              }
              break;

            case h_connection:
            case h_content_length:
            case h_transfer_encoding:
            case h_upgrade:
              if (ch != ' ') parser->header_state = h_general;
              break;

            default:
              assert(0 && "Unknown header_state");
              break;
          }
        }

        COUNT_HEADER_SIZE(p - start);

        if (p == data + len) {
          --p;
          break;
        }

        if (ch == ':') {
          UPDATE_STATE(s_header_value_discard_ws);
          CALLBACK_DATA(header_field);
          break;
        }

        SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
        goto error;
      }

      case s_header_value_discard_ws:
        if (ch == ' ' || ch == '\t') break;

        if (ch == CR) {
          UPDATE_STATE(s_header_value_discard_ws_almost_done);
          break;
        }

        if (ch == LF) {
          UPDATE_STATE(s_header_value_discard_lws);
          break;
        }

        /* FALLTHROUGH */

      case s_header_value_start:
      {
        MARK(header_value);

        UPDATE_STATE(s_header_value);
        parser->index = 0;

        c = LOWER(ch);

        switch (parser->header_state) {
          case h_upgrade:
            parser->flags |= F_UPGRADE;
            parser->header_state = h_general;
            break;

          case h_transfer_encoding:
            /* looking for 'Transfer-Encoding: chunked' */
            if ('c' == c) {
              parser->header_state = h_matching_transfer_encoding_chunked;
            } else {
              parser->header_state = h_general;
            }
            break;

          case h_content_length:
            if (UNLIKELY(!IS_NUM(ch))) {
              SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
              goto error;
            }

            if (parser->flags & F_CONTENTLENGTH) {
              SET_ERRNO(HPE_UNEXPECTED_CONTENT_LENGTH);
              goto error;
            }

            parser->flags |= F_CONTENTLENGTH;
            parser->content_length = ch - '0';
            break;

          case h_connection:
            /* looking for 'Connection: keep-alive' */
            if (c == 'k') {
              parser->header_state = h_matching_connection_keep_alive;
            /* looking for 'Connection: close' */
            } else if (c == 'c') {
              parser->header_state = h_matching_connection_close;
            } else if (c == 'u') {
              parser->header_state = h_matching_connection_upgrade;
            } else {
              parser->header_state = h_matching_connection_token;
            }
            break;

          /* Multi-value `Connection` header */
          case h_matching_connection_token_start:
            break;

          default:
            parser->header_state = h_general;
            break;
        }
        break;
      }

      case s_header_value:
      {
        const char* start = p;
        enum header_states h_state = (enum header_states) parser->header_state;
        for (; p != data + len; p++) {
          ch = *p;
          if (ch == CR) {
            UPDATE_STATE(s_header_almost_done);
            parser->header_state = h_state;
            CALLBACK_DATA(header_value);
            break;
          }

          if (ch == LF) {
            UPDATE_STATE(s_header_almost_done);
            COUNT_HEADER_SIZE(p - start);
            parser->header_state = h_state;
            CALLBACK_DATA_NOADVANCE(header_value);
            REEXECUTE();
          }

          if (!lenient && !IS_HEADER_CHAR(ch)) {
            SET_ERRNO(HPE_INVALID_HEADER_TOKEN);
            goto error;
          }

          c = LOWER(ch);

          switch (h_state) {
            case h_general:
            {
              const char* p_cr;
              const char* p_lf;
              size_t limit = data + len - p;

              limit = MIN(limit, HTTP_MAX_HEADER_SIZE);

              p_cr = (const char*) memchr(p, CR, limit);
              p_lf = (const char*) memchr(p, LF, limit);
              if (p_cr != NULL) {
                if (p_lf != NULL && p_cr >= p_lf)
                  p = p_lf;
                else
                  p = p_cr;
              } else if (UNLIKELY(p_lf != NULL)) {
                p = p_lf;
              } else {
                p = data + len;
              }
              --p;

              break;
            }

            case h_connection:
            case h_transfer_encoding:
              assert(0 && "Shouldn't get here.");
              break;

            case h_content_length:
            {
              uint64_t t;

              if (ch == ' ') break;

              if (UNLIKELY(!IS_NUM(ch))) {
                SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                parser->header_state = h_state;
                goto error;
              }

              t = parser->content_length;
              t *= 10;
              t += ch - '0';

              /* Overflow? Test against a conservative limit for simplicity. */
              if (UNLIKELY((ULLONG_MAX - 10) / 10 < parser->content_length)) {
                SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
                parser->header_state = h_state;
                goto error;
              }

              parser->content_length = t;
              break;
            }

            /* Transfer-Encoding: chunked */
            case h_matching_transfer_encoding_chunked:
              parser->index++;
              if (parser->index > sizeof(CHUNKED)-1
                  || c != CHUNKED[parser->index]) {
                h_state = h_general;
              } else if (parser->index == sizeof(CHUNKED)-2) {
                h_state = h_transfer_encoding_chunked;
              }
              break;

            case h_matching_connection_token_start:
              /* looking for 'Connection: keep-alive' */
              if (c == 'k') {
                h_state = h_matching_connection_keep_alive;
              /* looking for 'Connection: close' */
              } else if (c == 'c') {
                h_state = h_matching_connection_close;
              } else if (c == 'u') {
                h_state = h_matching_connection_upgrade;
              } else if (STRICT_TOKEN(c)) {
                h_state = h_matching_connection_token;
              } else if (c == ' ' || c == '\t') {
                /* Skip lws */
              } else {
                h_state = h_general;
              }
              break;

            /* looking for 'Connection: keep-alive' */
            case h_matching_connection_keep_alive:
              parser->index++;
              if (parser->index > sizeof(KEEP_ALIVE)-1
                  || c != KEEP_ALIVE[parser->index]) {
                h_state = h_matching_connection_token;
              } else if (parser->index == sizeof(KEEP_ALIVE)-2) {
                h_state = h_connection_keep_alive;
              }
              break;

            /* looking for 'Connection: close' */
            case h_matching_connection_close:
              parser->index++;
              if (parser->index > sizeof(CLOSE)-1 || c != CLOSE[parser->index]) {
                h_state = h_matching_connection_token;
              } else if (parser->index == sizeof(CLOSE)-2) {
                h_state = h_connection_close;
              }
              break;

            /* looking for 'Connection: upgrade' */
            case h_matching_connection_upgrade:
              parser->index++;
              if (parser->index > sizeof(UPGRADE) - 1 ||
                  c != UPGRADE[parser->index]) {
                h_state = h_matching_connection_token;
              } else if (parser->index == sizeof(UPGRADE)-2) {
                h_state = h_connection_upgrade;
              }
              break;

            case h_matching_connection_token:
              if (ch == ',') {
                h_state = h_matching_connection_token_start;
                parser->index = 0;
              }
              break;

            case h_transfer_encoding_chunked:
              if (ch != ' ') h_state = h_general;
              break;

            case h_connection_keep_alive:
            case h_connection_close:
            case h_connection_upgrade:
              if (ch == ',') {
                if (h_state == h_connection_keep_alive) {
                  parser->flags |= F_CONNECTION_KEEP_ALIVE;
                } else if (h_state == h_connection_close) {
                  parser->flags |= F_CONNECTION_CLOSE;
                } else if (h_state == h_connection_upgrade) {
                  parser->flags |= F_CONNECTION_UPGRADE;
                }
                h_state = h_matching_connection_token_start;
                parser->index = 0;
              } else if (ch != ' ') {
                h_state = h_matching_connection_token;
              }
              break;

            default:
              UPDATE_STATE(s_header_value);
              h_state = h_general;
              break;
          }
        }
        parser->header_state = h_state;

        COUNT_HEADER_SIZE(p - start);

        if (p == data + len)
          --p;
        break;
      }

      case s_header_almost_done:
      {
        if (UNLIKELY(ch != LF)) {
          SET_ERRNO(HPE_LF_EXPECTED);
          goto error;
        }

        UPDATE_STATE(s_header_value_lws);
        break;
      }

      case s_header_value_lws:
      {
        if (ch == ' ' || ch == '\t') {
          UPDATE_STATE(s_header_value_start);
          REEXECUTE();
        }

        /* finished the header */
        switch (parser->header_state) {
          case h_connection_keep_alive:
            parser->flags |= F_CONNECTION_KEEP_ALIVE;
            break;
          case h_connection_close:
            parser->flags |= F_CONNECTION_CLOSE;
            break;
          case h_transfer_encoding_chunked:
            parser->flags |= F_CHUNKED;
            break;
          case h_connection_upgrade:
            parser->flags |= F_CONNECTION_UPGRADE;
            break;
          default:
            break;
        }

        UPDATE_STATE(s_header_field_start);
        REEXECUTE();
      }

      case s_header_value_discard_ws_almost_done:
      {
        STRICT_CHECK(ch != LF);
        UPDATE_STATE(s_header_value_discard_lws);
        break;
      }

      case s_header_value_discard_lws:
      {
        if (ch == ' ' || ch == '\t') {
          UPDATE_STATE(s_header_value_discard_ws);
          break;
        } else {
          switch (parser->header_state) {
            case h_connection_keep_alive:
              parser->flags |= F_CONNECTION_KEEP_ALIVE;
              break;
            case h_connection_close:
              parser->flags |= F_CONNECTION_CLOSE;
              break;
            case h_connection_upgrade:
              parser->flags |= F_CONNECTION_UPGRADE;
              break;
            case h_transfer_encoding_chunked:
              parser->flags |= F_CHUNKED;
              break;
            default:
              break;
          }

          /* header value was empty */
          MARK(header_value);
          UPDATE_STATE(s_header_field_start);
          CALLBACK_DATA_NOADVANCE(header_value);
          REEXECUTE();
        }
      }

      case s_headers_almost_done:
      {
        STRICT_CHECK(ch != LF);

        if (parser->flags & F_TRAILING) {
          /* End of a chunked request */
          UPDATE_STATE(s_message_done);
          CALLBACK_NOTIFY_NOADVANCE(chunk_complete);
          REEXECUTE();
        }

        /* Cannot use chunked encoding and a content-length header together
           per the HTTP specification. */
        if ((parser->flags & F_CHUNKED) &&
            (parser->flags & F_CONTENTLENGTH)) {
          SET_ERRNO(HPE_UNEXPECTED_CONTENT_LENGTH);
          goto error;
        }

        UPDATE_STATE(s_headers_done);

        /* Set this here so that on_headers_complete() callbacks can see it */
        parser->upgrade =
          ((parser->flags & (F_UPGRADE | F_CONNECTION_UPGRADE)) ==
           (F_UPGRADE | F_CONNECTION_UPGRADE) ||
           parser->method == HTTP_CONNECT);

        /* Here we call the headers_complete callback. This is somewhat
         * different than other callbacks because if the user returns 1, we
         * will interpret that as saying that this message has no body. This
         * is needed for the annoying case of receiving a response to a HEAD
         * request.
         *
         * We'd like to use CALLBACK_NOTIFY_NOADVANCE() here but we cannot, so
         * we have to simulate it by handling a change in errno below.
         */
        if (settings->on_headers_complete) {
          switch (settings->on_headers_complete(parser)) {
            case 0:
              break;

            case 2:
              parser->upgrade = 1;

            case 1:
              parser->flags |= F_SKIPBODY;
              break;

            default:
              SET_ERRNO(HPE_CB_headers_complete);
              RETURN(p - data); /* Error */
          }
        }

        if (HTTP_PARSER_ERRNO(parser) != HPE_OK) {
          RETURN(p - data);
        }

        REEXECUTE();
      }

      case s_headers_done:
      {
        int hasBody;
        STRICT_CHECK(ch != LF);

        parser->nread = 0;

        hasBody = parser->flags & F_CHUNKED ||
          (parser->content_length > 0 && parser->content_length != ULLONG_MAX);
        if (parser->upgrade && (parser->method == HTTP_CONNECT ||
                                (parser->flags & F_SKIPBODY) || !hasBody)) {
          /* Exit, the rest of the message is in a different protocol. */
          UPDATE_STATE(NEW_MESSAGE());
          CALLBACK_NOTIFY(message_complete);
          RETURN((p - data) + 1);
        }

        if (parser->flags & F_SKIPBODY) {
          UPDATE_STATE(NEW_MESSAGE());
          CALLBACK_NOTIFY(message_complete);
        } else if (parser->flags & F_CHUNKED) {
          /* chunked encoding - ignore Content-Length header */
          UPDATE_STATE(s_chunk_size_start);
        } else {
          if (parser->content_length == 0) {
            /* Content-Length header given but zero: Content-Length: 0\r\n */
            UPDATE_STATE(NEW_MESSAGE());
            CALLBACK_NOTIFY(message_complete);
          } else if (parser->content_length != ULLONG_MAX) {
            /* Content-Length header given and non-zero */
            UPDATE_STATE(s_body_identity);
          } else {
            if (!http_message_needs_eof(parser)) {
              /* Assume content-length 0 - read the next */
              UPDATE_STATE(NEW_MESSAGE());
              CALLBACK_NOTIFY(message_complete);
            } else {
              /* Read body until EOF */
              UPDATE_STATE(s_body_identity_eof);
            }
          }
        }

        break;
      }

      case s_body_identity:
      {
        uint64_t to_read = MIN(parser->content_length,
                               (uint64_t) ((data + len) - p));

        assert(parser->content_length != 0
            && parser->content_length != ULLONG_MAX);

        /* The difference between advancing content_length and p is because
         * the latter will automaticaly advance on the next loop iteration.
         * Further, if content_length ends up at 0, we want to see the last
         * byte again for our message complete callback.
         */
        MARK(body);
        parser->content_length -= to_read;
        p += to_read - 1;

        if (parser->content_length == 0) {
          UPDATE_STATE(s_message_done);

          /* Mimic CALLBACK_DATA_NOADVANCE() but with one extra byte.
           *
           * The alternative to doing this is to wait for the next byte to
           * trigger the data callback, just as in every other case. The
           * problem with this is that this makes it difficult for the test
           * harness to distinguish between complete-on-EOF and
           * complete-on-length. It's not clear that this distinction is
           * important for applications, but let's keep it for now.
           */
          CALLBACK_DATA_(body, p - body_mark + 1, p - data);
          REEXECUTE();
        }

        break;
      }

      /* read until EOF */
      case s_body_identity_eof:
        MARK(body);
        p = data + len - 1;

        break;

      case s_message_done:
        UPDATE_STATE(NEW_MESSAGE());
        CALLBACK_NOTIFY(message_complete);
        if (parser->upgrade) {
          /* Exit, the rest of the message is in a different protocol. */
          RETURN((p - data) + 1);
        }
        break;

      case s_chunk_size_start:
      {
        assert(parser->nread == 1);
        assert(parser->flags & F_CHUNKED);

        unhex_val = unhex[(unsigned char)ch];
        if (UNLIKELY(unhex_val == -1)) {
          SET_ERRNO(HPE_INVALID_CHUNK_SIZE);
          goto error;
        }

        parser->content_length = unhex_val;
        UPDATE_STATE(s_chunk_size);
        break;
      }

      case s_chunk_size:
      {
        uint64_t t;

        assert(parser->flags & F_CHUNKED);

        if (ch == CR) {
          UPDATE_STATE(s_chunk_size_almost_done);
          break;
        }

        unhex_val = unhex[(unsigned char)ch];

        if (unhex_val == -1) {
          if (ch == ';' || ch == ' ') {
            UPDATE_STATE(s_chunk_parameters);
            break;
          }

          SET_ERRNO(HPE_INVALID_CHUNK_SIZE);
          goto error;
        }

        t = parser->content_length;
        t *= 16;
        t += unhex_val;

        /* Overflow? Test against a conservative limit for simplicity. */
        if (UNLIKELY((ULLONG_MAX - 16) / 16 < parser->content_length)) {
          SET_ERRNO(HPE_INVALID_CONTENT_LENGTH);
          goto error;
        }

        parser->content_length = t;
        break;
      }

      case s_chunk_parameters:
      {
        assert(parser->flags & F_CHUNKED);
        /* just ignore this shit. TODO check for overflow */
        if (ch == CR) {
          UPDATE_STATE(s_chunk_size_almost_done);
          break;
        }
        break;
      }

      case s_chunk_size_almost_done:
      {
        assert(parser->flags & F_CHUNKED);
        STRICT_CHECK(ch != LF);

        parser->nread = 0;

        if (parser->content_length == 0) {
          parser->flags |= F_TRAILING;
          UPDATE_STATE(s_header_field_start);
        } else {
          UPDATE_STATE(s_chunk_data);
        }
        CALLBACK_NOTIFY(chunk_header);
        break;
      }

      case s_chunk_data:
      {
        uint64_t to_read = MIN(parser->content_length,
                               (uint64_t) ((data + len) - p));

        assert(parser->flags & F_CHUNKED);
        assert(parser->content_length != 0
            && parser->content_length != ULLONG_MAX);

        /* See the explanation in s_body_identity for why the content
         * length and data pointers are managed this way.
         */
        MARK(body);
        parser->content_length -= to_read;
        p += to_read - 1;

        if (parser->content_length == 0) {
          UPDATE_STATE(s_chunk_data_almost_done);
        }

        break;
      }

      case s_chunk_data_almost_done:
        assert(parser->flags & F_CHUNKED);
        assert(parser->content_length == 0);
        STRICT_CHECK(ch != CR);
        UPDATE_STATE(s_chunk_data_done);
        CALLBACK_DATA(body);
        break;

      case s_chunk_data_done:
        assert(parser->flags & F_CHUNKED);
        STRICT_CHECK(ch != LF);
        parser->nread = 0;
        UPDATE_STATE(s_chunk_size_start);
        CALLBACK_NOTIFY(chunk_complete);
        break;

      default:
        assert(0 && "unhandled state");
        SET_ERRNO(HPE_INVALID_INTERNAL_STATE);
        goto error;
    }
  }

  /* Run callbacks for any marks that we have leftover after we ran our of
   * bytes. There should be at most one of these set, so it's OK to invoke
   * them in series (unset marks will not result in callbacks).
   *
   * We use the NOADVANCE() variety of callbacks here because 'p' has already
   * overflowed 'data' and this allows us to correct for the off-by-one that
   * we'd otherwise have (since CALLBACK_DATA() is meant to be run with a 'p'
   * value that's in-bounds).
   */

  assert(((header_field_mark ? 1 : 0) +
          (header_value_mark ? 1 : 0) +
          (url_mark ? 1 : 0)  +
          (body_mark ? 1 : 0) +
          (status_mark ? 1 : 0)) <= 1);

  CALLBACK_DATA_NOADVANCE(header_field);
  CALLBACK_DATA_NOADVANCE(header_value);
  CALLBACK_DATA_NOADVANCE(url);
  CALLBACK_DATA_NOADVANCE(body);
  CALLBACK_DATA_NOADVANCE(status);

  RETURN(len);

error:
  if (HTTP_PARSER_ERRNO(parser) == HPE_OK) {
    SET_ERRNO(HPE_UNKNOWN);
  }

  RETURN(p - data);
}