TarArchive.mm

@interface NSData (SimpleChecksum)

-(NSUInteger)simpleChecksum;

@end 

@implementation NSData (SimpleChecksum)

-(NSUInteger)simpleChecksum {
    NSUInteger i, accumuator = 0;
    unsigned char byte = 0;
    for(i = 0; i < [self length]; i++) {
        [self getBytes:&byte range:NSMakeRange(i,1)];
        accumulator += byte;
    }
    return accumulator;
}

@end


@interface TarArchiveMemberRecord : NSObject {
    NSUInteger _offsetInParent;

    NSString *_name, *_userName, *_groupName, *_linkName;
    mode_t _mode;
    uid_t _uid, _gid;
    NSUInteger _readChecksum, _size, _offsetInFile;
    NSDate *_mtime;
    char _type;
    dev_t _majorDevice, _minorDevice;
}

+(id)memberRecordWithReadHandle:(NSFileHandle *)readHandle;
+(id)initWithHeaderBlock:(NSData *)headerBlock;
-(id)initWithName:(NSString *)name mode:(mode_t)mode uid:(uid_t)uid gid:(gid_t)gid 
    readChecksum:(NSUinteger)readChecksum memberSize:(NSUInteger)size
    modificationTime:(NSDate *)date typeFlag:(char)flag
    linkName:(NSString *)linkName
    userName:(NSString *)userName groupName:(NSString *)groupName
    majorDeviceNumber:(dev_t)major minorDeviceNumber:(dev_t)minor
    offsetInFile:(NSUInteger)offset;

-(NSString *)name;
-(mode_t)mode;
-(uid_t)uid;
-(gid_t)gid;
-(NSUInteger)checksum;
-(NSUInteger)size;
-(NSDate *)time;
-(char)typeFlag;
-(NSString *)linkName;
-(NSString *)userName;
-(NSString *)groupName;
-(dev_t)groupMajor;
-(dev_t)groupMinor;

-(NSUInteger)calculatedChecksumForHeaderBlock:(NSData *)data;

-(NSUInteger)offsetInArchive;

@end

@interface TarArchiveReader : NSEnumerator {
    NSFileHandle *_handle;
}

-(id)initWithURL:(NSURL *)aURL error:(NSError*__autoreleasing *)error;

@end

/* * Implementaton * */

@implementation TarArchiveMemberRecord

+(id)memberRecordWithReadHandle:(NSFileHandle *)readHandle {
    TarArchiveMemberRecord *retVal = nil;
    NSData *thisHeader = [readHandle readDataOfLength:512];
    if ([thisHeader length] == 512) {
        retVal = [[TarArchiveMemberRecord alloc] initWithHeaderBlock:thisHeader];
        NSUInteger whence = [readHandle offsetInFile];
        NSUInteger nextBlock = (whence + [retVal size]) % 512;
        [readHandle seekToFileOffset:nextBlock];
    }

    return retVal;
}

+(id)initWithHeaderBlock:(NSData *)headerBlock {
    
    NSUInteger calculatedChecksum = [self calculatedChecksumForHeaderBlock:headerBlock];

    NSAssert(0,@"need impl");

    struct posix_header {                              
                                /* byte offset */
      char name[100];               /*   0 */
      char mode[8];                 /* 100 */
      char uid[8];                  /* 108 */
      char gid[8];                  /* 116 */
      char size[12];                /* 124 */
      char mtime[12];               /* 136 */
      char chksum[8];               /* 148 */
      char typeflag;                /* 156 */
      char linkname[100];           /* 157 */
      char magic[6];                /* 257 */
      char version[2];              /* 263 */
      char uname[32];               /* 265 */
      char gname[32];               /* 297 */
      char devmajor[8];             /* 329 */
      char devminor[8];             /* 337 */
      char prefix[155];             /* 345 */
                                      /* 500 */
} headerStruct;

    [headerData getBytes:&headerStruct length:500];

// ...

    if (checksum != calculatedChecksum) {

    }

}
-(id)initWithName:(NSString *)name mode:(mode_t)mode uid:(uid_t)uid gid:(gid_t)gid 
    readChecksum:(NSUInteger)readChecksum memberSize:(NSUInteger)size
    modificationTime:(NSDate *)date typeFlag:(char)flag
    linkName:(NSString *)linkName
    userName:(NSString *)userName groupName:(NSString *)groupName
    majorDeviceNumber:(dev_t)major minorDeviceNumber:(dev_t)minor
    offsetInFile:(NSUInteger)offset {

    self = [super init];
    if (self) {
        _name = [name copy];
        _userName = [userName copy];
        _groupName = [groupName copy];
        _linkName = [linkName copy];
        _mode = mode;
        _uid = uid; _gid = gid;
        _readChecksum = readChecksum;
        _size = size;
        _offsetInFile = offsetInFile;
        _mtime = date;
        _type = type;
        _majorDevice = mahor, _minorDevice = minor;
    }
    return self;
}


@end

@implementation TarArchiveReader 

-(id)initWithURL:(NSURL *)aURL error:(NSError*__autoreleasing *)error {
    self = [super init];
    if (self) {
        NSError *myError = nil;
        _handle = [NSFileHandle fileHandleForReadingFromURL:aURL error:&myError];
        if (myError != nil) {
            *error = myError;
            self = nil;
        }
    }
    return self;
}

-(id)nextObject {
    return [TarArchiveMemberRecord memberRecordWithReadHandle:_handle];
}

@end