tar.h

/*
tar.h
tar data structure and accompanying functions

Copyright (c) 2015 Jason Lee

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE
*/

#ifndef __TAR__
#define __TAR__

#define _BSD_SOURCE

#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include <dirent.h>
#include <fcntl.h>
#include <grp.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

#define DEFAULT_DIR_MODE S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH // 0755

#define BLOCKSIZE       512
#define BLOCKING_FACTOR 20
#define RECORDSIZE      10240

// file type values (1 octet)
#define REGULAR          0
#define NORMAL          '0'
#define HARDLINK        '1'
#define SYMLINK         '2'
#define CHAR            '3'
#define BLOCK           '4'
#define DIRECTORY       '5'
#define FIFO            '6'
#define CONTIGUOUS      '7'

// tar entry metadata structure (singly-linked list)
struct tar_t {
    char original_name[100];                // original filenme; only availible when writing into a tar
    unsigned int begin;                     // location of data in file (including metadata)
    union {
        union {
            // Pre-POSIX.1-1988 format
            struct {
                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];              // sum of unsigned characters in block block, with spaces in the check field while calculation is done (octal)
                char link;                  // link indicator
                char link_name[100];        // name of linked file
            };

            // UStar format (POSIX IEEE P1003.1)
            struct {
                char old[156];              // first 156 octets of Pre-POSIX.1-1988 format
                char type;                  // file type
                char also_link_name[100];   // name of linked file
                char ustar[8];              // ustar\000
                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];
            };
        };

        char block[512];                    // raw memory (500 octets of actual data, padded to 1 block)
    };

    struct tar_t * next;
};

// core functions //////////////////////////////////////////////////////////////
// read a tar file
// archive should be address to null pointer
int tar_read(const int fd, struct tar_t ** archive, const char verbosity);

// write to a tar file
// if archive contains data, the new data will be appended to the back of the file (terminating blocks will be rewritten)
int tar_write(const int fd, struct tar_t ** archive, const size_t filecount, const char * files[], const char verbosity);

// recursive freeing of entries
void tar_free(struct tar_t * archive);
// /////////////////////////////////////////////////////////////////////////////

// utilities ///////////////////////////////////////////////////////////////////
// print contents of archive
// verbosity should be greater than 0
int tar_ls(FILE * f, struct tar_t * archive, const size_t filecount, const char * files[], const char verbosity);

// extracts files from an archive
int tar_extract(const int fd, struct tar_t * archive, const size_t filecount, const char * files[], const char verbosity);

// update files in tar with provided list
int tar_update(const int fd, struct tar_t ** archive, const size_t filecount, const char * files[], const char verbosity);

// remove entries from tar
int tar_remove(const int fd, struct tar_t ** archive, const size_t filecount, const char * files[], const char verbosity);

// show files that are missing from the current directory
int tar_diff(FILE * f, struct tar_t * archive, const char verbosity);
// /////////////////////////////////////////////////////////////////////////////

// internal functions; generally don't call from outside ///////////////////////
// print raw data with definitions (meant for debugging)
int print_entry_metadata(FILE * f, struct tar_t * entry);

// print metadata of entire tar file
int print_tar_metadata(FILE * f, struct tar_t * archive);

// check if file with original name/modified name exists
struct tar_t * exists(struct tar_t * archive, const char * filename, const char ori);

// read file and construct metadata
int format_tar_data(struct tar_t * entry, const char * filename, const char verbosity);

// calculate checksum (6 ASCII octet digits + NULL + space)
unsigned int calculate_checksum(struct tar_t * entry);

// print single entry
// verbosity should be greater than 0
int ls_entry(FILE * f, struct tar_t * archive, unsigned int * max_space, const size_t filecount, const char * files[], const char verbosity);

// extracts a single entry
// expects file descriptor offset to already be set to correct location
int extract_entry(const int fd, struct tar_t * entry, const char verbosity);

// write entries to a tar file
int write_entries(const int fd, struct tar_t ** archive, struct tar_t ** head, const size_t filecount, const char * files[], int * offset, const char verbosity);

// add ending data
int write_end_data(const int fd, int size, const char verbosity);

// check if entry is a match for any of the given file names
// returns index + 1 if match is found
int check_match(struct tar_t * entry, const size_t filecount, const char * bad, const char * files[]);
// /////////////////////////////////////////////////////////////////////////////

// other functions (don't call from outside) ///////////////////////////////////
#define MIN(x, y) (((x) < (y)) ? (x) : (y))
#define MAX(x, y) (((x) > (y)) ? (x) : (y))
#define V_PRINT(f, ...) { if (verbosity) fprintf(f, __VA_ARGS__); }
#define RC_ERROR(f, ...) const int rc = errno; V_PRINT(f, __VA_ARGS__); return -1;
#define WRITE_ERROR(f, ...) { V_PRINT(f, __VA_ARGS__); tar_free(*tar); *tar = NULL; return -1; }
#define EXIST_ERROR(f, ...) const int rc = errno; if (rc != EEXIST) { V_PRINT(f, __VA_ARGS__); return -1; }

// force read() to complete
int read_size(int fd, char * buf, int size);

// force write() to complete
int write_size(int fd, char * buf, int size);

// convert octal string to unsigned integer
unsigned int oct2uint(char * oct, unsigned int size);

// check if a buffer is zeroed
int iszeroed(char * buf, size_t size);

// make directory recursively
int recursive_mkdir(const char * dir, const unsigned int mode, const char verbosity);
// /////////////////////////////////////////////////////////////////////////////

#endif