fat32.c

#include "fat32.h"
#include "printf.h"
#include "../virtio_disk.h"
#include "string.h"
#include "mbr.h"


struct fat32_bpb fat32_header;
struct fat32_volume fat32_volume;

uint8_t fat32_buf[VIRTIO_BLK_SECTOR_SIZE];
uint8_t fat32_table_buf[VIRTIO_BLK_SECTOR_SIZE];

uint64_t cluster_to_sector(uint64_t cluster) {
    return (cluster - 2) * fat32_volume.sec_per_cluster + fat32_volume.first_data_sec;
}

uint32_t next_cluster(uint64_t cluster) {
    uint64_t fat_offset = cluster * 4;
    uint64_t fat_sector = fat32_volume.first_fat_sec + fat_offset / VIRTIO_BLK_SECTOR_SIZE;
    virtio_blk_read_sector(fat_sector, fat32_table_buf);
    int index_in_sector = fat_offset % (VIRTIO_BLK_SECTOR_SIZE / sizeof(uint32_t));
    return *(uint32_t*)(fat32_table_buf + index_in_sector);
}

void fat32_init(uint64_t lba, uint64_t size) {
    virtio_blk_read_sector(lba, (void*)&fat32_header);
    fat32_volume.first_fat_sec = 0/* to calculate */;
    fat32_volume.sec_per_cluster = 0/* to calculate */;
    fat32_volume.first_data_sec = 0/* to calculate */;
    fat32_volume.fat_sz = 0/* to calculate */;
}

int is_fat32(uint64_t lba) {
    virtio_blk_read_sector(lba, (void*)&fat32_header);
    if (fat32_header.boot_sector_signature != 0xaa55) {
        return 0;
    }
    return 1;
}

int next_slash(const char* path) {  // util function to be used in fat32_open_file
    int i = 0;
    while (path[i] != '\0' && path[i] != '/') {
        i++;
    }
    if (path[i] == '\0') {
        return -1;
    }
    return i;
}

void to_upper_case(char *str) {     // util function to be used in fat32_open_file
    for (int i = 0; str[i] != '\0'; i++) {
        if (str[i] >= 'a' && str[i] <= 'z') {
            str[i] -= 32;
        }
    }
}

struct fat32_file fat32_open_file(const char *path) {
    struct fat32_file file;
    /* todo: open the file according to path */
    return file;
}

int64_t fat32_lseek(struct file* file, int64_t offset, uint64_t whence) {
    if (whence == SEEK_SET) {
        file->cfo = 0/* to calculate */;
    } else if (whence == SEEK_CUR) {