fix(decoder): handle large input sizes

Fixes #10

src/decoder.js

@@ -23,6 +23,9 @@ class Decoder {
 
     if (!opts.size || opts.size < 0x10000) {
       opts.size = 0x10000
+    } else {
+      // Ensure the size is a power of 2
+      opts.size = utils.nextPowerOf2(opts.size)
     }
 
     // Heap use to share the input with the parser
@@ -593,7 +596,7 @@ class Decoder {
       input = new Buffer(input, enc || 'hex')
     }
 
-    const dec = new Decoder()
+    const dec = new Decoder({size: input.length})
     return dec.decodeFirst(input)
   }
 
@@ -609,7 +612,7 @@ class Decoder {
       input = new Buffer(input, enc || 'hex')
     }
 
-    const dec = new Decoder()
+    const dec = new Decoder({size: input.length})
     return dec.decodeAll(input)
   }
 }

src/utils.js

@@ -155,3 +155,19 @@ exports.keySorter = function (a, b) {
 exports.isNegativeZero = (x) => {
   return x === 0 && (1 / x < 0)
 }
+
+exports.nextPowerOf2 = (n) => {
+  let count = 0
+  // First n in the below condition is for
+  // the case where n is 0
+  if (n && !(n & (n - 1))) {
+    return n
+  }
+
+  while (n !== 0) {
+    n >>= 1
+    count += 1
+  }
+
+  return 1 << count
+}

test/decoder.spec.js

@@ -101,6 +101,31 @@ describe('Decoder', function () {
       ).to.throw()
     })
 
+    it('decodeFirst large input', () => {
+      const largeInput = []
+      for (let i = 0; i < 0x10000; i++) {
+        largeInput.push('hi')
+      }
+
+      expect(
+        cbor.decodeFirst(cbor.encode(largeInput))
+      ).to.be.eql(
+        largeInput
+      )
+    })
+
+    it('decodeAll large input', () => {
+      const largeInput = []
+      for (let i = 0; i < 0x10000; i++) {
+        largeInput.push('hi')
+      }
+
+      expect(
+        cbor.decodeAll(cbor.encode(largeInput))
+      ).to.be.eql(
+        [largeInput]
+      )
+    })
     // TODO: implement depth limit
     it.skip('depth', () => {
       expect(

test/utils.spec.js

@@ -73,4 +73,15 @@ describe('utils', () => {
     expect(utils.isNegativeZero(12.5)).to.be.eql(false)
     expect(utils.isNegativeZero(-Infinity)).to.be.eql(false)
   })
+
+  it('nextPowerOf2', () => {
+    [
+      [1, 1],
+      [5, 8],
+      [127, 128],
+      [129, 256]
+    ].forEach((test) => {
+      expect(utils.nextPowerOf2(test[0])).to.be.eql(test[1])
+    })
+  })
 })