PMDF Programmer's Reference Manual
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1.12.2 Dequeuing Messages

Each of the two programs shown in Examples 1-5 and 1-6 constitutes a PMDF-to-batch-SMTP channel which reads messages from a message queue, converting each message to a batch SMTP format stored in a file on disk. If the conversion is successful, then the message is dequeued and deferred otherwise. Sample output is given in Example 1-7.

Note that these example programs always attempt to specify an envelope id in the batch SMTP message they output. This is done for illustration purposes only. In general, the code should check to see if the envelope id obtained with PMDFgetEnvelopeId is of zero length. Only if it has non-zero length should it then be outputting an envelope id.

Note
It is important to remember to define the PMDF_CHANNEL logical (OpenVMS) or environment variable (UNIX) to be the name of the channel (in lower case) to be serviced by this program. Also, if experimenting from your own account, do not leave this logical or environment variable defined while not experimenting --- PMDF can see it when you send mail and submit that mail as though it was enqueued by the channel given by PMDF_CHANNEL. (This is a debugging feature.)

The following items of note are identified with callouts in each of the two programs:

  1. In the event of an error, the current message being processed is deferred and the program exits.
  2. get_message is a routine which will return true (1) if PMDFgetMessage successfully accesses a message or false (0) otherwise. If PMDFgetMessage returns any error other than PMDF__EOF , then the check routine, , is invoked.
  3. read_line is a routine which will return true (1) if PMDFgetLine successfully reads a line from a message or false (0) otherwise. If PMDFreadLine returns any error other than PMDF__EOF , then the check routine, , is invoked.
  4. open_outbound is a routine which opens an output file to which to write the batch SMTP command. Output from PMDFgetUniqueString is used in generating the file name.
  5. notify is a routine which, builds an RFC 1891 NOTIFY= parameter based upon the NOTARY flags for an envelope "To:" recipient.
  6. PMDFinitialize is invoked with the ischannel argument true.
  7. PMDFdequeueInitialize creates and initializes a message dequeue context.
  8. Using the get_message routine, the program loops over all messages to be processed.
  9. Using PMDFgetRecipient , the program loops over the envelope "To:" address list in the currently accessed message.
  10. The NOTARY flags for the current envelope "To:" recipient are obtained with PMDFgetRecipientFlags .
  11. The disposition of the envelope "To:" recipient address is passed back to PMDF.
  12. Using the read_line routine, the program loops over the message header and body, copying each line to the batch SMTP file.
  13. Processing was successful; the processed message is dequeued.
  14. All done processing messages; dispose of the message dequeue context.

Example 1-5 Message Dequeuing (Pascal) 

(* api_example3.pas -- Dequeue a message and output it in batch SMTP format *) 
 
[inherit ('pmdf_exe:apidef')] program api_example3 (output); 
 
  type 
    uword     = [word] 0..65535; 
    string    = packed array [1..ALFA_SIZE] of char; 
    bigstring = packed array [1..BIGALFA_SIZE] of char; 
    vstring   = varying [64] of char; 
 
  var 
    dq_context                               : PMDF_dq; 
    empty                                    : varying [1] of char; 
    env_id, from_adr, host, orig_adr, to_adr : string; 
    env_id_len, from_adr_len, host_len, 
      orig_adr_len, to_adr_len, txt_len      : uword; 
    nflags, stat                             : integer; 
    outbound_open                            : boolean; 
    outfile                                  : text; 
    txt                                      : bigstring; 
 
procedure check (stat : integer); (1)
 
  var reason : varying [20] of char; 
 
  begin (* check *) 
    if not odd (stat) then begin 
      writev (reason, 'Error ', stat:0); 
      if dq_context <> nil then PMDF_defer_message (dq_context, true, reason); 
      if outbound_open then 
        close (file_variable := outfile, disposition := delete); 
      halt; 
    end; (* if *) 
  end; (* check *) 
 
function get_message : boolean; (2)
 
  var msg_file : string; msg_file_len : uword; 
 
  begin (* get_message *) 
    stat := PMDF_get_message (dq_context, msg_file, msg_file_len, 
                              from_adr, from_adr_len); 
    get_message := odd (stat); 
    if (not odd (stat)) and (stat <> PMDF__EOF) then check (stat); 
  end; (* get_message *) 
 
function read_line : boolean; (3)
 
  begin (* read_line *) 
    stat := PMDF_read_line (dq_context, txt, txt_len); 
    read_line := odd (stat); 
    if (not odd (stat)) and (stat <> PMDF__EOF) then check (stat); 
  end; (* read_line *) 
 
procedure open_outbound; (4)
 
  var 
    str     : string; 
    str_len : uword; 
 
  begin (* open_outbound *) 
    check (PMDF_get_unique_string (str, str_len)); 
    open (file_variable := outfile, 
          file_name := 'ZZ' + substr (str, 1, str_len) + '.00', 
          history := NEW, record_length := 1024); 
    stat := status (outfile); 
    if stat >= 0 then begin 
      rewrite (outfile); 
      outbound_open := true; 
    end else begin 
      writeln ('Pascal file error ', stat:0, '; aborting'); 
      check (0); 
    end; (* if *) 
  end; (* open_outbound *) 
 
function notify (nflags : integer) : vstring; (5)
 
  var str : vstring; 
 
  procedure add (bit : integer; toadd : varying [len] of char); 
    begin (* add *) 
      if 0 <> uand (nflags, bit) then begin 
        if length (str) = 0 then str := ' NOTIFY=' else str := str + ','; 
        str := str + toadd; 
      end; (* if *) 
    end; (* add *) 
 
  begin (* notify *) 
    str := ''; 
    add (PMDF_RECEIPT_NEVER,     'NEVER'); 
    add (PMDF_RECEIPT_FAILURES,  'FAILURE'); 
    add (PMDF_RECEIPT_DELAYS,    'DELAY'); 
    add (PMDF_RECEIPT_SUCCESSES, 'SUCCESS'); 
    notify := str; 
  end; (* notify *) 
 
begin (* api_example3 *) 
  empty         := ''; 
  dq_context    := nil; 
  outbound_open := false; 
  check (PMDF_initialize (true)); (6)
  check (PMDF_get_host_name (host, host_len)); 
  check (PMDF_dequeue_initialize (dq_context)); (7)
  while get_message do begin (8)
    check (PMDF_get_envelope_id (dq_context, env_id, env_id_len)); 
    open_outbound; 
    writeln (outfile, 'EHLO ', substr (host, 1, host_len)); 
    writeln (outfile, 'MAIL FROM:<', substr (from_adr, 1, from_adr_len), '>', 
             ' ENVID=', substr (env_id, 1, env_id_len)); 
    while odd (PMDF_get_recipient (dq_context, to_adr, to_adr_len, (9)
                                   orig_adr, orig_adr_len)) do begin 
      check (PMDF_get_recipient_flags (dq_context, nflags)); (10)
      writeln (outfile, 'RCPT TO:<', substr (to_adr, 1, to_adr_len), '>', 
               ' ORCPT=', substr (orig_adr, 1, orig_adr_len), 
               notify (nflags)); 
      check (PMDF_recipient_disposition (dq_context, nflags, (11)
                                PMDF_DISP_DELIVERED, 
                                substr (to_adr, 1, to_adr_len), 
                                substr (orig_adr, 1, orig_adr_len), empty)); 
    end; (* while *) 
    writeln (outfile, 'DATA'); 
    while read_line do begin (12)
      if txt_len > 0 then if txt[1] = '.' then write (outfile, '.'); 
      writeln (outfile, substr (txt, 1, txt_len)); 
    end; (* while *) 
    writeln (outfile, '.'); 
    writeln (outfile, 'QUIT'); 
    close (outfile); outbound_open := false; 
    check (PMDF_dequeue_message_end (dq_context, false, empty)); (13)
  end; (* while *) 
  check (PMDF_dequeue_end (dq_context)); (14)
  check (PMDF_done); 
end. (* api_example3 *)

Example 1-6 Message Dequeuing (C) 

/* api_example4.c -- Dequeue a message and output it in batch SMTP format */ 
 
#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#ifdef __VMS 
#include "pmdf_com:apidef.h" 
#else 
#include "/pmdf/include/apidef.h" 
#endif 
 
typedef char string[ALFA_SIZE+1]; 
 
string filename, from_adr, txt; 
int outbound_open, txt_len; 
PMDF_dq *dq_context = 0; 
FILE *outfile; 
 
void check (int stat) (1)
{ 
  char reason[20]; 
  if (!(1 & stat)) { 
    sprintf (reason, "Reason %d", stat); 
    if (dq_context) PMDFdeferMessage (&dq_context, 1, reason, strlen (reason)); 
    if (outbound_open) { 
      fclose (outfile); 
      remove (filename); 
    } 
    if (!stat) exit (0); 
    else exit (stat); 
  } 
} 
 
int get_message (void) (2)
{ 
    string msg_file; 
    int from_adr_len, msg_file_len, stat; 
 
    from_adr_len = msg_file_len = ALFA_SIZE; 
    stat = PMDFgetMessage (&dq_context, msg_file, &msg_file_len, 
                           from_adr, &from_adr_len); 
    if (!(1 & stat) && stat != PMDF__EOF) check (stat); 
    return (1 & stat); 
} 
 
int read_line (void) (3)
{ 
    int stat; 
 
    txt_len = BIGALFA_SIZE; 
    stat = PMDFreadLine (&dq_context, txt, &txt_len); 
    if ( !(1 & stat) && stat != PMDF__EOF) check (stat); 
    return (1 & stat); 
} 
 
void open_outbound (void) (4)
{ 
  char str[18+5+1]; 
  int str_len = 18; 
 
  check (PMDFgetUniqueString (str, &str_len)); 
  sprintf (filename, "ZZ%s.00", str); 
  outfile = fopen (filename, "w"); 
  if (!outfile) { 
    fprintf (stderr, "Error opening output file; aborting\n", filename); 
    check (0); 
  } 
  outbound_open = 1; 
} 
 
void add (int nflags, int bit, char *src, char *dst) 
{ 
  if (!(nflags & bit)) return; 
  if (*dst) strcat (dst, ","); 
  strcat (dst, src); 
} 
 
void make_notify (int nflags, char *buf) (5)
{ 
  *buf = '\0'; 
  add (nflags, PMDF_RECEIPT_NEVER,     "NEVER",   buf); 
  add (nflags, PMDF_RECEIPT_FAILURES,  "FAILURE", buf); 
  add (nflags, PMDF_RECEIPT_DELAYS,    "DELAY",   buf); 
  add (nflags, PMDF_RECEIPT_SUCCESSES, "SUCCESS", buf); 
} 
 
main () 
{ 
  string env_id, host, orig_adr, to_adr; 
  int env_id_len, nflags, host_len, orig_adr_len, to_adr_len; 
  char notify[64]; 
 
  outbound_open = 0; 
  check (PMDFinitialize (1)); (6)
  host_len = ALFA_SIZE; 
  check (PMDFgetHostName (host, &host_len)); 
  check (PMDFdequeueInitialize (&dq_context)); (7)
  while (get_message ()) { (8)
    env_id_len = ALFA_SIZE; 
    check (PMDFgetEnvelopeId (&dq_context, env_id, &env_id_len)); 
    open_outbound (); 
    fprintf (outfile, "EHLO %s\n", host); 
    fprintf (outfile, "MAIL FROM:<%s> ENVID=%s\n", from_adr, env_id); 
    to_adr_len = orig_adr_len = ALFA_SIZE; 
    while (1 & PMDFgetRecipient (&dq_context, to_adr, &to_adr_len, (9)
                                 orig_adr, &orig_adr_len)) 
    { 
      check (PMDFgetRecipientFlags (&dq_context, &nflags)); (10)
      make_notify (nflags, notify); 
      fprintf (outfile, "RCPT TO:<%s> ORCPT=%s", to_adr, orig_adr); 
      if (notify[0]) fprintf (outfile, " NOTIFY=%s\n", notify); 
      else fprintf (outfile, "\n"); 
      check (PMDFrecipientDisposition (&dq_context, nflags, (11)
                                       PMDF_DISP_DELIVERED, to_adr, 
                                       to_adr_len, orig_adr, orig_adr_len, 
                                       NULL, 0)); 
      to_adr_len = orig_adr_len = ALFA_SIZE; 
    } 
    fprintf (outfile, "DATA\n"); 
    while (read_line ()) { (12)
      if (txt_len > 0) if (txt[0] == '.') fprintf (outfile, "."); 
      fprintf (outfile, "%s\n", txt); 
    } 
    fprintf (outfile, ".\nQUIT\n"); 
    fclose (outfile); outbound_open = 0; 
    check (PMDFdequeueMessageEnd (&dq_context, 0, NULL, 0)); (13)
  } 
  check (PMDFdequeueEnd (&dq_context)); (14)
  check (PMDFdone ()); 
}

Example 1-7 Output of Examples 1-5 and 1-6 

EHLO EXAMPLE.COM 
MAIL FROM:<stephano@example.com> ENVID=01ISXU84PB929AMHQL@EXAMPLE.COM 
RCPT TO:<caliban@example.com> 
  ORCPT=rfc822;caliban@island.example.com NOTIFY=FAILURES,DELAY 
DATA 
Received: from EXAMPLE.COM by EXAMPLE.COM (PMDF #1339) id 
 <01GP3A97QW9CAATXKZ@EXAMPLE.COM>; Sat, 04 May 2012 18:04:00 EDT 
Date: 04 May 2012 18:04:00 -0400 (EDT) 
From: "Stephano the Drunken Butler" <stephano@example.com> 
Subject: Testing 
To: "Caliban the Savage" <caliban@island.example.com> 
Message-id: <01GP3A97R5WIAATXKZ@EXAMPLE.COM> 
MIME-version: 1.0 
Content-type: TEXT/PLAIN; CHARSET=US-ASCII 
Content-transfer-encoding: 7BIT 
 
This is a test of the emergency broadcasting system. 
Please do not be alarmed.  Please do not hold your breath. 
 
Bye 
. 
QUIT

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