hamnet70/impl/src/layer1/tx.c

#include <liquid/liquid.h>

#include <stdbool.h>
#include <malloc.h>

#include "results.h"
#include "tx.h"

static inline bool resize_buffer(layer1_tx_t *tx, size_t new_size)
{
	void *tmpptr = realloc(tx->samples, new_size * sizeof(*(tx->samples)));
	if(tmpptr) {
		tx->samples = tmpptr;
		tx->samples_allocated = new_size;
		return true;
	} else {
		return false;
	}
}


static inline bool can_append_n_samples(layer1_tx_t *tx, size_t samples)
{
	return (tx->samples_used + samples) <= tx->samples_allocated;
}


static inline size_t get_free_space(layer1_tx_t *tx)
{
	return tx->samples_allocated - tx->samples_used;
}


static inline float complex* get_write_ptr(layer1_tx_t *tx)
{
	return tx->samples + tx->samples_used;
}


result_t layer1_tx_init(layer1_tx_t *tx)
{
	tx->samples = NULL;
	tx->samples_allocated = 0;
	tx->samples_used = 0;

	tx->carrier_frequency_offset = 0.0f;

	transmission_init(&tx->transmission);
	packet_mod_init(&tx->pmod);
	return OK;
}


result_t layer1_tx_shutdown(layer1_tx_t *tx)
{
	if(tx->samples) {
		free(tx->samples);
		tx->samples = NULL;
	}

	tx->samples_allocated = 0;
	tx->samples_used = 0;

	transmission_free(&tx->transmission);
	packet_mod_free(&tx->pmod);

	return OK;
}


result_t layer1_tx_reset(layer1_tx_t *tx)
{
	tx->samples_used = 0;
	return OK;
}


result_t layer1_tx_add_packet_to_burst(layer1_tx_t *tx, const uint8_t *data, size_t length)
{
	if(tx->samples_used == 0) {
		if((tx->samples_allocated == 0)
				&& !resize_buffer(tx, 4096 + transmission_calculate_ramp_up_length(&tx->transmission))) {
			return ERR_NO_MEM;
		}

		// nothing is in the buffer yet, so we must first generate a ramp-up.
		size_t len = get_free_space(tx);
		result_t res = transmission_ramp_up(&tx->transmission, get_write_ptr(tx), &len);

		if(res != OK) {
			fprintf(stderr, "Ramp-up requires %zd samples at offset %zd.\n", len, tx->samples_used);
			return res;
		}

		tx->samples_used += len;
	}

	// encode and modulate the packet
	ERR_CHECK(packet_mod_reset(&tx->pmod));
	ERR_CHECK(packet_mod_set_data(&tx->pmod, data, length));
	ERR_CHECK(packet_mod_encode(&tx->pmod));
	ERR_CHECK(packet_mod_modulate(&tx->pmod));
	ERR_CHECK(packet_mod_add_header(&tx->pmod));
	ERR_CHECK(packet_mod_add_preamble(&tx->pmod));

	// determine number of symbols in the packet
	size_t nsyms;
	packet_mod_get_result_cf(&tx->pmod, NULL, &nsyms);

	// calculate the number of filtered samples
	size_t filtered_size = transmission_calculate_packet_length(&tx->transmission, nsyms);

	// resize the buffer if necessary (and add some reserve)
	if(!can_append_n_samples(tx, filtered_size)) {
		if(!resize_buffer(tx, tx->samples_allocated + 2*filtered_size)) {
			return ERR_NO_MEM;
		}
	}

	// store the packet symbols into a temporary buffer
	float complex msg_mod[nsyms];
	packet_mod_get_result_cf(&tx->pmod, msg_mod, &nsyms);

	// filter the packet and append it to the output buffer
	size_t len = get_free_space(tx);
	result_t res = transmission_filter_packet(&tx->transmission, msg_mod, nsyms, get_write_ptr(tx), &len);

	if(res != OK) {
		fprintf(stderr, "Packet requires %zd samples at offset %zd.\n", len, tx->samples_used);
		return res;
	}

	tx->samples_used += len;

	return OK;
}


result_t layer1_tx_finalize_burst(layer1_tx_t *tx)
{
	// calculate the number of samples for the ramp down
	size_t len = transmission_calculate_ramp_down_length(&tx->transmission);

	// resize the buffer if necessary
	if(!can_append_n_samples(tx, len)) {
		if(!resize_buffer(tx, tx->samples_allocated + len)) {
			return ERR_NO_MEM;
		}
	}

	// generate the ramp-down
	len = get_free_space(tx);
	result_t res = transmission_ramp_down(&tx->transmission, get_write_ptr(tx), &len);

	if(res != OK) {
		fprintf(stderr, "Ramp-down requires %zd samples at offset %zd.\n", len, tx->samples_used);
		return res;
	}

	tx->samples_used += len;

	// mix the signal up to the carrier offset frequency

	// allocate a temporary buffer
	float complex *tmp = malloc(sizeof(float complex) * tx->samples_used);
	if(!tmp) {
		fprintf(stderr, "Could not allocate buffer for TX frequency correction.\n", len, tx->samples_used);
		return ERR_NO_MEM;
	}

	nco_crcf carrier_nco = nco_crcf_create(LIQUID_NCO);
	nco_crcf_set_frequency(carrier_nco, tx->carrier_frequency_offset);

	nco_crcf_mix_block_up(carrier_nco, tx->samples, tmp, tx->samples_used);

	nco_crcf_destroy(carrier_nco);

	// swap the buffers
	free(tx->samples);
	tx->samples = tmp;
	tx->samples_allocated = tx->samples_used;

	return OK;
}


size_t layer1_tx_get_sample_count(const layer1_tx_t *tx)
{
	return tx->samples_used;
}


const float complex* layer1_tx_get_sample_data(const layer1_tx_t *tx)
{
	return tx->samples;
}


void layer1_tx_set_carrier_frequency_offset(layer1_tx_t *tx, float freq)
{
	tx->carrier_frequency_offset = freq;
}