diff options
Diffstat (limited to 'src/gsm_utils.c')
| -rw-r--r-- | src/gsm_utils.c | 99 |
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; } |