// Calculate the size of data in an IR-package.
// return : size or zero.
int uncompressed_detect_ir_size(unsigned char * first_byte, int second_byte_add)
{
int ret = 10;
int d = GET_BIT_0(first_byte);
if (d) ret += 5 + 2;
if (first_byte[second_byte_add + 2] != 0x40) return 0;
return ret;
}
/**
* @brief Get the bit in the given byte at the given position
*
* @param byte The byte to analyse
* @param pos The position between 0 and 7
* @return The requested bit
*/
static uint8_t rohc_get_bit(const unsigned char byte, const size_t pos)
{
uint8_t bit;
switch(pos)
{
case 0:
bit = GET_REAL(GET_BIT_0(&byte));
break;
case 1:
bit = GET_REAL(GET_BIT_1(&byte));
break;
case 2:
bit = GET_REAL(GET_BIT_2(&byte));
break;
case 3:
bit = GET_REAL(GET_BIT_3(&byte));
break;
case 4:
bit = GET_REAL(GET_BIT_4(&byte));
break;
case 5:
bit = GET_REAL(GET_BIT_5(&byte));
break;
case 6:
bit = GET_REAL(GET_BIT_6(&byte));
break;
case 7:
bit = GET_REAL(GET_BIT_7(&byte));
break;
default:
/* there is no such bit in a byte */
assert(0); /* should not happen */
bit = 0;
break;
}
return bit;
}
//----------------------------------------------------------------------------------------------------------------------------------
// Main function for decompressing a ROHC-packet.
// Param state: pointer to decompressor
// Param ibuf: pointer to incoming packet
// Param isize: size of incoming packet
// Param obuf: pointer to output buffer
// Param osize: size of output buffer
// Param ddata: struct that holds important information to pass between several functions
// Return: size of decompressed packet
//----------------------------------------------------------------------------------------------------------------------------------
int d_decode_header(struct sd_rohc * state, unsigned char * ibuf, int isize, unsigned char * obuf, int osize, struct sd_decode_data * ddata)
{
int largecid=0, size, irdynvar=0, casenew=0;
struct s_profile * profile;
unsigned char * walk = ibuf;
if(isize < 2)
return(ROHC_ERROR_NO_CONTEXT);
ddata->cid = d_decode_feedback_first(state, &walk, isize);
if(ddata->cid == ROHC_FEEDBACK_ONLY || ddata->cid == ROHC_ERROR_NO_CONTEXT)
return(ddata->cid);
if(ddata->cid > 0 && state->medium->cid_type == ROHC_SMALL_CID)
ddata->addcidUsed=1;
if(!ddata->addcidUsed && state->medium->cid_type == ROHC_LARGE_CID) { // check if large cids are used
largecid = d_sdvalue_size(walk+1);
if(largecid >0 && largecid < 3) {
ddata->cid = d_sdvalue_decode(walk+1);
ddata->largecidUsed=1;
} else
return(ROHC_ERROR_NO_CONTEXT);
}
if(d_is_ir(walk)) {
profile = find_profile(walk[largecid+1]);
if(!rohc_ir_packet_crc_ok(walk, largecid, ddata->addcidUsed, profile))
return(ROHC_ERROR_CRC);
if(ddata->cid >= state->context_array_size)
context_array_increase(state, ddata->cid);
if(state->context[ddata->cid] && state->context[ddata->cid]->profile == profile) {
ddata->active = state->context[ddata->cid];
state->context[ddata->cid] = NULL;
} else {
casenew=1;
ddata->active = context_create(state, ddata->cid, profile);
if(!ddata->active)
return(ROHC_ERROR_NO_CONTEXT);
}
ddata->active->num_recv_ir ++;
size = ddata->active->profile->decode_ir(state, ddata->active, walk+largecid+3, (isize-(walk-ibuf))-3-largecid, GET_BIT_0(walk), obuf);
if(size>0) {
context_free(state->context[ddata->cid]);
state->context[ddata->cid] = ddata->active;
return(size);
}
if(casenew)
context_free(ddata->active);
else
state->context[ddata->cid] = ddata->active;
return(size);
} else {
ddata->active = find_context(state, ddata->cid); // find context
if(ddata->active && ddata->active->profile) { // context is valid
ddata->active->latest_used = get_milliseconds();
if(d_is_irdyn(walk)) {
ddata->active->num_recv_ir_dyn ++;
profile = find_profile(walk[largecid+1]);
if(profile != ddata->active->profile) { // if IR-DYN changes profile, make comp. transit to NO_CONTEXT-state
state->curval = state->maxval;
rohc_debugf(2,"IR-DYN changed profile, sending S-NACK.\n");
return(ROHC_ERROR_NO_CONTEXT);
}
if(!rohc_ir_dyn_packet_crc_ok(walk, largecid, ddata->addcidUsed, profile, ddata->active))
return(ROHC_ERROR_CRC);
irdynvar += 2;
}
return(ddata->active->profile->decode(state, ddata->active, walk, (isize-(walk-ibuf)), (ddata->largecidUsed ? (1+largecid+irdynvar) : 1+irdynvar), obuf));
} else
return(ROHC_ERROR_NO_CONTEXT);
}
return(ROHC_ERROR_NO_CONTEXT);
}