What is the easiest way to wrap a forward-only non-seekable source Stream (with CanSeek being false, e.g. an incoming network response) into a Stream that supports seeking, but does only read the same bytes from the source once?
Does .NET Standard (C#) offer any implementation of Stream which can be used for this or do I have to write this functionality by myself?
I can imagine an implementation of Stream which gets the source Stream at construction, reads from it and stores bytes that are read for the first time in a cache or buffer which is then used for each subsequent read of the same bytes.
I don't want to wait for the source Stream to be read completely before accessing the wrapped Stream (because it's very large). Therefore copying the source into a local buffer before accessing the buffer is not what I want.
I have a scenario that every file uploaded that may be of any MIME type should be encrypted and when use wants to download they should be decrypted.
For this I have decrypted a requested file and saved that file in a temporary location.
My decryption method writes to a filestream by reading encrypted filestream.
Now should I change my algorithm to save encrypted filestream to a memory stream
and download directly from memory stream instead of writing to filestream and downloading that file.
In term of performance which would be better filestream or memory stream in this case.
I am thinking that if multiple huge file is requested by multiple users lets say 100 different files are requested by 100 different users. In this case memory may run out and we may face some unwanted troubles.
Which one I should implement.
Have you considered streaming directly into the NetworkStream for output? You will need no memory and no disc space for that. If you expect higher performance from buffering the data in a BufferedStream as an intermediate.
If direct or buffered streaming is not an option for you, the correct answer depends on your requirements. You need to know the size of your files and the expected umber of requests. If you think your web servers memory can handle it and you need the added performance, go for it. Otherwise you should buffer on the hard drive. Remember: you only need sufficient performance, not perfect performance.
I'm porting over some C++ and Java code to C# and see all the data IO as Streams, when all the streams are less than 1K in size.
Given that the buffer size of the stream equals the whole stream in almost all circumstances, is there any reason I shouldn't simply use a Byte[]?
The 1K data units are arriving from a stream source (network or disk) however, once read into memory, the stream access is a little random. I think direct byte[x] access might be more efficient (or logical).
So my question, is it generally acceptable from a security and architecture perspective to use Byte[] array directly instead of wrapping it in a stream? Assume that no further "stream" access is needed for other operations (e.g. an encoded media stream).
Since you stated that the usage is "a little random," I think a byte array makes the most sense; these are inherently good for lookup at a given position, while a stream would require you to do a linear read and reset the position. I'm not sure what security concerns you might have, but if you're passing the array to any unmanaged resources you might want to consider pinning it in memory.
i want to transfer data over sockets and currently i am creating a memory stream.
i can also use a network stream.
Can anyone please help me understand the difference between c# network stream and memory stream?
A NetworkStream is directly related to a socket; it does not know it's own length, you cannot seek, and the read/write functions are directly bound to the receive/send APIs (and therefore, read and write are entirely unrelated to eachother). It can timeout, and a read can take a considerable time if waiting for more data.
A MemoryStream is basically a wrapper over a local byte[]. It has a known length (which can change), you can seek, and read/write are directly related: both increment the same position cursor, and you can write something, rewind, and then read it. All operations are very timely.
It might be easier to ask "what are the similarities", which would be simply: both have a read/write API, by virtue of being subclasses of Stream.
both streams are derive of Stream, this classes are warper for different purpose
According to my understanding, Network Stream reads from the network interface, where if you use a Memory Stream (I mean, in the same scenario), all the data will be loaded to memory first (I assume it reads to the end of the actual stream), then the read operations will read from memory.
The first read operation to occur on the Memory Stream, all the data needs to be loaded in to memory.
Where network stream, you can read the data as they arrive.
During the serialization we can use either memory stream or file stream.
What is the basic difference between these two? What does memory stream mean?
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.Serialization.Formatters.Binary;
namespace Serilization
{
class Program
{
static void Main(string[] args)
{
MemoryStream aStream = new MemoryStream();
BinaryFormatter aBinaryFormat = new BinaryFormatter();
aBinaryFormat.Serialize(aStream, person);
aStream.Close();
}
}
}
Stream is a representation of bytes. Both these classes derive from the Stream class which is abstract by definition.
As the name suggests, a FileStream reads and writes to a file whereas a MemoryStream reads and writes to the memory. So it relates to where the stream is stored.
Now it depends how you plan to use both of these. For eg: Let us assume you want to read binary data from the database, you would go in for a MemoryStream. However if you want to read a file on your system, you would go in for a FileStream.
One quick advantage of a MemoryStream is that there is not need to create temporary buffers and files in an application.
The other answers here are great, but I thought one that takes a really high level look at what purpose steams serve might be useful. There's a bit of simplification going on in the explanation below, but hopefully this gets the idea across:
What is a stream?
A stream is effectively the flow of data between two places, it's the pipe rather than the contents of that pipe.
A bad analogy to start
Imagine a water desalination plant (something that takes seawater, removes the salt and outputs clean drinking water to the water network):
The desalination plant can't remove the salt from all of the sea at one time (and nor would we want it to… where would the saltwater fish live?), so instead we have:
A SeaStream that sucks a set amount of water at a time into the plant.
That SeaStream is connected to the DesalinationStream to remove the salt
And the output of the DesalinationStream is connected to the DrinkingWaterNetworkStream to output the now saltless water to the drinking water supply.
OK, so what's that got to do with computers?
Moving big files all at once can be problematic
Frequently in computing we want to move data between two locations, e.g. from an external hard drive to a binary field in a database (to use the example given in another answer). We can do that by copying all of the data from the file from location A into the computer's memory and from there to to Location B, but if the file is large or the source or destination are potentially unreliable then moving the whole file at once may be either unfeasible or unwise.
For example, say we want to move a large file on a USB stick to a field in a database. We could use a 'System.IO.File' object to retrieve that whole file into the computer's memory and then use a database connection to pass that file onto the database.
But, that's potentially problematic, what if the file is larger than the computer's available RAM? Now the file will potentially be cached to the hard drive, which is slow, and it might even slow the computer down too.
Likewise, what if the data source is unreliable, e.g. copying a file from a network drive with a slow and flaky WiFi connection? Trying to copy a large file in one go can be infuriating because you get half the file and then the connection drops out and you have to start all over again, only for it to potentially fail again.
It can be better to split the file and move it a piece at a time
So, rather than getting whole file at once, it would be better to retrieve the file a piece at a time and pass each piece on to the destination one at a time. This is what a Stream does and that's where the two different types of stream you mentioned come in:
We can use a FileStream to retrieve data from a file a piece at a time
and the database API may make available a MemoryStream endpoint we can write to a piece at a time.
We connect those two 'pipes' together to flow the file pieces from file to database.
Even if the file wasn't too big to be held in RAM, without streams we were still doing a number or read/write operations that we didn't need to. The stages we we're carrying out were:
Retrieving the data from the disk (slow)
Writing to a File object in the computer's memory (a bit faster)
Reading from that File object in the computer's memory (faster again)
Writing to the database (probably slow as there's probably a spinning disk hard-drive at the end of that pipe)
Streams allow us to conceptually do away with the middle two stages, instead of dragging the whole file into computer memory at once, we take the output of the operation to retrieve the data and pipe that straight to the operation to pass the data onto the database.
Other benefits of streams
Separating the retrieval of the data from the writing of the data like this also allows us to perform actions between retrieving the data and passing it on. For example, we could add an encryption stage, or we could write the incoming data to more than one type of output stream (e.g. to a FileStream and a NetworkStream).
Streams also allow us to write code where we can resume the operation should the transfer fail part way through. By keeping track of the number of pieces we've moved, if the transfer fails (e.g. if the network connection drops out) we can restart the Stream from the point at which we received the last piece (this is the offset in the BeginRead method).
In simplest form, a MemoryStream writes data to memory, while a FileStream writes data to a file.
Typically, I use a MemoryStream if I need a stream, but I don't want anything to hit the disk, and I use a FileStream when writing a file to disk.
While a file stream reads from a file, a memory stream can be used to read data mapped in the computer's internal memory (RAM). You are basically reading/writing streams of bytes from memory.
Having a bitter experience on the subject, here's what I've found out. if performance is required, you should copy the contents of a filestream to a memorystream. I had to process the contents of 144 files, 528kbytes each and present the outcome to the user. It took 250 seconds aprox. (!!!!). When I just copied the contents of each filestream to a memorystream, (CopyTo method) without changing anything at all, the time dropped to approximately 32 seconds. Note that each time you copy one stream to another, the stream is appended at the end of the destination stream, so you may need to 'rewind' it prior to copying to it. Hope it helps.
In regards to stream itself, in general, it means that when you put a content into the stream (memory), it will not put all the content of whatever data source (file, db...) you are working with, to the memory. As opposed to for example Arrays or Buffers, where you feed everything to the memory. In stream, you get a chunk of eg. file to the memory. When you reach the end of chunk, stream gets the next chunk from file to the memory. It all happens in low-level background while you are just iterating the stream. That's why it's called stream.
A memory stream handles data via an in memory buffer. A filestream deals with files on disk.
Serializing objects in memory is hardly any useful, in my opinion. You need to serialize an object when you want to save it on disk. Typically, serialization is done from the object(which is in memory) to the disk while deserialization is done from the saved serialized object(on the disk) to the object(in memory).
So, most of the times, you want to serialize to disk, thus you use a Filestream for serialization.