Write the whole memory stream into the stream writer

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Write the whole memory stream into the stream writer

StewartBW 1,805

Hello experts

How to write the whole contents of a memory stream which is some text into my stream writer?

On a separate note, I need to write one single text line and then the whole contents of memory stream which is also text into a system file, in a loop.

Which writer to choose to get the best performance? stream writer or binary writer?

I tested binary writer, but each time I call its .Write("Some String") it adds an empty space initial unwanted character to the beginning of the line :(

Thanks for the help :)

.net fw 4.0 full profile

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Answer 1

Jiachen Li-MSFT 34,221 Microsoft External Staff

Hi @StewartBW ,

StreamWriter is optimized for writing text and handles encoding automatically. It is the best choice when you need to work with textual data, such as writing strings to a file.
BinaryWriter is designed for writing primitive types in binary form. When you use BinaryWriter.Write("Some String"), it writes additional metadata (like the length of the string) and possibly other information, which is why you might see extra characters or spaces. It’s not suitable for pure text writing.

   Using memoryStream As New MemoryStream()
       memoryStream.Position = 0 
       Using streamReader As New StreamReader(memoryStream)
           Using streamWriter As New StreamWriter("output.txt")
               streamWriter.WriteLine("one single text line")
               streamWriter.Write(streamReader.ReadToEnd())
           End Using
       End Using
   End Using

Best Regards.

Jiachen Li

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StewartBW 1,805 Reputation points

2024-08-16T07:00:44.86+00:00

Hello and thanks for the sample, I've got the idea how to do the job.

Just one query about the StreamReader initialization.

StreamReader(Stream, Encoding, Boolean, Int32)

StreamReader(Stream, Encoding, detectEncodingFromByteOrderMarks, bufferSize)

In the docs, it's not mentioned the default value of detectEncodingFromByteOrderMarks, but this is from the documentation:

When reading from a Stream, it is more efficient to use a buffer that is the same size as the internal buffer of the stream.

So to initialize the StreamReader with the same buffer size as the MemoryStream, if I initialize like this:

StreamReader(memorystream, Encoding.UTF8, True, memorystream.Capacity)

Is it correctly setting the buffer size from the source MemoryStream buffer size?

Thanks.
Jiachen Li-MSFT 34,221 Reputation points Microsoft External Staff

2024-08-16T08:01:57.7966667+00:00

Hi @StewartBW ,

Yes, your initialization of StreamReader using StreamReader(memoryStream, Encoding.UTF8, True, memoryStream.Capacity) is correctly setting the buffer size to match the Capacity of the MemoryStream.

The bufferSize parameter in StreamReader is the size of the buffer it uses internally to read chunks of data from the underlying stream.

memoryStream.Capacity represents the total number of bytes that the MemoryStream can hold. This includes both used and unused space in the stream's buffer.

If you intend to match the buffer size to the actual amount of data in the MemoryStream, you might want to consider using memoryStream.Length instead of memoryStream.Capacity .
StewartBW 1,805 Reputation points

2024-08-16T08:45:24.78+00:00

Hello and thanks, ok so:

StreamReader(memorystream, Encoding.UTF8, True, memorystream.Length)

Generally, do you prefer it over:

StreamReader(memoryStream)

Because I'm not aware of possible exceptions of the first usage.

Thanks :)
StewartBW 1,805 Reputation points

2024-08-16T08:59:34.7233333+00:00

oops, first thing is that bufferSize and Capacity are interger but Length is long!

Although have no idea what happens to Capacity if length of stream goes higher that integer?

But is there any .Net function to convert Long to Integer and if input is more than int32.Max value then return int32.Max value instead of zero?
Bruce (SqlWork.com) 77,686 Reputation points Volunteer Moderator

2024-08-16T15:46:18.44+00:00

With a MemoryStream, .Capacity is the current size of the internal buffer. If you write the stream without reading, the capacity will need to increase. You can buffer the whole content if it’s not too large (2gb is the max, but memory restrictions may limit to less).

if you know the max size of the stream buffer, you can use the constructor to do one allocation, rather than re-allocating as the buffer grows.

if the stream are handling large data, then normally you would not buffer the data, but read and write in manageable chunks.

Answer 2

Bruce (SqlWork.com) 77,686 Volunteer Moderator

a StreamWriter() is for writing string or char[] values to stream. its default encoder is UTF-8 no BOM. a BinaryStream is for writing byte buffers. if a char[] or string is passed, it is internally converted to a byte[] based on the Encoding specified in the constructor (UTF-8 BOM is the default). the extra char is the BOM.

https://en.wikipedia.org/wiki/Byte_order_mark

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Write the whole memory stream into the stream writer

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