New to .net but still confuse about the concept of BinaryFormatter and Filestream, from all i read they both seem to be doing the same thing or similar concept. Ex. is Binaryformatter.serialize, how can that incorporate filestream and the object as parameter while i thought filestream function was to transfer the stream object to the file. I'm just confuse, can someone tell me how they work together and the difference between the two?
Streams represent raw data that can be accessed sequentially. They are used (directly or indirectly) whenever you input or output. There are different kinds of streams. For example:
NetworkStream and FileStream read and write data from a network port and disk without performing any transformations.
GzipStream or CryptoStream decorate an underlying stream by adding compression and encryption.
BinaryFormatter requires a Stream to write or read from. But its responsibility is very different: it's used to convert .NET objects to sequence of bytes that can saved or transmitted through a network. Concrete medium and additional transformations are determined by the type of stream you use.
All streams inherit from the Stream class and share the same interface which is very convenient. Classes like BinaryFormatter can rely on this shared interface without knowing the specifics of particular implementation.
Once again, BinaryFormatter is for converting an object to and from a sequence of bytes.
Streams are for reading and writing these bytes to a particular medium.
Related
We use BinaryFormatter to serialize objects into a NetworkStream and transfer them through TCP Sockets.
I was just trying to figure out if the Endiannes is fixed or if is system dependent.
I know that BinaryWriter uses always LittleEndian, I was trying to find the same type of information for BinaryFormatter.
BinaryFormatter uses the internal __BinaryParser class to take care of decoding bytes. Look at its ReadInt16() method as one that has an endian dependency. Click on "dataReader" to see that it is simply a BinaryReader that gets that job done.
BinaryReader always uses little-endian, regardless of the system default.
Same story for __BinaryWriter.WriteInt16(), the internal method that BinaryFormatter uses to write an Int16, uses BinaryWriter. Do note that you'll never actually test this, the only non-trivial big-endian host that can execute C# code is the olden XBox 360. Which does not support System.Net
If you are working with two applications use the BinaryReader/BinaryWriter, not the BinaryFormatter. BinaryFormatter is not a good for serializing data across a wire, it was designed mainly for IPC in mind. if you pass data onto another system its not a good idea.
Read here https://msdn.microsoft.com/en-us/library/system.runtime.serialization.formatters.binary.binaryformatter(v=vs.110).aspx.
Also here: http://ambracode.com/index/show/244765
I am writing a simple client-server application, and looking the MSDN docs, I came across some interesting stream types...
http://msdn.microsoft.com/en-us/library/system.io.compression.deflatestream.aspx
http://msdn.microsoft.com/en-us/library/system.io.compression.gzipstream.aspx
Apparently, there is such a thing as a compressed stream! Naturally, this is very attractive, considering we are dealing with networking. However, most unfortunately, TcpClient.GetStream() only returns a NetworkStream -- Not any form of compressed stream.
I was wondering if it is possible to wire a compressed stream to redirect to the NetworkStream, meaning I could write the the compressed stream and that stream would write its compressed output to my NetworkStream. I'd also need to know how to do the reverse, get a compressed stream to read from a NetworkStream.
On the side, which do you recommend I do -- Which offers the fastest compression, GZip or Deflate? And what is the difference in compression between the two?
These are wrapper streams.
You can create a GzipStream around any existing stream to read or write compressed data to the inner stream.
Checkout networkComms.net, an open source network communication library which includes the option of using many different types of compression when sending data. All you have to do is change the NetworkComms.DefaultCompressor property. You can choose from:
None
LZMA (Slow Speed, Best Compression)
GZip (Good Speed, Good Compression)
QuickLZ (Best Speed, Basic Compression)
In order to to support these plus any further number of different compression methods networkComms.net uses a basic networkStream at the base and just makes sure everything has been compressed before it reaches that point.
does anyone know of an unbuffered XmlReader implementation?
Not the XmlTextReaderImpl which uses a byte[] buffer internally and reads from a stream at construction! I find this incredibly annoying. I only want the XmlReader to read when actually calling Read* on the object. Not to buffer data or similar.
NOTE: I am not talking about cached vs non-cached. But stream buffering, which happens internally in the XmlTextReader for example.
I want to use this in a scenario where I currently have to create a new XmlTextReader each time I want to deserialize an object, but since this creates a buffer of size 4096 every time it puts a lot of pressure on the garbage collector. So I would like to keep an instance of the XmlReader around (which can continously read from a stream of xml objects), but this is not possible with the BCL implementation or have an XmlReader that does not create a buffer.
Not creating a buffer coule be impossible.
The parser needs to have lookahead, not to mention NameTables for fast processing.
4096 seems big, but might be the most efficient unit: it coincides with a page of virtual memory, and it could be used in stead of many repeated small allocations (? guessing)
However, reusing the instance would have been nice. You could have a look at the mono implementation and work it to your liking:
https://github.com/mono/mono/blob/master/mcs/class/System.XML/System.Xml/XmlTextReader.cs
C++ and C# both use the word stream to name many classes.
C++: iostream, istream, ostream, stringstream, ostream_iterator, istream_iterator...
C#: Stream, FileStream,MemoryStream, BufferedStream...
So it made me curious to know, what does stream mean?
What are the characteristics of a stream?
When can I use this term to name my classes?
Is this limited to file I/O classes only?
Interestingly, C doesn’t use this word anywhere, as far as I know.
Many data-structures (lists, collections, etc) act as containers - they hold a set of objects. But not a stream; if a list is a bucket, then a stream is a hose. You can pull data from a stream, or push data into a stream - but normally only once and only in one direction (there are exceptions of course). For example, TCP data over a network is a stream; you can send (or receive) chunks of data, but only in connection with the other computer, and usually only once - you can't rewind the Internet.
Streams can also manipulate data passing through them; compression streams, encryption streams, etc. But again - the underlying metaphor here is a hose of data. A file is also generally accessed (at some level) as a stream; you can access blocks of sequential data. Of course, most file systems also provide random access, so streams do offer things like Seek, Position, Length etc - but not all implementations support such. It has no meaning to seek some streams, or get the length of an open socket.
There's a couple different meanings. #1 is what you probably mean, but you might want to look at #2 too.
In the libraries like those you mentioned, a "stream" is just an abstraction for "binary data", that may or may not be random-access (as opposed to data that is continuously generated, such as if you were writing a stream that generated random data), or that may be stored anywhere (in RAM, on the hard disk, over a network, in the user's brain, etc.). They're useful because they let you avoid the details, and write generic code that doesn't care about the particular source of the stream.
As a more general computer science concept, a "stream" is sometimes thought of (loosely) as "finite or infinite amount of data". The concept is a bit difficult to explain without an example, but in functional programming (like in Scheme), you can turn a an object with state into a stateless object, by treating the object's history as a "stream" of changes. (The idea is that an object's state may change over time, but if you treat the object's entire life as a "stream" of changes, the stream as a whole never changes, and you can do functional programming with it.)
From I/O Streams (though in java, the meaning is the same in C++ / C#)
An I/O Stream represents an input
source or an output destination. A
stream can represent many different
kinds of sources and destinations,
including disk files, devices, other
programs, and memory arrays.
Streams support many different kinds
of data, including simple bytes,
primitive data types, localized
characters, and objects. Some streams
simply pass on data; others manipulate
and transform the data in useful ways.
No matter how they work internally,
all streams present the same simple
model to programs that use them: A
stream is a sequence of data. A
program uses an input stream to read
data from a source, one item at a
time.
In C#, the streams you have mentioned derive from the abstract base class Stream. Each implementation of this base class has a specific purpose.
For example, FileStream supports read / write operations on a file, while the MemoryStream works on an in-memory stream object. Unlike the FileStream and MemoryStream classes, BufferedStream class allows the user to buffer the I/O.
In addition to the above classes, there are several other classes that implement the Stream class. For a complete list, refer the MSDN documentation on Stream class.
Official terms and explanations aside, the word stream itself was taken from the "real life" stream - instead of water, data is transferred from one place to another.
Regarding question you asked and still wasn't ansewered, you can name your own classes in names that contain stream but only if you implement some sort of new stream it will have correct meaning.
In C functions defined in <stdio.h> operate on streams.
Section 7.19.2 Streams in C99 discusses how they behave, though not what they are, apart from "an ordered sequence of characters".
The rationale gives more context in the corresponding section, starting with:
C inherited its notion of text streams from the UNIX environment in which it was born.
So that's where the concept comes from.
Some streams in c# appear to have a "direction" in that they are meant to be used on one way. For some of them, such as FileStream and NetworkStream that makes sense, but others does not.
For example with a GZipStream you can either compress or decompress data by writing it to the stream depending on constructor parameters. CryptoStream on the other hand force the encrypted data to the far side where decryption is forced to a read operation and encryption is a write operation.
Especially when working with cryptographic implementations It has been annoying to be forced pushing the data in a specific direction.
Is there any specific design motivation for implementing some streams in one direction only?
Update: To clarify, what I'm looking for is an understanding on why a some designs only use a single direction, not what the choice of direction is. Did anyone think of this before and found a explanation or maybe there is none.
Receiving a running stream of data that need to be processed as soon as possible. Therefore you want to write the bytes to the decoding stream as they are received.
With CryptoStream there is no natural relation to how many bytes you put in the memorystream and how many bytes you can read decrypted. Here you must take implementation specific details into consideration such as block size.
GZipStream can handle this by changing the direction of the compression.
decryption is forced to a read operation and encryption is a write operation
Is there any specific design motivation for implementing some streams in one direction only?
Well, suppose it was the other way round. It sounds sensible to decrypt-while-writing to a file, but the data still has to come from somewhere.
Meaning you would need a Stream.CopyTo() and the occasional MemoryStream. And those are the tools you can use now as well.
The choice may have been slightly arbitrary but you need to pick a direction, and encrypt-while-writing seems (to me) the most natural.
If you think of the CryptoStream as a container for encrypted content, it becomes obvious that sth. you want to Read() out of it should be decryptet and sth. you Write() into it should be encrypted.
The stream direction is arbitrary to the implementer and sometimes it doesn't match up with the direction we would like to use.
e.g. FTP file downloader only accepts a write stream, but you want to read the stream instead. Or in Reverse, the FTP uploader only accepts a read stream, but you want to write to the stream instead.
Stream is about moving data in chunks so it can be changed to move in either direction.
Here's an implementation:
https://github.com/djpai/StreamConduit