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#include "hybbx/ax25.h"
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
static void address_upper(char *call)
{
size_t i;
for (i = 0; call[i] != '\0'; i++) {
call[i] = (char)toupper((unsigned char)call[i]);
}
}
hybbx_result_t hybbx_ax25_address_parse(const char *text,
hybbx_ax25_address_t *out)
{
const char *dash;
size_t call_len;
char *end = NULL;
unsigned long ssid;
if (text == NULL || out == NULL) {
return HYBBX_ERR_INVALID;
}
memset(out, 0, sizeof(*out));
dash = strchr(text, '-');
if (dash != NULL) {
call_len = (size_t)(dash - text);
ssid = strtoul(dash + 1, &end, 10);
if (end == dash + 1 || ssid > HYBBX_AX25_SSID_MAX) {
return HYBBX_ERR_INVALID;
}
out->ssid = (unsigned)ssid;
} else {
call_len = strlen(text);
}
if (call_len == 0 || call_len > HYBBX_AX25_CALL_MAX) {
return HYBBX_ERR_INVALID;
}
memcpy(out->call, text, call_len);
out->call[call_len] = '\0';
address_upper(out->call);
return HYBBX_OK;
}
void hybbx_ax25_encode_address(uint8_t *out, const hybbx_ax25_address_t *addr,
int last)
{
size_t i;
char padded[HYBBX_AX25_CALL_MAX];
memset(padded, ' ', sizeof(padded));
for (i = 0; i < HYBBX_AX25_CALL_MAX && addr->call[i] != '\0'; i++) {
padded[i] = addr->call[i];
}
for (i = 0; i < HYBBX_AX25_CALL_MAX; i++) {
out[i] = (uint8_t)((unsigned char)padded[i] << 1);
}
out[6] = (uint8_t)(((addr->ssid & 0x0Fu) << 1) | 0x60u);
if (last) {
out[6] |= 0x01u;
}
}
uint16_t hybbx_ax25_crc(const uint8_t *data, size_t len)
{
uint16_t crc = 0xFFFFu;
size_t i;
int bit;
for (i = 0; i < len; i++) {
crc ^= (uint16_t)data[i] << 8;
for (bit = 0; bit < 8; bit++) {
if (crc & 0x8000u) {
crc = (uint16_t)((crc << 1) ^ 0x1021u);
} else {
crc = (uint16_t)(crc << 1);
}
}
}
return crc;
}
static size_t append_addresses(const hybbx_ax25_path_t *path,
uint8_t *out, size_t out_cap)
{
size_t pos = 0;
unsigned i;
if (out_cap < (size_t)(2 + path->digi_count) * HYBBX_AX25_ADDR_ENCODED) {
return 0;
}
hybbx_ax25_encode_address(out + pos, &path->dest, 0);
pos += HYBBX_AX25_ADDR_ENCODED;
for (i = 0; i < path->digi_count; i++) {
hybbx_ax25_encode_address(out + pos, &path->digi[i], 0);
pos += HYBBX_AX25_ADDR_ENCODED;
}
hybbx_ax25_encode_address(out + pos, &path->source, 1);
pos += HYBBX_AX25_ADDR_ENCODED;
return pos;
}
size_t hybbx_ax25_build_ui(const hybbx_ax25_path_t *path,
const uint8_t *payload, size_t payload_len,
uint8_t *out, size_t out_cap)
{
size_t pos;
uint16_t crc;
if (path == NULL || out == NULL ||
(payload_len > 0 && payload == NULL)) {
return 0;
}
if (payload_len + 32 > out_cap || payload_len > HYBBX_AX25_FRAME_MAX) {
return 0;
}
pos = append_addresses(path, out, out_cap);
if (pos + 4 + payload_len > out_cap) {
return 0;
}
out[pos++] = HYBBX_AX25_CTRL_UI;
out[pos++] = HYBBX_AX25_PID_NOL3;
if (payload_len > 0) {
memcpy(out + pos, payload, payload_len);
pos += payload_len;
}
crc = hybbx_ax25_crc(out, pos);
out[pos++] = (uint8_t)(crc & 0xFFu);
out[pos++] = (uint8_t)((crc >> 8) & 0xFFu);
return pos;
}
static void decode_address(const uint8_t *in, hybbx_ax25_address_t *out)
{
size_t i;
for (i = 0; i < HYBBX_AX25_CALL_MAX; i++) {
char ch = (char)((in[i] >> 1) & 0x7Fu);
out->call[i] = ch == ' ' ? '\0' : ch;
}
out->call[HYBBX_AX25_CALL_MAX] = '\0';
for (i = HYBBX_AX25_CALL_MAX; i > 0; i--) {
if (out->call[i - 1] != '\0') {
break;
}
}
out->call[i] = '\0';
out->ssid = (unsigned)((in[6] >> 1) & 0x0Fu);
}
size_t hybbx_ax25_parse_ui(const uint8_t *frame, size_t frame_len,
hybbx_ax25_path_t *path,
uint8_t *payload, size_t payload_cap)
{
size_t pos = 0;
unsigned digi = 0;
uint16_t crc_rx;
uint16_t crc_calc;
if (frame == NULL || frame_len < 16) {
return 0;
}
if (path != NULL) {
memset(path, 0, sizeof(*path));
}
while (pos + HYBBX_AX25_ADDR_ENCODED <= frame_len) {
int last = frame[pos + 6] & 0x01;
hybbx_ax25_address_t tmp;
decode_address(frame + pos, &tmp);
if (path != NULL) {
if (digi == 0) {
path->dest = tmp;
} else if (!last) {
if (digi - 1 < HYBBX_AX25_MAX_DIGI) {
path->digi[digi - 1] = tmp;
path->digi_count = digi;
}
} else {
path->source = tmp;
}
}
pos += HYBBX_AX25_ADDR_ENCODED;
digi++;
if (last) {
break;
}
if (digi > HYBBX_AX25_MAX_DIGI + 1) {
return 0;
}
}
if (pos + 4 > frame_len) {
return 0;
}
if (frame[pos] != HYBBX_AX25_CTRL_UI) {
return 0;
}
pos += 2; /* control + PID */
if (frame_len < pos + 2) {
return 0;
}
crc_rx = (uint16_t)frame[frame_len - 2] |
((uint16_t)frame[frame_len - 1] << 8);
crc_calc = hybbx_ax25_crc(frame, frame_len - 2);
if (crc_rx != crc_calc) {
return 0;
}
{
size_t payload_len = frame_len - pos - 2;
if (payload_len > payload_cap) {
return 0;
}
if (payload_len > 0 && payload != NULL) {
memcpy(payload, frame + pos, payload_len);
}
return payload_len;
}
}
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