/*
	file-counter.c -- ファイルに値を保存するカウンタ
	~yas/syspro/file/file-counter.c
*/

#include <stdio.h>	/* stderr, fopen(), fread(), frwite(), fclose() */
#include <stdlib.h>	/* exit(), strtol() */
#include <string.h>	/* strcmp() */

int counter_load();
void counter_save(int counter);

#define DATA_FILENAME "file-counter-value.data"
char *comname = "";

void usage()
{
	printf("Usage$ %s {init,get,up,set newvalue} {args}\n", comname);
	printf("Data file: %s\n", DATA_FILENAME);
	exit( 1 );
}

int main( int argc, char *argv[] )
{
	char *cmd;
	int counter, newvalue;
	comname = argv[0];
	if( argc <= 1 )
		usage();
	cmd = argv[1];
	if( strcmp(cmd,"init") == 0 )
	{
		counter = 0;
	}
	else if( strcmp(cmd,"get") == 0 )
	{
		counter = counter_load();
	}
	else if( strcmp(cmd,"up") == 0 )
	{
		counter = counter_load();
		counter ++;
	}
	else if( strcmp(cmd,"set") == 0 )
	{
		if( argc != 3 )
			usage();
		newvalue = strtol(argv[2], 0, 10);
		counter = newvalue;
	}
	else {
		usage();
	}
	printf("%d\n", counter);
	if( strcmp(cmd,"get") != 0 )
		counter_save(counter);
	return 0;
}

void counter_save(int counter)
{
	FILE *f;
	f = fopen( DATA_FILENAME, "w" );
	if( f == NULL )
	{
		perror( DATA_FILENAME );
		exit( 2 );
	}
	if( fwrite( &counter, sizeof(counter), 1, f) != 1 )
	{
		perror("fwrite");
		fclose( f );
		exit( 2 );
	}
	fclose( f );
}

int counter_load()
{
	FILE *f;
	int counter;
	f = fopen( DATA_FILENAME, "r" );
	if( f == NULL )
	{
		perror( DATA_FILENAME );
		exit( 2 );
	}
	if( fread( &counter, sizeof(counter), 1, f) != 1 )
	{
		perror("fread");
		fclose( f );
		exit( 2 );
	}
	fclose( f );
	return counter;
}