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* rewrite GSM 7bit default encoding/decoding based on a lookup table as the previous code produced wrong encodings for certain characters.

This commit is contained in:
Nico Golde 2010-07-09 17:19:12 +02:00 committed by Holger Hans Peter Freyther
parent 383134b5ac
commit 28de05336b
3 changed files with 135 additions and 33 deletions
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28
include/osmocore/gsm_utils.h
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@ -3,6 +3,7 @@
* (C) 2008 by Daniel Willmann <daniel@totalueberwachung.de>
* (C) 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
* (C) 2009-2010 by Harald Welte <laforge@gnumonks.org>
* (C) 2010 by Nico Golde <nico@ngolde.de>
*
* All Rights Reserved
*
@ -53,6 +54,33 @@ enum gsm_band {
GSM_BAND_810 = 0x80,
};
/* ETSI GSM 03.38 6.2.1 and 6.2.1.1 default alphabet
* Greek symbols at hex positions 0x10 and 0x12-0x1a
* left out as they can't be handled with a char and
* since most phones don't display or write these
* characters this would only needlessly make the code
* more complex
*/
unsigned char gsm_7bit_alphabet[] = {
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x0a, 0xff, 0xff, 0x0d, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0x20, 0x21, 0x22, 0x23, 0x02, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c,
0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b,
0x3c, 0x3d, 0x3e, 0x3f, 0x00, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a,
0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
0x5a, 0x3c, 0x2f, 0x3e, 0x14, 0x11, 0xff, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
0x78, 0x79, 0x7a, 0x28, 0x40, 0x29, 0x3d, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0x0c, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x5e, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x40, 0xff, 0x01, 0xff,
0x03, 0xff, 0x7b, 0x7d, 0xff, 0xff, 0xff, 0xff, 0xff, 0x5c, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x5b, 0x7e, 0x5d, 0xff, 0x7c, 0xff, 0xff, 0xff,
0xff, 0x5b, 0x0e, 0x1c, 0x09, 0xff, 0x1f, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x5d,
0xff, 0xff, 0xff, 0xff, 0x5c, 0xff, 0x0b, 0xff, 0xff, 0xff, 0x5e, 0xff, 0xff, 0x1e, 0x7f,
0xff, 0xff, 0xff, 0x7b, 0x0f, 0x1d, 0xff, 0x04, 0x05, 0xff, 0xff, 0x07, 0xff, 0xff, 0xff,
0xff, 0x7d, 0x08, 0xff, 0xff, 0xff, 0x7c, 0xff, 0x0c, 0x06, 0xff, 0xff, 0x7e, 0xff, 0xff
};
const char *gsm_band_name(enum gsm_band band);
enum gsm_band gsm_band_parse(const char *mhz);

123
src/gsm_utils.c
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@ -2,6 +2,7 @@
* (C) 2008 by Daniel Willmann <daniel@totalueberwachung.de>
* (C) 2009 by Holger Hans Peter Freyther <zecke@selfish.org>
* (C) 2009-2010 by Harald Welte <laforge@gnumonks.org>
* (C) 2010 by Nico Golde <nico@ngolde.de>
*
* All Rights Reserved
*
@ -34,52 +35,110 @@
#include "../config.h"
/* GSM 03.38 6.2.1 Charachter packing */
/* GSM 03.38 6.2.1 Character lookup for decoding */
static int gsm_septet_lookup(uint8_t ch)
{
int i = 0;
for(; i < sizeof(gsm_7bit_alphabet); i++){
if(gsm_7bit_alphabet[i] == ch)
return i;
}
return -1;
}
/* GSM 03.38 6.2.1 Character unpacking */
int gsm_7bit_decode(char *text, const uint8_t *user_data, uint8_t length)
{
int i = 0;
int l = 0;
uint8_t *rtext = calloc(length, sizeof(uint8_t));
uint8_t tmp;
/* FIXME: We need to account for user data headers here */
/* FIXME: We need to account for user data headers here */
i += l;
for (; i < length; i ++)
*(text ++) =
for (; i < length; i ++){
rtext[i] =
((user_data[(i * 7 + 7) >> 3] <<
(7 - ((i * 7 + 7) & 7))) |
(user_data[(i * 7) >> 3] >>
((i * 7) & 7))) & 0x7f;
*text = '\0';
return i - l;
}
/* GSM 03.38 6.2.1 Charachter packing */
int gsm_7bit_encode(uint8_t *result, const char *data)
{
int i,j = 0;
unsigned char ch1, ch2;
int shift = 0;
for ( i=0; i<strlen(data); i++ ) {
ch1 = data[i] & 0x7F;
ch1 = ch1 >> shift;
ch2 = data[(i+1)] & 0x7F;
ch2 = ch2 << (7-shift);
ch1 = ch1 | ch2;
result[j++] = ch1;
shift++;
if ((shift == 7) && (i+1<strlen(data))) {
shift = 0;
}
for(i = 0; i < length; i++){
/* this is an extension character */
if(rtext[i] == 0x1b){
tmp = rtext[i+1];
*(text++) = gsm_7bit_alphabet[0x7f + tmp];
i++;
continue;
}
*(text++) = gsm_septet_lookup(rtext[i]);
}
*text = '\0';
free(rtext);
return i;
}
/* GSM 03.38 6.2.1 Prepare character packing */
static int gsm_septet_encode(uint8_t *result, const char *data)
{
int i, y = 0;
uint8_t ch;
for(i = 0; i < strlen(data); i++){
ch = data[i];
switch(ch){
/* fall-through for extension characters */
case 0x0c:
case 0x5e:
case 0x7b:
case 0x7d:
case 0x5c:
case 0x5b:
case 0x7e:
case 0x5d:
case 0x7c:
result[y++] = 0x1b;
default:
result[y] = gsm_7bit_alphabet[ch];
break;
}
y++;
}
return y;
}
/* GSM 03.38 6.2.1 Character packing */
int gsm_7bit_encode(uint8_t *result, const char *data)
{
int i,y,z = 0;
/* prepare for the worst case, every character expanding to two bytes */
uint8_t *rdata = calloc(strlen(data) * 2, sizeof(uint8_t));
uint8_t cb, nb;
int shift = 0;
y = gsm_septet_encode(rdata, data);
for(i = 0; i < y; i++) {
if(shift == 7 && i + 1 < y){
shift = 0;
continue;
}
cb = (rdata[i] & 0x7f) >> shift;
if(i + 1 < y){
nb = (rdata[i + 1] & 0x7f) << (7 - shift);
cb = cb | nb;
}
result[z++] = cb;
shift++;
}
free(rdata);
return i;
}

17
tests/sms/sms_test.c
View File

@ -1,5 +1,6 @@
/*
* (C) 2008 by Daniel Willmann <daniel@totalueberwachung.de>
* (C) 2010 by Nico Golde <nico@ngolde.de>
* All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
@ -32,7 +33,7 @@ int main(int argc, char** argv)
uint8_t *sms;
uint8_t i;
/* test 7-bit coding/decoding */
/* test 7-bit coding/decoding */
const char *input = "test text";
uint8_t length;
uint8_t coded[256];
@ -43,5 +44,19 @@ int main(int argc, char** argv)
if (strcmp(result, input) != 0) {
printf("7 Bit coding failed... life sucks\n");
printf("Wanted: '%s' got '%s'\n", input, result);
return -1;
}
memset(coded, 0, sizeof(coded));
memset(result, 0, sizeof(coded));
input = strdup("!$ a more#^- complicated test@@?_\%! case");
length = gsm_7bit_encode(coded, input);
gsm_7bit_decode(result, coded, length);
if (strcmp(result, input) != 0) {
printf("7 Bit coding failed... life sucks\n");
printf("Wanted: '%s' got '%s'\n", input, result);
return -2;
}
return 0;
}