Use initialCapacity in ASN.1 templates for some primitives

[vcsjones]

In our ASN.1 templated encoding, we encode managed values with AsnWriter to determine if they are equal to defaultDerInit.

For some primitives types, like an ASN.1 Boolean and ASN.1 Integer (where the integer is known to be a managed int) this has some waste as AsnWriter has an initial capacity of 1024 bytes.

For booleans, we know the encoded length is always going to be 3 bytes for DER. For integers (where the backing type is int) we know it will encode to at most 6 bytes.

Where possible, let's give these size hints to reduce the initial allocation size. For example, the Critical boolean in X.509 extensions has a default. Before and after of encoding a basic constraints extension:

Method	Job	Toolchain	Mean	Error	StdDev	Ratio	Gen 0	Gen 1	Gen 2	Allocated
NewX509BasicConstraints	Job-KCCSSM	branch	114.83 ns	0.219 ns	0.205 ns	0.76	0.2154	0.0005	-	1,352 B
NewX509BasicConstraints	Job-AGAYBV	main	150.80 ns	0.413 ns	0.387 ns	1.00	0.3774	0.0019	-	2,368 B

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Issue Details

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In our ASN.1 templated encoding, we encode managed values with AsnWriter to determine if they are equal to defaultDerInit.

For some primitives types, like an ASN.1 Boolean and ASN.1 Integer (where the integer is known to be a managed int) this has some waste as AsnWriter has an initial capacity of 1024 bytes.

For booleans, we know the encoded length is always going to be 3 bytes for DER. For integers (where the backing type is int) we know it will encode to at most 6 bytes.

Where possible, let's give these size hints to reduce the initial allocation size. For example, the Critical boolean in X.509 extensions has a default. Before and after of encoding a basic constraints extension:

Method	Job	Toolchain	Mean	Error	StdDev	Ratio	Gen 0	Gen 1	Gen 2	Allocated
NewX509BasicConstraints	Job-KCCSSM	branch	114.83 ns	0.219 ns	0.205 ns	0.76	0.2154	0.0005	-	1,352 B
NewX509BasicConstraints	Job-AGAYBV	main	150.80 ns	0.413 ns	0.387 ns	1.00	0.3774	0.0019	-	2,368 B

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

[vcsjones]

(If we ever get one-shot encoding that can write to a stack buffer, that would obviously be better, but we can do this right now)

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Tagging subscribers to this area: @dotnet/area-system-formats-asn1, @vcsjones
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Issue Details

---

In our ASN.1 templated encoding, we encode managed values with AsnWriter to determine if they are equal to defaultDerInit.

For some primitives types, like an ASN.1 Boolean and ASN.1 Integer (where the integer is known to be a managed int) this has some waste as AsnWriter has an initial capacity of 1024 bytes.

For booleans, we know the encoded length is always going to be 3 bytes for DER. For integers (where the backing type is int) we know it will encode to at most 6 bytes.

Where possible, let's give these size hints to reduce the initial allocation size. For example, the Critical boolean in X.509 extensions has a default. Before and after of encoding a basic constraints extension:

Method	Job	Toolchain	Mean	Error	StdDev	Ratio	Gen 0	Gen 1	Gen 2	Allocated
NewX509BasicConstraints	Job-KCCSSM	branch	114.83 ns	0.219 ns	0.205 ns	0.76	0.2154	0.0005	-	1,352 B
NewX509BasicConstraints	Job-AGAYBV	main	150.80 ns	0.413 ns	0.387 ns	1.00	0.3774	0.0019	-	2,368 B

Author:	vcsjones
Assignees:	vcsjones
Labels:	area-System.Formats.Asn1
Milestone:	-