參考網站: https://github.com/calccrypto/tar/tree/master,
改寫成我想用的: listtar.cpp
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <grp.h>
#include <pwd.h>
#include <dirent.h>
#define debug_printf(fmt, ...) fprintf(stderr, fmt, ##__VA_ARGS__)
typedef struct Link_list_meta TarLinkList;
struct Link_list_meta {
union {
char block[512];// metadata
union {
struct {// Pre-POSIX.1-1988 format
char name[100]; // file name
char mode[8]; // permissions
char uid[8]; // user id (octal)
char gid[8]; // group id (octal)
char size[12]; // size (octal)
char mtime[12]; // modification time (octal)
char check[8]; // checksum of the block, with spaces in the check field while calculation is done (octal)
char link; // link indicator
char link_name[100]; // name of linked file
};
struct {// UStar: Unix Standard TAR format (POSIX IEEE P1003.1)
char old[156]; // first 156 octets of Pre-POSIX.1-1988 format
char filetype; // file type
char also_link_name[100]; // name of linked file
char ustar[6]; // ustar\0
char version[2]; // #Version
char owner[32]; // user name (string)
char group[32]; // group name (string)
char major[8]; // device major number
char minor[8]; // device minor number
char prefix[155];
};
};
};
TarLinkList *next;
ssize_t append(int fd, void *buf, int n) { return write(fd, buf, n); }// todo: append buf into fd at the end
void block_update(int fd, char *filename, off_t filesize, mode_t filemode = 0, time_t *ct = nullptr) {
if (fd < 0) return;
memset(check, ' ', sizeof(check));// init string, It must be empty before caculation.
sprintf(name, "%s" , filename);
sprintf(mode, "%07o", filemode > 0 ? filemode & 0777 : 0664);
if (filesize > 0) sprintf(size , "%011o",(unsigned int)filesize);
else memset(size , '0', sizeof(size));
if (ct) sprintf(mtime, "%011o",(unsigned int)*ct);
else { // using current time if not provide.
time_t now;
time(&now);
sprintf(mtime, "%011o",(unsigned int)now);
}
int n = sizeof(block), checksum = 0;
for (int i = 0; i < n; i++) checksum += (unsigned char)block[i];// caculate checksum in the block
sprintf(check, "%07o", checksum);
append(fd, block, n);
}
int open_ram2tar(char *dir_name, char *create_name=nullptr) {//todo: validate dir_name
char backup_name[strlen(dir_name) + 16];
if (create_name == nullptr) {
sprintf(backup_name, "_%s.tar", dir_name);
create_name = backup_name;
}
int tar_fd = open(create_name, O_RDWR | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
if (tar_fd < 0) return -1;
block_update(tar_fd, dir_name, 0, 0775);// chmod ug+rwx o+rx dir_name
filetype = '0';// change to normal file.
debug_printf("createe file: %s\n", create_name);
return tar_fd;
}
Link_list_meta(bool is_directory = true) {// constructor to initialize the block
memset(block, 0, sizeof(block));
version[0] = '0', version[1] = '0';
filetype = is_directory ? '5' : '0';// todo: other type
uid_t user_id = getuid();
sprintf(uid, "%07o", user_id);
sprintf(gid, "%07o", getgid());
sprintf(ustar, "%s", "ustar");
struct passwd *pwd = getpwuid(user_id);// user info get from UID
if (pwd) {
struct group *grp = getgrgid(pwd->pw_gid);
sprintf(owner, "%s", pwd->pw_name);
sprintf(group, "%s", grp ? grp->gr_name: "None");
}
}
};
bool is_empty(char *buffer, int n) { // make sure first n's data in buffer are all 0s
for (int i = 0; i < n; i ++) if (*buffer ++) return false;
return true;
}
long int o2l(char *octal_str, int n) {// 8 進位轉長整數, todo: negative number
long int val_long = 0l;
for (int i = 0; i < n; i ++, octal_str ++) {
if (*octal_str == 0) break;
val_long <<= 3;
val_long |= *octal_str - '0';
}
return val_long;
}
void dir2tar(const char *foldername, char *create_name = nullptr) {
char *path2folder = (char *)foldername;
if (*path2folder == '.') {
path2folder ++;
if (*path2folder == '.') path2folder ++;
}
if (*path2folder == '/' ) path2folder ++;
else path2folder = (char *)foldername;
while (*path2folder == '/') path2folder ++;// remove another '/'
struct stat file_st;
if (lstat(path2folder, &file_st)!=0 || (file_st.st_mode & S_IFMT)!=S_IFDIR) return;
DIR *cd = opendir(path2folder);// change into the directory
if (!cd) return; // make sure user has rights to access
TarLinkList metadata;
int tar_fd = metadata.open_ram2tar(path2folder);
if (tar_fd > 0) {
char fd_buf[512];
struct dirent *temp;
while ((temp = readdir(cd))) { // todo: to proceed child directory
if (temp->d_name[0] == '.') continue;// skip . and ..
char temp_fullname[strlen(path2folder) + strlen(temp->d_name) + 2];// + '/' and EOS
sprintf(temp_fullname, "%s/%s", path2folder, temp->d_name);// fullname
lstat(temp_fullname, &file_st);
if ((file_st.st_mode & S_IFMT) != S_IFREG || file_st.st_size <= 0) continue; // todo: other type support
int temp_fd = open(temp_fullname, O_RDONLY);
if (temp_fd < 0) continue;
off_t temp_len = file_st.st_size;// to append file content
off_t zeros_pad = temp_len % 512;// check remain
if (zeros_pad) zeros_pad = 512 - zeros_pad;// number of zeros need to pad
metadata.block_update(tar_fd, temp_fullname, temp_len, file_st.st_mode, &file_st.st_mtim.tv_sec);
debug_printf("%s: size = %ld, checksum = %6s\n", temp_fullname, temp_len, metadata.check);
while (temp_len > 0) {
ssize_t l = read(temp_fd, fd_buf, temp_len > 512 ? 512 : temp_len);
if (l <= 0) break;//todo: error correction
metadata.append(tar_fd, fd_buf, l);
temp_len -= l;
}
close(temp_fd);
if (zeros_pad) {
memset(fd_buf, 0, zeros_pad);
metadata.append(tar_fd, fd_buf, zeros_pad);
}
}
memset(fd_buf, 0, 512);// need 2 block of zeros in the end for tar file
for (int i = 0; i < 2; i ++) metadata.append(tar_fd, fd_buf, 512);
close(tar_fd);
}
closedir(cd);
}
void list_tarfile(const char *tar) {
int fd = open(tar, O_RDONLY);
if (fd > 0) {// in linux: stdin = 0, stdout = 1, stderr = 2
TarLinkList *archive = nullptr;// start
TarLinkList **tarlist = &archive;// get pointer of archive
int block_size = sizeof(archive->block);
while (true) {
TarLinkList *temp = (TarLinkList *)calloc(1, sizeof(TarLinkList));// 分配空間並初始為 0
if (temp == nullptr) break;
if (read(fd, temp->block, block_size) != block_size) {// to read 512 bytes metadata
debug_printf("讀取錯誤,忽略!\n");
free(temp);
break;
}
if (is_empty(temp->block, block_size)) {// EOF, enough to stop
if (read(fd, temp->block, block_size) == block_size) {// check 2nd EOF
if (is_empty(temp->block, block_size)) {
debug_printf("正常檔尾,結束:\n");
}
}
free(temp);
break;
}
*tarlist = temp;// fill temp as current entry
tarlist = &temp->next;// to fill for next time
long int goahead = o2l(temp->size, 11);// 檔案長度: 8 進位(12 bytes)
int r = goahead % 512; // 取餘數
if (r) goahead += 512 - r;// 若非 512 倍數, 無條件補滿成 512 倍數
if (lseek(fd, goahead, SEEK_CUR) < 0) { // 前進到下個位置
debug_printf("前進錯誤,忽略!\n");
break;
}
}
*tarlist = nullptr;// end of List
while (archive) {// list and free
time_t t = o2l(archive->mtime, 11);// 更新時間
struct tm *ct = localtime(&t);
debug_printf("%s@%s\t", archive->owner, archive->group); // 使用者@群組
debug_printf("%d-%02d-%02d:%02d.%02d\t",
ct->tm_year + 1900,
ct->tm_mon + 1,
ct->tm_mday,
ct->tm_hour,
ct->tm_min
);// 年-月-日-時:分
switch (archive->filetype) {
case '0':
debug_printf("%ld (bytes)", o2l(archive->size, 11));// 檔案長度
break;
case '1': case '2':
debug_printf("檔案連結");
break;
case '3': case '4':
debug_printf("裝置檔案-%04ld::%04ld-", o2l(archive->major, 7), o2l(archive->minor, 7));// 設備編號
break;
case '5':
debug_printf(" <目錄> ");
break;
case '6':
debug_printf("先進先出");
break;
default:
debug_printf("????");
break;
}
debug_printf("\t<- (%6s) %-32s\n", archive->check, archive->name);// 檔名
TarLinkList *temp = archive -> next;// remove later
free(archive);
archive = temp;
}
close(fd);
}
}
void dump_tarfile(const char *tar, const char *filename) {
int fd = open(tar, O_RDONLY);
if (fd > 0) {
char fd_buf[512];// as buffer
TarLinkList *archive = (TarLinkList *)fd_buf; // point to fd_buf
long int goahead = 0l;
while (lseek(fd, goahead, SEEK_CUR)>= 0 && read(fd, fd_buf, 512) == 512 && !is_empty(fd_buf, 512)) {
if (strcmp(archive->name, filename) == 0) {
long int filesize = o2l(archive->size, 11);
while (filesize > 0) {
int l = read(fd, fd_buf, (filesize > 512) ? 512 : filesize);
if (l <= 0) continue;
for (int i = 0; i < l; i++) debug_printf("%c", fd_buf[i]);
filesize -= l;
}
break;
}
goahead = o2l(archive->size, 11);// 檔案長度: 8 進位(12 bytes)
int r = goahead % 512; // 取餘數
if (r) goahead += 512 - r;// 若非 512 倍數, 無條件補滿成 512 倍數
}
close(fd);
}
}
int main(int argc, char *argv[]) {
if (argc > 1 && argv[1]) {
struct stat file_st;
if (lstat(argv[1], &file_st) == 0) {// make sure argv[1] file exists.
if ((file_st.st_mode & S_IFMT) == S_IFDIR) {
dir2tar(argv[1]);// createe tar file to store all files in argv[1] which is a directory.
} else {// todo: make sure argv[1] is a tar file
if (argc > 2 && argv[2]) {
printf("===%s:%s===\n", argv[1], argv[2]);
dump_tarfile(argv[1], argv[2]); // to dump argv[2] in argv[1]
printf("\n=== EOF ===\n");// end of file
} else {
list_tarfile(argv[1]);// list all files in tar
}
}
}
}
return 0;
}
一個將 ram 資料寫入 tar file 測試程式: test_ram2tar.c
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <fcntl.h>
#include <unistd.h>
#include <grp.h>
#include <pwd.h>
#define debug_printf(fmt, ...) fprintf(stderr, fmt, ##__VA_ARGS__)
typedef struct Link_list_meta TarLinkList;
struct Link_list_meta {
union {
char block[512];// metadata
union {
struct {// Pre-POSIX.1-1988 format
char name[100]; // file name
char mode[8]; // permissions
char uid[8]; // user id (octal)
char gid[8]; // group id (octal)
char size[12]; // size (octal)
char mtime[12]; // modification time (octal)
char check[8]; // checksum of the block, with spaces in the check field while calculation is done (octal)
char link; // link indicator
char link_name[100]; // name of linked file
};
struct {// UStar: Unix Standard TAR format (POSIX IEEE P1003.1)
char old[156]; // first 156 octets of Pre-POSIX.1-1988 format
char filetype; // file type
char also_link_name[100]; // name of linked file
char ustar[6]; // ustar\0
char version[2]; // #Version
char owner[32]; // user name (string)
char group[32]; // group name (string)
char major[8]; // device major number
char minor[8]; // device minor number
char prefix[155];
};
};
};
TarLinkList *next;
ssize_t append(int fd, void *buf, int n) { return write(fd, buf, n); }// todo: append buf into fd at the end
void block_update(int fd, char *filename, off_t filesize, mode_t filemode = 0, time_t *ct = nullptr) {
if (fd < 0) return;
memset(check, ' ', sizeof(check));// init string, It must be empty before caculation.
sprintf(name, "%s" , filename);
sprintf(mode, "%07o", filemode > 0 ? filemode & 0777 : 0664);
if (filesize > 0) sprintf(size , "%011o",(unsigned int)filesize);
else memset(size , '0', sizeof(size));
if (ct) sprintf(mtime, "%011o",(unsigned int)*ct);
else { // using current time if not provide.
time_t now;
time(&now);
sprintf(mtime, "%011o",(unsigned int)now);
}
int n = sizeof(block), checksum = 0;
for (int i = 0; i < n; i++) checksum += (unsigned char)block[i];// caculate checksum in the block
sprintf(check, "%07o", checksum);
append(fd, block, n);
}
int open_ram2tar(char *dir_name, char *create_name=nullptr) {//todo: validate dir_name
char backup_name[strlen(dir_name) + 16];
if (create_name == nullptr) {
sprintf(backup_name, "_%s.tar", dir_name);
create_name = backup_name;
}
int tar_fd = open(create_name, O_RDWR | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR);
if (tar_fd < 0) return -1;
block_update(tar_fd, dir_name, 0, 0775);// chmod ug+rwx o+rx dir_name
filetype = '0';// change to normal file.
debug_printf("createe file: %s\n", create_name);
return tar_fd;
}
Link_list_meta(bool is_directory = true) {// constructor to initialize the block
memset(block, 0, sizeof(block));
version[0] = '0', version[1] = '0';
filetype = is_directory ? '5' : '0';// todo: other type
uid_t user_id = getuid();
sprintf(uid, "%07o", user_id);
sprintf(gid, "%07o", getgid());
sprintf(ustar, "%s", "ustar");
struct passwd *pwd = getpwuid(user_id);// user info get from UID
if (pwd) {
struct group *grp = getgrgid(pwd->pw_gid);
sprintf(owner, "%s", pwd->pw_name);
sprintf(group, "%s", grp ? grp->gr_name: "None");
}
}
};
int main(int argc, char *argv[]) {
TarLinkList metadata;
char dir_name[16] = {"bb"};
int tar_fd = metadata.open_ram2tar(dir_name);// create folder first
if (tar_fd > 0) {
char fd_buf[512], ram_name[100];
for(int i = 0; i < 10; i ++) { // to create 10 example files
sprintf(ram_name, "%s/%d", dir_name, i);// combine folder name with specific name as ram file name
sprintf(fd_buf, "%s:%d", ram_name, i + 1);// fill content for the ram file
metadata.block_update(tar_fd, ram_name, strlen(fd_buf));// append metadata into tar
metadata.append(tar_fd, fd_buf, 512);// append 512 bytes of ram into tar
}
memset(fd_buf, 0, 512);
for (int i = 0; i < 2; i ++) metadata.append(tar_fd, fd_buf, 512);// append 2 block of zeros in the end
close(tar_fd);
}
return 0;
}
