feat: replace hashAlg option with actual hasher

Instead of passing it a number, you now pass in a hasher implementation.

Author: vmx

packages/ipfs-unixfs-importer/src/dag-builder/file/buffer-importer.js

@@ -26,7 +26,7 @@ async function * bufferImporter (file, block, options) {
       const opts = {
         codec: mc.DAG_PB,
         cidVersion: options.cidVersion,
-        hashAlg: options.hashAlg,
+        hasher: options.hasher,
         onlyHash: options.onlyHash
       }
 

packages/ipfs-unixfs-importer/src/dag-builder/file/index.js

@@ -96,11 +96,28 @@ const reduce = (file, block, options) => {
         const multihash = mh.decode(leaf.cid.multihash.bytes)
         buffer = encode(prepare({ Data: leaf.unixfs.marshal() }))
 
+        //// TODO vmx 2021-03-26: This is what the original code does, it checks
+        //// the multihash of the original leaf node and uses then the same
+        //// hasher. i wonder if that's really needed or if we could just use
+        //// the hasher from `options.hasher` instead.
+        //let hasher
+        //switch multihash {
+        //  case sha256.code {
+        //    hasher = sha256
+        //    break;
+        //  }
+        //  //case identity.code {
+        //  //  hasher = identity
+        //  //  break;
+        //  //}
+        //  default: {
+        //    throw new Error(`Unsupported hasher "${multihash}"`)
+        //  }
+        //}
         leaf.cid = await persist(buffer, block, {
           ...options,
           codec: mc.DAG_PB,
-          // @ts-ignore
-          hashAlg: multihash.code,
+          hasher: options.hasher,
           cidVersion: options.cidVersion
         })
         leaf.size = buffer.length

packages/ipfs-unixfs-importer/src/options.js

@@ -2,7 +2,7 @@
 
 const mergeOptions = require('merge-options').bind({ ignoreUndefined: true })
 const multihashing = require('multihashing-async')
-const mc = require('multicodec')
+const { sha256 } = require('multiformats/hashes/sha2')
 
 /**
  * @param {Uint8Array} buf
@@ -39,7 +39,7 @@ const defaultOptions = {
   rawLeaves: false,
   onlyHash: false,
   reduceSingleLeafToSelf: true,
-  hashAlg: mc.SHA2_256,
+  hasher: sha256,
   leafType: 'file', // 'raw'
   cidVersion: 0,
   progress: () => () => {},

packages/ipfs-unixfs-importer/src/types.d.ts

@@ -2,6 +2,7 @@ import { UnixFS, Mtime } from 'ipfs-unixfs'
 import CID from 'multiformats/cid'
 import { HashName } from 'multihashes'
 import { CodecName } from 'multicodec'
+import MultihashDigest from 'multiformats/hashes/hasher'
 
 interface ImportCandidate {
   path?: string
@@ -52,7 +53,7 @@ interface UserImporterOptions {
   rawLeaves?: boolean
   onlyHash?: boolean
   reduceSingleLeafToSelf?: boolean
-  hashAlg?: CodecCode
+  hasher?: MultihashDigest
   leafType?: 'file' | 'raw'
   cidVersion?: CIDVersion
   progress?: ProgressHandler
@@ -87,7 +88,7 @@ interface ImporterOptions {
   rawLeaves: boolean
   onlyHash: boolean
   reduceSingleLeafToSelf: boolean
-  hashAlg: CodecCode
+  hasher: MultihashDigest
   leafType: 'file' | 'raw'
   cidVersion: CIDVersion
   progress: ProgressHandler
@@ -133,7 +134,7 @@ export interface PersistOptions {
   //codec?: string
   codec?: number
   cidVersion: CIDVersion
-  hashAlg: CodecCode
+  hasher: MultihashDigest
   onlyHash: boolean
   preload?: boolean
   timeout?: number

packages/ipfs-unixfs-importer/src/utils/persist.js

@@ -1,7 +1,6 @@
 'use strict'
 
 const mc = require('multicodec')
-const { sha256 } = require('multiformats/hashes/sha2')
 const CID = require('multiformats/cid')
 
 /**
@@ -10,30 +9,19 @@ const CID = require('multiformats/cid')
  * @param {import('../types').PersistOptions} options
  */
 const persist = async (buffer, block, options) => {
-  if (!options.codec) {
-    options.codec = mc.DAG_PB
-  }
-
-  if (!options.cidVersion) {
-    options.cidVersion = 0
+  if (!options.hasher) {
+    throw new Error(`Hasher must be specified.`)
   }
 
-  if (!options.hashAlg) {
-    options.hashAlg = mc.SHA2_256
+  if (!options.codec) {
+    options.codec = mc.DAG_PB
   }
 
-  if (options.hashAlg !== mc.SHA2_256) {
+  if (options.cidVersion === undefined) {
     options.cidVersion = 1
   }
 
-  let multihash
-  switch (options.hashAlg) {
-    case mc.SHA2_256:
-      multihash = await sha256.digest(buffer)
-      break
-    default:
-      throw(`TODO vmx 2021-02-24: support other hash algorithms. ${options.hashAlg} not found.`)
-  }
+  const multihash = await options.hasher.digest(buffer)
   // TODO vmx 2021-02-24: no idea why TypeScript fails here, it should work
   // @ts-ignore
   const cid = CID.create(options.cidVersion, options.codec, multihash)