What is the best method of writing a StringBuilder to a System.IO.Stream?
I am currently doing:
StringBuilder message = new StringBuilder("All your base");
message.Append(" are belong to us");
System.IO.MemoryStream stream = new System.IO.MemoryStream();
System.Text.ASCIIEncoding encoding = new ASCIIEncoding();
stream.Write(encoder.GetBytes(message.ToString()), 0, message.Length);
Don't use a StringBuilder, if you're writing to a stream, do just that with a StreamWriter:
using (var memoryStream = new MemoryStream())
using (var writer = new StreamWriter(memoryStream ))
{
// Various for loops etc as necessary that will ultimately do this:
writer.Write(...);
}
That is the best method. Other wise loss the StringBuilder and use something like following:
using (MemoryStream ms = new MemoryStream())
{
using (StreamWriter sw = new StreamWriter(ms, Encoding.Unicode))
{
sw.WriteLine("dirty world.");
}
//do somthing with ms
}
Perhaps it will be usefull.
var sb= new StringBuilder("All your money");
sb.Append(" are belong to us, dude.");
var myString = sb.ToString();
var myByteArray = System.Text.Encoding.UTF8.GetBytes(myString);
var ms = new MemoryStream(myByteArray);
// Do what you need with MemoryStream
EDIT: As @ramon-smits points out, if you have access to StringBuilder.GetChunks(), you will also have access to StreamWriter.WriteAsync(StringBuilder). So you can just do this instead:
StringBuilder stringBuilder = new StringBuilder();
// Write data to StringBuilder...
Stream stream = GetStream(); // Get output stream from somewhere.
using (var streamWriter = new StreamWriter(stream, Encoding.UTF8, leaveOpen: true))
{
await streamWriter.WriteAsync(stringBuilder);
}
Much simpler.
I recently had to do exactly this thing and found this question with unsatisfactory answers.
You can write a StringBuilder to a Stream without materializing the entire string:
StringBuilder stringBuilder = new StringBuilder();
// Write data to StringBuilder...
Stream stream = GetStream(); // Get output stream from somewhere.
using (var streamWriter = new StreamWriter(stream, Encoding.UTF8, leaveOpen: true))
{
foreach (ReadOnlyMemory<char> chunk in stringBuilder.GetChunks())
{
await streamWriter.WriteAsync(chunk);
}
}
N.B. This API (StringBuilder.GetChunks()) is only available in .NET Core 3.0 and above
If this operation happens frequently, you could further reduce GC pressure by using a StringBuilder object pool.
streamWriter.WriteAsync(stringBuilder)
Depending on your use case it may also make sense to just start with a StringWriter:
StringBuilder sb = null;
// StringWriter - a TextWriter backed by a StringBuilder
using (var writer = new StringWriter())
{
writer.WriteLine("Blah");
. . .
sb = writer.GetStringBuilder(); // Get the backing StringBuilder out
}
// Do whatever you want with the StringBuilder
If you want to use something like a StringBuilder because it is cleaner to pass around and work with, then you can use something like the following StringBuilder alternate I created.
The most important thing it does different is that it allows access to the internal data without having to assemble it into a String or ByteArray first. This means you don't have to double up the memory requirements and risk trying to allocate a contiguous chunk of memory that fits your entire object.
NOTE: I am sure there are better options then using a List<string>() internally but this was simple and proved to be good enough for my purposes.
public class StringBuilderEx
{
List<string> data = new List<string>();
public void Append(string input)
{
data.Add(input);
}
public void AppendLine(string input)
{
data.Add(input + "\n");
}
public void AppendLine()
{
data.Add("\n");
}
/// <summary>
/// Copies all data to a String.
/// Warning: Will fail with an OutOfMemoryException if the data is too
/// large to fit into a single contiguous string.
/// </summary>
public override string ToString()
{
return String.Join("", data);
}
/// <summary>
/// Process Each section of the data in place. This avoids the
/// memory pressure of exporting everything to another contiguous
/// block of memory before processing.
/// </summary>
public void ForEach(Action<string> processData)
{
foreach (string item in data)
processData(item);
}
}
Now you can dump the entire contents to file using the following code.
var stringData = new StringBuilderEx();
stringData.Append("Add lots of data");
using (StreamWriter file = new System.IO.StreamWriter(localFilename))
{
stringData.ForEach((data) =>
{
file.Write(data);
});
}
