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/*
* Invoke gsmstack() with any kind of burst. Automaticly decode and retrieve
* information.
*/
#include "system.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "gsmstack.h"
#include "gsm_constants.h"
#include "interleave.h"
#include "sch.h"
#include "cch.h"
static void out_gsmdecode(char type, int arfcn, int ts, int fn, char *data, int len);
static void
diff_decode(char *dst, char *src, int len)
{
const char *end = src + len;
unsigned char last;
src += 3;
last = 0;
memset(dst, 0, 3);
dst += 3;
while (src < end)
{
*dst = !*src ^ last;
last = *dst;
src++;
dst++;
}
}
/*
* Initialize a new GSMSTACK context.
*/
int
GS_new(GS_CTX *ctx)
{
memset(ctx, 0, sizeof *ctx);
interleave_init(&ctx->interleave_ctx, 456, 114);
ctx->fn = -1;
ctx->bsic = -1;
return 0;
}
/*
* 156 bit
*/
int
GS_process(GS_CTX *ctx, int ts, int type, char *src)
{
int fn;
int bsic;
int ret;
char buf[156];
unsigned char *data;
int len;
if (ts != 0)
return;
diff_decode(buf, src, 156);
if (type == SCH)
{
ret = decode_sch(buf, &fn, &bsic);
if (ret != 0)
return 0;
if ((ctx->bsic > 0) && (bsic != ctx->bsic))
fprintf(stderr, "WARN: BSIC changed.\n");
//DEBUGF("FN %d, BSIC %d\n", fn, bsic);
ctx->fn = fn;
ctx->bsic = bsic;
/* Reset message concatenator */
ctx->burst_count = 0;
return 0;
}
/* If we did not get Frame Number yet then return */
if (ctx->fn < 0)
return 0;
ctx->fn++;
if (type == NORMAL)
{
/* Interested in these frame numbers (cch)
* 2-5, 12-15, 22-25, 23-35, 42-45
* 6-9, 16-19, 26-29, 36-39, 46-49
*/
/* Copy content data into new array */
//DEBUGF("burst count %d\n", ctx->burst_count);
memcpy(ctx->burst + (116 * ctx->burst_count), buf + 3, 58);
memcpy(ctx->burst + (116 * ctx->burst_count) + 58, buf + 3 + 58 + 26, 58);
ctx->burst_count++;
/* Return if not enough bursts for a full gsm message */
if (ctx->burst_count < 4)
return 0;
ctx->burst_count = 0;
data = decode_cch(ctx, ctx->burst, &len);
if (data == NULL)
return -1;
//DEBUGF("OK TS %d, len %d\n", ts, len);
out_gsmdecode(0, 0, ts, ctx->fn - 4, data, len);
#if 0
if (ctx->fn % 51 != 0) && ( (((ctx->fn % 51 + 5) % 10 == 0) || (((ctx->fn % 51) + 1) % 10 ==0) ) )
ready = 1;
#endif
return 0;
}
}
/*
* Output data so that it can be parsed from gsmdeocde.
*/
static void
out_gsmdecode(char type, int arfcn, int ts, int fn, char *data, int len)
{
char *end = data + len;
/* FIXME: speed this up by first printing into an array */
while (data < end)
printf(" %02.2x", (unsigned char)*data++);
printf("\n");
fflush(stdout);
}
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