text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
   *
   * This software is licensed as described in the file COPYING, which
   * you should have received as part of this distribution. The terms
   * are also available at http://curl.haxx.se/docs/copyright.html.
   *
   * You may opt to use, copy, modify, merge, publish, distribute and/or sell
   * copies of the Software, and permit persons to whom the Software is
   * furnished to do so, under the terms of the COPYING file.
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
   * KIND, either express or implied.
   *
   ***************************************************************************/
  
  #include "curl_setup.h"
  
  #ifndef CURL_DISABLE_RTSP
  
  #include "urldata.h"
  #include <curl/curl.h>
  #include "transfer.h"
  #include "sendf.h"
  #include "multiif.h"
  #include "http.h"
  #include "url.h"
  #include "progress.h"
  #include "rtsp.h"
  #include "rawstr.h"
  #include "select.h"
  #include "connect.h"
  #include "curl_printf.h"
  
  /* The last #include files should be: */
  #include "curl_memory.h"
  #include "memdebug.h"
  
  #define RTP_PKT_CHANNEL(p)   ((int)((unsigned char)((p)[1])))
  
  #define RTP_PKT_LENGTH(p)  ((((int)((unsigned char)((p)[2]))) << 8) | \
                               ((int)((unsigned char)((p)[3]))))
  
  /* protocol-specific functions set up to be called by the main engine */
  static CURLcode rtsp_do(struct connectdata *conn, bool *done);
  static CURLcode rtsp_done(struct connectdata *conn, CURLcode, bool premature);
  static CURLcode rtsp_connect(struct connectdata *conn, bool *done);
  static CURLcode rtsp_disconnect(struct connectdata *conn, bool dead);
  
  static int rtsp_getsock_do(struct connectdata *conn,
                             curl_socket_t *socks,
                             int numsocks);
  
  /*
   * Parse and write out any available RTP data.
   *
   * nread: amount of data left after k->str. will be modified if RTP
   *        data is parsed and k->str is moved up
   * readmore: whether or not the RTP parser needs more data right away
   */
  static CURLcode rtsp_rtp_readwrite(struct SessionHandle *data,
                                     struct connectdata *conn,
                                     ssize_t *nread,
                                     bool *readmore);
  
  static CURLcode rtsp_setup_connection(struct connectdata *conn);
  
  
  /* this returns the socket to wait for in the DO and DOING state for the multi
     interface and then we're always _sending_ a request and thus we wait for
     the single socket to become writable only */
  static int rtsp_getsock_do(struct connectdata *conn,
                             curl_socket_t *socks,
                             int numsocks)
  {
    /* write mode */
    (void)numsocks; /* unused, we trust it to be at least 1 */
    socks[0] = conn->sock[FIRSTSOCKET];
    return GETSOCK_WRITESOCK(0);
  }
  
  static
  CURLcode rtp_client_write(struct connectdata *conn, char *ptr, size_t len);
  
  
  /*
   * RTSP handler interface.
   */
  const struct Curl_handler Curl_handler_rtsp = {
    "RTSP",                               /* scheme */
    rtsp_setup_connection,                /* setup_connection */
    rtsp_do,                              /* do_it */
    rtsp_done,                            /* done */
    ZERO_NULL,                            /* do_more */
    rtsp_connect,                         /* connect_it */
    ZERO_NULL,                            /* connecting */
    ZERO_NULL,                            /* doing */
    ZERO_NULL,                            /* proto_getsock */
    rtsp_getsock_do,                      /* doing_getsock */
    ZERO_NULL,                            /* domore_getsock */
    ZERO_NULL,                            /* perform_getsock */
    rtsp_disconnect,                      /* disconnect */
    rtsp_rtp_readwrite,                   /* readwrite */
    PORT_RTSP,                            /* defport */
    CURLPROTO_RTSP,                       /* protocol */
    PROTOPT_NONE                          /* flags */
  };
  
  
  static CURLcode rtsp_setup_connection(struct connectdata *conn)
  {
    struct RTSP *rtsp;
  
    conn->data->req.protop = rtsp = calloc(1, sizeof(struct RTSP));
    if(!rtsp)
      return CURLE_OUT_OF_MEMORY;
  
    return CURLE_OK;
  }
  
  
  /*
   * The server may send us RTP data at any point, and RTSPREQ_RECEIVE does not
   * want to block the application forever while receiving a stream. Therefore,
   * we cannot assume that an RTSP socket is dead just because it is readable.
   *
   * Instead, if it is readable, run Curl_getconnectinfo() to peek at the socket
   * and distinguish between closed and data.
   */
  bool Curl_rtsp_connisdead(struct connectdata *check)
  {
    int sval;
    bool ret_val = TRUE;
  
    sval = Curl_socket_ready(check->sock[FIRSTSOCKET], CURL_SOCKET_BAD, 0);
    if(sval == 0) {
      /* timeout */
      ret_val = FALSE;
    }
    else if(sval & CURL_CSELECT_ERR) {
      /* socket is in an error state */
      ret_val = TRUE;
    }
    else if((sval & CURL_CSELECT_IN) && check->data) {
      /* readable with no error. could be closed or could be alive but we can
         only check if we have a proper SessionHandle for the connection */
      curl_socket_t connectinfo = Curl_getconnectinfo(check->data, &check);
      if(connectinfo != CURL_SOCKET_BAD)
        ret_val = FALSE;
    }
  
    return ret_val;
  }
  
  static CURLcode rtsp_connect(struct connectdata *conn, bool *done)
  {
    CURLcode httpStatus;
    struct SessionHandle *data = conn->data;
  
    httpStatus = Curl_http_connect(conn, done);
  
    /* Initialize the CSeq if not already done */
    if(data->state.rtsp_next_client_CSeq == 0)
      data->state.rtsp_next_client_CSeq = 1;
    if(data->state.rtsp_next_server_CSeq == 0)
      data->state.rtsp_next_server_CSeq = 1;
  
    conn->proto.rtspc.rtp_channel = -1;
  
    return httpStatus;
  }
  
  static CURLcode rtsp_disconnect(struct connectdata *conn, bool dead)
  {
    (void) dead;
    Curl_safefree(conn->proto.rtspc.rtp_buf);
    return CURLE_OK;
  }
  
  
  static CURLcode rtsp_done(struct connectdata *conn,
                            CURLcode status, bool premature)
  {
    struct SessionHandle *data = conn->data;
    struct RTSP *rtsp = data->req.protop;
    CURLcode httpStatus;
    long CSeq_sent;
    long CSeq_recv;
  
    /* Bypass HTTP empty-reply checks on receive */
    if(data->set.rtspreq == RTSPREQ_RECEIVE)
      premature = TRUE;
  
    httpStatus = Curl_http_done(conn, status, premature);
  
    if(rtsp) {
      /* Check the sequence numbers */
      CSeq_sent = rtsp->CSeq_sent;
      CSeq_recv = rtsp->CSeq_recv;
      if((data->set.rtspreq != RTSPREQ_RECEIVE) && (CSeq_sent != CSeq_recv)) {
        failf(data,
              "The CSeq of this request %ld did not match the response %ld",
              CSeq_sent, CSeq_recv);
        return CURLE_RTSP_CSEQ_ERROR;
      }
      else if(data->set.rtspreq == RTSPREQ_RECEIVE &&
              (conn->proto.rtspc.rtp_channel == -1)) {
        infof(data, "Got an RTP Receive with a CSeq of %ld\n", CSeq_recv);
      }
    }
  
    return httpStatus;
  }
  
  static CURLcode rtsp_do(struct connectdata *conn, bool *done)
  {
    struct SessionHandle *data = conn->data;
    CURLcode result=CURLE_OK;
    Curl_RtspReq rtspreq = data->set.rtspreq;
    struct RTSP *rtsp = data->req.protop;
    struct HTTP *http;
    Curl_send_buffer *req_buffer;
    curl_off_t postsize = 0; /* for ANNOUNCE and SET_PARAMETER */
    curl_off_t putsize = 0; /* for ANNOUNCE and SET_PARAMETER */
  
    const char *p_request = NULL;
    const char *p_session_id = NULL;
    const char *p_accept = NULL;
    const char *p_accept_encoding = NULL;
    const char *p_range = NULL;
    const char *p_referrer = NULL;
    const char *p_stream_uri = NULL;
    const char *p_transport = NULL;
    const char *p_uagent = NULL;
    const char *p_proxyuserpwd = NULL;
    const char *p_userpwd = NULL;
  
    *done = TRUE;
  
    http = &(rtsp->http_wrapper);
    /* Assert that no one has changed the RTSP struct in an evil way */
    DEBUGASSERT((void *)http == (void *)rtsp);
  
    rtsp->CSeq_sent = data->state.rtsp_next_client_CSeq;
    rtsp->CSeq_recv = 0;
  
    /* Setup the 'p_request' pointer to the proper p_request string
     * Since all RTSP requests are included here, there is no need to
     * support custom requests like HTTP.
     **/
    data->set.opt_no_body = TRUE; /* most requests don't contain a body */
    switch(rtspreq) {
    default:
      failf(data, "Got invalid RTSP request");
      return CURLE_BAD_FUNCTION_ARGUMENT;
    case RTSPREQ_OPTIONS:
      p_request = "OPTIONS";
      break;
    case RTSPREQ_DESCRIBE:
      p_request = "DESCRIBE";
      data->set.opt_no_body = FALSE;
      break;
    case RTSPREQ_ANNOUNCE:
      p_request = "ANNOUNCE";
      break;
    case RTSPREQ_SETUP:
      p_request = "SETUP";
      break;
    case RTSPREQ_PLAY:
      p_request = "PLAY";
      break;
    case RTSPREQ_PAUSE:
      p_request = "PAUSE";
      break;
    case RTSPREQ_TEARDOWN:
      p_request = "TEARDOWN";
      break;
    case RTSPREQ_GET_PARAMETER:
      /* GET_PARAMETER's no_body status is determined later */
      p_request = "GET_PARAMETER";
      data->set.opt_no_body = FALSE;
      break;
    case RTSPREQ_SET_PARAMETER:
      p_request = "SET_PARAMETER";
      break;
    case RTSPREQ_RECORD:
      p_request = "RECORD";
      break;
    case RTSPREQ_RECEIVE:
      p_request = "";
      /* Treat interleaved RTP as body*/
      data->set.opt_no_body = FALSE;
      break;
    case RTSPREQ_LAST:
      failf(data, "Got invalid RTSP request: RTSPREQ_LAST");
      return CURLE_BAD_FUNCTION_ARGUMENT;
    }
  
    if(rtspreq == RTSPREQ_RECEIVE) {
      Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE,
                          &http->readbytecount, -1, NULL);
  
      return result;
    }
  
    p_session_id = data->set.str[STRING_RTSP_SESSION_ID];
    if(!p_session_id &&
       (rtspreq & ~(RTSPREQ_OPTIONS | RTSPREQ_DESCRIBE | RTSPREQ_SETUP))) {
      failf(data, "Refusing to issue an RTSP request [%s] without a session ID.",
            p_request);
      return CURLE_BAD_FUNCTION_ARGUMENT;
    }
  
    /* Stream URI. Default to server '*' if not specified */
    if(data->set.str[STRING_RTSP_STREAM_URI]) {
      p_stream_uri = data->set.str[STRING_RTSP_STREAM_URI];
    }
    else {
      p_stream_uri = "*";
    }
  
    /* Transport Header for SETUP requests */
    p_transport = Curl_checkheaders(conn, "Transport:");
    if(rtspreq == RTSPREQ_SETUP && !p_transport) {
      /* New Transport: setting? */
      if(data->set.str[STRING_RTSP_TRANSPORT]) {
        Curl_safefree(conn->allocptr.rtsp_transport);
  
        conn->allocptr.rtsp_transport =
          aprintf("Transport: %s\r\n",
                  data->set.str[STRING_RTSP_TRANSPORT]);
        if(!conn->allocptr.rtsp_transport)
          return CURLE_OUT_OF_MEMORY;
      }
      else {
        failf(data,
              "Refusing to issue an RTSP SETUP without a Transport: header.");
        return CURLE_BAD_FUNCTION_ARGUMENT;
      }
  
      p_transport = conn->allocptr.rtsp_transport;
    }
  
    /* Accept Headers for DESCRIBE requests */
    if(rtspreq == RTSPREQ_DESCRIBE) {
      /* Accept Header */
      p_accept = Curl_checkheaders(conn, "Accept:")?
        NULL:"Accept: application/sdp\r\n";
  
      /* Accept-Encoding header */
      if(!Curl_checkheaders(conn, "Accept-Encoding:") &&
         data->set.str[STRING_ENCODING]) {
        Curl_safefree(conn->allocptr.accept_encoding);
        conn->allocptr.accept_encoding =
          aprintf("Accept-Encoding: %s\r\n", data->set.str[STRING_ENCODING]);
  
        if(!conn->allocptr.accept_encoding)
          return CURLE_OUT_OF_MEMORY;
  
        p_accept_encoding = conn->allocptr.accept_encoding;
      }
    }
  
    /* The User-Agent string might have been allocated in url.c already, because
       it might have been used in the proxy connect, but if we have got a header
       with the user-agent string specified, we erase the previously made string
       here. */
    if(Curl_checkheaders(conn, "User-Agent:") && conn->allocptr.uagent) {
      Curl_safefree(conn->allocptr.uagent);
      conn->allocptr.uagent = NULL;
    }
    else if(!Curl_checkheaders(conn, "User-Agent:") &&
            data->set.str[STRING_USERAGENT]) {
      p_uagent = conn->allocptr.uagent;
    }
  
    /* setup the authentication headers */
    result = Curl_http_output_auth(conn, p_request, p_stream_uri, FALSE);
    if(result)
      return result;
  
    p_proxyuserpwd = conn->allocptr.proxyuserpwd;
    p_userpwd = conn->allocptr.userpwd;
  
    /* Referrer */
    Curl_safefree(conn->allocptr.ref);
    if(data->change.referer && !Curl_checkheaders(conn, "Referer:"))
      conn->allocptr.ref = aprintf("Referer: %s\r\n", data->change.referer);
    else
      conn->allocptr.ref = NULL;
  
    p_referrer = conn->allocptr.ref;
  
    /*
     * Range Header
     * Only applies to PLAY, PAUSE, RECORD
     *
     * Go ahead and use the Range stuff supplied for HTTP
     */
    if(data->state.use_range &&
       (rtspreq  & (RTSPREQ_PLAY | RTSPREQ_PAUSE | RTSPREQ_RECORD))) {
  
      /* Check to see if there is a range set in the custom headers */
      if(!Curl_checkheaders(conn, "Range:") && data->state.range) {
        Curl_safefree(conn->allocptr.rangeline);
        conn->allocptr.rangeline = aprintf("Range: %s\r\n", data->state.range);
        p_range = conn->allocptr.rangeline;
      }
    }
  
    /*
     * Sanity check the custom headers
     */
    if(Curl_checkheaders(conn, "CSeq:")) {
      failf(data, "CSeq cannot be set as a custom header.");
      return CURLE_RTSP_CSEQ_ERROR;
    }
    if(Curl_checkheaders(conn, "Session:")) {
      failf(data, "Session ID cannot be set as a custom header.");
      return CURLE_BAD_FUNCTION_ARGUMENT;
    }
  
    /* Initialize a dynamic send buffer */
    req_buffer = Curl_add_buffer_init();
  
    if(!req_buffer)
      return CURLE_OUT_OF_MEMORY;
  
    result =
      Curl_add_bufferf(req_buffer,
                       "%s %s RTSP/1.0\r\n" /* Request Stream-URI RTSP/1.0 */
                       "CSeq: %ld\r\n", /* CSeq */
                       p_request, p_stream_uri, rtsp->CSeq_sent);
    if(result)
      return result;
  
    /*
     * Rather than do a normal alloc line, keep the session_id unformatted
     * to make comparison easier
     */
    if(p_session_id) {
      result = Curl_add_bufferf(req_buffer, "Session: %s\r\n", p_session_id);
      if(result)
        return result;
    }
  
    /*
     * Shared HTTP-like options
     */
    result = Curl_add_bufferf(req_buffer,
                              "%s" /* transport */
                              "%s" /* accept */
                              "%s" /* accept-encoding */
                              "%s" /* range */
                              "%s" /* referrer */
                              "%s" /* user-agent */
                              "%s" /* proxyuserpwd */
                              "%s" /* userpwd */
                              ,
                              p_transport ? p_transport : "",
                              p_accept ? p_accept : "",
                              p_accept_encoding ? p_accept_encoding : "",
                              p_range ? p_range : "",
                              p_referrer ? p_referrer : "",
                              p_uagent ? p_uagent : "",
                              p_proxyuserpwd ? p_proxyuserpwd : "",
                              p_userpwd ? p_userpwd : "");
  
    /*
     * Free userpwd now --- cannot reuse this for Negotiate and possibly NTLM
     * with basic and digest, it will be freed anyway by the next request
     */
    Curl_safefree (conn->allocptr.userpwd);
    conn->allocptr.userpwd = NULL;
  
    if(result)
      return result;
  
    if((rtspreq == RTSPREQ_SETUP) || (rtspreq == RTSPREQ_DESCRIBE)) {
      result = Curl_add_timecondition(data, req_buffer);
      if(result)
        return result;
    }
  
    result = Curl_add_custom_headers(conn, FALSE, req_buffer);
    if(result)
      return result;
  
    if(rtspreq == RTSPREQ_ANNOUNCE ||
       rtspreq == RTSPREQ_SET_PARAMETER ||
       rtspreq == RTSPREQ_GET_PARAMETER) {
  
      if(data->set.upload) {
        putsize = data->state.infilesize;
        data->set.httpreq = HTTPREQ_PUT;
  
      }
      else {
        postsize = (data->state.infilesize != -1)?
          data->state.infilesize:
          (data->set.postfields? (curl_off_t)strlen(data->set.postfields):0);
        data->set.httpreq = HTTPREQ_POST;
      }
  
      if(putsize > 0 || postsize > 0) {
        /* As stated in the http comments, it is probably not wise to
         * actually set a custom Content-Length in the headers */
        if(!Curl_checkheaders(conn, "Content-Length:")) {
          result = Curl_add_bufferf(req_buffer,
              "Content-Length: %" CURL_FORMAT_CURL_OFF_T"\r\n",
              (data->set.upload ? putsize : postsize));
          if(result)
            return result;
        }
  
        if(rtspreq == RTSPREQ_SET_PARAMETER ||
           rtspreq == RTSPREQ_GET_PARAMETER) {
          if(!Curl_checkheaders(conn, "Content-Type:")) {
            result = Curl_add_bufferf(req_buffer,
                "Content-Type: text/parameters\r\n");
            if(result)
              return result;
          }
        }
  
        if(rtspreq == RTSPREQ_ANNOUNCE) {
          if(!Curl_checkheaders(conn, "Content-Type:")) {
            result = Curl_add_bufferf(req_buffer,
                "Content-Type: application/sdp\r\n");
            if(result)
              return result;
          }
        }
  
        data->state.expect100header = FALSE; /* RTSP posts are simple/small */
      }
      else if(rtspreq == RTSPREQ_GET_PARAMETER) {
        /* Check for an empty GET_PARAMETER (heartbeat) request */
        data->set.httpreq = HTTPREQ_HEAD;
        data->set.opt_no_body = TRUE;
      }
    }
  
    /* RTSP never allows chunked transfer */
    data->req.forbidchunk = TRUE;
    /* Finish the request buffer */
    result = Curl_add_buffer(req_buffer, "\r\n", 2);
    if(result)
      return result;
  
    if(postsize > 0) {
      result = Curl_add_buffer(req_buffer, data->set.postfields,
                               (size_t)postsize);
      if(result)
        return result;
    }
  
    /* issue the request */
    result = Curl_add_buffer_send(req_buffer, conn,
                                  &data->info.request_size, 0, FIRSTSOCKET);
    if(result) {
      failf(data, "Failed sending RTSP request");
      return result;
    }
  
    Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE, &http->readbytecount,
                        putsize?FIRSTSOCKET:-1,
                        putsize?&http->writebytecount:NULL);
  
    /* Increment the CSeq on success */
    data->state.rtsp_next_client_CSeq++;
  
    if(http->writebytecount) {
      /* if a request-body has been sent off, we make sure this progress is
         noted properly */
      Curl_pgrsSetUploadCounter(data, http->writebytecount);
      if(Curl_pgrsUpdate(conn))
        result = CURLE_ABORTED_BY_CALLBACK;
    }
  
    return result;
  }
  
  
  static CURLcode rtsp_rtp_readwrite(struct SessionHandle *data,
                                     struct connectdata *conn,
                                     ssize_t *nread,
                                     bool *readmore) {
    struct SingleRequest *k = &data->req;
    struct rtsp_conn *rtspc = &(conn->proto.rtspc);
  
    char *rtp; /* moving pointer to rtp data */
    ssize_t rtp_dataleft; /* how much data left to parse in this round */
    char *scratch;
    CURLcode result;
  
    if(rtspc->rtp_buf) {
      /* There was some leftover data the last time. Merge buffers */
      char *newptr = realloc(rtspc->rtp_buf, rtspc->rtp_bufsize + *nread);
      if(!newptr) {
        Curl_safefree(rtspc->rtp_buf);
        rtspc->rtp_buf = NULL;
        rtspc->rtp_bufsize = 0;
        return CURLE_OUT_OF_MEMORY;
      }
      rtspc->rtp_buf = newptr;
      memcpy(rtspc->rtp_buf + rtspc->rtp_bufsize, k->str, *nread);
      rtspc->rtp_bufsize += *nread;
      rtp = rtspc->rtp_buf;
      rtp_dataleft = rtspc->rtp_bufsize;
    }
    else {
      /* Just parse the request buffer directly */
      rtp = k->str;
      rtp_dataleft = *nread;
    }
  
    while((rtp_dataleft > 0) &&
          (rtp[0] == '$')) {
      if(rtp_dataleft > 4) {
        int rtp_length;
  
        /* Parse the header */
        /* The channel identifier immediately follows and is 1 byte */
        rtspc->rtp_channel = RTP_PKT_CHANNEL(rtp);
  
        /* The length is two bytes */
        rtp_length = RTP_PKT_LENGTH(rtp);
  
        if(rtp_dataleft < rtp_length + 4) {
          /* Need more - incomplete payload*/
          *readmore = TRUE;
          break;
        }
        else {
          /* We have the full RTP interleaved packet
           * Write out the header including the leading '$' */
          DEBUGF(infof(data, "RTP write channel %d rtp_length %d\n",
                rtspc->rtp_channel, rtp_length));
          result = rtp_client_write(conn, &rtp[0], rtp_length + 4);
          if(result) {
            failf(data, "Got an error writing an RTP packet");
            *readmore = FALSE;
            Curl_safefree(rtspc->rtp_buf);
            rtspc->rtp_buf = NULL;
            rtspc->rtp_bufsize = 0;
            return result;
          }
  
          /* Move forward in the buffer */
          rtp_dataleft -= rtp_length + 4;
          rtp += rtp_length + 4;
  
          if(data->set.rtspreq == RTSPREQ_RECEIVE) {
            /* If we are in a passive receive, give control back
             * to the app as often as we can.
             */
            k->keepon &= ~KEEP_RECV;
          }
        }
      }
      else {
        /* Need more - incomplete header */
        *readmore = TRUE;
        break;
      }
    }
  
    if(rtp_dataleft != 0 && rtp[0] == '$') {
      DEBUGF(infof(data, "RTP Rewinding %zd %s\n", rtp_dataleft,
            *readmore ? "(READMORE)" : ""));
  
      /* Store the incomplete RTP packet for a "rewind" */
      scratch = malloc(rtp_dataleft);
      if(!scratch) {
        Curl_safefree(rtspc->rtp_buf);
        rtspc->rtp_buf = NULL;
        rtspc->rtp_bufsize = 0;
        return CURLE_OUT_OF_MEMORY;
      }
      memcpy(scratch, rtp, rtp_dataleft);
      Curl_safefree(rtspc->rtp_buf);
      rtspc->rtp_buf = scratch;
      rtspc->rtp_bufsize = rtp_dataleft;
  
      /* As far as the transfer is concerned, this data is consumed */
      *nread = 0;
      return CURLE_OK;
    }
    else {
      /* Fix up k->str to point just after the last RTP packet */
      k->str += *nread - rtp_dataleft;
  
      /* either all of the data has been read or...
       * rtp now points at the next byte to parse
       */
      if(rtp_dataleft > 0)
        DEBUGASSERT(k->str[0] == rtp[0]);
  
      DEBUGASSERT(rtp_dataleft <= *nread); /* sanity check */
  
      *nread = rtp_dataleft;
    }
  
    /* If we get here, we have finished with the leftover/merge buffer */
    Curl_safefree(rtspc->rtp_buf);
    rtspc->rtp_buf = NULL;
    rtspc->rtp_bufsize = 0;
  
    return CURLE_OK;
  }
  
  static
  CURLcode rtp_client_write(struct connectdata *conn, char *ptr, size_t len)
  {
    struct SessionHandle *data = conn->data;
    size_t wrote;
    curl_write_callback writeit;
  
    if(len == 0) {
      failf (data, "Cannot write a 0 size RTP packet.");
      return CURLE_WRITE_ERROR;
    }
  
    writeit = data->set.fwrite_rtp?data->set.fwrite_rtp:data->set.fwrite_func;
    wrote = writeit(ptr, 1, len, data->set.rtp_out);
  
    if(CURL_WRITEFUNC_PAUSE == wrote) {
      failf (data, "Cannot pause RTP");
      return CURLE_WRITE_ERROR;
    }
  
    if(wrote != len) {
      failf (data, "Failed writing RTP data");
      return CURLE_WRITE_ERROR;
    }
  
    return CURLE_OK;
  }
  
  CURLcode Curl_rtsp_parseheader(struct connectdata *conn,
                                 char *header)
  {
    struct SessionHandle *data = conn->data;
    long CSeq = 0;
  
    if(checkprefix("CSeq:", header)) {
      /* Store the received CSeq. Match is verified in rtsp_done */
      int nc = sscanf(&header[4], ": %ld", &CSeq);
      if(nc == 1) {
        struct RTSP *rtsp = data->req.protop;
        rtsp->CSeq_recv = CSeq; /* mark the request */
        data->state.rtsp_CSeq_recv = CSeq; /* update the handle */
      }
      else {
        failf(data, "Unable to read the CSeq header: [%s]", header);
        return CURLE_RTSP_CSEQ_ERROR;
      }
    }
    else if(checkprefix("Session:", header)) {
      char *start;
  
      /* Find the first non-space letter */
      start = header + 8;
      while(*start && ISSPACE(*start))
        start++;
  
      if(!*start) {
        failf(data, "Got a blank Session ID");
      }
      else if(data->set.str[STRING_RTSP_SESSION_ID]) {
        /* If the Session ID is set, then compare */
        if(strncmp(start, data->set.str[STRING_RTSP_SESSION_ID],
                   strlen(data->set.str[STRING_RTSP_SESSION_ID]))  != 0) {
          failf(data, "Got RTSP Session ID Line [%s], but wanted ID [%s]",
                start, data->set.str[STRING_RTSP_SESSION_ID]);
          return CURLE_RTSP_SESSION_ERROR;
        }
      }
      else {
        /* If the Session ID is not set, and we find it in a response, then
           set it */
  
        /* The session ID can be an alphanumeric or a 'safe' character
         *
         * RFC 2326 15.1 Base Syntax:
         * safe =  "\$" | "-" | "_" | "." | "+"
         * */
        char *end = start;
        while(*end &&
              (ISALNUM(*end) || *end == '-' || *end == '_' || *end == '.' ||
               *end == '+' ||
               (*end == '\\' && *(end + 1) && *(end + 1) == '$' && (++end, 1))))
          end++;
  
        /* Copy the id substring into a new buffer */
        data->set.str[STRING_RTSP_SESSION_ID] = malloc(end - start + 1);
        if(data->set.str[STRING_RTSP_SESSION_ID] == NULL)
          return CURLE_OUT_OF_MEMORY;
        memcpy(data->set.str[STRING_RTSP_SESSION_ID], start, end - start);
        (data->set.str[STRING_RTSP_SESSION_ID])[end - start] = '\0';
      }
    }
    return CURLE_OK;
  }
  
  #endif /* CURL_DISABLE_RTSP */
  