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extract.c
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extract.c
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/*
CPE 357 Asgn4
Author: Dylan Baxter (dybaxter), Van Park (vpark05)
File: extract.c
Description: This file contains functions necessary for extraction from
tar archives
*/
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <dirent.h>
#include <limits.h>
#include <errno.h>
#include <utime.h>
#include <time.h>
#include <sys/time.h>
#include "extract.h"
#include "extr_helper.h"
int giveExecute(mode_t e_mode){
/* Takes a given filename and gives execute to everyone
* if at least on person has execute permissions
* returns 0 on success and -1 on failure */
if((e_mode & S_IXUSR) ||
(e_mode & S_IXGRP) ||
(e_mode & S_IXOTH)){
return 1;
}
return 0;
}
int checksum(struct Header *head){
/* Returns 1 on valid header
* Returns -1 on invalid header/blank block
Returns 0 on null block
*/
char smallOct[8] = {'\0'};
unsigned char* countPt = (unsigned char*)head;
int realsum = unoctal(head->chksum);
int checksum = 0;
memset(head->chksum, ' ', 8);
memset(smallOct, '0', 8);
int i;
for(i=0;i<BLOCK_SIZE;i++){
checksum = checksum+*countPt;
countPt++;
}
strcpy(head->chksum, octalConvert(realsum, smallOct, 8));
if(DEBUG){
printf("Checksum %s: %d %d\n", head->name, checksum, realsum);
}
if(checksum == 256){
return 0;
}
else if(checksum == realsum){
return 1;
}
else{
return -1;
}
}
void extract_file(char *path, struct Header *head, int fdHead){
/* Takes a path name of a file and the header for said file and
* extracts its contents from the archive into a new file with the
* given path
*/
mode_t e_mode = unoctal(head->mode);
off_t e_size = unoctal(head->size);
time_t e_mtime = unoctal(head->mtime);
time_t atime = time(NULL);
struct utimbuf timebuf;
int i = e_size;
int fd;
/*struct utimbuf oldtime;
oldtime.modtime = e_mtime;
utime(path, oldtime);*/
char buffer[512] = {0};
ensureDir(path);
if(giveExecute(e_mode)){
e_mode = 0777;
}else{
e_mode = 0666;
}
if(e_size > 0){
if(-1 ==(fd = open(path, O_CREAT|O_TRUNC|O_WRONLY,e_mode))){
perror(path);
exit(EXIT_FAILURE);
}
if(DEBUG){
printf("File Descriptor is %d\n", fd);
}
while (i >= 512){
if(-1 == read(fdHead, buffer, 512)){
perror("Read Body TAR");
exit(EXIT_FAILURE);
}
if(DEBUG){
printf("Writing Chunk of size %d", 512);
}
if(-1 == write(fd, buffer, 512)){
perror("Write Body");
exit(EXIT_FAILURE);
}
i -= 512;
}
if(-1==read(fdHead, buffer, 512)){
perror("Read Final Block");
exit(EXIT_FAILURE);
}
if(DEBUG){
printf("Writing Chunk of size %d\n", i);
printf("Writing: %d %s %d\n", fd, buffer, i);
}
if(-1==write(fd, buffer, i)){
perror("Write Final Block");
exit(EXIT_FAILURE);
}
}
else{
fd = 0;
if(-1 ==(fd = open(path, O_CREAT|O_TRUNC|O_WRONLY, e_mode))){
perror(path);
exit(EXIT_FAILURE);
}
}
if(close(fd) == -1){
perror("Close Body Write");
exit(EXIT_FAILURE);
}
/*Time Stuff*/
struct stat sb;
if(stat(path, &sb) == -1){
perror("Time Stat");
exit(EXIT_FAILURE);
}
atime = sb.st_atime;
timebuf.actime = atime;
timebuf.modtime = e_mtime;
if(-1 == utime(path, &timebuf)){
perror("Time Stuff");
exit(EXIT_FAILURE);
}
}
void extract_link(char *path, struct Header *head){
/* Takes a path name of a file and the header for said file and
* extracts its contents from the archive into a new file with the
* given path
*/
ensureDir(path);
if (symlink(head->linkname, path) == -1){
if(errno == EEXIST){
return;
}
else{
perror("symlink");
exit(EXIT_FAILURE);
}
}
}
void extract_directory(char *path, struct Header *head){
/* Takes a path for a given directory and extracts the directory from
* the given archive *
*/
mode_t e_mode = unoctal(head->mode);
if(giveExecute(e_mode)){
e_mode = 0777;
}else{
e_mode = 0666;
}
ensureDir(path);
if (mkdir(path, e_mode) == -1){
if(errno == EEXIST){
return;
}
else{
perror("mkdir");
exit(EXIT_FAILURE);
}
}
}
void extract(char **fileNames, int pathcount,
char *archive, unsigned int optMask){
/* Searches through the archive for the given file name.
* If it exists it attempts to extract the file.
*/
/*Define Variables*/
char buffer[512];
struct Header *head;
int numblocks = 0;
int readsize = 0;
int checkVal = 0;
int endblock = 0;
int i = 0;
int fd;
/*Open the archive*/
if (-1==(fd = open(archive, O_RDONLY, 0666))){
perror(archive);
exit(EXIT_FAILURE);
}
/*For each header in the file*/
while((readsize = read(fd, buffer, 512)) > 0){
if(DEBUG){
printf("Reading block of size %d\n", readsize);
}
/*If not a body block*/
if (numblocks == 0){
/*Extract the header*/
head = (struct Header *)(buffer);
/*Check for null blocks and invalid headers*/
checkVal = checksum(head);
if(checkVal == -1){
perror("INVALID HEADER\n");
exit(EXIT_FAILURE);
}
/*Exit On encountering 2 empty blocks*/
if(checkVal == 0){
endblock++;
if(DEBUG){
printf(" End Block %d Encountered \n", endblock);
}
if(endblock > 1){
if(DEBUG){
printf("EOF \n");
}
return;
}
}
else{
/*Get Size of body and calculate number of body blocks to skip*/
int size = unoctal(head->size);
/* If there is a remainder we need and entire 512 byte block
*/
if ((size % 512) == 0){
numblocks = size / 512;
}
else{
numblocks = (size / 512) + 1;
}
/*Parse Path name*/
char fname[257] = {0};
char delim[2] = "/\0";
for(i=0;i<155;i++){
if(head->prefix[i] != '\0'){
fname[i] = head->prefix[i];
}
else{
break;
}
}
if(strlen(fname)){
strcat(fname, delim);
}
strncat(fname, head->name, 100);
/*Find type*/
int extractFlag = 0;
for(i=0;i<pathcount;i++){
if (!(strcmp(fname, fileNames[i]))
|| checkpre(fileNames[i], fname)){
extractFlag = 1;
break;
}
}
if((optMask & ALLFLAG)){
extractFlag = 1;
}
/*Check if the fileNames match */
if (extractFlag){
if(optMask & VERBOSE){
printf("%s\n", fname);
}
if (head->typeflag == '5'){
/* Checks if the file is a directory */
if(DEBUG){
printf("Extracting directory: %s\n", fname);
}
extract_directory(fname, head);
}
else if ((head->typeflag == '0')
||(head->typeflag == '\0')){
/* Checks if the file is a REG file*/
if(DEBUG){
printf("Extracting File: %s\n", fname);
}
extract_file(fname, head, fd);
numblocks = 0;
}
else if (head->typeflag == '2'){
/* Checks if the file is a SYMLNK file*/
if(DEBUG){
printf("Extracting SYMLNK: %s\n", fname);
}
extract_link(fname, head);
numblocks = 0;
}
}
}
}
else{
numblocks--;
}
}
}