ObjFW  Diff

			_mode = OF_TAR_ARCHIVE_MODE_WRITE;
		else if ([mode isEqual: @"a"])
			_mode = OF_TAR_ARCHIVE_MODE_APPEND;
		else
			@throw [OFInvalidArgumentException exception];

		if (_mode == OF_TAR_ARCHIVE_MODE_APPEND) {
			union {
				char c[1024];
				uint32_t u32[1024 / sizeof(uint32_t)];
			uint32_t buffer[1024 / sizeof(uint32_t)];
			} buffer;
			bool empty = true;

			if (![_stream isKindOfClass: [OFSeekableStream class]])
				@throw [OFInvalidArgumentException exception];

			[(OFSeekableStream *)_stream seekToOffset: -1024
							   whence: SEEK_END];
			[_stream readIntoBuffer: buffer.c
			[_stream readIntoBuffer: buffer
				    exactLength: 1024];

			for (size_t i = 0; i < 1024 / sizeof(uint32_t); i++)
				if (buffer.u32[i] != 0)
				if (buffer[i] != 0)
					empty = false;

			if (!empty)
				@throw [OFInvalidFormatException exception];

			[(OFSeekableStream *)stream seekToOffset: -1024
							  whence: SEEK_END];

	[super dealloc];
}

- (OFTarArchiveEntry *)nextEntry
{
	OFTarArchiveEntry *entry;
	union {
		unsigned char c[512];
		uint32_t u32[512 / sizeof(uint32_t)];
	uint32_t buffer[512 / sizeof(uint32_t)];
	} buffer;
	bool empty = true;

	if (_mode != OF_TAR_ARCHIVE_MODE_READ)
		@throw [OFInvalidArgumentException exception];

	[(OFTarArchiveFileReadStream *)_lastReturnedStream of_skip];
	@try {
		[_lastReturnedStream close];
	} @catch (OFNotOpenException *e) {
		/* Might have already been closed by the user - that's fine. */
	}
	[_lastReturnedStream release];
	_lastReturnedStream = nil;

	if (_stream.atEndOfStream)
		return nil;

	[_stream readIntoBuffer: buffer.c
	[_stream readIntoBuffer: buffer
		    exactLength: 512];

	for (size_t i = 0; i < 512 / sizeof(uint32_t); i++)
		if (buffer.u32[i] != 0)
		if (buffer[i] != 0)
			empty = false;

	if (empty) {
		[_stream readIntoBuffer: buffer.c
		[_stream readIntoBuffer: buffer
			    exactLength: 512];

		for (size_t i = 0; i < 512 / sizeof(uint32_t); i++)
			if (buffer.u32[i] != 0)
			if (buffer[i] != 0)
				@throw [OFInvalidFormatException exception];

		return nil;
	}

	entry = [[[OFTarArchiveEntry alloc]
	    of_initWithHeader: buffer.c
	    of_initWithHeader: (unsigned char *)buffer
		     encoding: _encoding] autorelease];

	_lastReturnedStream = [[OFTarArchiveFileReadStream alloc]
	    of_initWithStream: _stream
			entry: entry];

	return entry;