FAT12 img tool

NJU/2019/OS

Description：

CODE:

Main.cpp:

/*
@author: Edwin Xu
@Date:2019/11/13
@Note: just ASCII
*/
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <string>
#include <iostream>
#include <vector>

#define IMG_PATH "a.img"

using namespace std;

//myPrint in NASM
extern "C" {void myPrint(char *c,int len,int color);}
//print func using myPrint()
char chars[513]; 
void print(string s,int color){
    const char * c = s.c_str();
    strcpy(chars,s.c_str());
    myPrint(chars,s.length(),color);
}



//Part1: struct and util functions 
struct File
{
    string filename;
    int size;
    int firstCluster;
    File(string n, int s, int cluster) {
        filename = n;
        size = s;
        firstCluster = cluster;
    }
    File(){
        size = 0;
        filename = "";
        firstCluster = 0;
    }
};
struct Directory
{
    string dirName ;
    //子目录
    vector <Directory>subDirs ;
    //当前文件夹的文件
    vector <File>subFiles ;
    int dirNum=0;
    int fileNum=0;

    void addDir(Directory d) {
        this->subDirs.push_back(d);
        dirNum++;
    }
    void addFile(string name,int size,int cluster) {
        this->subFiles.push_back(File(name,size,cluster));
        fileNum++;
    }

    Directory() {
        dirName = "";
    }
    Directory(string n) {
        this->dirName = n;
    }

    //判断有没有son这个儿子
    int hasSon(string son) {
        for (int i = 0; i < dirNum; i++) {
            if (son.compare(subDirs[i].dirName) == 0) {
                return 1;
            }
        }
        return 0;
    }
    //判断有没有这个file, 并返回cluster
    int hasFile(string file) {
        for (int i = 0; i < fileNum; i++) {
            if (file.compare(subFiles[i].filename) == 0) {
                return subFiles[i].firstCluster; //存在文件，返回cluster
            }
        }
        return -1; //不存在文件，返回-1
    }

};


vector<string> path; //当前已经遍历的目录

string getPath() {
    string res = "/";
    for (int i = 0; i < path.size(); i++) {
        res += (path[i] + "/");
    }
    return res ;
}

void ls_display(Directory d) {
    if (d.dirName.length()>0) path.push_back(d.dirName); //if not root dir
    print(getPath()+":
",0);
    if(d.dirName.length()>0) print(".  ..  ",1);
    for (int i = 0; i < d.dirNum; i++) {
        print(d.subDirs[i].dirName+"  ",1);
    }
    for (int i = 0; i < d.fileNum; i++) {
        print(d.subFiles[i].filename+"  ",0);
    }
    print("
",0);
    for (int i = 0; i < d.dirNum; i++) {
        ls_display(d.subDirs[i]);
    }
    if (d.dirName.length() > 0)
    {
        path.pop_back();
    }
}

void ls_l_display(Directory d) {
    if (d.dirName.length() > 0) path.push_back(d.dirName); //if not root dir
    print(getPath() +" " + to_string(d.dirNum) + " " + to_string(d.fileNum)+":
",0);
    if (d.dirName.length() > 0) print( ".
..
",1);
    for (int i = 0; i < d.dirNum; i++) {
        print(d.subDirs[i].dirName,1);
        print("  " + to_string(d.subDirs[i].dirNum) + " " + to_string(d.subDirs[i].fileNum)+"
",0);
    }
    for (int i = 0; i < d.fileNum; i++) {
        print(d.subFiles[i].filename +"  " + to_string(d.subFiles[i].size)+"
",0);
    }
    print("
",0);
    for (int i = 0; i < d.dirNum; i++) {
        ls_l_display(d.subDirs[i]);
    }
    if (d.dirName.length() > 0) path.pop_back();
}


/*
    get dir node by dir name (note: name is unique)
*/
Directory getDirectory(Directory beginDir,string dirName) {
    if (beginDir.dirName.compare(dirName) == 0) {
        return beginDir; //get it, the current dir is what i want
    }
    //fond in the subdir:
    for (int i = 0; i < beginDir.dirNum; i++) {
        Directory temp_dir= getDirectory(beginDir.subDirs[i], dirName);
        if (temp_dir.dirName.length() != 0)return temp_dir;
    }
    return Directory();
}




//Part2: BPB and FAT operations

typedef unsigned char u8;    //1B
typedef unsigned short u16;    //2B
typedef unsigned int u32;    //4B

int  BytsPerSec;    //Bytes of every sector
int  SecPerClus;    //sectors of a cluster
int  RsvdSecCnt;    //Boot记录占用的扇区数
int  NumFATs;    //FAT tables Num
int  RootEntCnt;    //max files Num of root directory
int  FATSz;    //num of FAT sectors 

#pragma pack (1) /*指定按1字节对齐*/

//offset is 11 bytes
struct BPB {
    u16  BPB_BytsPerSec;    //每扇区字节数
    u8   BPB_SecPerClus;    //每簇扇区数
    u16  BPB_RsvdSecCnt;    //Boot记录占用的扇区数
    u8   BPB_NumFATs;    //FAT表个数
    u16  BPB_RootEntCnt;    //根目录最大文件数
    u16  BPB_TotSec16;
    u8   BPB_Media;
    u16  BPB_FATSz16;    //FAT扇区数
    u16  BPB_SecPerTrk;
    u16  BPB_NumHeads;
    u32  BPB_HiddSec;
    u32  BPB_TotSec32;    //如果BPB_FATSz16为0，该值为FAT扇区数
};
//BPB over，length is 25 bytes

//root directory entry
struct RootEntry {
    char DIR_Name[11];
    u8   DIR_Attr;        //file attr
    char reserved[10];
    u16  DIR_WrtTime;
    u16  DIR_WrtDate;
    u16  DIR_FstClus;    //start cluster No
    u32  DIR_FileSize;
};
//根目录条目结束，32字节
#pragma pack () /*取消指定对齐，恢复缺省对齐*/

struct subEntry {
    char DIR_Name[11];
    u8  DIR_Attr;
    char reserved[10];
    u16  DIR_WrTime;
    u16  DIR_WrDate;
    u16  DIR_FstClus;
    u32  DIR_FileSize;
};

#pragma pack () /*取消指定对齐，恢复缺省对齐*/


void fillBPB(struct BPB* bpb_ptr);    //载入BPB
void printFiles(struct RootEntry* rootEntry_ptr, Directory* rootnode);    //打印文件名，这个函数在打印目录时会调用下面的printChildren
void printChildren(char * directory, int startClus,Directory * d);    //打印目录及目录下子文件名
int  getFATValue(int num);    //读取num号FAT项所在的两个字节，并从这两个连续字节中取出FAT项的值，
void printFileContent(int startClus);
int getFATValue(int num);

Directory root;
FILE* fat12;  //global variable

void init() {
    struct BPB bpb;
    struct BPB* bpb_ptr = &bpb;

    //载入BPB
    fillBPB(bpb_ptr);

    //init all global variables
    BytsPerSec = bpb_ptr->BPB_BytsPerSec;
    SecPerClus = bpb_ptr->BPB_SecPerClus;
    RsvdSecCnt = bpb_ptr->BPB_RsvdSecCnt;
    NumFATs = bpb_ptr->BPB_NumFATs;
    RootEntCnt = bpb_ptr->BPB_RootEntCnt;
    if (bpb_ptr->BPB_FATSz16 != 0) {
        FATSz = bpb_ptr->BPB_FATSz16;
    }
    else {
        FATSz = bpb_ptr->BPB_TotSec32;
    }

    struct RootEntry rootEntry;
    struct RootEntry* rootEntry_ptr = &rootEntry;

    //print in cursion
    printFiles(rootEntry_ptr,&root);
}
//erase the spaces in the biginning and end
string& trim(std::string &s)
{
    if (s.empty()) return s;
    s.erase(0, s.find_first_not_of(" "));
    s.erase(s.find_last_not_of(" ") + 1);
    return s;
}

string ls_l_resolve(string command) {
    const char * cmd1 = command.c_str();
    int len = command.length();

    //处理 -lll这种多个l的情况
    int _l_beginIndex = 0;
    for (int i = 0; i < len-1; i++) {
        if (cmd1[i] == '-'&&cmd1[i + 1] == 'l') {
            _l_beginIndex = i + 1;
            break;
        }
    }
    int l_endIndex = _l_beginIndex;
    for (int i = _l_beginIndex + 1; i < len; i++) {
        if (cmd1[i] != 'l') {
            l_endIndex = i;
            break;
        }
    }
    if (_l_beginIndex != l_endIndex) {
        command = command.substr(0, _l_beginIndex+1) + command.substr(l_endIndex,len-l_endIndex);
    }
    //cout << "comm:" << command << endl;
    const char * cmd = command.c_str();
    len = command.length();

    int beginIndex = 0, endIndex = 0;
    int hasBegun = 0; //是否已经进入目录的 beginIndex

    //form1：ls path -l
    if (cmd[len - 1] == 'l'&&cmd[len - 2] == '-') {
        for (int i = 3; i < len; i++) {
            if (cmd[i] != ' '&&!hasBegun) {
                beginIndex = i;
                hasBegun = 1;
                //break;
            }
            if (hasBegun && (cmd[i] == ' ' || cmd[i] == '-')) {
                endIndex = i;
                break;
            }
        }
    }
    else {
        //form2：ls -l path
        for (int i = 3; i < len; i++) {
            if (cmd[i] == '-'&&cmd[i + 1] == 'l') {
                beginIndex = i + 1;
                break;
            }
        }
        for (int i = beginIndex+1; i < len; i++) {
            if (cmd[i] != ' ') {
                beginIndex = i;
                break;
            }
        }
        endIndex = len;
    }
    string res = command.substr(beginIndex, endIndex - beginIndex);
    return res;
}
//to upper
string upper(string s) {
    string res;
    const char* c = s.c_str();
    for (int i = 0; i < s.length(); i++) {
        if (c[i] > 96&&c[i]<127)res += (c[i] - 32);
        else res += c[i];
    }
    return res;
}
//tranform path like '/a/b/c', return a vector
vector<string> getPathVector(string path) {
    vector<string> pathVec;
    const char* pathChars = path.c_str();
    int len = path.length();
    int beginIndex = 0;
    if (pathChars[0] == '/')beginIndex++;
    char temp[20];//temp char arr
    for (int i = beginIndex; i < len; i++) {
        if (pathChars[i] == '/'||i==len-1) {
            pathVec.push_back(path.substr(beginIndex,(i==len-1)?len:i-beginIndex));
            beginIndex = i + 1;
        }
    }
    return pathVec;
}

//得到路径中的目录
Directory locateDirectory(string path) {
    path = upper(path);
    vector<string> pathVector = getPathVector(path);
    vector <Directory> dirArr;

    for (int i = 0; i < pathVector.size(); i++) {
        dirArr.push_back(getDirectory(root, pathVector[i]));
    }
    
    Directory res = dirArr[dirArr.size() - 1];
    int isOK = 1;
    if(dirArr.size()==1){
        if(dirArr[0].dirName.length()==0)isOK=0;
    }
    else{
        for (int i = 0; i < pathVector.size() - 1; i++) {
            if (!dirArr[i].hasSon(dirArr[i + 1].dirName)) {
                isOK = 0;
                break;
            }
        }
    }
    if (!isOK) res.dirNum = -1; //如果路径不正确，将返回目录节点的dirName置-1
    return res;
}

void Main() {
    string inp;
    while (1)
    {
        print(">",0);
        getline(cin, inp);
        inp = trim(inp);

        const char* c_inp = inp.c_str();
        
        int has_ = 0;
        for(int i =0;i<inp.length();i++){
            if(c_inp[i]=='-'){
                has_ = 1;
                break;
            }
        }
        
        if (inp.compare("exit") == 0) {
            print( "Bye!
",0);
            break;
        }
        if (inp.length() >= 2 && c_inp[0] == 'l'&&c_inp[1] == 's') {
            if (!inp.compare("ls")) {
                ls_display(root);
            }
            else if(!inp.substr(0,2).compare("ls")&&!has_){
                string path = inp.substr(2,inp.length()-2);
                path = trim(path);
                Directory dir = locateDirectory(path);
                ls_display(dir);
            }
            else if(!inp.compare("ls -l")) {
                ls_l_display(root);
            }
            else if(!inp.substr(0,5).compare("ls -L")) {
                print("your command is invalid!
",0);
            }
            else {
                string path = ls_l_resolve(inp);  
                //cout << "path: " << path << endl;
                
                if (path.length() == 0) {
                    print("The path is invalid！ Try again!
",0);
                }
                else {
                    Directory dir = locateDirectory(path);
                    if (dir.dirNum==-1) {
                        print("The path is invalid！ Try again!
",0);
                    }
                    else {
                        ls_l_display(dir);
                    }
                }
            }
        }
        else if (!inp.substr(0,3).compare("cat")) {
            int i;
            for (i = 3; i < inp.length(); i++) {
                if (c_inp[i] != ' ')break;  //取出cat后面的space
            }
            //取出文件和目录:
            int endIndex = inp.length() - 1;
            for (int i = endIndex; i >= 3; i--) {
                if (c_inp[i] == '/') {
                    endIndex = i;
                    break;
                }
            }

            string path = inp.substr(i, endIndex - i);
            string fileName = inp.substr(endIndex + 1, inp.length() - endIndex - 1);

            if (endIndex == inp.length() - 1) {
                path = "";
                fileName = inp.substr(i, inp.length()-i);
            }
            //cout << "path: " << path << " file: " << fileName << endl;
            Directory dir;
            if (path.length() == 0) { //path is empty, so it's root entry
                dir = root;
            }
            else {
                dir = locateDirectory(path);
            }
            if (dir.dirNum == -1) {
                print("The path is invalid！
",0);
            }
            else {
                int cluster = dir.hasFile(upper(fileName));
                if (cluster==-1) {
                    print("The file is not exist!
",0);
                }
                else {
                    if (cluster >= 2) 
                        printFileContent(cluster);
                }

            }
        }
        else if(inp.length()>0){
            string s = "Wrong Command! Try Again!
";
            print(s,0);
        }
    }
}


void fillBPB( struct BPB* bpb_ptr) {
    int check;
    //BPB从偏移11个字节处开始
    check = fseek(fat12, 11, SEEK_SET);
    if (check == -1)
        print("fseek in fillBPB failed!
",0);

    //BPB长度为25字节
    check = fread(bpb_ptr, 1, 25, fat12);
    if (check != 25)
        print("fread in fillBPB failed!
",0);
}


void printFiles(struct RootEntry* rootEntry_ptr, Directory* root) {
    int base = (RsvdSecCnt + NumFATs * FATSz) * BytsPerSec;    //根目录首字节的偏移数
    int check;
    char realName[12];    //暂存将空格替换成点后的文件名

    //依次处理根目录中的各个条目
    int i;
    for (i = 0; i < RootEntCnt; i++) {

        check = fseek(fat12, base, SEEK_SET);
        if (check == -1)
            print("fseek in printFiles failed!
",0);

        check = fread(rootEntry_ptr, 1, 32, fat12);
        if (check != 32)
            print("fread in printFiles failed!
",0);
        base += 32;
        if (rootEntry_ptr->DIR_Name[0] == '') continue;    //empty entry

        //filliter ilvalid
        int j;
        int boolean = 0;
        for (j = 0; j < 11; j++) {
            if (!(((rootEntry_ptr->DIR_Name[j] >= 48) && (rootEntry_ptr->DIR_Name[j] <= 57)) ||
                ((rootEntry_ptr->DIR_Name[j] >= 65) && (rootEntry_ptr->DIR_Name[j] <= 90)) ||
                ((rootEntry_ptr->DIR_Name[j] >= 97) && (rootEntry_ptr->DIR_Name[j] <= 122)) ||
                (rootEntry_ptr->DIR_Name[j] == ' '))) {
                boolean = 1;    //invalid char
                break;
            }
        }
        if (boolean == 1) continue;    //not object

        int k;
        if ((rootEntry_ptr->DIR_Attr & 0x10) == 0) {
            //it's a file 
            int tempLong = -1;
            for (k = 0; k < 11; k++) {
                if (rootEntry_ptr->DIR_Name[k] != ' ') {
                    tempLong++;
                    realName[tempLong] = rootEntry_ptr->DIR_Name[k];
                }
                else {
                    tempLong++;
                    realName[tempLong] = '.';
                    while (rootEntry_ptr->DIR_Name[k] == ' ') k++;
                    k--;
                }
            }
            tempLong++;
            realName[tempLong] = '';    //filename is realName

            root->addFile(realName,rootEntry_ptr->DIR_FileSize,rootEntry_ptr->DIR_FstClus);
            //output fileName:
            //printf("FileName: %s
", realName);
        }
        else {
            //it's a dir
            int tempLong = -1;
            for (k = 0; k < 11; k++) {
                if (rootEntry_ptr->DIR_Name[k] != ' ') {
                    tempLong++;
                    realName[tempLong] = rootEntry_ptr->DIR_Name[k];
                }
                else {
                    tempLong++;
                    realName[tempLong] = '';
                    break;
                }
            }    //dir name is realName

            Directory d = Directory(realName);
            root->addDir(d);

            //priint recurisively
            printChildren(realName, rootEntry_ptr->DIR_FstClus, &root->subDirs[root->dirNum-1]);
        }
    }
}


void printChildren(char * directory, int startClus,Directory* d) {
    //offset of No.2 cluster(the first cluster)
    int dataBase = BytsPerSec * (RsvdSecCnt + FATSz * NumFATs + (RootEntCnt * 32 + BytsPerSec - 1) / BytsPerSec);
    char fullName[240];    //file /dir fullname
    int strLength = strlen(directory);
    strcpy(fullName, directory);
    fullName[strLength] = '/';
    strLength++;
    fullName[strLength] = '';
    char* fileName = &fullName[strLength];

    int currentClus = startClus;
    int value = 0;
    int ifOnlyDirectory = 0;

    while (value < 0xFF8) { //value <FF8H
        value = getFATValue(currentClus);
        if (value < 0) {
            break;
        }
        if (value == 0xFF7) {
            print("Bad cluster，failed!
",0);
            break;
        }

        char* str = (char*)malloc(SecPerClus*BytsPerSec);    //暂存从簇中读出的数据
        char* content = str;

        int startByte = dataBase + (currentClus - 2)*SecPerClus*BytsPerSec;
        int check;
        check = fseek(fat12, startByte, SEEK_SET);
        if (check == -1)
            print("fseek in printChildren failed!
",0);

        check = fread(content, 1, SecPerClus*BytsPerSec, fat12);
        if (check != SecPerClus * BytsPerSec)
            print("fread in printChildren failed!
",0);

        //solve date of content,the regular entry structure is as same as root dir entry.
        int count = SecPerClus * BytsPerSec;    //bytes of a cluster
        int loop = 0;
        while (loop < count) {
            int i;
            char tempName[120];    //暂存替换空格为点后的文件名
            if (content[loop] == '') {
                loop += 32;
                continue;
            }    //empty entry

                //filiter the invaild things
            int j;
            int boolean = 0;
            for (j = loop; j < loop + 11; j++) {
                if (!(((content[j] >= 48) && (content[j] <= 57)) ||
                    ((content[j] >= 65) && (content[j] <= 90)) ||
                    ((content[j] >= 97) && (content[j] <= 122)) ||
                    (content[j] == ' '))) {
                    boolean = 1;    //invaild char
                    break;
                }
            }
            if (boolean == 1) {
                loop += 32;
                continue;
            }    //not object file

            if ((content[loop + 11] & 0x10) == 0) {
                //File :
                int k;
                int tempLong = -1;
                for (k = 0; k < 11; k++) {
                    if (content[loop + k] != ' ') {
                        tempLong++;
                        tempName[tempLong] = content[loop + k];
                    }
                    else {
                        tempLong++;
                        tempName[tempLong] = '.';
                        while (content[loop + k] == ' ') k++;
                        k--;
                    }
                }
                tempLong++;
                tempName[tempLong] = '';    

                int a = content[loop+28],
                    b = content[loop + 29],
                    c = content[loop + 30],
                    d1 = content[loop + 31];
                a = a >= 0 ? a : 256 + a;//处理负数
                b = b >= 0 ? b: 256 + b;
                c = c >= 0 ? c : 256 + c;
                d1 = d1 >= 0 ? d1 : 256 + d1;

                int size = a + 256*b + 256*256*c + 256*256*256*d1;

                int x = content[loop + 26];
                int y = content[loop + 27];
                //cout << "cluster of : " << fullName<<"/"<<tempName<<" :" <<y * 256 + x << endl;
                d->addFile(tempName,size, y * 256 + x);
                strcpy(fileName, tempName);
                //printf("%s
", fullName);
                ifOnlyDirectory = 1;
            }
            else {
                //dir
                int k;
                int tempLong = -1;

                for (k = 0; k < 11; k++) {
                    if (content[loop + k] != ' ') {
                        tempLong++;
                        tempName[tempLong] = content[loop + k];
                    }
                    else {
                        while (content[loop + k] == ' ') k++;
                        k--;
                    }
                }
                tempLong++;
                tempName[tempLong] = '';
                strcpy(fileName, tempName);
                ifOnlyDirectory == 1;

                Directory dir = Directory(tempName);
                d->addDir(dir);

                int a = content[loop + 26];
                int b = content[loop + 27];
                printChildren(fullName, b*256+a, &d->subDirs[d->dirNum-1]);
            }
            loop += 32;
        }
        free(str);
        currentClus = value;
    };
    //if (ifOnlyDirectory == 0)
    //    printf("%s
", fullName);    //空目录的情况下，输出目录
}

//输出文件内容：
void printFileContent(int startClus) {
    int dataBase = BytsPerSec * (RsvdSecCnt + FATSz * NumFATs + (RootEntCnt * 32 + BytsPerSec - 1) / BytsPerSec);
    int check;
    int curclus = startClus;
    int value = 0;
    while (value < 0xFF8) {//4088
        value = getFATValue(curclus);
        if (value < 0) {
            break;
        }
        if (value == 0xFF7) {
            print( "bad cluster
",0);
        }
        char temp[513];
        int startByte = dataBase + 512 * (curclus - 2);
        check = fseek(fat12, startByte, SEEK_SET);
        if (check == -1)print( "Failed!
",0);
        check = fread(temp, 1, 512, fat12);
        temp[512] = '';
        print(temp,0);
        print("
",0);
        curclus = value;
    }
}


int getFATValue(int num) {
    int fatBase = RsvdSecCnt * BytsPerSec;
    int fatPos = fatBase + num * 3 / 2;
    int type = 0;
    if (num % 2 == 0) {
        type = 0; //even
    }
    else {
        type = 1; //odd
    }
    u16 bytes;
    u16* bytes_ptr = &bytes;
    int check;
    check = fseek(fat12, fatPos, SEEK_SET);
    if (check == -1) {
        print("fseek in getFATValue failed!
",0);
        return -1;
    }
    check = fread(bytes_ptr, 1, 2, fat12);
    if (check != 2) {
        print("fread in getFATValue failed!
",0);
        return -1;
    }
    //u16为short，结合存储的小端顺序和FAT项结构可以得到
    //type为0的话，取byte2的低4位和byte1构成的值，type为1的话，取byte2和byte1的高4位构成的值
    if (type == 0) {
        bytes = bytes << 4;
        bytes = bytes >> 4;
    }
    else {
        bytes = bytes >> 4;
    }
    return bytes;
}



// Main, entrance of this program
int main() {
    fat12 = fopen(IMG_PATH, "rb");    //open the fat12 image
    init(); //init, build the file tree
    Main(); //command solve and execute
    fclose(fat12); //clost the file stream in the last。
    return 0;
}

NASM CODE:

my_print.asm

global myPrint
;void myPrint(char *,int len,int color);
;color: 0-default, 1-red
;EdwinXu
section .data
    color_default:  db  1Bh, '[37;0m', 0 
    .length            equ $ - color_default
    color_red:      db  1Bh, '[31;1m', 0
    .length            equ $ - color_red  

section .text

myPrint:
    mov eax, [esp+12]
    cmp eax, 0
    je default_color
    
;set red 
    mov eax, 4
    mov ebx, 1
    mov ecx, color_red
    mov edx, color_red.length
    int 80h
    jmp color_end
;set default color:
default_color:
    mov eax, 4
    mov ebx, 1
    mov ecx, color_default
    mov edx, color_default.length
    int 80h

;print the str
color_end:
    mov eax, 4
    mov ebx, 1
    mov ecx, [esp+4] ;str
    mov edx, [esp+8] ;len
    int 80h
;recover the color
    mov eax, 4
    mov ebx, 1
    mov ecx, color_default
    mov edx, color_default.length
    int 80h
    
    ret

Makefile:

all:

ALL:
    nasm -f elf32 my_print.asm
    g++ -m32 my_print.o Main.cpp -o main
    ./main