#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <time.h>
#include <sys/time.h>

#define MAXREAD 1024*1024 // We don't read more than 1MB in one call

struct timeval t_start, t_end;
void starttime() {
    gettimeofday(&t_start, NULL);
}
void gettime_r(char* desc, int repeat) {
    gettimeofday(&t_end, NULL);         
    long int timedif = (t_end.tv_sec*1e6 + t_end.tv_usec) -
        (t_start.tv_sec*1e6 + t_start.tv_usec);
    printf("%s time: %.3f, average: %.4f\n", desc, (double)timedif/1e6f, (double)timedif/1e6f/(double)repeat);
}
void gettime(char* desc) { gettime_r(desc, 1); }

int main(int argc, char **argv) {
	int64_t filesize = 4096;
	int count = 10;
	float loop = 1.0f;
	int rvalue;
	int debug = 0;
	unsigned char *data = (unsigned char*)malloc(MAXREAD);
	while ((rvalue = getopt(argc, argv, "h--s:n:l:d")) != -1) 
		switch (rvalue) {
			case 'h':
				printf("Usage: %s [-h] [-s filesize] [-n filecount] [-l loopcount (float)]\n",
						argv[0]);
				exit(0);
			case 's':
				sscanf(optarg, "%ld", &filesize);
				if (filesize < 0 || filesize > 1e12) { // 0 .. 1 terabyte
					fprintf(stderr, "Filesize of %ld bytes is out of bounds, resetting to 4096\n", filesize);
					filesize = 4096;
				}
				break;
			case 'n':
				sscanf(optarg, "%d", &count);
				if (count < 0 || count > 1e9) { // 0 .. 1 billion
					fprintf(stderr, "Count out of bounds, resetting to 10\n", count);
					count = 10;
				}
				break;
			case 'l':
				sscanf(optarg, "%f", &loop);
				if (loop < 0.0f || loop > (float)1e6) { // 0 .. 1 million
					fprintf(stderr, "Loop out of bounds, resetting to 1.0\n", count);
					loop = 1.0f;
				}
				break;
			case 'd':
				debug = 1;
				break;
		}

	printf("Creating %d files of size %Ld B", //, total data %.2f MB\n",
		count, filesize); //, (double)(filesize*count)/(1024.0*1024.0));
	printf(", total data %.2f MB\n", (double)(filesize*count)/(1024.0*1024.0));


	char filename[1024];
	for (int i = 0; i < MAXREAD && i < filesize; ++i)
		data[i] = i%256;
	for (int i = 0; i < count; ++i) {
		sprintf(filename, "rand%09d", i);
		if (debug) printf("Creating file %s\n", filename);
		FILE *f = fopen(filename, "w");
		// Full 1MB blocks
		int64_t left = filesize;
		while (left > MAXREAD) {
			if (debug) printf("\twriting %d bytes\n", MAXREAD);
			fwrite(data, sizeof(char), MAXREAD, f);
			left -= MAXREAD;
		}
		if (left) {
			if (debug) printf("\twriting %d bytes\n", left);
			fwrite(data, sizeof(char), left, f);
		}
		left = 0;
		fclose(f);
	}

	printf("Reading\n");
	srand(time(0));
	starttime();
	for (double i = 0.0; i < (double)count*loop; ++i) {
		int index = rand()%count;
		sprintf(filename, "rand%09d", index);
		if (debug)
			printf("Loop %d/%d: opening file %s\n", 
				(int)i, (int)((double)count*loop), filename);
		FILE *f = fopen(filename, "r");
		
		int64_t left = filesize;
		while (left > MAXREAD) {
			if (debug) printf("\treading %d bytes\n", MAXREAD);
			fread(data, sizeof(char), MAXREAD, f);
			left -= MAXREAD;
		}
		if (left) {
			if (debug) printf("\treading %d bytes\n", left);
			fread(data, sizeof(char), left, f);
		}
		left = 0;
		fclose(f);
	}	
	gettime("File read");

	printf("Removing\n");
	for (int i = 0; i < count; ++i) {
		sprintf(filename, "rand%09d", i);
		remove(filename);
	}
}