杭电操作系统实验5-简单文件系统的实现

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <sys/stat.h>

//要正常运行应该把所有出现路径的地方修改为自己的当前文件目录
#define SHOWSIZE 15
#define BLOCKSIZE 1024
#define SIZE 1024000
#define END 65535 //2^16 -> FAT16
#define FREE 0
#define ROOTBLOCKNUM 2
#define MAXOPENFILE 10
#define DISKFSADD "/home/oz/FileSys"
#define MAXFCBNUM (int)1024/sizeof(fcb)
#define CURDIR_DES (DE*)((((DE*)(openfilelist[curdir].DE_open+basis))->file_fcb).first * BLOCKSIZE+my_v_disk)

typedef struct FCB{
    char filename[20];
    char exname[3];
    unsigned char attribute; //0 dir 1 data
    unsigned short time;
    unsigned short date;
    unsigned short first; //starting disk-block
    unsigned long length;
    char free; //0 empty 1 allocated
}fcb;

typedef struct DE{
    struct DE* p;
    int valid;
    fcb file_fcb;
    char dir[80];
    unsigned short last_modify_time;
    long next; //point to sibling directories
    long child;//point to child directories
    long parent;
}DE;

unsigned char* basis;

typedef struct FAT{                // [present-block] : next-block
    unsigned short id[SIZE/BLOCKSIZE];
}fat;

fcb file_fcb;

typedef struct USEROPEN{
    fcb open_file_fcb;
    long DE_open;
    char dir[80];    //file address
    int count;    //
    char fcbstate; // fcb changed? if so, write back to update
    char topenfile; //notify if this item has been taken
}useropen;

typedef struct BLOCK0{
    char information[200];
    unsigned short root;
    unsigned char* startblock;
}block0;

DE CurDirDEarray[SHOWSIZE];
char currentdir[80];
char dir_new[80];
unsigned char *data_start_p;
unsigned char *my_v_disk;
useropen openfilelist[MAXOPENFILE];
int curdir = -1;
//from textbook

unsigned char *guideBlock, *dataBlock;
DE* rootBlock; //  *** All directories are DE pointer
int *fat1, *fat2;

void fcbcpy(fcb* dst, fcb* src){
    strcpy(dst->filename, src->filename);
    strcpy(dst->exname, src->exname);
    dst->attribute = src->attribute;
    dst->time = src->time;
    dst->date = src->date;
     dst->first = src->first;
    dst->length = src->length;
     dst->free = src->free;
}

DE rootDE = {.file_fcb =  { .attribute = 0, .first = 5, .length = 0, .free = 1}, .valid = 1, };



void showCURDIR_DES(DE* CurDirDEarray){
    for (int i =0; i<SHOWSIZE; i++) {
        CurDirDEarray[i] = *(CURDIR_DES+i);
        CurDirDEarray[i].p = CURDIR_DES+i;
    }
}
//全局变量一级连接局部变量可以保存，二级链接的会被回收
void my_format(void);
//
void startsys(void){
    my_v_disk = (unsigned char*)malloc(sizeof(char) * SIZE);FILE* fs_on_disk; //saved_fs
    basis = my_v_disk;
    guideBlock = my_v_disk;
    fat1 = (int*)my_v_disk + sizeof(char)*BLOCKSIZE*1;
    fat2 = (int*)my_v_disk + sizeof(char)*BLOCKSIZE*3;
    rootBlock = (DE*)(my_v_disk + sizeof(char)*BLOCKSIZE*5);
    dataBlock = (unsigned char*)(my_v_disk + sizeof(char)*BLOCKSIZE*7);
    rootDE.next = (unsigned char*)&rootDE-basis;

    if( (fs_on_disk = fopen("/home/oz/FileSys/myfilesys", "rb")) == NULL){
        printf("FS has not been created, creating now....\n");
        my_format();
    }
    else{
        if(fread(my_v_disk,sizeof(char), SIZE, fs_on_disk) == 0){
            printf("Read FS_on_disk error!\n");
            return;
        }
        
    }
    //printf("DESIZE:%d\n", sizeof(DE));
    memset(openfilelist , 0 ,sizeof(useropen)*MAXOPENFILE);
    strcpy( openfilelist[0].dir, "");
    //every time the v-disk starts, fs should make these basic pointers point to right place.
    openfilelist[0].count = 0;openfilelist[0].fcbstate = 0;openfilelist[0].topenfile = 1;
    openfilelist[0].DE_open = ( guideBlock + sizeof(block0) - basis );
    curdir = 0;
    guideBlock = my_v_disk;
    showCURDIR_DES(CurDirDEarray);
    printf("FS Intials successfully!\n");
}

void my_format(void){
    strcpy( rootDE.file_fcb.filename, "");strcpy( rootDE.file_fcb.exname, ""); strcpy( rootDE.dir, "");
    rootDE.child = (unsigned char*)rootBlock-basis;
    //set all-0
    memset(my_v_disk, 0, sizeof(char)*SIZE);
    //initial block0
    block0 block_guide = {.information = "disk_size:1024\ndisk_num:1000\n", .root = 5, .startblock = my_v_disk + sizeof(char)*BLOCKSIZE*7};
    *(block0*)guideBlock = block_guide;
    DE* rootDE_pointer = (DE*)(guideBlock+sizeof(block0));
    *rootDE_pointer = rootDE;
    //initial fat/root/data address
    fat1[0] = -1; fat1[1] = 2; fat1[2] = -1; fat1[3] = 2; fat1[4] = -1; fat1[5] = 6; fat1[6] = -1;
    fat2[0] = -1; fat2[1] = 2; fat2[2] = -1; fat2[3] = 2; fat2[4] = -1; fat2[5] = 6; fat2[6] = -1;
    DE dotDE = {.file_fcb = {.attribute = 0,