mirror of https://github.com/ArduPilot/ardupilot
114 lines
2.8 KiB
C++
114 lines
2.8 KiB
C++
/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "NMEA.h"
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extern const AP_HAL::HAL &hal;
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/*
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formatted print of NMEA message to an allocated string, with
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checksum appended
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*/
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char *nmea_vaprintf(const char *fmt, va_list ap)
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{
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va_list ap_copy;
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// we print once to nullptr to get the length
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va_copy(ap_copy, ap);
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int len = hal.util->vsnprintf(nullptr, 0, fmt, ap_copy);
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va_end(ap_copy);
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if (len <= 0) {
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// can't print this format
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return nullptr;
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}
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// now allocate the right length, including trailer
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char *s = (char *)malloc(len+6);
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if (s == nullptr) {
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// allocation failed
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return nullptr;
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}
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if (hal.util->vsnprintf(s, len+5, fmt, ap) < len) {
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free(s);
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// inconsistent formatting
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return nullptr;
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}
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// calculate the checksum
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uint8_t cs = 0;
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const uint8_t *b = (const uint8_t *)s+1;
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while (*b) {
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cs ^= *b++;
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}
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hal.util->snprintf(s+len, 6, "*%02X\r\n", (unsigned)cs);
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return s;
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}
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/*
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formatted print of NMEA message to the port, with checksum appended
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*/
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bool nmea_printf(AP_HAL::UARTDriver *uart, const char *fmt, ...)
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{
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va_list ap;
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va_start(ap, fmt);
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char *s = nmea_vaprintf(fmt, ap);
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va_end(ap);
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if (s == nullptr) {
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return false;
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}
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size_t len = strlen(s);
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if (uart->txspace() < len) {
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free(s);
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return false;
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}
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uart->write((const uint8_t*)s, len);
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free(s);
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return true;
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}
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/*
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formatted print of NMEA message to a buffer, with checksum appended.
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Returns the length of the string filled into buf. If the NMEA string does not fit in the buffer, returns 0
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*/
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uint16_t nmea_printf_buffer(char* buf, const uint16_t buf_max_len, const char *fmt, ...)
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{
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va_list ap;
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va_start(ap, fmt);
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char *s = nmea_vaprintf(fmt, ap);
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va_end(ap);
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if (s == nullptr) {
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return 0;
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}
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size_t len = strlen(s);
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if (len > buf_max_len) {
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// our string is larger than the buffer we've supplied.
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// Instead of populating the buffer with a partial message, just quietly fail and do nothing
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len = 0;
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} else {
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strncpy(buf, s, buf_max_len);
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}
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free(s);
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return len;
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}
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