disk.c

#include <stdio.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <unistd.h>
#include "disk.h"
#include "utils.h"

void display_fsinfo(BootEntry *disk_info) {
    printf("Number of FATs = %d\n", disk_info->BPB_NumFATs);
    printf("Number of bytes per sector = %d\n", disk_info->BPB_BytsPerSec);
    printf("Number of sectors per cluster = %d\n", disk_info->BPB_SecPerClus);
    printf("Number of reserved sectors = %d\n", disk_info->BPB_RsvdSecCnt);
}

unsigned int cluster_to_sector(BootEntry *disk_info, unsigned int cluster) {
    return disk_info->BPB_RsvdSecCnt + disk_info->BPB_NumFATs * disk_info->BPB_FATSz32 + (cluster - 2) * disk_info->BPB_SecPerClus;
}

unsigned int cluster_to_bytes(BootEntry *disk_info, unsigned int cluster) {
    return cluster_to_sector(disk_info, cluster) * disk_info->BPB_BytsPerSec;
}

unsigned int *read_fat(unsigned char *disk, BootEntry *disk_info, unsigned int cluster, int nfat) {
    return (unsigned int *) (disk + (disk_info->BPB_RsvdSecCnt + disk_info->BPB_FATSz32 * (nfat - 1)) * disk_info->BPB_BytsPerSec) + cluster;
}

DirEntry *read_directory(unsigned char *disk, BootEntry *disk_info, unsigned int cluster) {
    return (DirEntry *) (disk + cluster_to_bytes(disk_info, cluster));
}

unsigned char *read_cluster(unsigned char *disk, BootEntry *disk_info, unsigned int cluster) {
    return disk + cluster_to_bytes(disk_info, cluster);
}

unsigned char *map_disk(char *disk_name, int *disk_size, char mode) {
    int fd = open(disk_name, mode == 'r' ? O_RDONLY : O_RDWR);
    if (fd < 0) {
        fprintf(stderr, "Error opening disk\n");
        return NULL;
    }

    *disk_size = get_file_size(fd);
    if (*disk_size < 0)
        return NULL;

    unsigned char *disk = mmap(NULL, *disk_size, mode == 'r' ? PROT_READ : PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (disk == MAP_FAILED) {
        fprintf(stderr, "Error reading disk\n");
        return NULL;
    }

    close(fd);
    return disk;
}

void unmap_disk(unsigned char *disk, int disk_size) {
    munmap(disk, disk_size);
}

void update_disk(unsigned char *disk, BootEntry *disk_info, unsigned int root_cluster, unsigned int cluster_offset, unsigned char data) {
    disk[cluster_to_bytes(disk_info, root_cluster) + cluster_offset] = data;
}

void update_fat(unsigned char *disk, BootEntry *disk_info, unsigned int cluster, unsigned int value) {
    for(int i = 1; i <= disk_info->BPB_NumFATs; i++) {
        *read_fat(disk, disk_info, cluster, i) = value;
    }
}