feat: use a rabin chunker in wasm (#31)

* feat: use a rabin chunker in wasm
* chore: fix package.json

Author: hugomrdias

package.json

@@ -5,8 +5,7 @@
   "leadMaintainer": "Alex Potsides <[email protected]>",
   "main": "src/index.js",
   "browser": {
-    "fs": false,
-    "rabin": false
+    "fs": false
   },
   "scripts": {
     "test": "aegir test",
@@ -65,10 +64,8 @@
     "long": "^4.0.0",
     "multicodec": "~0.5.1",
     "multihashing-async": "~0.7.0",
-    "superstruct": "~0.6.1"
-  },
-  "optionalDependencies": {
-    "rabin": "^1.6.0"
+    "superstruct": "~0.6.1",
+    "rabin-wasm": "~0.0.4"
   },
   "contributors": [
     "Alan Shaw <[email protected]>",

src/chunker/rabin.js

@@ -1,19 +1,10 @@
 'use strict'
 
-const errCode = require('err-code')
-const Long = require('long')
 const BufferList = require('bl')
-let rabin
+const { create } = require('rabin-wasm')
 
 module.exports = async function * rabinChunker (source, options) {
-  if (!rabin) {
-    try {
-      rabin = nativeRabin()
-    } catch (_) {
-      // fallback to js implementation
-      rabin = jsRabin()
-    }
-  }
+  const rabin = jsRabin()
 
   let min, max, avg
 
@@ -40,191 +31,17 @@ module.exports = async function * rabinChunker (source, options) {
   }
 }
 
-const nativeRabin = () => {
-  const createRabin = require('rabin')
-
-  if (typeof rabin !== 'function') {
-    throw errCode(new Error(`rabin was not a function`), 'ERR_UNSUPPORTED')
-  }
-
-  return async function * (source, options) {
-    const rabin = createRabin(options)
-
-    // TODO: rewrite rabin using node streams v3
-    for await (const chunk of source) {
-      rabin.buffers.append(chunk)
-      rabin.pending.push(chunk)
-
-      const sizes = []
-
-      rabin.rabin.fingerprint(rabin.pending, sizes)
-      rabin.pending = []
-
-      for (let i = 0; i < sizes.length; i++) {
-        const size = sizes[i]
-        const buf = rabin.buffers.slice(0, size)
-        rabin.buffers.consume(size)
-
-        yield buf
-      }
-    }
-
-    if (rabin.buffers.length) {
-      yield rabin.buffers.slice(0)
-    }
-  }
-}
-
 const jsRabin = () => {
-  // see https://github.com/datproject/rabin/blob/c0378395dc0a125ab21ac176ec504f9995b34e62/src/rabin.cc
-  class Rabin {
-    constructor (options) {
-      this.window = new Array(options.window || 64).fill(Long.fromInt(0))
-      this.wpos = 0
-      this.count = 0
-      this.digest = Long.fromInt(0)
-      this.chunkLength = 0
-      this.polynomial = options.polynomial
-      this.polynomialDegree = 53
-      this.polynomialShift = this.polynomialDegree - 8
-      this.averageBits = options.bits || 12
-      this.minSize = options.min || 8 * 1024
-      this.maxSize = options.max || 32 * 1024
-      this.mask = Long.fromInt(1).shiftLeft(this.averageBits).subtract(1)
-      this.modTable = []
-      this.outTable = []
-
-      this.calculateTables()
-    }
-
-    calculateTables () {
-      for (let i = 0; i < 256; i++) {
-        let hash = Long.fromInt(0, true)
-
-        hash = this.appendByte(hash, i)
-
-        for (let j = 0; j < this.window.length - 1; j++) {
-          hash = this.appendByte(hash, 0)
-        }
-
-        this.outTable[i] = hash
-      }
-
-      const k = this.deg(this.polynomial)
-
-      for (let i = 0; i < 256; i++) {
-        const b = Long.fromInt(i, true)
-
-        this.modTable[i] = b.shiftLeft(k)
-          .modulo(this.polynomial)
-          .or(b.shiftLeft(k))
-      }
-    }
-
-    deg (p) {
-      let mask = Long.fromString('0x8000000000000000', true, 16)
-
-      for (let i = 0; i < 64; i++) {
-        if (mask.and(p).greaterThan(0)) {
-          return Long.fromInt(63 - i)
-        }
-
-        mask = mask.shiftRight(1)
-      }
-
-      return Long.fromInt(-1)
-    }
-
-    appendByte (hash, b) {
-      hash = hash.shiftLeft(8)
-      hash = hash.or(b)
-
-      return hash.modulo(this.polynomial)
-    }
-
-    getFingerprints (bufs) {
-      const lengths = []
-
-      for (let i = 0; i < bufs.length; i++) {
-        let buf = bufs[i]
-
-        while (true) {
-          const remaining = this.nextChunk(buf)
-
-          if (remaining < 0) {
-            break
-          }
-
-          buf = buf.slice(remaining)
-
-          lengths.push(this.chunkLength)
-        }
-      }
-
-      return lengths
-    }
-
-    nextChunk (buf) {
-      for (let i = 0; i < buf.length; i++) {
-        const val = Long.fromInt(buf[i])
-
-        this.slide(val)
-
-        this.count++
-
-        if ((this.count >= this.minSize && this.digest.and(this.mask).equals(0)) || this.count >= this.maxSize) {
-          this.chunkLength = this.count
-
-          this.reset()
-
-          return i + 1
-        }
-      }
-
-      return -1
-    }
-
-    slide (value) {
-      const out = this.window[this.wpos].toInt() & 255
-      this.window[this.wpos] = value
-      this.digest = this.digest.xor(this.outTable[out])
-      this.wpos = (this.wpos + 1) % this.window.length
-
-      this.append(value)
-    }
-
-    reset () {
-      this.window = this.window.map(() => Long.fromInt(0))
-      this.wpos = 0
-      this.count = 0
-      this.digest = Long.fromInt(0)
-
-      this.slide(Long.fromInt(1))
-    }
-
-    append (value) {
-      const index = this.digest.shiftRight(this.polynomialShift).toInt() & 255
-      this.digest = this.digest.shiftLeft(8)
-      this.digest = this.digest.or(value)
-
-      const entry = this.modTable[index]
-
-      if (entry) {
-        this.digest = this.digest.xor(entry)
-      }
-    }
-  }
-
   return async function * (source, options) {
-    const r = new Rabin(options)
+    const r = await create(options.bits, options.min, options.max, options.window)
     const buffers = new BufferList()
     let pending = []
 
     for await (const chunk of source) {
       buffers.append(chunk)
       pending.push(chunk)
 
-      const sizes = r.getFingerprints(pending)
+      const sizes = r.fingerprint(Buffer.concat(pending))
       pending = []
 
       for (let i = 0; i < sizes.length; i++) {