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hash: allow Hash to implement encoding.BinaryMarshaler, encoding.BinaryUnmarshaler #20573

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Capstan opened this issue Jun 4, 2017 · 4 comments
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hash: allow Hash to implement encoding.BinaryMarshaler, encoding.BinaryUnmarshaler #20573

Capstan opened this issue Jun 4, 2017 · 4 comments
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FeatureRequest Issues asking for a new feature that does not need a proposal. FrozenDueToAge Proposal Proposal-Accepted
Milestone
Go1.10

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@Capstan
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Capstan commented Jun 4, 2017

There are some use cases that aren't met by current hashing functions

  • Serialize state of a partial byte stream processing for later work; recalculating the hash from the beginning is inefficient and, in our case, infeasible due to the size of the data and legacy compatibility requirements that inhibit use of, say, a Merkle tree.
  • Sharing calculation of common prefix hashes; this only requires in-memory copying rather than serialization.
  • Conditional append based on hash matches, which is a corollary of the previous.

Previous thread on golang-dev.

In my specific case, I'm looking for MD5 [de]serialization.

/cc @jlhawn
@bradfitz
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bradfitz commented Jun 5, 2017

Seems like we could make the concrete types implement https://golang.org/pkg/encoding/#BinaryMarshaler and https://golang.org/pkg/encoding/#BinaryUnmarshaler at least.

We can't change the signature of e.g. https://golang.org/pkg/crypto/md5/#New but we could document in an Example that you can type-assert that the returned hash.Hash is also an encoding.BinaryUnmarshaler etc.

@bradfitz bradfitz changed the title FR: Serializable intermediate hash state proposal: Serializable intermediate hash state Jun 5, 2017
@bradfitz bradfitz added the FeatureRequest Issues asking for a new feature that does not need a proposal. label Jun 5, 2017
@gopherbot gopherbot added this to the Proposal milestone Jun 5, 2017
@rsc
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rsc commented Jun 5, 2017

Any objections to hashes implementing BinaryMarshaler and BinaryUnmarshaler? Will leave this open for a week.

@bradfitz bradfitz changed the title proposal: Serializable intermediate hash state proposal: hash: Serializable intermediate hash state Jun 5, 2017
@rsc rsc changed the title proposal: hash: Serializable intermediate hash state hash: allow Hash to implement encoding.BinaryMarshaler, encoding.BinaryUnmarshaler Jun 12, 2017
@rsc rsc modified the milestones: Go1.10, Proposal Jun 12, 2017
@rsc
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rsc commented Jun 12, 2017

Proposal accepted. CLs welcome for the Go 1.10 cycle for

  • Updating hash.Hash docs to document the convention.
  • Updating hash/* and crypto/* hashes to implement it.

@gopherbot
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Change https://golang.org/cl/66710 mentions this issue: crypto, hash: implement BinaryMarshaler, BinaryUnmarshaler in hash implementations

@aead aead mentioned this issue Mar 27, 2018
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FeatureRequest Issues asking for a new feature that does not need a proposal. FrozenDueToAge Proposal Proposal-Accepted
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Go1.10
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@bradfitz @rsc @Capstan @gopherbot