/* decode_as_utils.c
 *
 * Routines to modify dissector tables on the fly.
 *
 * By David Hampton <dhampton@mac.com>
 * Copyright 2001 David Hampton
 *
 * 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
 * of the License, 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.
 *
 * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#include "config.h"

#include <stdlib.h>

#include <errno.h>

#include "epan/decode_as.h"
#include "epan/packet.h"
#include "epan/prefs.h"
#include "epan/prefs-int.h"

#include "ui/decode_as_utils.h"
#include "ui/simple_dialog.h"

#include "wsutil/file_util.h"
#include "wsutil/filesystem.h"
#include "wsutil/cmdarg_err.h"
#include "ws_version_info.h"

/* XXX - We might want to switch this to a UAT */

static const char* prev_display_dissector_name = NULL;

/*
* For a dissector table, print on the stream described by output,
* its short name (which is what's used in the "-d" option) and its
* descriptive name.
*/
static void
display_dissector_table_names(const char *table_name, const char *ui_name,
gpointer output)
{
    if ((prev_display_dissector_name == NULL) ||
        (strcmp(prev_display_dissector_name, table_name) != 0)) {
        fprintf((FILE *)output, "\t%s (%s)\n", table_name, ui_name);
        prev_display_dissector_name = table_name;
    }
}

/*
* For a dissector handle, print on the stream described by output,
* the filter name (which is what's used in the "-d" option) and the full
* name for the protocol that corresponds to this handle.
*/
static void
display_dissector_names(const gchar *table _U_, gpointer handle, gpointer output)
{
    int          proto_id;
    const gchar *proto_filter_name;
    const gchar *proto_ui_name;

    proto_id = dissector_handle_get_protocol_index((dissector_handle_t)handle);

    if (proto_id != -1) {
        proto_filter_name = proto_get_protocol_filter_name(proto_id);
        proto_ui_name = proto_get_protocol_name(proto_id);
        g_assert(proto_filter_name != NULL);
        g_assert(proto_ui_name != NULL);

        if ((prev_display_dissector_name == NULL) ||
            (strcmp(prev_display_dissector_name, proto_filter_name) != 0)) {
            fprintf((FILE *)output, "\t%s (%s)\n",
                proto_filter_name,
                proto_ui_name);
            prev_display_dissector_name = proto_filter_name;
        }
    }
}

/*
* Allow dissector key names to be sorted alphabetically
*/

static gint
compare_dissector_key_name(gconstpointer dissector_a, gconstpointer dissector_b)
{
    return strcmp((const char*)dissector_a, (const char*)dissector_b);
}

/*
* Print all layer type names supported.
* We send the output to the stream described by the handle output.
*/
static void
fprint_all_layer_types(FILE *output)

{
    prev_display_dissector_name = NULL;
    dissector_all_tables_foreach_table(display_dissector_table_names, (gpointer)output, (GCompareFunc)compare_dissector_key_name);
}

/*
* Print all protocol names supported for a specific layer type.
* table_name contains the layer type name in which the search is performed.
* We send the output to the stream described by the handle output.
*/
static void
fprint_all_protocols_for_layer_types(FILE *output, gchar *table_name)

{
    prev_display_dissector_name = NULL;
    dissector_table_foreach_handle(table_name,
        display_dissector_names,
        (gpointer)output);
}

/*
* The protocol_name_search structure is used by find_protocol_name_func()
* to pass parameters and store results
*/
struct protocol_name_search{
    gchar              *searched_name;  /* Protocol filter name we are looking for */
    dissector_handle_t  matched_handle; /* Handle for a dissector whose protocol has the specified filter name */
    guint               nb_match;       /* How many dissectors matched searched_name */
};
typedef struct protocol_name_search *protocol_name_search_t;

/*
* This function parses all dissectors associated with a table to find the
* one whose protocol has the specified filter name.  It is called
* as a reference function in a call to dissector_table_foreach_handle.
* The name we are looking for, as well as the results, are stored in the
* protocol_name_search struct pointed to by user_data.
* If called using dissector_table_foreach_handle, we actually parse the
* whole list of dissectors.
*/
static void
find_protocol_name_func(const gchar *table _U_, gpointer handle, gpointer user_data)

{
    int                     proto_id;
    const gchar            *protocol_filter_name;
    protocol_name_search_t  search_info;

    g_assert(handle);

    search_info = (protocol_name_search_t)user_data;

    proto_id = dissector_handle_get_protocol_index((dissector_handle_t)handle);
    if (proto_id != -1) {
        protocol_filter_name = proto_get_protocol_filter_name(proto_id);
        g_assert(protocol_filter_name != NULL);
        if (strcmp(protocol_filter_name, search_info->searched_name) == 0) {
            /* Found a match */
            if (search_info->nb_match == 0) {
                /* Record this handle only if this is the first match */
                search_info->matched_handle = (dissector_handle_t)handle; /* Record the handle for this matching dissector */
            }
            search_info->nb_match++;
        }
    }
}

/*
* The function below parses the command-line parameters for the decode as
* feature (a string pointer by cl_param).
* It checks the format of the command-line, searches for a matching table
* and dissector.  If a table/dissector match is not found, we display a
* summary of the available tables/dissectors (on stderr) and return FALSE.
* If everything is fine, we get the "Decode as" preference activated,
* then we return TRUE.
*/
gboolean decode_as_command_option(const gchar *cl_param)
{
    gchar                        *table_name;
    guint32                       selector, selector2;
    gchar                        *decoded_param;
    gchar                        *remaining_param;
    gchar                        *selector_str;
    gchar                        *dissector_str;
    dissector_handle_t            dissector_matching;
    dissector_table_t             table_matching;
    ftenum_t                      dissector_table_selector_type;
    struct protocol_name_search   user_protocol_name;
    guint64                       i;
    char                          op;

    /* The following code will allocate and copy the command-line options in a string pointed by decoded_param */

    g_assert(cl_param);
    decoded_param = g_strdup(cl_param);
    g_assert(decoded_param);


    /* The lines below will parse this string (modifying it) to extract all
    necessary information.  Note that decoded_param is still needed since
    strings are not copied - we just save pointers. */

    /* This section extracts a layer type (table_name) from decoded_param */
    table_name = decoded_param; /* Layer type string starts from beginning */

    remaining_param = strchr(table_name, '=');
    if (remaining_param == NULL) {
        cmdarg_err("Parameter \"%s\" doesn't follow the template \"%s\"", cl_param, DECODE_AS_ARG_TEMPLATE);
        /* If the argument does not follow the template, carry on anyway to check
        if the table name is at least correct.  If remaining_param is NULL,
        we'll exit anyway further down */
    }
    else {
        *remaining_param = '\0'; /* Terminate the layer type string (table_name) where '=' was detected */
    }

    /* Remove leading and trailing spaces from the table name */
    while (table_name[0] == ' ')
        table_name++;
    while (table_name[strlen(table_name) - 1] == ' ')
        table_name[strlen(table_name) - 1] = '\0'; /* Note: if empty string, while loop will eventually exit */

    /* The following part searches a table matching with the layer type specified */
    table_matching = NULL;

    /* Look for the requested table */
    if (!(*(table_name))) { /* Is the table name empty, if so, don't even search for anything, display a message */
        cmdarg_err("No layer type specified"); /* Note, we don't exit here, but table_matching will remain NULL, so we exit below */
    }
    else {
        table_matching = find_dissector_table(table_name);
        if (!table_matching) {
            cmdarg_err("Unknown layer type -- %s", table_name); /* Note, we don't exit here, but table_matching will remain NULL, so we exit below */
        }
    }

    if (!table_matching) {
        /* Display a list of supported layer types to help the user, if the
        specified layer type was not found */
        cmdarg_err("Valid layer types are:");
        fprint_all_layer_types(stderr);
    }
    if (remaining_param == NULL || !table_matching) {
        /* Exit if the layer type was not found, or if no '=' separator was found
        (see above) */
        g_free(decoded_param);
        return FALSE;
    }

    if (*(remaining_param + 1) != '=') { /* Check for "==" and not only '=' */
        cmdarg_err("WARNING: -d requires \"==\" instead of \"=\". Option will be treated as \"%s==%s\"", table_name, remaining_param + 1);
    }
    else {
        remaining_param++; /* Move to the second '=' */
        *remaining_param = '\0'; /* Remove the second '=' */
    }
    remaining_param++; /* Position after the layer type string */

    /* This section extracts a selector value (selector_str) from decoded_param */

    selector_str = remaining_param; /* Next part starts with the selector number */

    remaining_param = strchr(selector_str, ',');
    if (remaining_param == NULL) {
        cmdarg_err("Parameter \"%s\" doesn't follow the template \"%s\"", cl_param, DECODE_AS_ARG_TEMPLATE);
        /* If the argument does not follow the template, carry on anyway to check
        if the selector value is at least correct.  If remaining_param is NULL,
        we'll exit anyway further down */
    }
    else {
        *remaining_param = '\0'; /* Terminate the selector number string (selector_str) where ',' was detected */
    }

    dissector_table_selector_type = get_dissector_table_selector_type(table_name);

    switch (dissector_table_selector_type) {

    case FT_UINT8:
    case FT_UINT16:
    case FT_UINT24:
    case FT_UINT32:
        /* The selector for this table is an unsigned number.  Parse it as such.
        There's no need to remove leading and trailing spaces from the
        selector number string, because sscanf will do that for us. */
        switch (sscanf(selector_str, "%u%c%u", &selector, &op, &selector2)) {
        case 1:
            op = '\0';
            break;
        case 3:
            if (op != ':' && op != '-') {
                cmdarg_err("Invalid selector numeric range \"%s\"", selector_str);
                g_free(decoded_param);
                return FALSE;
            }
            if (op == ':') {
                if ((selector2 == 0) || ((guint64)selector + selector2 - 1) > G_MAXUINT32) {
                    cmdarg_err("Invalid selector numeric range \"%s\"", selector_str);
                    g_free(decoded_param);
                    return FALSE;
                }
            }
            else if (selector2 < selector) {
                /* We could swap them for the user, but maybe it's better to call
                * this out as an error in case it's not what was intended? */
                cmdarg_err("Invalid selector numeric range \"%s\"", selector_str);
                g_free(decoded_param);
                return FALSE;
            }
            break;
        default:
            cmdarg_err("Invalid selector number \"%s\"", selector_str);
            g_free(decoded_param);
            return FALSE;
        }
        break;

    case FT_STRING:
    case FT_STRINGZ:
    case FT_UINT_STRING:
    case FT_STRINGZPAD:
        /* The selector for this table is a string. */
        break;

    default:
        /* There are currently no dissector tables with any types other
        than the ones listed above. */
        g_assert_not_reached();
    }

    if (remaining_param == NULL) {
        /* Exit if no ',' separator was found (see above) */
        cmdarg_err("Valid protocols for layer type \"%s\" are:", table_name);
        fprint_all_protocols_for_layer_types(stderr, table_name);
        g_free(decoded_param);
        return FALSE;
    }

    remaining_param++; /* Position after the selector number string */

    /* This section extracts a protocol filter name (dissector_str) from decoded_param */

    dissector_str = remaining_param; /* All the rest of the string is the dissector (decode as protocol) name */

    /* Remove leading and trailing spaces from the dissector name */
    while (dissector_str[0] == ' ')
        dissector_str++;
    while (dissector_str[strlen(dissector_str) - 1] == ' ')
        dissector_str[strlen(dissector_str) - 1] = '\0'; /* Note: if empty string, while loop will eventually exit */

    dissector_matching = NULL;

    /* We now have a pointer to the handle for the requested table inside the variable table_matching */
    if (!(*dissector_str)) { /* Is the dissector name empty, if so, don't even search for a matching dissector and display all dissectors found for the selected table */
        cmdarg_err("No protocol name specified"); /* Note, we don't exit here, but dissector_matching will remain NULL, so we exit below */
    }
    else {
        user_protocol_name.nb_match = 0;
        user_protocol_name.searched_name = dissector_str;
        user_protocol_name.matched_handle = NULL;

        dissector_table_foreach_handle(table_name, find_protocol_name_func, &user_protocol_name); /* Go and perform the search for this dissector in the this table's dissectors' names and shortnames */

        if (user_protocol_name.nb_match != 0) {
            dissector_matching = user_protocol_name.matched_handle;
            if (user_protocol_name.nb_match > 1) {
                cmdarg_err("WARNING: Protocol \"%s\" matched %u dissectors, first one will be used", dissector_str, user_protocol_name.nb_match);
            }
        }
        else {
            /* OK, check whether the problem is that there isn't any such
            protocol, or that there is but it's not specified as a protocol
            that's valid for that dissector table.
            Note, we don't exit here, but dissector_matching will remain NULL,
            so we exit below */
            if (proto_get_id_by_filter_name(dissector_str) == -1) {
                /* No such protocol */
                cmdarg_err("Unknown protocol -- \"%s\"", dissector_str);
            }
            else {
                cmdarg_err("Protocol \"%s\" isn't valid for layer type \"%s\"",
                    dissector_str, table_name);
            }
        }
    }

    if (!dissector_matching) {
        cmdarg_err("Valid protocols for layer type \"%s\" are:", table_name);
        fprint_all_protocols_for_layer_types(stderr, table_name);
        g_free(decoded_param);
        return FALSE;
    }

    /* This is the end of the code that parses the command-line options.
    All information is now stored in the variables:
    table_name
    selector
    dissector_matching
    The above variables that are strings are still pointing to areas within
    decoded_parm.  decoded_parm thus still needs to be kept allocated in
    until we stop needing these variables
    decoded_param will be deallocated at each exit point of this function */


    /* We now have a pointer to the handle for the requested dissector
    (requested protocol) inside the variable dissector_matching */
    switch (dissector_table_selector_type) {

    case FT_UINT8:
    case FT_UINT16:
    case FT_UINT24:
    case FT_UINT32:
        /* The selector for this table is an unsigned number. */
        if (op == '\0') {
            dissector_change_uint(table_name, selector, dissector_matching);
        }
        else if (op == ':') {
            for (i = selector; i < (guint64)selector + selector2; i++) {
                dissector_change_uint(table_name, (guint32)i, dissector_matching);
            }
        }
        else { /* op == '-' */
            for (i = selector; i <= selector2; i++) {
                dissector_change_uint(table_name, (guint32)i, dissector_matching);
            }
        }
        break;

    case FT_STRING:
    case FT_STRINGZ:
    case FT_UINT_STRING:
    case FT_STRINGZPAD:
        /* The selector for this table is a string. */
        dissector_change_string(table_name, selector_str, dissector_matching);
        break;

    default:
        /* There are currently no dissector tables with any types other
        than the ones listed above. */
        g_assert_not_reached();
    }
    g_free(decoded_param); /* "Decode As" rule has been successfully added */
    return TRUE;
}

/*
 * Editor modelines
 *
 * Local Variables:
 * c-basic-offset: 4
 * tab-width: 8
 * indent-tabs-mode: nil
 * End:
 *
 * ex: set shiftwidth=4 tabstop=8 expandtab:
 * :indentSize=4:tabSize=8:noTabs=true:
 */