Use Unsafe.Read<> for faster Vector ctors

[benaadams]

Needs System.Runtime.CompilerServices.Unsafe added to feed

Also using Vector for validation of longer headers which is good for Content-Security-Policy and Cookie

[halter73]

Cool PR. I didn't know about the System.Runtime.CompilerServices.Unsafe package. Here is a branch I used to compare different ValidateHeaderCharacters implementations.

I had a somewhat similar implementation (TestValidateHeaderValues3) to yours (TestValidateHeaderValues5) that is much slower since it uses ToCharArray and Buffer.BlockCopy.

Here are the results I got when testing against all the fake header values:

BenchmarkDotNet=v0.9.4.0
OS=Microsoft Windows NT 6.2.9200.0
Processor=Intel(R) Core(TM) i7-3667U CPU @ 2.00GHz, ProcessorCount=4
Frequency=2435884 ticks, Resolution=410.5286 ns, Timer=TSC
HostCLR=MS.NET 4.0.30319.42000, Arch=64-bit RELEASE [RyuJIT]
JitModules=clrjit-v4.6.1078.0

Type=Program  Mode=Throughput

Method	Median	StdDev
TestValidateHeaderValues1	66.4891 us	3.0924 us
TestValidateHeaderValues2	84.8861 us	2.1947 us
TestValidateHeaderValues3	161.7872 us	10.0224 us
TestValidateHeaderValues4	69.0152 us	4.5343 us
TestValidateHeaderValues5	40.8759 us	2.1885 us

Here are the results I got when removing the three largest header values:

BenchmarkDotNet=v0.9.4.0
OS=Microsoft Windows NT 6.2.9200.0
Processor=Intel(R) Core(TM) i7-3667U CPU @ 2.00GHz, ProcessorCount=4
Frequency=2435884 ticks, Resolution=410.5286 ns, Timer=TSC
HostCLR=MS.NET 4.0.30319.42000, Arch=64-bit RELEASE [RyuJIT]
JitModules=clrjit-v4.6.1078.0

Type=Program  Mode=Throughput

Method	Median	StdDev
TestValidateHeaderValues1	569.0469 ns	53.4758 ns
TestValidateHeaderValues2	658.3479 ns	29.6889 ns
TestValidateHeaderValues3	3,111.6132 ns	533.1012 ns
TestValidateHeaderValues4	549.9138 ns	55.9223 ns
TestValidateHeaderValues5	384.3479 ns	45.7377 ns

[halter73]

You're right that we should wait to get System.Runtime.CompilerServices.Unsafe pushed to our MyGet. Once we do that I would like to see this split into two commits. One to update our Seek methods (a benchmark for that would be great too if you could provide it), and one to update ValidateHeaderCharacters. It probably also nice to use if (Vector.IsHardwareAccelerated) in ValidateHeaderCharacters for consistency even though it isn't the major issue it once was.

[benaadams]

I didn't know about the System.Runtime.CompilerServices.Unsafe package

I think it only appeared 2 days ago :)

[benaadams]

Closing and have split to #811 and #812