#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/xattr.h>
#include <sys/time.h>
#include <errno.h>
#include <string.h>

#define PVFS_IMMUTABLE_XATTR_KEY "user.pvfs2.meta_hint"
#define PVFS_IMMUTABLE_XATTR_VALUE "+immutable"

int do_read(int fd, void *buff, int size);

int main(int argc, char *argv[])
{
    int size, fd, i, ret;
    char *buff;

    if(argc < 3)
    {
        fprintf(stderr, "usage: %s <filename> <size in MB>\n", argv[0]);
        exit(1);
    }

    size = atoi(argv[2]) * 1024 * 1024;

    fd = open(argv[1], O_RDWR|O_CREAT, 0644);
    if(fd < 0)
    {
        fprintf(stderr, "Failed opening file: %s: %s\n",
                argv[1], strerror(errno));
        exit(1);
    }

    buff = malloc(size);
    if(!buff)
    {
        fprintf(stderr, "Failed allocating %dMB for buffer\n", argv[2]);
        close(fd);
        exit(1);
    }

    for(i = 0; i < atoi(argv[2]); ++i)
    {
        memset(buff+(i*1024*1024), i, 1024*1024);
    }

    ret = write(fd, buff, size);
    if(ret < 0)
    {
        fprintf(stderr, "Failed writing %dMB to file: %s\n",
                atoi(argv[2]), strerror(errno));
        goto error;
    }

    printf("BEFORE IMMUTABLE: ");
    ret = do_read(fd, buff, size);
    if(ret != 0)
    {
        goto error;
    }

    /* set the extended attribute to make the file immutable */
    ret = fsetxattr(fd,
                    PVFS_IMMUTABLE_XATTR_KEY,
                    PVFS_IMMUTABLE_XATTR_VALUE,
                    sizeof(PVFS_IMMUTABLE_XATTR_VALUE),
                    XATTR_CREATE);
    if(ret != 0)
    {
        fprintf(stderr, "Failed setting file to immutable: %s\n",
                strerror(errno));
        goto error;
    }

    printf("AFTER IMMUTABLE: ");
    ret = do_read(fd, buff, size);
    if(ret != 0)
    {
        goto error;
    }

    printf("AFTER IMMUTABLE 2x: ");
    ret = do_read(fd, buff, size);
    if(ret != 0)
    {
        goto error;
    }

    close(fd);

    fd = open(argv[1], O_RDWR, 0644);
    if(fd < 0)
    {
        fprintf(stderr, "Failed opening file: %s: %s\n",
                argv[1], strerror(errno));
        free(buff);
        exit(1);
    }

    printf("AFTER CLOSE/OPEN: ");
    ret = do_read(fd, buff, size);
    if(ret != 0)
    {
        goto error;
    }

    close(fd);

    return 0;

error:
    close(fd);
    free(buff);
    exit(1);
}

int do_read(int fd, void *buff, int size)
{
    int ret;
    struct timeval start, end;
    double bw;

    gettimeofday(&start, NULL);
    ret = pread(fd, buff, size, 0);
    if(ret < 0)
    {
        fprintf(stderr, "Failed reading the file: %s\n", strerror(errno));
        return ret;
    }
    if(ret < size)
    {
        fprintf(stderr, "Short read.  Only able to read: %d bytes\n", ret);
        return ret;
    }
    gettimeofday(&end, NULL);

    bw = (size * 1e-6) / (end.tv_sec + end.tv_usec * 1e-6 - 
                          start.tv_sec - start.tv_usec * 1e-6);

    printf("%f MB/s\n", bw);

    return 0;
}


/*
 * Local variables:
 *  c-indent-level: 4
 *  c-basic-offset: 4
 * End:
 *
 * vim: ts=8 sts=4 sw=4 expandtab
 */