[PATCH] * rewrite GSM 7bit default encoding/decoding based on a lookup table as the previous code produced wrong encodings for certain characters.
--- include/osmocore/gsm_utils.h | 28 ++++++++++++ src/gsm_utils.c | 99 +++++++++++++++++++++++++++++++++-------- tests/sms/sms_test.c | 17 +++++++- 3 files changed, 123 insertions(+), 21 deletions(-)
diff --git a/include/osmocore/gsm_utils.h b/include/osmocore/gsm_utils.h index 7dc2388..64f9edc 100644 --- a/include/osmocore/gsm_utils.h +++ b/include/osmocore/gsm_utils.h @@ -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);
diff --git a/src/gsm_utils.c b/src/gsm_utils.c index dc97cef..fb69377 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; }
diff --git a/tests/sms/sms_test.c b/tests/sms/sms_test.c index f5183d5..4daf003 100644 --- a/tests/sms/sms_test.c +++ b/tests/sms/sms_test.c @@ -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; }
-
Nico Golde