Add char[] buffer to XmlRawWriter.

[TrayanZapryanov]

This PR suggest using small char[] buffer in XmlRawWriter and use it for formatting primitive types in it. Then using WriteRaw(char[]) method instead of creating temporary string and WriteRaw(string) method.
Also exposing XmlConverter.TryFormat methods for already exposed ToString(xxx) primitive types, allowing writes to Span destination.
Last change is to expose TryFormat in XsdDateTime and XsdDuration.

This PR will open possibilities in XmlSerializers to use typed methods of XmlWriter instead of always fallback to WriteString one.
Sample optimization

[ghost]

Tagging subscribers to this area: @dotnet/area-system-xml
See info in area-owners.md if you want to be subscribed.

Issue Details

---

This PR suggest using small char[] buffer in XmlRawWriter and use it for formatting primitive types in it and then using WriteRaw(char[]) method instead of creating temporary string and using WriteRaw(string).
Also exposing TryFormat methods for already exposed ToString(xxx) primitive types, allowing writes to Span destination.
Last change is to expose TryFormat in XsdDateTime and XsdDuration.

This PR will open possibilities in XmlSerializers to use typed methods of XmlWriter instead of always fallback to WriteString one.

Author:	TrayanZapryanov
Assignees:	-
Labels:	area-System.Xml
Milestone:	-

[TrayanZapryanov]

I saw that there is difference between

runtime/src/libraries/System.Private.Xml/src/System/Xml/Core/XmlUtf8RawTextWriter.cs

Line 560 in abb5c34

public override unsafe void WriteChars(char[] buffer, int index, int count)

and

runtime/src/libraries/System.Private.Xml/src/System/Xml/Core/XmlUtf8RawTextWriter.cs

Line 582 in abb5c34

public override unsafe void WriteRaw(char[] buffer, int index, int count)

Which one should be used ?

[TrayanZapryanov]

This comment seems not relevant as even now it is using

runtime/src/libraries/System.Private.Xml/src/System/Xml/XmlConvert.cs

Line 746 in abb5c34

public static string ToString(DateTimeOffset value)

[TrayanZapryanov]

Maybe it is connected with base code ?

runtime/src/libraries/System.Private.Xml/src/System/Xml/Core/XmlWriter.cs

Line 275 in 8f33fd5

public virtual void WriteValue(DateTimeOffset value)

[TrayanZapryanov]

@krwq Do you know if somebody is changing this Mode ?

runtime/src/libraries/System.Private.Xml/src/System/Xml/Serialization/Xmlcustomformatter.cs

Lines 20 to 34 in 4486805

	internal static class XmlCustomFormatter
	{
	private static DateTimeSerializationSection.DateTimeSerializationMode s_mode;
	private static DateTimeSerializationSection.DateTimeSerializationMode Mode
	{
	get
	{
	if (s_mode == DateTimeSerializationSection.DateTimeSerializationMode.Default)
	{
	s_mode = DateTimeSerializationSection.DateTimeSerializationMode.Roundtrip;
	}
	return s_mode;
	}
	}

I saw similar code in XmlSerializers and the only way to change is with Reflection and directly manipulating fiedl.

[TrayanZapryanov]

This limitation is really strange, but we need to adapt XmlValueConverter to allow Guid in it's methods.

[TrayanZapryanov]

Added proposal for this Add WriteValue(Guid/TimeSpan) in System.Xml.XmlWriter

[PaulusParssinen]

I believe this one can do same optimization as in #64782 but with correct casing.

[TrayanZapryanov]

Whole logic for writing with buffer is duplicated in XmlTextWriter and XmlRawWriter.
One suggestion is to create "public" class( this is needed as XmlTextWriter is public) and encapsulate logic in it.
The other is to have some static helper class which works by ref with char[].

Which one do you prefer ?

[TrayanZapryanov]

Duplication logic reduced, but the question still stays open.

[TrayanZapryanov]

@krwq, @eiriktsarpalis Is it possible to receive some initial feedback on these changes and to the following ones(changes in serializators to use typed methods instead of converting to string first) ?
Do you see any value in this idea or you expect some problem later that will stop it?
Should I continue with following PRs to change one by one serializers(Reflection, Primitive, IlGen....) based on this or to wait until this one is merged?
I am quite new in proposing changes and will need some guidance if possible.

[eiriktsarpalis]

This seems to be adding a lot of branching where it previously didn't exist. Could this be done differently? I'm not super familiar with this code, but one thought might be to expose a TryFormat method to XmlUntypedConverter.Untyped.

[TrayanZapryanov]

The code in XmlUntypedConverter.ToString(object) is already similar:
```cs
public override string ToString(object value, IXmlNamespaceResolver? nsResolver)
{
ArgumentNullException.ThrowIfNull(value);

    Type sourceType = value.GetType();

    if (sourceType == BooleanType) return XmlConvert.ToString((bool)value);
    if (sourceType == ByteType) return XmlConvert.ToString((byte)value);
    if (sourceType == ByteArrayType) return Base64BinaryToString((byte[])value);
    if (sourceType == DateTimeType) return DateTimeToString((DateTime)value);
    if (sourceType == DateTimeOffsetType) return DateTimeOffsetToString((DateTimeOffset)value);
    if (sourceType == DecimalType) return XmlConvert.ToString((decimal)value);
    if (sourceType == DoubleType) return XmlConvert.ToString((double)value);
    if (sourceType == Int16Type) return XmlConvert.ToString((short)value);
    if (sourceType == Int32Type) return XmlConvert.ToString((int)value);
    if (sourceType == Int64Type) return XmlConvert.ToString((long)value);
    if (sourceType == SByteType) return XmlConvert.ToString((sbyte)value);
    if (sourceType == SingleType) return XmlConvert.ToString((float)value);
    if (sourceType == StringType) return ((string)value);
    if (sourceType == TimeSpanType) return DurationToString((TimeSpan)value);
    if (sourceType == UInt16Type) return XmlConvert.ToString((ushort)value);
    if (sourceType == UInt32Type) return XmlConvert.ToString((uint)value);
    if (sourceType == UInt64Type) return XmlConvert.ToString((ulong)value);
    if (IsDerivedFrom(sourceType, UriType)) return AnyUriToString((Uri)value);
    if (sourceType == XmlAtomicValueType) return ((string)((XmlAtomicValue)value).ValueAs(StringType, nsResolver));
    if (IsDerivedFrom(sourceType, XmlQualifiedNameType)) return QNameToString((XmlQualifiedName)value, nsResolver);

    return (string)ChangeTypeWildcardDestination(value, StringType, nsResolver);
}

[TrayanZapryanov]

Closing this in favor of 76436