disk.c

/*
Do not modify this file.
Make all of your changes to main.c instead.
*/

#include "disk.h"

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>

extern ssize_t pread(int __fd, void *__buf, size_t __nbytes, __off_t __offset);
extern ssize_t pwrite(int __fd, const void *__buf, size_t __nbytes, __off_t __offset);

struct disk
{
    int fd;
    int block_size;
    int nblocks;
};

struct disk *disk_open(const char *diskname, int nblocks)
{
    struct disk *d;

    d = malloc(sizeof(*d));
    if (!d)
        return 0;

    d->fd = open(diskname, O_CREAT | O_RDWR, 0777);
    if (d->fd < 0)
    {
        free(d);
        return 0;
    }

    d->block_size = BLOCK_SIZE;
    d->nblocks = nblocks;

    if (ftruncate(d->fd, d->nblocks * d->block_size) < 0)
    {
        close(d->fd);
        free(d);
        return 0;
    }

    return d;
}

void disk_write(struct disk *d, int block, const char *data)
{
    if (block < 0 || block >= d->nblocks)
    {
        fprintf(stderr, "disk_write: invalid block #%d\n", block);
        abort();
    }

    int actual = pwrite(d->fd, data, d->block_size, block * d->block_size);
    if (actual != d->block_size)
    {
        fprintf(stderr, "disk_write: failed to write block #%d: %s\n", block, strerror(errno));
        abort();
    }
}

void disk_read(struct disk *d, int block, char *data)
{
    if (block < 0 || block >= d->nblocks)
    {
        fprintf(stderr, "disk_read: invalid block #%d\n", block);
        abort();
    }

    int actual = pread(d->fd, data, d->block_size, block * d->block_size);
    if (actual != d->block_size)
    {
        fprintf(stderr, "disk_read: failed to read block #%d: %s\n", block, strerror(errno));
        abort();
    }
}

int disk_nblocks(struct disk *d)
{
    return d->nblocks;
}

void disk_close(struct disk *d)
{
    close(d->fd);
    free(d);
}