path: root/mail/mail-identify.c

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: t; c-basic-offset: 8 -*- */

/*
 * Author :
 *  Dan Winship <danw@ximian.com>
 *
 *  Copyright 2000, Ximian, Inc. (www.ximian.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <string.h>

#include <glib.h>
#include <libgnomevfs/gnome-vfs-mime-utils.h>
#include "mail.h"

static const char *identify_by_magic (CamelDataWrapper *data, MailDisplay *md);

/**
 * mail_identify_mime_part:
 * @part: a CamelMimePart
 * @md: the MailDisplay @part is being shown in
 *
 * Try to identify the MIME type of the data in @part (which presumably
 * doesn't have a useful Content-Type).
 *
 * Return value: the MIME type, which the caller must free, or %NULL
 * if it could not be identified.
 **/
char *
mail_identify_mime_part (CamelMimePart *part, MailDisplay *md)
{
    const char *filename, *magic_type = NULL;
    CamelDataWrapper *data;
    char *name_type = NULL;

    filename = camel_mime_part_get_filename (part);
    if (filename) {
        /* GNOME-VFS will misidentify TNEF attachments as MPEG */
        if (!strcmp (filename, "winmail.dat"))
            return g_strdup ("application/vnd.ms-tnef");

#warning "does gnome_vfs_get_mime_type handle a plain filename as the 'text_uri'?"
        name_type = gnome_vfs_get_mime_type(filename);
    }

    data = camel_medium_get_content_object (CAMEL_MEDIUM (part));
    if (!camel_data_wrapper_is_offline (data))
        magic_type = identify_by_magic (data, md);

    if (magic_type && name_type) {
        /* If GNOME-VFS doesn't recognize the data by magic, but it
         * contains English words, it will call it text/plain. If the
         * filename-based check came up with something different, use
         * that instead.
         */
        if (!strcmp (magic_type, "text/plain"))
            return name_type;

        /* If if returns "application/octet-stream" try to
         * do better with the filename check.
         */
        if (!strcmp (magic_type, "application/octet-stream"))
            return name_type;
    }

    /* If the MIME part data was online, and the magic check
     * returned something, use that, since it's more reliable.
     */
    if (magic_type) {
        g_free(name_type);
        return g_strdup (magic_type);
    }

    /* Otherwise try guessing based on the filename */
    if (name_type)
        return name_type;

    /* Another possibility to try is the x-mac-type / x-mac-creator
     * parameter to Content-Type used by some Mac email clients. That
     * would require a Mac type to mime type conversion table.
     */

#if 0
    /* If the data part is offline, then we didn't try magic
     * before, so force it to be loaded so we can try again later.
     * FIXME: In a perfect world, we would not load the content
     * just to identify the MIME type.
     */
    /* This is disabled as it just frustrates users more than it helps,
       see discussion in bug #11778 */
    if (camel_data_wrapper_is_offline (data))
        mail_content_loaded (data, md, TRUE, NULL, NULL, NULL);
#endif

    return NULL;
}

static const char *
identify_by_magic (CamelDataWrapper *data, MailDisplay *md)
{
    CamelStreamMem *memstream;
    const char *type;

    memstream = (CamelStreamMem *)camel_stream_mem_new();
    if (camel_data_wrapper_write_to_stream (data, (CamelStream *)memstream) > 0)
        type = gnome_vfs_get_mime_type_for_data(memstream->buffer->data, memstream->buffer->len);
    else
        type = NULL;
    camel_object_unref(memstream);

    return type;
}