parse.c

这是有名的＜＜嵌入式系统TCP/IP应用层协议＞＞,M.Tim Jones 著

/*
 *  Embedded SMTP Server Attachment Parsing Functions
 *
 *  ./software/ch5/emsmtpd/parse.c
 *
 *  [e-mail]
 *
 *  Copyright 2001,2002 M. Tim Jones <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 */

#include <stdio.h>
#include <errno.h>
#include "server.h"
#include "client.h"

/*
 *  parseMail()
 *
 *  Performs mail parsing for content after the mail header.  This
 *  includes the subject and a single file attachment of any kind.
 *  The mail arguemnt is the incoming mail structure and len is the
 *  length of the mail body.
 *
 *  The subject line will contain the commmand:
 *
 *    STATUS - Return a device status email
 *    UPDATE - Parse out the attachment
 *
 *  Returns -1 on failure or 0 on success.
 *
 */

int parseMail(parseMailType *mail, int len)
{
  int i = 0, index;

  int extractAttachment ( parseMailType *, int, int );

  // First, grab the subject which is the location for the file
  for (i = 0 ; i < len ; i++) {
    if (mail->rawMail[i] == 'S') {
      if (!strncmp(&mail->rawMail[i], "Subject:", 8)) {
        i+= 9;
        index = 0;
        while ((mail->rawMail[i] != 0x0d) && (mail->rawMail[i] != 0x0a)) {
          mail->subject[index++] = mail->rawMail[i++];
        }
        mail->subject[index] = 0;
        break;
      }
    }
  }

  if (i == len) {
    return(-1);
  }

  /* This is our parser.  We look at the subject of the received email
   * and then determine how to deal with the email and its contents.
   */

  if (!strncmp(mail->subject, "STATUS", 6)) {

    emitStatusResponse(mail);

  } else if (!strncmp(mail->subject, "UPDATE", 6)) {

    /* Extract the attachment from the email */
    extractAttachment(mail, i, len);

    /* At this point, the mail structure will have the attachment stored
     * in the attachment array.  The attachlen will contain the length of
     * the attachment, or -1 if an error occured.
     */

    emitUpdateResponse(mail);

  } else {
    /* Don't understand the command, silently ignore... */
  }

  return 0;
}


/*
 *  extractAttachment()
 *
 *  Extract a single attachement from the body of the email and store it
 *  in the attachment array.  The mail structure is the incoming email,
 *  i is the current position in the rawMail array and len is the total
 *  length of the email body.
 *
 *  Returns -1 on failure, 0 on success.
 *
 */

int extractAttachment ( parseMailType *mail, int i, int len )
{
  int  index, status;

  // Next, grab the filename 
  for ( ; i < len ; i++) {
    if (mail->rawMail[i] == 'f') {
      if (!strncmp(&mail->rawMail[i], "filename=", 9)) {
        i+= 10;
        index = 0;
        while ((mail->rawMail[i] != 0x0d) && (mail->rawMail[i] != 0x0a)) {
          if (mail->rawMail[i] == '"') i++;
          else mail->filename[index++] = mail->rawMail[i++];
        }
        mail->filename[index] = 0;
        break;
      }
    }
  }

  if (i == len) {
    printf("Couldn't find the filename...\n");
    return(-1);
  } else {
    printf("The filename was [%s]\n", mail->filename);
  }

  /* Finally, find the start of the Base64 encoded data and decode...
   */
  for ( ; i < len ; i++) {
    /* We're looking for a CR/LF on a blank line after the
     * filename specification (since this is in the attachment
     * boundary).
     */
    if ((mail->rawMail[i] == 0x0d) && (mail->rawMail[i+1] == 0x0a) &&
        (mail->rawMail[i+2] == 0x0d) && (mail->rawMail[i+3] == 0x0a)) {
      i+=4;
      break;
    }
  }

  if (i == len) {
    printf("Couldn't find the Base64 MIME section...\n");
    return(-1);
  } 

  /* At this point, i is the index to the start of the Base64
   * encoded section, start the decoding process...
   */
  mail->attachlen = b64decode(&mail->rawMail[i], mail->attachment);

  return(mail->attachlen ? 0 : -1);
}