- Dmg Files With Lzfse Compression Size
- Dmg Files With Lzfse Compression Tape
- Dmg Files With Lzfse Compression Pants
Perform compression or the appropriate kind of decompression to a file based on its path extension.
There isn’t: dragging the application to your Applications folder is the entire process.You don’t have to put your programs in the Applications folder, though: they’ll run from anywhere. Some people create a “Games” directory, to keep games separate from other applications. But Applications is the most convenient place to put things, so we suggest you just put everything there.DMG files are mounted by your system, like a sort of virtual hard drive. Often these will include the application itself, some form of arrow, and a shortcut to the Applications folder.Simply drag the application’s icon to your Applications folder and you’re done: the software is now installed. Can delete dmg files after installation. It’s so simple it confuses some people—surely there must be more to it than that?
Jan 17, 2018 Apple introduced new LZFSE type of compression inside DMG files. Currently it's not supported, in progress. Changes to the volume change the dmg file instead of an actual disk drive. The dmg format includes options such as various volume types (APFS or HFS+), compression options, encryption (password protection) and file spanning (segmenting). Compressed dmg files are generally read-only. Dmg files are often used for Mac software installation.
Framework
- Compression
Overview
This sample code project uses the Compression framework to encode (compress) and decode (decompress) files by dragging them to the app window. The app decompresses files with an extension that matches a supported compression algorithm (that is,
.lz4
, .zlib
, .lzma
, or .lzfse
), and compresses all other files. The app writes the encoded or decoded result to the temporary directory returned by the NSTemporaryDirectory()
function.This sample implements stream compression, where the app calls the encode or decode functions repeatedly to compress or decompress data from a source buffer to a destination buffer. Between calls, the app removes processed data from the source buffer and loads the new data into the destination buffer:
The advantage of this approach is that by moving the encoding or decoding to a background thread, you’re able to keep your app interactive and update the user with progress of the operation (for example, with an
NSProgressIndicator
). Stream compression also enables tasks such as:- Decoding a compressed stream into a buffer with the ability to grow the buffer and resume decoding if the expanded stream is too large to fit, without repeating any work.
- Encoding a stream as pieces of it become available, without ever needing to create a buffer large enough to hold all the uncompressed data at one time.
Accept Dropped Files
Register the app’s view,
DragDropCompressView
, as a destination for file URLs by adding registerForDraggedTypes(_:)
to the viewDidMoveToSuperview()
method:After the user drops a conforming file onto the app, the view calls the
performDragOperation(_:)
method. Iterate over the dragged items inside performDragOperation
, using guard
to ensure each item is a URL
instance:Select a Compression Algorithm
If speed and compression ratio are important, use
COMPRESSION_LZFSE
:If you require interoperability with non-Apple devices, use
COMPRESSION_ZLIB
instead. For more information about other compression algorithms, see compression_algorithm
.Distinguish Between Compressed and Uncompressed Files
Use the path extension to infer whether a file is already compressed, or if the file needs compressing. To simplify this process, create a failable initializer in an extension to the Compression framework’s
compression_algorithm
structure:Use this new initializer to define the
algorithm
and operation
constants:Define the Source and Destination File Handles
The sample uses
FileHandle
instances to read from the source file and write to the destination file. Use optional binding to define the required file handles:If the optional binding succeeded, the destination file handle points to the source filename with the compression algorithm appended as an extension (for compression), or the source filename with the compression name extension removed (for decopression). For example, the source file
MyCompressedFile.PDF.lzfse
would have a destination of MyCompressedFile.PDF
, and MyRawFile.PDF
would have a destination of MyRawFile.PDF.lzfse
.Pass the source and destination file handles, with the operation and algorithm values to the helper function
streamingCompression
:Create a Destination Buffer
The
streamingCompression
method iterates over the source data, encoding or decoding data in blocks based on the length defined by bufferSize
. The method writes the result into the destination buffer, and writes the destination buffer data to the destination file handle. The following declares the buffer size and allocates the destination buffer: Dmg to iso.Create a Compression Stream
The
compression_stream
structure defines the source and destination pointers and sizes. To simplify the instantiation of a compression_stream
structure, create an extension that allocates the required memory:Use the following extension to declare and initialize the compression stream:
After you’re finished with the
compression_stream
structure, it’s important that you free the memory allocated to it with compression_stream_destroy(_:)
. Use a defer block to ensure the memory is freed even if the streamingCompression
method exits early:With the compression stream inialized, set up the stream by defining its source and destination sizes and destination pointer:
Read the Source File Data Iteratively
Use a
repeat-while
loop to manage the read-encode/decode-write process. If the stream’s source size is zero, read a block of data from the source file handle and point the stream’s source pointer to that data. If the read data is shorter than the buffer size, you can infer that you’re reading the last block of the source file and set the stream’s status to COMPRESSION_STREAM_FINALIZE
:Compress or Decompress the Dragged File
Use
compression_stream_process(_:_:)
to encode or decode the current block:On return,
destinationBufferPointer
points to the encoded or decoded data.Write Encoded or Decoded Data to a Destination File
Check the status returned by
compression_stream_process
, if it’s either COMPRESSION_STATUS_OK
or COMPRESSION_STATUS_END
, you can write the destination data to the destination file handler:This read-encode/decode-write loop continues while
status
equals COMPRESSION_STATUS_OK
.Close the Source and Destination Files
After you’re finished with the source and destination file handles, close them with the
closeFile()
method:See Also
struct compression_stream
func compression_stream_init(UnsafeMutablePointer<compression_stream>, compression_stream_operation, compression_algorithm) -> compression_status
Initializes a compression stream for either compression or decompression.
func compression_stream_process(UnsafeMutablePointer<compression_stream>, Int32) -> compression_status
Performs compression or decompression using an initialized compression stream structure.
func compression_stream_destroy(UnsafeMutablePointer<compression_stream>) -> compression_status
Dmg Files With Lzfse Compression Size
Frees any memory allocated by stream initialization function.
Dmg Files With Lzfse Compression Tape
struct compression_status
A set of values used to represent the status of stream compression.
struct compression_stream_flags
A set of values used to represent stream compression flags.
struct compression_stream_operation
Dmg Files With Lzfse Compression Pants
A set of values used to represent a stream compression operation.