#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

#define WRITE_CHUNK (64*1024*1024)


void
show_timeval (const struct timeval *tv)
{
    printf("%d.%06d\n", (int)tv->tv_sec, (int)tv->tv_usec);
}

void
elapsed_time (struct timeval *t, const struct timeval *a, const struct timeval *b)
{
    /* insure that a < b */
    if ((a->tv_sec > b->tv_sec) ||
        ((a->tv_sec == b->tv_sec) && (a->tv_usec > b->tv_usec)))
    {
        const struct timeval *tmp;
        tmp = a;
        a = b;
    b = tmp;
    }
    *t = *b;
    t->tv_sec -= a->tv_sec;
    t->tv_usec -= a->tv_usec;
    while (t->tv_usec < 0) {
        t->tv_sec -= 1;
    t->tv_usec += 1000000;
    }
    while (t->tv_usec >= 1000000) {
        t->tv_sec += 1;
    t->tv_usec -= 1000000;
    }
}

void *
writer (void *dummy)
{
    int fd;
    char *data;
    int i;
    struct timeval start;
    struct timeval end;
    struct timeval diff;
    ssize_t write_ret;

    fd = open("test.dat", O_WRONLY | O_CREAT, 0666);
    if (fd == -1) {
        fprintf(stderr, "Error %d opening file; %s\n", errno, strerror(errno));
        exit(1);
    }
    data = (char *)calloc(WRITE_CHUNK, 1);
    if (data == NULL) {
        fprintf(stderr, "Error allocating memory\n");
        exit(1);
    }
    for (i=0; i<16; i++) {
    if (lseek(fd, 0, SEEK_SET) != 0) {
            fprintf(stderr, "Error %d seeking to start of file; %s\n", errno, strerror(errno));
            exit(1);
        }
    gettimeofday(&start, NULL);
        write_ret = write(fd, data, WRITE_CHUNK);
    if (write_ret != WRITE_CHUNK) {
        fprintf(stderr, "write() returned %d\n", write_ret);
        if (write_ret == -1) {
            fprintf(stderr, "Error is %d; %s\n", errno, strerror(errno));
        }
        exit(1);
    }
    gettimeofday(&end, NULL);
        elapsed_time(&diff, &start, &end);
    printf("%d bytes in %d.%03d seconds\n", write_ret, (int)diff.tv_sec, (int)diff.tv_usec / 1000);
    }
    free(data);
    if (remove("test.dat") != 0) {
        fprintf(stderr, "WARNING: could not remove file, error %d; %s\n", errno, strerror(errno));
    }
    return NULL;
}

void *
happy (void *dummy)
{
    int cnt;
    for (cnt = 0; ; cnt++) {
        printf("Not blocked... (%d)\n", cnt);
        usleep(200000);
    }
    return NULL;
}


int
main (int argc, char *argv[])
{
    pthread_t writer_tid;
    pthread_t happy_tid;
    int errnum;

    errnum = pthread_create(&writer_tid, NULL, writer, NULL);
    if (errnum != 0) {
        fprintf(stderr, "pthread_create() failed, error %d\n", errnum);
    return 1;
    }
    errnum = pthread_create(&happy_tid, NULL, happy, NULL);
    if (errnum != 0) {
        fprintf(stderr, "pthread_create() failed, error %d\n", errnum);
    return 1;
    }
    errnum = pthread_join(writer_tid, NULL);
    if (errnum != 0) {
        fprintf(stderr, "pthread_join() failed, error %d\n", errnum);
    return 1;
    }

    return 0;
}