Improve and dedup GetNonZeroBytes

[stephentoub]

• RsaPaddingProcessor has its own complete copy; that now appears to be an unnecessary duplication.
• If a zero byte is found, the implementation currently looks at the rest of the bytes byte by byte. We expect 0s to be rare, so copy in bulk instead.

Method	Toolchain	Length	Mean	Ratio
GetNonZero	\main\corerun.exe	64	184.0 ns	1.00
GetNonZero	\pr\corerun.exe	64	176.5 ns	0.93
GetNonZero	\main\corerun.exe	1024	1,053.4 ns	1.00
GetNonZero	\pr\corerun.exe	1024	660.5 ns	0.63
GetNonZero	\main\corerun.exe	16384	15,511.9 ns	1.00
GetNonZero	\pr\corerun.exe	16384	6,679.8 ns	0.43

[Params(64, 1024, 16384)]
public int Length { get; set; }

private byte[] _buffer;

[GlobalSetup]
public void Setup() => _buffer = new byte[Length];

[Benchmark]
public void GetNonZero() => RandomNumberGenerator.Create().GetNonZeroBytes(_buffer);

[ghost]

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Issue Details

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• RsaPaddingProcessor has its own complete copy; that now appears to be an unnecessary duplication.
• If a zero byte is found, the implementation currently looks at the rest of the bytes byte by byte. We expect 0s to be rare, so copy in bulk instead.

Method	Toolchain	Length	Mean	Ratio
GetNonZero	\main\corerun.exe	64	184.0 ns	1.00
GetNonZero	\pr\corerun.exe	64	176.5 ns	0.93
GetNonZero	\main\corerun.exe	1024	1,053.4 ns	1.00
GetNonZero	\pr\corerun.exe	1024	660.5 ns	0.63
GetNonZero	\main\corerun.exe	16384	15,511.9 ns	1.00
GetNonZero	\pr\corerun.exe	16384	6,679.8 ns	0.43

[Params(64, 1024, 16384)]
public int Length { get; set; }

private byte[] _buffer;

[GlobalSetup]
public void Setup() => _buffer = new byte[Length];

[Benchmark]
public void GetNonZero() => RandomNumberGenerator.Create().GetNonZeroBytes(_buffer);

Author:	stephentoub
Assignees:	stephentoub
Labels:	area-System.Security
Milestone:	-

[adamsitnik]

LGTM, removing duplicated code and making it faster at the same time is always good! 👍