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authorNico Golde <nico@ngolde.de>2010-07-09 17:19:12 +0200
committerHolger Hans Peter Freyther <zecke@selfish.org>2010-07-20 02:48:17 +0800
commit28de05336b01aa72d7f191b33467e6c57be178a4 (patch)
treed9af4b09de02795661993ea65aff3ab57e42f94f /src
parent383134b5ac0b94393cd46e2f00aeb1fd6f1a540f (diff)
* rewrite GSM 7bit default encoding/decoding based on a lookup table as the previous code produced wrong encodings for certain characters.
Diffstat (limited to 'src')
-rw-r--r--src/gsm_utils.c99
1 files changed, 79 insertions, 20 deletions
diff --git a/src/gsm_utils.c b/src/gsm_utils.c
index dc97ceff..fb69377f 100644
--- a/src/gsm_utils.c
+++ b/src/gsm_utils.c
@@ -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;
+ }
+ 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 - l;
+ 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++;
+ }
-/* GSM 03.38 6.2.1 Charachter packing */
+ return y;
+}
+
+/* GSM 03.38 6.2.1 Character packing */
int gsm_7bit_encode(uint8_t *result, const char *data)
{
- int i,j = 0;
- unsigned char ch1, ch2;
+ 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;
- for ( i=0; i<strlen(data); i++ ) {
+ y = gsm_septet_encode(rdata, data);
- ch1 = data[i] & 0x7F;
- ch1 = ch1 >> shift;
- ch2 = data[(i+1)] & 0x7F;
- ch2 = ch2 << (7-shift);
+ for(i = 0; i < y; i++) {
+ if(shift == 7 && i + 1 < y){
+ shift = 0;
+ continue;
+ }
- ch1 = ch1 | ch2;
+ cb = (rdata[i] & 0x7f) >> shift;
+ if(i + 1 < y){
+ nb = (rdata[i + 1] & 0x7f) << (7 - shift);
+ cb = cb | nb;
+ }
- result[j++] = ch1;
+ result[z++] = cb;
shift++;
-
- if ((shift == 7) && (i+1<strlen(data))) {
- shift = 0;
- i++;
- }
}
+ free(rdata);
return i;
}