fix: validate rabin args (#32)

* fix: validate rabin args

go-ipfs requires a min chunk size of 16 and will use that for the
max/avg if they are set smaller than the min, so perform the same
sort of validation.

Author: achingbrain

src/chunker/rabin.js

@@ -2,6 +2,7 @@
 
 const BufferList = require('bl')
 const { create } = require('rabin-wasm')
+const errcode = require('err-code')
 
 module.exports = async function * rabinChunker (source, options) {
   const rabin = jsRabin()
@@ -12,12 +13,27 @@ module.exports = async function * rabinChunker (source, options) {
     avg = options.avgChunkSize
     min = options.minChunkSize
     max = options.maxChunkSize
+  } else if (!options.avgChunkSize) {
+    throw errcode(new Error('please specify an average chunk size'), 'ERR_INVALID_AVG_CHUNK_SIZE')
   } else {
     avg = options.avgChunkSize
     min = avg / 3
     max = avg + (avg / 2)
   }
 
+  // validate min/max/avg in the same way as go
+  if (min < 16) {
+    throw errcode(new Error('rabin min must be greater than 16'), 'ERR_INVALID_MIN_CHUNK_SIZE')
+  }
+
+  if (max < min) {
+    max = min
+  }
+
+  if (avg < min) {
+    avg = min
+  }
+
   const sizepow = Math.floor(Math.log2(avg))
 
   for await (const chunk of rabin(source, {

test/chunker-rabin.spec.js

@@ -56,7 +56,7 @@ describe('chunker: rabin', function () {
     const chunks = await all(chunker([b1], {
       ...defaultOptions,
       maxChunkSize: 262144,
-      minChunkSize: 1,
+      minChunkSize: 18,
       avgChunkSize: 256
     }))
 
@@ -83,4 +83,53 @@ describe('chunker: rabin', function () {
       expect(chunk).to.have.length.lte(opts.maxChunkSize)
     })
   })
+
+  it('throws when min chunk size is too small', async () => {
+    const opts = {
+      ...defaultOptions,
+      minChunkSize: 1,
+      maxChunkSize: 100
+    }
+
+    try {
+      await all(chunker([], opts))
+      throw new Error('Should have thrown')
+    } catch (err) {
+      expect(err.code).to.equal('ERR_INVALID_MIN_CHUNK_SIZE')
+    }
+  })
+
+  it('throws when avg chunk size is not specified', async () => {
+    const opts = {
+      ...defaultOptions,
+      avgChunkSize: undefined
+    }
+
+    try {
+      await all(chunker([], opts))
+      throw new Error('Should have thrown')
+    } catch (err) {
+      expect(err.code).to.equal('ERR_INVALID_AVG_CHUNK_SIZE')
+    }
+  })
+
+  it('uses the min chunk size when max and avg are too small', async () => {
+    let file = Buffer.concat([rawFile, Buffer.from('hello')])
+    const opts = {
+      ...defaultOptions,
+      minChunkSize: 100,
+      maxChunkSize: 5,
+      avgChunkSize: 5
+    }
+
+    const chunks = await all(chunker([file], opts))
+
+    chunks.forEach((chunk, index) => {
+      if (index === chunks.length - 1) {
+        expect(chunk.length).to.equal(81)
+      } else {
+        expect(chunk.length).to.equal(100)
+      }
+    })
+  })
 })