http.c

       host is a IDN-name, we must make sure that the request we produce only
       uses the encoded host name! */
    if(conn->host.dispname != conn->host.name) {
      char *url = data->change.url;
      ptr = strstr(url, conn->host.dispname);
      if(ptr) {
        /* This is where the display name starts in the URL, now replace this
           part with the encoded name. TODO: This method of replacing the host
           name is rather crude as I believe there's a slight risk that the
           user has entered a user name or password that contain the host name
           string. */
        size_t currlen = strlen(conn->host.dispname);
        size_t newlen = strlen(conn->host.name);
        size_t urllen = strlen(url);

        char *newurl;

        newurl = malloc(urllen + newlen - currlen + 1);
        if(newurl) {
          /* copy the part before the host name */
          memcpy(newurl, url, ptr - url);
          /* append the new host name instead of the old */
          memcpy(newurl + (ptr - url), conn->host.name, newlen);
          /* append the piece after the host name */
          memcpy(newurl + newlen + (ptr - url),
                 ptr + currlen, /* copy the trailing zero byte too */
                 urllen - (ptr-url) - currlen + 1);
          if(data->change.url_alloc) {
            Curl_safefree(data->change.url);
            data->change.url_alloc = FALSE;
          }
          data->change.url = newurl;
          data->change.url_alloc = TRUE;
        }
        else
          return CURLE_OUT_OF_MEMORY;
      }
    }
    ppath = data->change.url;
    if(checkprefix("ftp://", ppath)) {
      if(data->set.proxy_transfer_mode) {
        /* when doing ftp, append ;type=<a|i> if not present */
        char *type = strstr(ppath, ";type=");
        if(type && type[6] && type[7] == 0) {
          switch (Curl_raw_toupper(type[6])) {
          case 'A':
          case 'D':
          case 'I':
            break;
          default:
            type = NULL;
          }
        }
        if(!type) {
          char *p = ftp_typecode;
          /* avoid sending invalid URLs like ftp://example.com;type=i if the
           * user specified ftp://example.com without the slash */
          if(!*data->state.path && ppath[strlen(ppath) - 1] != '/') {
            *p++ = '/';
          }
          snprintf(p, sizeof(ftp_typecode) - 1, ";type=%c",
                   data->set.prefer_ascii ? 'a' : 'i');
        }
      }
      if(conn->bits.user_passwd && !conn->bits.userpwd_in_url)
        paste_ftp_userpwd = TRUE;
    }
  }
#endif /* CURL_DISABLE_PROXY */

  if(HTTPREQ_POST_FORM == httpreq) {
    /* we must build the whole post sequence first, so that we have a size of
       the whole transfer before we start to send it */
    result = Curl_getformdata(data, &http->sendit, data->set.httppost,
                              Curl_checkheaders(conn, "Content-Type:"),
                              &http->postsize);
    if(result)
      return result;
  }

  http->p_accept = Curl_checkheaders(conn, "Accept:")?NULL:"Accept: */*\r\n";

  if(( (HTTPREQ_POST == httpreq) ||
       (HTTPREQ_POST_FORM == httpreq) ||
       (HTTPREQ_PUT == httpreq) ) &&
     data->state.resume_from) {
    /**********************************************************************
     * Resuming upload in HTTP means that we PUT or POST and that we have
     * got a resume_from value set. The resume value has already created
     * a Range: header that will be passed along. We need to "fast forward"
     * the file the given number of bytes and decrease the assume upload
     * file size before we continue this venture in the dark lands of HTTP.
     *********************************************************************/

    if(data->state.resume_from < 0 ) {
      /*
       * This is meant to get the size of the present remote-file by itself.
       * We don't support this now. Bail out!
       */
      data->state.resume_from = 0;
    }

    if(data->state.resume_from && !data->state.this_is_a_follow) {
      /* do we still game? */

      /* Now, let's read off the proper amount of bytes from the
         input. */
      if(conn->seek_func) {
        seekerr = conn->seek_func(conn->seek_client, data->state.resume_from,
                                  SEEK_SET);
      }

      if(seekerr != CURL_SEEKFUNC_OK) {
        if(seekerr != CURL_SEEKFUNC_CANTSEEK) {
          failf(data, "Could not seek stream");
          return CURLE_READ_ERROR;
        }
        /* when seekerr == CURL_SEEKFUNC_CANTSEEK (can't seek to offset) */
        else {
          curl_off_t passed=0;
          do {
            size_t readthisamountnow =
              (data->state.resume_from - passed > CURL_OFF_T_C(BUFSIZE)) ?
              BUFSIZE : curlx_sotouz(data->state.resume_from - passed);

            size_t actuallyread =
              data->set.fread_func(data->state.buffer, 1, readthisamountnow,
                                   data->set.in);

            passed += actuallyread;
            if((actuallyread == 0) || (actuallyread > readthisamountnow)) {
              /* this checks for greater-than only to make sure that the
                 CURL_READFUNC_ABORT return code still aborts */
              failf(data, "Could only read %" CURL_FORMAT_CURL_OFF_T
                    " bytes from the input", passed);
              return CURLE_READ_ERROR;
            }
          } while(passed < data->state.resume_from);
        }
      }

      /* now, decrease the size of the read */
      if(data->state.infilesize>0) {
        data->state.infilesize -= data->state.resume_from;

        if(data->state.infilesize <= 0) {
          failf(data, "File already completely uploaded");
          return CURLE_PARTIAL_FILE;
        }
      }
      /* we've passed, proceed as normal */
    }
  }
  if(data->state.use_range) {
    /*
     * A range is selected. We use different headers whether we're downloading
     * or uploading and we always let customized headers override our internal
     * ones if any such are specified.
     */
    if(((httpreq == HTTPREQ_GET) || (httpreq == HTTPREQ_HEAD)) &&
       !Curl_checkheaders(conn, "Range:")) {
      /* if a line like this was already allocated, free the previous one */
      if(conn->allocptr.rangeline)
        free(conn->allocptr.rangeline);
      conn->allocptr.rangeline = aprintf("Range: bytes=%s\r\n",
                                         data->state.range);
    }
    else if((httpreq != HTTPREQ_GET) &&
            !Curl_checkheaders(conn, "Content-Range:")) {

      /* if a line like this was already allocated, free the previous one */
      if(conn->allocptr.rangeline)
        free(conn->allocptr.rangeline);

      if(data->set.set_resume_from < 0) {
        /* Upload resume was asked for, but we don't know the size of the
           remote part so we tell the server (and act accordingly) that we
           upload the whole file (again) */
        conn->allocptr.rangeline =
          aprintf("Content-Range: bytes 0-%" CURL_FORMAT_CURL_OFF_T
                  "/%" CURL_FORMAT_CURL_OFF_T "\r\n",
                  data->state.infilesize - 1, data->state.infilesize);

      }
      else if(data->state.resume_from) {
        /* This is because "resume" was selected */
        curl_off_t total_expected_size=
          data->state.resume_from + data->state.infilesize;
        conn->allocptr.rangeline =
          aprintf("Content-Range: bytes %s%" CURL_FORMAT_CURL_OFF_T
                  "/%" CURL_FORMAT_CURL_OFF_T "\r\n",
                  data->state.range, total_expected_size-1,
                  total_expected_size);
      }
      else {
        /* Range was selected and then we just pass the incoming range and
           append total size */
        conn->allocptr.rangeline =
          aprintf("Content-Range: bytes %s/%" CURL_FORMAT_CURL_OFF_T "\r\n",
                  data->state.range, data->state.infilesize);
      }
      if(!conn->allocptr.rangeline)
        return CURLE_OUT_OF_MEMORY;
    }
  }

  /* Use 1.1 unless the user specifically asked for 1.0 or the server only
     supports 1.0 */
  httpstring= use_http_1_1plus(data, conn)?"1.1":"1.0";

  /* initialize a dynamic send-buffer */
  req_buffer = Curl_add_buffer_init();

  if(!req_buffer)
    return CURLE_OUT_OF_MEMORY;

  /* add the main request stuff */
  /* GET/HEAD/POST/PUT */
  result = Curl_add_bufferf(req_buffer, "%s ", request);
  if(result)
    return result;

  /* url */
  if(paste_ftp_userpwd)
    result = Curl_add_bufferf(req_buffer, "ftp://%s:%s@%s",
                              conn->user, conn->passwd,
                              ppath + sizeof("ftp://") - 1);
  else
    result = Curl_add_buffer(req_buffer, ppath, strlen(ppath));
  if(result)
    return result;

  result =
    Curl_add_bufferf(req_buffer,
                     "%s" /* ftp typecode (;type=x) */
                     " HTTP/%s\r\n" /* HTTP version */
                     "%s" /* proxyuserpwd */
                     "%s" /* userpwd */
                     "%s" /* range */
                     "%s" /* user agent */
                     "%s" /* host */
                     "%s" /* accept */
                     "%s" /* TE: */
                     "%s" /* accept-encoding */
                     "%s" /* referer */
                     "%s" /* Proxy-Connection */
                     "%s",/* transfer-encoding */

                     ftp_typecode,
                     httpstring,
                     conn->allocptr.proxyuserpwd?
                     conn->allocptr.proxyuserpwd:"",
                     conn->allocptr.userpwd?conn->allocptr.userpwd:"",
                     (data->state.use_range && conn->allocptr.rangeline)?
                     conn->allocptr.rangeline:"",
                     (data->set.str[STRING_USERAGENT] &&
                      *data->set.str[STRING_USERAGENT] &&
                      conn->allocptr.uagent)?
                     conn->allocptr.uagent:"",
                     (conn->allocptr.host?conn->allocptr.host:""),
                     http->p_accept?http->p_accept:"",
                     conn->allocptr.te?conn->allocptr.te:"",
                     (data->set.str[STRING_ENCODING] &&
                      *data->set.str[STRING_ENCODING] &&
                      conn->allocptr.accept_encoding)?
                     conn->allocptr.accept_encoding:"",
                     (data->change.referer && conn->allocptr.ref)?
                     conn->allocptr.ref:"" /* Referer: <data> */,
                     (conn->bits.httpproxy &&
                      !conn->bits.tunnel_proxy &&
                      !Curl_checkProxyheaders(conn, "Proxy-Connection:"))?
                     "Proxy-Connection: Keep-Alive\r\n":"",
                     te
      );

  /*
   * 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(!(conn->handler->flags&PROTOPT_SSL) &&
     (data->set.httpversion == CURL_HTTP_VERSION_2_0)) {
    /* append HTTP2 upgrade magic stuff to the HTTP request if it isn't done
       over SSL */
    result = Curl_http2_request_upgrade(req_buffer, conn);
    if(result)
      return result;
  }

#if !defined(CURL_DISABLE_COOKIES)
  if(data->cookies || addcookies) {
    struct Cookie *co=NULL; /* no cookies from start */
    int count=0;

    if(data->cookies) {
      Curl_share_lock(data, CURL_LOCK_DATA_COOKIE, CURL_LOCK_ACCESS_SINGLE);
      co = Curl_cookie_getlist(data->cookies,
                               conn->allocptr.cookiehost?
                               conn->allocptr.cookiehost:host,
                               data->state.path,
                               (conn->handler->protocol&CURLPROTO_HTTPS)?
                               TRUE:FALSE);
      Curl_share_unlock(data, CURL_LOCK_DATA_COOKIE);
    }
    if(co) {
      struct Cookie *store=co;
      /* now loop through all cookies that matched */
      while(co) {
        if(co->value) {
          if(0 == count) {
            result = Curl_add_bufferf(req_buffer, "Cookie: ");
            if(result)
              break;
          }
          result = Curl_add_bufferf(req_buffer,
                                    "%s%s=%s", count?"; ":"",
                                    co->name, co->value);
          if(result)
            break;
          count++;
        }
        co = co->next; /* next cookie please */
      }
      Curl_cookie_freelist(store, FALSE); /* free the cookie list */
    }
    if(addcookies && (CURLE_OK == result)) {
      if(!count)
        result = Curl_add_bufferf(req_buffer, "Cookie: ");
      if(CURLE_OK == result) {
        result = Curl_add_bufferf(req_buffer, "%s%s",
                                  count?"; ":"",
                                  addcookies);
        count++;
      }
    }
    if(count && (CURLE_OK == result))
      result = Curl_add_buffer(req_buffer, "\r\n", 2);

    if(result)
      return result;
  }
#endif

  if(data->set.timecondition) {
    result = Curl_add_timecondition(data, req_buffer);
    if(result)
      return result;
  }

  result = Curl_add_custom_headers(conn, FALSE, req_buffer);
  if(result)
    return result;

  http->postdata = NULL;  /* nothing to post at this point */
  Curl_pgrsSetUploadSize(data, 0); /* upload size is 0 atm */

  /* If 'authdone' is FALSE, we must not set the write socket index to the
     Curl_transfer() call below, as we're not ready to actually upload any
     data yet. */

  switch(httpreq) {

  case HTTPREQ_POST_FORM:
    if(!http->sendit || conn->bits.authneg) {
      /* nothing to post! */
      result = Curl_add_bufferf(req_buffer, "Content-Length: 0\r\n\r\n");
      if(result)
        return result;

      result = Curl_add_buffer_send(req_buffer, conn,
                                    &data->info.request_size, 0, FIRSTSOCKET);
      if(result)
        failf(data, "Failed sending POST request");
      else
        /* setup variables for the upcoming transfer */
        Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE, &http->readbytecount,
                            -1, NULL);
      break;
    }

    if(Curl_FormInit(&http->form, http->sendit)) {
      failf(data, "Internal HTTP POST error!");
      return CURLE_HTTP_POST_ERROR;
    }

    /* Get the currently set callback function pointer and store that in the
       form struct since we might want the actual user-provided callback later
       on. The conn->fread_func pointer itself will be changed for the
       multipart case to the function that returns a multipart formatted
       stream. */
    http->form.fread_func = conn->fread_func;

    /* Set the read function to read from the generated form data */
    conn->fread_func = (curl_read_callback)Curl_FormReader;
    conn->fread_in = &http->form;

    http->sending = HTTPSEND_BODY;

    if(!data->req.upload_chunky &&
       !Curl_checkheaders(conn, "Content-Length:")) {
      /* only add Content-Length if not uploading chunked */
      result = Curl_add_bufferf(req_buffer,
                                "Content-Length: %" CURL_FORMAT_CURL_OFF_T
                                "\r\n", http->postsize);
      if(result)
        return result;
    }

    result = expect100(data, conn, req_buffer);
    if(result)
      return result;

    {

      /* Get Content-Type: line from Curl_formpostheader.
       */
      char *contentType;
      size_t linelength=0;
      contentType = Curl_formpostheader((void *)&http->form,
                                        &linelength);
      if(!contentType) {
        failf(data, "Could not get Content-Type header line!");
        return CURLE_HTTP_POST_ERROR;
      }

      result = Curl_add_buffer(req_buffer, contentType, linelength);
      if(result)
        return result;
    }

    /* make the request end in a true CRLF */
    result = Curl_add_buffer(req_buffer, "\r\n", 2);
    if(result)
      return result;

    /* set upload size to the progress meter */
    Curl_pgrsSetUploadSize(data, http->postsize);

    /* fire away the whole request to the server */
    result = Curl_add_buffer_send(req_buffer, conn,
                                  &data->info.request_size, 0, FIRSTSOCKET);
    if(result)
      failf(data, "Failed sending POST request");
    else
      /* setup variables for the upcoming transfer */
      Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE,
                          &http->readbytecount, FIRSTSOCKET,
                          &http->writebytecount);

    if(result) {
      Curl_formclean(&http->sendit); /* free that whole lot */
      return result;
    }

    /* convert the form data */
    result = Curl_convert_form(data, http->sendit);
    if(result) {
      Curl_formclean(&http->sendit); /* free that whole lot */
      return result;
    }

    break;

  case HTTPREQ_PUT: /* Let's PUT the data to the server! */

    if(conn->bits.authneg)
      postsize = 0;
    else
      postsize = data->state.infilesize;

    if((postsize != -1) && !data->req.upload_chunky &&
       !Curl_checkheaders(conn, "Content-Length:")) {
      /* only add Content-Length if not uploading chunked */
      result = Curl_add_bufferf(req_buffer,
                                "Content-Length: %" CURL_FORMAT_CURL_OFF_T
                                "\r\n", postsize);
      if(result)
        return result;
    }

    if(postsize != 0) {
      result = expect100(data, conn, req_buffer);
      if(result)
        return result;
    }

    result = Curl_add_buffer(req_buffer, "\r\n", 2); /* end of headers */
    if(result)
      return result;

    /* set the upload size to the progress meter */
    Curl_pgrsSetUploadSize(data, postsize);

    /* this sends the buffer and frees all the buffer resources */
    result = Curl_add_buffer_send(req_buffer, conn,
                                  &data->info.request_size, 0, FIRSTSOCKET);
    if(result)
      failf(data, "Failed sending PUT request");
    else
      /* prepare for transfer */
      Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE,
                          &http->readbytecount, postsize?FIRSTSOCKET:-1,
                          postsize?&http->writebytecount:NULL);
    if(result)
      return result;
    break;

  case HTTPREQ_POST:
    /* this is the simple POST, using x-www-form-urlencoded style */

    if(conn->bits.authneg)
      postsize = 0;
    else {
      /* figure out the size of the postfields */
      postsize = (data->set.postfieldsize != -1)?
        data->set.postfieldsize:
        (data->set.postfields? (curl_off_t)strlen(data->set.postfields):-1);
    }

    /* We only set Content-Length and allow a custom Content-Length if
       we don't upload data chunked, as RFC2616 forbids us to set both
       kinds of headers (Transfer-Encoding: chunked and Content-Length) */
    if((postsize != -1) && !data->req.upload_chunky &&
       !Curl_checkheaders(conn, "Content-Length:")) {
      /* we allow replacing this header if not during auth negotiation,
         although it isn't very wise to actually set your own */
      result = Curl_add_bufferf(req_buffer,
                                "Content-Length: %" CURL_FORMAT_CURL_OFF_T
                                "\r\n", postsize);
      if(result)
        return result;
    }

    if(!Curl_checkheaders(conn, "Content-Type:")) {
      result = Curl_add_bufferf(req_buffer,
                                "Content-Type: application/"
                                "x-www-form-urlencoded\r\n");
      if(result)
        return result;
    }

    /* For really small posts we don't use Expect: headers at all, and for
       the somewhat bigger ones we allow the app to disable it. Just make
       sure that the expect100header is always set to the preferred value
       here. */
    ptr = Curl_checkheaders(conn, "Expect:");
    if(ptr) {
      data->state.expect100header =
        Curl_compareheader(ptr, "Expect:", "100-continue");
    }
    else if(postsize > TINY_INITIAL_POST_SIZE || postsize < 0) {
      result = expect100(data, conn, req_buffer);
      if(result)
        return result;
    }
    else
      data->state.expect100header = FALSE;

    if(data->set.postfields) {

      /* In HTTP2, we send request body in DATA frame regardless of
         its size. */
      if(conn->httpversion != 20 &&
         !data->state.expect100header &&
         (postsize < MAX_INITIAL_POST_SIZE))  {
        /* if we don't use expect: 100  AND
           postsize is less than MAX_INITIAL_POST_SIZE

           then append the post data to the HTTP request header. This limit
           is no magic limit but only set to prevent really huge POSTs to
           get the data duplicated with malloc() and family. */

        result = Curl_add_buffer(req_buffer, "\r\n", 2); /* end of headers! */
        if(result)
          return result;

        if(!data->req.upload_chunky) {
          /* We're not sending it 'chunked', append it to the request
             already now to reduce the number if send() calls */
          result = Curl_add_buffer(req_buffer, data->set.postfields,
                                   (size_t)postsize);
          included_body = postsize;
        }
        else {
          if(postsize) {
            /* Append the POST data chunky-style */
            result = Curl_add_bufferf(req_buffer, "%x\r\n", (int)postsize);
            if(CURLE_OK == result) {
              result = Curl_add_buffer(req_buffer, data->set.postfields,
                                       (size_t)postsize);
              if(CURLE_OK == result)
                 result = Curl_add_buffer(req_buffer, "\r\n", 2);
              included_body = postsize + 2;
            }
          }
          if(CURLE_OK == result)
            result = Curl_add_buffer(req_buffer,
                                     "\x30\x0d\x0a\x0d\x0a", 5);
          /* 0  CR  LF  CR  LF */
          included_body += 5;
        }
        if(result)
          return result;
        /* Make sure the progress information is accurate */
        Curl_pgrsSetUploadSize(data, postsize);
      }
      else {
        /* A huge POST coming up, do data separate from the request */
        http->postsize = postsize;
        http->postdata = data->set.postfields;

        http->sending = HTTPSEND_BODY;

        conn->fread_func = (curl_read_callback)readmoredata;
        conn->fread_in = (void *)conn;

        /* set the upload size to the progress meter */
        Curl_pgrsSetUploadSize(data, http->postsize);

        result = Curl_add_buffer(req_buffer, "\r\n", 2); /* end of headers! */
        if(result)
          return result;
      }
    }
    else {
      result = Curl_add_buffer(req_buffer, "\r\n", 2); /* end of headers! */
      if(result)
        return result;

      if(data->req.upload_chunky && conn->bits.authneg) {
        /* Chunky upload is selected and we're negotiating auth still, send
           end-of-data only */
        result = Curl_add_buffer(req_buffer,
                                 "\x30\x0d\x0a\x0d\x0a", 5);
        /* 0  CR  LF  CR  LF */
        if(result)
          return result;
      }

      else if(data->set.postfieldsize) {
        /* set the upload size to the progress meter */
        Curl_pgrsSetUploadSize(data, postsize?postsize:-1);

        /* set the pointer to mark that we will send the post body using the
           read callback, but only if we're not in authenticate
           negotiation  */
        if(!conn->bits.authneg) {
          http->postdata = (char *)&http->postdata;
          http->postsize = postsize;
        }
      }
    }
    /* issue the request */
    result = Curl_add_buffer_send(req_buffer, conn, &data->info.request_size,
                                  (size_t)included_body, FIRSTSOCKET);

    if(result)
      failf(data, "Failed sending HTTP POST request");
    else
      Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE,
                          &http->readbytecount, http->postdata?FIRSTSOCKET:-1,
                          http->postdata?&http->writebytecount:NULL);
    break;

  default:
    result = Curl_add_buffer(req_buffer, "\r\n", 2);
    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 HTTP request");
    else
      /* HTTP GET/HEAD download: */
      Curl_setup_transfer(conn, FIRSTSOCKET, -1, TRUE, &http->readbytecount,
                          http->postdata?FIRSTSOCKET:-1,
                          http->postdata?&http->writebytecount:NULL);
  }
  if(result)
    return result;

  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;

    if(http->writebytecount >= postsize) {
      /* already sent the entire request body, mark the "upload" as
         complete */
      infof(data, "upload completely sent off: %" CURL_FORMAT_CURL_OFF_T
            " out of %" CURL_FORMAT_CURL_OFF_T " bytes\n",
            http->writebytecount, postsize);
      data->req.upload_done = TRUE;
      data->req.keepon &= ~KEEP_SEND; /* we're done writing */
      data->req.exp100 = EXP100_SEND_DATA; /* already sent */
    }
  }

  return result;
}

/*
 * checkhttpprefix()
 *
 * Returns TRUE if member of the list matches prefix of string
 */
static bool
checkhttpprefix(struct SessionHandle *data,
                const char *s)
{
  struct curl_slist *head = data->set.http200aliases;
  bool rc = FALSE;
#ifdef CURL_DOES_CONVERSIONS
  /* convert from the network encoding using a scratch area */
  char *scratch = strdup(s);
  if(NULL == scratch) {
    failf (data, "Failed to allocate memory for conversion!");
    return FALSE; /* can't return CURLE_OUT_OF_MEMORY so return FALSE */
  }
  if(CURLE_OK != Curl_convert_from_network(data, scratch, strlen(s)+1)) {
    /* Curl_convert_from_network calls failf if unsuccessful */
    free(scratch);
    return FALSE; /* can't return CURLE_foobar so return FALSE */
  }
  s = scratch;
#endif /* CURL_DOES_CONVERSIONS */

  while(head) {
    if(checkprefix(head->data, s)) {
      rc = TRUE;
      break;
    }
    head = head->next;
  }

  if(!rc && (checkprefix("HTTP/", s)))
    rc = TRUE;

#ifdef CURL_DOES_CONVERSIONS
  free(scratch);
#endif /* CURL_DOES_CONVERSIONS */
  return rc;
}

#ifndef CURL_DISABLE_RTSP
static bool
checkrtspprefix(struct SessionHandle *data,
                const char *s)
{

#ifdef CURL_DOES_CONVERSIONS
  /* convert from the network encoding using a scratch area */
  char *scratch = strdup(s);
  if(NULL == scratch) {
    failf (data, "Failed to allocate memory for conversion!");
    return FALSE; /* can't return CURLE_OUT_OF_MEMORY so return FALSE */
  }
  if(CURLE_OK != Curl_convert_from_network(data, scratch, strlen(s)+1)) {
    /* Curl_convert_from_network calls failf if unsuccessful */
    free(scratch);
    return FALSE; /* can't return CURLE_foobar so return FALSE */
  }
  s = scratch;
#else
  (void)data; /* unused */
#endif /* CURL_DOES_CONVERSIONS */
  if(checkprefix("RTSP/", s))
    return TRUE;
  else
    return FALSE;
}
#endif /* CURL_DISABLE_RTSP */

static bool
checkprotoprefix(struct SessionHandle *data, struct connectdata *conn,
                 const char *s)
{
#ifndef CURL_DISABLE_RTSP
  if(conn->handler->protocol & CURLPROTO_RTSP)
    return checkrtspprefix(data, s);
#else
  (void)conn;
#endif /* CURL_DISABLE_RTSP */

  return checkhttpprefix(data, s);
}

/*
 * header_append() copies a chunk of data to the end of the already received
 * header. We make sure that the full string fit in the allocated header
 * buffer, or else we enlarge it.
 */
static CURLcode header_append(struct SessionHandle *data,
                              struct SingleRequest *k,
                              size_t length)
{
  if(k->hbuflen + length >= data->state.headersize) {
    /* We enlarge the header buffer as it is too small */
    char *newbuff;
    size_t hbufp_index;
    size_t newsize;

    if(k->hbuflen + length > CURL_MAX_HTTP_HEADER) {
      /* The reason to have a max limit for this is to avoid the risk of a bad
         server feeding libcurl with a never-ending header that will cause
         reallocs infinitely */
      failf (data, "Avoided giant realloc for header (max is %d)!",
             CURL_MAX_HTTP_HEADER);
      return CURLE_OUT_OF_MEMORY;
    }

    newsize=CURLMAX((k->hbuflen+ length)*3/2, data->state.headersize*2);
    hbufp_index = k->hbufp - data->state.headerbuff;
    newbuff = realloc(data->state.headerbuff, newsize);
    if(!newbuff) {
      failf (data, "Failed to alloc memory for big header!");
      return CURLE_OUT_OF_MEMORY;
    }
    data->state.headersize=newsize;
    data->state.headerbuff = newbuff;
    k->hbufp = data->state.headerbuff + hbufp_index;
  }
  memcpy(k->hbufp, k->str_start, length);
  k->hbufp += length;
  k->hbuflen += length;
  *k->hbufp = 0;

  return CURLE_OK;
}

static void print_http_error(struct SessionHandle *data)
{
  struct SingleRequest *k = &data->req;
  char *beg = k->p;

  /* make sure that data->req.p points to the HTTP status line */
  if(!strncmp(beg, "HTTP", 4)) {

    /* skip to HTTP status code */
    beg = strchr(beg, ' ');
    if(beg && *++beg) {

      /* find trailing CR */
      char end_char = '\r';
      char *end = strchr(beg, end_char);
      if(!end) {
        /* try to find LF (workaround for non-compliant HTTP servers) */
        end_char = '\n';
        end = strchr(beg, end_char);
      }

      if(end) {
        /* temporarily replace CR or LF by NUL and print the error message */
        *end = '\0';
        failf(data, "The requested URL returned error: %s", beg);

        /* restore the previously replaced CR or LF */
        *end = end_char;
        return;
      }
    }
  }

  /* fall-back to printing the HTTP status code only */
  failf(data, "The requested URL returned error: %d", k->httpcode);
}

/*
 * Read any HTTP header lines from the server and pass them to the client app.
 */
CURLcode Curl_http_readwrite_headers(struct SessionHandle *data,
                                       struct connectdata *conn,
                                       ssize_t *nread,
                                       bool *stop_reading)
{
  CURLcode result;
  struct SingleRequest *k = &data->req;

  /* header line within buffer loop */
  do {
    size_t rest_length;
    size_t full_length;
    int writetype;

    /* str_start is start of line within buf */
    k->str_start = k->str;

    /* data is in network encoding so use 0x0a instead of '\n' */
    k->end_ptr = memchr(k->str_start, 0x0a, *nread);

    if(!k->end_ptr) {
      /* Not a complete header line within buffer, append the data to
         the end of the headerbuff. */
      result = header_append(data, k, *nread);
      if(result)
        return result;

      if(!k->headerline && (k->hbuflen>5)) {
        /* make a first check that this looks like a protocol header */
        if(!checkprotoprefix(data, conn, data->state.headerbuff)) {
          /* this is not the beginning of a protocol first header line */
          k->header = FALSE;
          k->badheader = HEADER_ALLBAD;
          break;
        }
      }

      break; /* read more and try again */
    }

    /* decrease the size of the remaining (supposed) header line */
    rest_length = (k->end_ptr - k->str)+1;
    *nread -= (ssize_t)rest_length;

    k->str = k->end_ptr + 1; /* move past new line */

    full_length = k->str - k->str_start;

    result = header_append(data, k, full_length);
    if(result)
      return result;

    k->end_ptr = k->hbufp;
    k->p = data->state.headerbuff;

    /****
     * We now have a FULL header line that p points to
     *****/

    if(!k->headerline) {
      /* the first read header */
      if((k->hbuflen>5) &&
         !checkprotoprefix(data, conn, data->state.headerbuff)) {
        /* this is not the beginning of a protocol first header line */
        k->header = FALSE;
        if(*nread)
          /* since there's more, this is a partial bad header */
          k->badheader = HEADER_PARTHEADER;
        else {
          /* this was all we read so it's all a bad header */
          k->badheader = HEADER_ALLBAD;
          *nread = (ssize_t)rest_length;
        }
        break;
      }
    }

    /* headers are in network encoding so
       use 0x0a and 0x0d instead of '\n' and '\r' */
    if((0x0a == *k->p) || (0x0d == *k->p)) {
      size_t headerlen;
      /* Zero-length header line means end of headers! */

#ifdef CURL_DOES_CONVERSIONS
      if(0x0d == *k->p) {
        *k->p = '\r'; /* replace with CR in host encoding */
        k->p++;       /* pass the CR byte */
      }
      if(0x0a == *k->p) {
        *k->p = '\n'; /* replace with LF in host encoding */
        k->p++;       /* pass the LF byte */
      }
#else
      if('\r' == *k->p)
        k->p++; /* pass the \r byte */
      if('\n' == *k->p)
        k->p++; /* pass the \n byte */
#endif /* CURL_DOES_CONVERSIONS */

      if(100 <= k->httpcode && 199 >= k->httpcode) {
        /*
         * We have made a HTTP PUT or POST and this is 1.1-lingo
         * that tells us that the server is OK with this and ready
         * to receive the data.
         * However, we'll get more headers now so we must get
         * back into the header-parsing state!
         */
        k->header = TRUE;
        k->headerline = 0; /* restart the header line counter */

        /* "A user agent MAY ignore unexpected 1xx status responses." */
        switch(k->httpcode) {
        case 100:
          /* if we did wait for this do enable write now! */
          if(k->exp100) {
            k->exp100 = EXP100_SEND_DATA;
            k->keepon |= KEEP_SEND;
          }
          break;