epan/frequency-utils.c

   1 /* frequency-utils.c
   2  * Frequency conversion utility definitions
   3  *
   4  * $Id$
   5  *
   6  * Wireshark - Network traffic analyzer
   7  * By Gerald Combs <gerald@wireshark.org>
   8  * Copyright 2007 Gerald Combs
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License
  12  * as published by the Free Software Foundation; either version 2
  13  * of the License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  23  */
  24
  25 #include "config.h"
  26
  27 #include <glib.h>
  28
  29 #include "frequency-utils.h"
  30
  31 typedef struct freq_cvt_s {
  32     guint fmin;         /* Minimum frequency in MHz */
  33     guint fmax;         /* Maximum frequency in MHz */
  34     gint cmin;          /* Minimum/base channel */
  35     gboolean is_bg;     /* B/G channel? */
  36 } freq_cvt_t;
  37
  38 #define FREQ_STEP 5     /* MHz. This seems to be consistent, thankfully */
  39
  40 /* From "802.11 Wireless Networks: The Definitive Guide", 2nd Ed. by Matthew Gast */
  41 static freq_cvt_t freq_cvt[] = {
  42     { 2412, 2472,   1, TRUE },   /* Table 12-1, p 257 */
  43     { 2484, 2484,  14, TRUE },   /* Table 12-1, p 257 */
  44     { 5000, 5995,   0, FALSE },  /* Table 13-1, p 289 */
  45     { 4920, 4995, 240, FALSE }   /* Table 13-1, p 289 */
  46 };
  47
  48 #define NUM_FREQ_CVT (sizeof(freq_cvt) / sizeof(freq_cvt_t))
  49 #define MAX_CHANNEL(fc) ( (gint) ((fc.fmax - fc.fmin) / FREQ_STEP) + fc.cmin )
  50
  51 /*
  52  * Get channel number given a Frequency
  53  */
  54 gint
  55 ieee80211_mhz_to_chan(guint freq) {
  56     guint i;
  57
  58     for (i = 0; i < NUM_FREQ_CVT; i++) {
  59         if (freq >= freq_cvt[i].fmin && freq <= freq_cvt[i].fmax) {
  60             return ((freq - freq_cvt[i].fmin) / FREQ_STEP) + freq_cvt[i].cmin;
  61         }
  62     }
  63     return -1;
  64 }
  65
  66 /*
  67  * Get Frequency given a Channel number
  68  */
  69 guint
  70 ieee80211_chan_to_mhz(gint chan, gboolean is_bg) {
  71     guint i;
  72
  73     for (i = 0; i < NUM_FREQ_CVT; i++) {
  74         if (is_bg == freq_cvt[i].is_bg &&
  75                 chan >= freq_cvt[i].cmin && chan <= MAX_CHANNEL(freq_cvt[i])) {
  76             return ((chan - freq_cvt[i].cmin) * FREQ_STEP) + freq_cvt[i].fmin;
  77         }
  78     }
  79     return 0;
  80 }
  81
  82 /*
  83  * Get channel representation string given a Frequency
  84  */
  85 gchar*
  86 ieee80211_mhz_to_str(guint freq){
  87     gint chan = ieee80211_mhz_to_chan(freq);
  88     gboolean is_bg = FREQ_IS_BG(freq);
  89
  90     if (chan < 0) {
  91         return g_strdup_printf("%u", freq);
  92     } else {
  93         return g_strdup_printf("%u [%s %u]", freq, is_bg ? "BG" : "A",
  94             chan);
  95     }
  96 }
  97
  98 /*
  99  * Editor modelines
 100  *
 101  * Local Variables:
 102  * c-basic-offset: 4
 103  * tab-width: 8
 104  * indent-tabs-mode: nil
 105  * End:
 106  *
 107  * ex: set shiftwidth=4 tabstop=8 expandtab:
 108  * :indentSize=4:tabSize=8:noTabs=true:
 109  */