Improve JsonEncoder.WriteDateTime

Proposed changes

The default implementation using ToString("yyyy-MM-dd'T'HH:mm:ss.FFFFFFFK" was identified in a CPU hotpath analysis when decoded DataValues are JSON encoded.
The "o" time conversion implementations is up to 10 times faster (see .NET6.0), but as a caveat it does not omit trailing zeroes.
Even with handling the special case to omit the trailing zeroes, the o version used with ConvertToUniversalTime with .NET8 runs still 3 to 7 times faster than the default implementation.


BenchmarkDotNet v0.13.12, Windows 11 (10.0.22000.2652/21H2/SunValley)
Intel Core i9-10885H CPU 2.40GHz, 1 CPU, 16 logical and 8 physical cores
  [Host]     : .NET Framework 4.8.1 (4.8.9195.0), X64 RyuJIT VectorSize=256
  Job-FYOECP : .NET 6.0.26 (6.0.2623.60508), X64 RyuJIT AVX2
  Job-ACBKDI : .NET 8.0.1 (8.0.123.58001), X64 RyuJIT AVX2
  Job-XTPWQX : .NET Framework 4.8.1 (4.8.9195.0), X64 RyuJIT VectorSize=256

Method	Runtime	OmittedZeros	Mean	Error	StdDev	Median	Ratio	RatioSD	Gen0	Code Size	Allocated	Alloc Ratio
DateTimeEncodeToString	.NET 6.0	0	774.14 ns	41.641 ns	122.780 ns	740.98 ns	0.73	0.16	0.0095	707 B	80 B	0.22
DateTimeEncodeToString	.NET 8.0	0	402.21 ns	15.714 ns	45.837 ns	395.37 ns	0.38	0.05	0.0095	1,738 B	80 B	0.22
DateTimeEncodeToString	.NET Framework 4.8	0	1,082.08 ns	44.020 ns	128.409 ns	1,047.75 ns	1.00	0.00	0.0572	479 B	369 B	1.00

ConvertToUniversalTime	.NET 6.0	0	83.37 ns	3.494 ns	9.968 ns	82.00 ns	0.23	0.04	0.0095	280 B	80 B	0.91
ConvertToUniversalTime	.NET 8.0	0	59.51 ns	1.679 ns	4.924 ns	58.37 ns	0.16	0.02	0.0095	1,578 B	80 B	0.91
ConvertToUniversalTime	.NET Framework 4.8	0	364.16 ns	10.851 ns	31.308 ns	352.88 ns	1.00	0.00	0.0138	149 B	88 B	1.00

DateTimeEncodeToString	.NET 6.0	4	492.33 ns	15.977 ns	46.606 ns	481.02 ns	0.45	0.07	0.0086	707 B	72 B	0.20
DateTimeEncodeToString	.NET 8.0	4	347.51 ns	9.949 ns	27.898 ns	340.83 ns	0.31	0.04	0.0086	1,738 B	72 B	0.20
DateTimeEncodeToString	.NET Framework 4.8	4	1,124.20 ns	47.988 ns	139.982 ns	1,089.04 ns	1.00	0.00	0.0553	479 B	353 B	1.00

ConvertToUniversalTime	.NET 6.0	4	92.98 ns	2.617 ns	7.510 ns	90.97 ns	0.22	0.03	0.0181	280 B	152 B	0.90
ConvertToUniversalTime	.NET 8.0	4	80.22 ns	2.779 ns	7.928 ns	77.55 ns	0.19	0.03	0.0181	1,870 B	152 B	0.90
ConvertToUniversalTime	.NET Framework 4.8	4	434.21 ns	16.813 ns	49.045 ns	422.54 ns	1.00	0.00	0.0267	149 B	168 B	1.00

DateTimeEncodeToString	.NET 6.0	7	462.28 ns	11.506 ns	33.014 ns	458.98 ns	0.52	0.05	0.0076	707 B	64 B	0.20
DateTimeEncodeToString	.NET 8.0	7	271.40 ns	7.663 ns	22.109 ns	268.63 ns	0.30	0.04	0.0076	1,816 B	64 B	0.20
DateTimeEncodeToString	.NET Framework 4.8	7	897.91 ns	24.849 ns	70.896 ns	888.67 ns	1.00	0.00	0.0496	479 B	313 B	1.00

ConvertToUniversalTime	.NET 6.0	7	119.99 ns	5.272 ns	15.462 ns	118.03 ns	0.30	0.05	0.0172	280 B	144 B	0.90
ConvertToUniversalTime	.NET 8.0	7	85.46 ns	3.500 ns	10.209 ns	83.34 ns	0.21	0.03	0.0172	1,870 B	144 B	0.90
ConvertToUniversalTime	.NET Framework 4.8	7	404.68 ns	13.675 ns	39.890 ns	399.14 ns	1.00	0.00	0.0253	149 B	160 B	1.00

Related Issues

Fixes #

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OPCFoundation / UA-.NETStandard