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docs: update block api documentation #4124

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Jun 10, 2022
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docs: update block api documentation #4124

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26 changes: 6 additions & 20 deletions docs/core-api/BLOCK.md
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Expand Up @@ -39,6 +39,7 @@ An optional object which may have the following keys:
| ---- | ---- | ------- | ----------- |
| timeout | `Number` | `undefined` | A timeout in ms |
| signal | [AbortSignal][] | `undefined` | Can be used to cancel any long running requests started as a result of this call |
| preload | `boolean` | `false` | Whether to preload all blocks created during this operation |
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### Returns

Expand All @@ -63,7 +64,7 @@ A great source of [examples][] can be found in the tests for this API.

| Name | Type | Description |
| ---- | ---- | ----------- |
| block | A `Uint8Array` or [Block][] instance | The block or data to store |
| block | `Uint8Array` | The block of data to store |
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### Options

Expand All @@ -73,19 +74,18 @@ An optional object which may have the following keys:
| ---- | ---- | ------- | ----------- |
| format | `String` | `'dag-pb'` | The codec to use to create the CID |
| mhtype | `String` | `sha2-256` | The hashing algorithm to use to create the CID |
| mhlen | `Number` | | |
| mhlen | `Number` | `undefined` | The hash length (only relevant for `go-ipfs`) |
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https://github.com/ipfs/js-ipfs/blob/master/packages/ipfs-core-types/src/block/index.ts does not include this option. However, the go-ipfs CLI seems to support this option and found this mentions in this repository:

js-ipfs/packages/ipfs-cli/src/commands/block/put.js

Lines 34 to 37 in 548cfb2

mhlen: {
describe: 'multihash hash length',
default: undefined
},

js-ipfs/packages/ipfs-http-server/src/api/resources/block.js

Line 111 in 548cfb2

mhlen: Joi.number(),

  • Is this option relevant? Should it be removed?
  • Is it supported by js-ipfs or only go-ipfs?

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It's not supported by js-ipfs and I'm not clear on what it even does for go-ipfs. It defaults to -1 which means.. 🤷

If you could find out the what and the why maybe we could even remove it entirely.

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Well, it seems to be literally the multihash length, but doesn't seem to be very useful looking at the very limited search results. I tried figuring out if this was useful when opening this PR, but couldn't find anything that explained why it may be needed.

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@lidel lidel Jun 6, 2022 •
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I had to refactor relevant go-ipfs code around this recently and can provide some details.

afaik the only place where this is used, is when mhlen gets passed deep into go-multihash code responsible for digert (Sum) calculation: https://github.com/multiformats/go-multihash/blob/75ae3688857d036ea15947be9df68d3172b19470/sum.go

tldr:

  • -1 is the implicit default which means "set length based on hashing function output"
    • same applies to any value <=0
  • setting custom mhlen allows for truncating longer digests produces by alternative hash functions
  • setting it to longer than the default output of specific hash function will produce error

| version | `Number` | `0` | The version to use to create the CID |
| pin | `boolean` | `false` | If true, pin added blocks recursively |
| timeout | `Number` | `undefined` | A timeout in ms |
| signal | [AbortSignal][] | `undefined` | Can be used to cancel any long running requests started as a result of this call |

**Note:** If you pass a [`Block`][block] instance as the block parameter, you don't need to pass options, as the block instance will carry the CID value as a property.
| preload | `boolean` | `false` | Whether to preload all blocks created during this operation |
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### Returns

| Type | Description |
| -------- | -------- |
| `Promise<Block>` | A [Block][block] type object, containing both the data and the hash of the block |
| `Promise<CID>` | A [CID][CID] type object containing the hash of the block |
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### Example

Expand All @@ -96,21 +96,6 @@ const decoder = new TextDecoder()

const block = await ipfs.block.put(buf)

console.log(decoder.decode(block.data))
// Logs:
// a serialized object
console.log(block.cid.toString())
// Logs:
// the CID of the object

// With custom format and hashtype through CID
import { CID } from 'multiformats/cid'
import * as dagPB from '@ipld/dag-pb'
const buf = new TextEncoder().encode('another serialized object')
const cid = CID.createV1(dagPB.code, multihash)

const block = await ipfs.block.put(blob, cid)
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console.log(decoder.decode(block.data))
// Logs:
// a serialized object
Expand Down Expand Up @@ -191,6 +176,7 @@ An optional object which may have the following keys:
| ---- | ---- | ------- | ----------- |
| timeout | `Number` | `undefined` | A timeout in ms |
| signal | [AbortSignal][] | `undefined` | Can be used to cancel any long running requests started as a result of this call |
| preload | `boolean` | `false` | Whether to preload all blocks created during this operation |
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### Returns

Expand Down
13 changes: 0 additions & 13 deletions packages/ipfs-core-types/src/block/index.ts
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Expand Up @@ -32,19 +32,6 @@ export interface API<OptionExtension = {}> {
* console.log(block.cid.toString())
* // Logs:
* // the CID of the object
*
* // With custom format and hashtype through CID
* import { CID } from 'multiformats/cid'
* const another = encoder.encode('another serialized object')
* const cid = CID.createV1(dagPB.code, multihash)
* const block = await ipfs.block.put(another, cid)
* console.log(decoder.decode(block.data))
*
* // Logs:
* // a serialized object
* console.log(block.cid.toString())
* // Logs:
* // the CID of the object
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* ```
*/
put: (block: Uint8Array, options?: PutOptions & OptionExtension) => Promise<CID>
Expand Down