//talk to DGPS  to get logfiles - WITH TPS
// log events in a logfile
// KM July 2003
// version 1.1
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#define BYTE unsigned char
/*
#define INT16 unsigned short
#define INTS16 short
#define INT32 unsigned int
#define INTS32 int
*/
#define SERIALPORT "/dev/ttyS0"
#define LOGFILE "/home/km/incoming/gps.log"

/*
struct Block {
	BYTE type;
	union {
		INT16 number;
		INTS16 count;
	};
	BYTE data[512];
	INT16 cs;
	BYTE eob;
	} TPSblock;
*/

// GLOBAL variables for simplicity
int serialport; // serial port 
int outfile;	// where we write log files to
FILE *logfd; // log file 
BYTE tps_data[512];
unsigned char crcbuffer[1 + 2 + 512]; // make a brainless copy of the data
char mesg[512]; // somewhere to make logfile strings!
//---------------------- HELPERS-------------------------
BYTE getbyte () 
{
  BYTE byte;
  read (serialport, &byte, 1);
  return byte;
}

// write a byte
BYTE putbyte(BYTE b)
{
        return(write(serialport, &b, 1));
}

// write a string
int putstring(char *s)
{
        int l = strlen(s);
//log(s);
        if ( write(serialport, s, l) != l)
                return(-1);
        else return(0);
}

// print message to log file 
void logfile(char *str)
{
fprintf(logfd, str);
fflush(logfd);
}
// print error message to log file and exit
erexit(char *str)
{
fprintf(logfd, str);
// exit is a bit severe - means we'd have to restart externally
exit(1);
}
//----------- TPS protocol-------------

#define BLOCKTYPE_ORDINAL 0x02
#define BLOCKTYPE_LAST 0x04
#define BLOCKTYPE_ABORT 0x23

// send this after checking block to get next block
void tps_ack()
{
putbyte(0x06);
}
// send this to get first block OR to ask for a resend
void tps_nack()
{
putbyte(0x15);
}

// CRC CHECK
typedef unsigned short Crc16;
enum {
	WIDTH = 16,
	POLY = 0x1021,
	BYTE_BITS = 8,
	TABLE_SIZE = 1 << BYTE_BITS,
	MSB_MASK = 1 << (WIDTH - 1)
	};
static Crc16 table[TABLE_SIZE];

void crc16init()
{
Crc16 i;
for(i = 0; i < TABLE_SIZE; ++i) {
	Crc16 val = i << (WIDTH - BYTE_BITS);
	int j;
	for(j = 0; j < BYTE_BITS; ++j) 
		val = (val << 1) ^ ((val & MSB_MASK) ? POLY : 0);
	table[i] = val;
	}
}

Crc16 crc16(Crc16 crc, void const* src, int cnt)
{
unsigned char const* s = (unsigned char const*)src;
while(cnt--)
crc = (crc << BYTE_BITS) ^ table[(crc >> (WIDTH - BYTE_BITS)) ^ *s++];
return(crc);
}

Crc16 crc = 0;
crc_check(unsigned short checksum)
{
crc = crc16(crc, crcbuffer, 1 + 2 + 512);
if(checksum != crc){
	logfile("CRC error\n");
	}
}

// GET A BLOCK OF DATA FROM GPS
// returns the number of bytes copied into the 512b buffer
int tps_getblock(unsigned short *returned_bytecount)
{
BYTE type, lsb, msb, eob;
int counter;
unsigned short blocknum, checksum, bytecount;

type = getbyte();
crcbuffer[0] = type;
switch(type) {
	case BLOCKTYPE_ORDINAL: 
		lsb = getbyte();
		msb = getbyte();
crcbuffer[1] = lsb; crcbuffer[2] = msb;
		blocknum = (((unsigned short)msb) << 8) | (unsigned short)lsb;
		for(counter=0; counter<512; counter++){
			tps_data[counter] = getbyte();
			crcbuffer[counter + 3] = tps_data[counter];
			}
		lsb = getbyte();
		msb = getbyte();
		checksum = (((unsigned short)msb) << 8) | (unsigned short)lsb;
		// should check it!
		crc_check(checksum);
		eob = getbyte();

		// DEBUG sprintf(mesg,"block number %d\n",blocknum);
		logfile(mesg);

		*returned_bytecount = 512;
		return(type);	
	case BLOCKTYPE_LAST: 
		lsb = getbyte();
		msb = getbyte();
		bytecount = (((unsigned short)msb) << 8) | (unsigned short)lsb;
		for(counter=0; counter<bytecount; counter++)
			tps_data[counter] = getbyte();
		lsb = getbyte();
		msb = getbyte();
		checksum = (((unsigned short)msb) << 8) | (unsigned short)lsb;
		// should check it!
		eob = getbyte();

		// DEBUG sprintf(mesg,"LAST block number size %d \n",(int)bytecount);
		logfile(mesg);

		*returned_bytecount = bytecount;
		return(type);	
	case BLOCKTYPE_ABORT: 
		// should do something
		logfile("got a TPS abort!\n");
		return(type);
	default:
		logfile("got an unknown TPS block type!\n");
		return(-1);
		
	}
}


	
tps_get_log(char *name, char *out_name)
{
	char command[512];
	unsigned short bytecount;
	int blocktype;
	FILE *out;

// open the file we write the logfile to
out = fopen(out_name,"w");
sprintf(command, "get,/log/%s\n",name);
logfile(command);
putstring(command);
tps_nack();
	do {
	blocktype = tps_getblock(&bytecount);
	fwrite(tps_data,1,bytecount, out);
	tps_ack();
	} while( blocktype != BLOCKTYPE_LAST);
fclose(out);
}

//-------------------- INITIALISE-----------------
// open serial port for raw byte transfers
// open log file
// arg is name of serial port to use
initialise()
{
	struct termios term;

	// open log file for appending
	logfd = fopen(LOGFILE, "a");
	if( logfd == NULL) erexit("failed to open log file!");

	// now the serial port
serialport = open (SERIALPORT, O_RDWR | O_NOCTTY );
if (serialport == -1)
      erexit ("can not open serial port!\n");

if( tcgetattr(serialport, &term) == -1)  erexit("getattr failed!");
// set BAUD rate
cfsetospeed(&term, B38400);
cfsetispeed(&term, B38400);
cfmakeraw(&term);
// Set the serial port mode NOW
if( tcsetattr(serialport, TCSANOW, &term) == -1) erexit("setattr failed!");

// initialise the CRC algorithm
crc16init();
logfile("initialised OK\n");
}

//-------------------- MAIN------------------------
main (int argc, char **argv) 
{
if(argc != 3){
	logfile("gps-getlog: args wrong! need: logname dstname\n");
	exit(1);
	}
// set up rs232
initialise();

// request a file
tps_get_log(argv[1],argv[2]);
}