# CGI Library and core of a web server

#

# Juergen Kahrs, Juergen.Kahrs@vr-web.de

# with Arnold Robbins, arnold@skeeve.com

# September 2000

# Global arrays

#   GETARG --- arguments to CGI GET command

#   MENU   --- menu items (path names)

#   PARAM  --- parameters of form x=y

# Optional variable MyHost contains host address

# Optional variable MyPort contains port number

# Needs TopHeader, TopDoc, TopFooter

# Sets MyPrefix, HttpService, Status, Reason

BEGIN {

  if (MyHost == "") {

     "uname -n" | getline MyHost

     close("uname -n")

  }

  if (MyPort ==  0) MyPort = 8080

  HttpService = "/inet/tcp/" MyPort "/0/0"

  MyPrefix    = "http://" MyHost ":" MyPort

  SetUpServer()

  while ("awk" != "complex") {

    # header lines are terminated this way

    RS = ORS    = "\r\n"

    Status      = 200             # this means OK

    Reason      = "OK"

    Header      = TopHeader

    Document    = TopDoc

    Footer      = TopFooter

    if        (GETARG["Method"] == "GET") {

        HandleGET()

    } else if (GETARG["Method"] == "HEAD") {

        # not yet implemented

    } else if (GETARG["Method"] != "") {

        print "bad method", GETARG["Method"]

    }

    Prompt = Header Document Footer

    print "HTTP/1.0", Status, Reason     |& HttpService

    print "Connection: Close"            |& HttpService

    print "Pragma: no-cache"             |& HttpService

    len = length(Prompt) + length(ORS)

    print "Content-length:", len         |& HttpService

    print ORS Prompt                     |& HttpService

    # ignore all the header lines

    while ((HttpService |& getline) > 0)

        continue

    # stop talking to this client

    close(HttpService)

    # wait for new client request

    HttpService |& getline

    # do some logging

    print systime(), strftime(), $0

    CGI_setup($1, $2, $3)

  }

}

function CGI_setup(   method, uri, version, i)

{

    delete GETARG

    delete MENU

    delete PARAM

    GETARG["Method"] = method

    GETARG["URI"] = uri

    GETARG["Version"] = version

    i = index(uri, "?")

    if (i > 0) {  # is there a "?" indicating a CGI request?

        split(substr(uri, 1, i-1), MENU, "[/:]")

        split(substr(uri, i+1), PARAM, "&")

        for (i in PARAM) {

            PARAM[i] = _CGI_decode(PARAM[i])

            j = index(PARAM[i], "=")

            GETARG[substr(PARAM[i], 1, j-1)] = \

                                         substr(PARAM[i], j+1)

        }

    } else { # there is no "?", no need for splitting PARAMs

        split(uri, MENU, "[/:]")

    }

    for (i in MENU)     # decode characters in path

        if (i > 4)      # but not those in host name

            MENU[i] = _CGI_decode(MENU[i])

}

function _CGI_decode(str,   hexdigs, i, pre, code1, code2,

                            val, result)

{

   hexdigs = "123456789abcdef"

   i = index(str, "%")

   if (i == 0) # no work to do

      return str

   do {

      pre = substr(str, 1, i-1)   # part before %xx

      code1 = substr(str, i+1, 1) # first hex digit

      code2 = substr(str, i+2, 1) # second hex digit

      str = substr(str, i+3)      # rest of string

      code1 = tolower(code1)

      code2 = tolower(code2)

      val = index(hexdigs, code1) * 16 \

            + index(hexdigs, code2)

      result = result pre sprintf("%c", val)

      i = index(str, "%")

   } while (i != 0)

   if (length(str) > 0)

      result = result str

   return result

}