Fixes #52, but uses Uint8Array not ArrayBuffer

hildjj · Jan 12, 2021 · 871e0f7 · 871e0f7
1 parent 50077a2
commit 871e0f7
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Showing 3 changed files with 28 additions and 4 deletions.
diff --git a/lib/decoder.js b/lib/decoder.js
@@ -80,6 +80,9 @@ class Decoder extends BinaryParseStream {
    *   function returns the correctly-created value for that tag.
    * @param {boolean} [options.bigint=true] generate JavaScript BigInt's
    *   instead of BigNumbers, when possible.
+   * @param {boolean} [options.preferWeb=false] if true, prefer Uint8Arrays to
+   *   be generated instead of node Buffers.  This might turn on some more
+   *   changes in the future, so forward-compatibility is not guaranteed yet.
    */
   constructor(options) {
     options = options || {}
@@ -89,11 +92,14 @@ class Decoder extends BinaryParseStream {
     delete options.max_depth
     const bigI = (options.bigint != null) ? options.bigint : true
     delete options.bigint
+    const preferWeb = !!options.preferWeb
+    delete options.preferWeb
     super(options)
 
     this.running = true
     this.max_depth = max_depth
     this.tags = tags
+    this.preferWeb = preferWeb
     this.bigint = bigI
     if (bigI) {
       if (this.tags == null) {
@@ -435,7 +441,11 @@ class Decoder extends BinaryParseStream {
           switch (val) {
             case 0:
               this.emit('start-string', mt, val, parent_major, parent_length)
-              val = (mt === MT.BYTE_STRING) ? Buffer.allocUnsafe(0) : ''
+              if (mt === MT.UTF8_STRING) {
+                val = ''
+              } else {
+                val = this.preferWeb ? new Uint8Array(0) : Buffer.allocUnsafe(0)
+              }
               break
             case -1:
               this.emit('start', mt, SYMS.STREAM, parent_major, parent_length)
@@ -447,6 +457,8 @@ class Decoder extends BinaryParseStream {
               val = yield val
               if (mt === MT.UTF8_STRING) {
                 val = utils.utf8(val)
+              } else if (this.preferWeb) {
+                val = new Uint8Array(val.buffer, val.byteOffset, val.length)
               }
           }
           break
@@ -552,6 +564,9 @@ class Decoder extends BinaryParseStream {
           switch (parent[MAJOR]) {
             case MT.BYTE_STRING:
               val = parent.slice()
+              if (this.preferWeb) {
+                val = new Uint8Array(val.buffer, val.byteOffset, val.length)
+              }
               break
             case MT.UTF8_STRING:
               val = parent.toString('utf-8')

diff --git a/lib/utils.js b/lib/utils.js
@@ -268,9 +268,7 @@ exports.guessEncoding = function guessEncoding(input, encoding) {
     return new NoFilter(input)
   } else if (ArrayBuffer.isView(input)) {
     return new NoFilter(
-      Buffer.from(input.buffer.slice(
-        input.byteOffset,
-        input.byteOffset + input.byteLength)))
+      Buffer.from(input.buffer, input.byteOffset, input.byteLength))
   } else if (input instanceof ArrayBuffer) {
     return new NoFilter(Buffer.from(input))
   } else if (input instanceof stream.Readable) {

diff --git a/test/decoder.ava.js b/test/decoder.ava.js
@@ -244,3 +244,14 @@ test('typed arrays', t => {
   t.is(cbor.decode(new Uint32Array(u8abc.buffer)), 'abc')
   t.is(cbor.decode(new DataView(u8abc.buffer)), 'abc')
 })
+
+test('preferWeb', t => {
+  t.deepEqual(cbor.decodeFirstSync('40', {preferWeb: true}),
+    new Uint8Array([]))
+  t.deepEqual(cbor.decodeFirstSync('4141', {preferWeb: true}),
+    new Uint8Array([0x41]))
+  t.deepEqual(cbor.decodeFirstSync('5fff', {preferWeb: true}),
+    new Uint8Array([]))
+  t.deepEqual(cbor.decodeFirstSync('5f42010243030405ff', {preferWeb: true}),
+    new Uint8Array([0x01, 0x02, 0x03, 0x04, 0x05]))
+})