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#include "stx_deframer.h"
#include <cstdint>
#include <cstring>
namespace orbcomm
{
STXDeframer::STXDeframer(int cadu_size) : FRM_SIZE(cadu_size)
{
frame_buffer = new uint8_t[FRM_SIZE];
}
STXDeframer::~STXDeframer()
{
delete[] frame_buffer;
}
int STXDeframer::getState()
{
return d_state;
}
int STXDeframer::work(uint8_t *input, int size, uint8_t *output)
{
int frame_count = 0;
for (int ibit = 0; ibit < size; ibit++) // We work bit-per-bit
{
shifter = (shifter << 1 | input[ibit]) & 0xFFFFFF;
if (in_frame)
{
write_bit(input[ibit] ^ bit_inversion);
if (bit_of_frame == FRM_SIZE) // Write frame out
{
memcpy(&output[frame_count * (FRM_SIZE / 8)], frame_buffer, FRM_SIZE / 8);
frame_count++;
}
else if (bit_of_frame == FRM_SIZE + FRM_ASM_SIZE - 1) // Skip to the next ASM
{
in_frame = false;
}
continue;
}
if (d_state == STATE_NOSYNC)
{
if (shifter == FRM_ASM)
{
bit_inversion = false;
reset_frame();
in_frame = true;
d_state = STATE_SYNCING;
d_good_asm = d_invalid_asm = 0;
}
else if (shifter == FRM_ASM_INV)
{
bit_inversion = true;
reset_frame();
in_frame = true;
d_state = STATE_SYNCING;
d_good_asm = d_invalid_asm = 0;
}
}
else if (d_state == STATE_SYNCING)
{
if (compare_32(shifter, bit_inversion ? FRM_ASM_INV : FRM_ASM) < d_state)
{
reset_frame();
in_frame = true;
d_invalid_asm = 0;
d_good_asm++;
if (d_good_asm > 10)
d_state = STATE_SYNCED;
}
else
{
d_invalid_asm++;
d_good_asm = 0;
if (d_invalid_asm > 2)
{
d_state = STATE_NOSYNC;
}
}
}
else if (d_state == STATE_SYNCED)
{
if (compare_32(shifter, bit_inversion ? FRM_ASM_INV : FRM_ASM) < d_state)
{
reset_frame();
in_frame = true;
}
else
{
d_good_asm = d_invalid_asm = 0;
d_state = STATE_NOSYNC; // Reset to hard NOSYNC, so we correct for a possible new inversion state
}
}
}
return frame_count;
}
void STXDeframer::write_bit(uint8_t b)
{
frame_buffer[bit_of_frame / 8] = frame_buffer[bit_of_frame / 8] << 1 | b;
bit_of_frame++;
}
void STXDeframer::reset_frame()
{
memset(frame_buffer, 0, FRM_SIZE / 8);
bit_of_frame = 0;
for (int i = FRM_ASM_SIZE - 1; i >= 0; i--)
write_bit((FRM_ASM >> i) & 1);
}
}
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