Merge pull request #2 from maxogden/buffer-read

switch out the accumulator reader for a faster buffer reader

README.md

@@ -1,20 +1,13 @@
 # varint
 
-decode [protobuf-style varint bytes](https://developers.google.com/protocol-buffers/docs/encoding#varints) and emit whole integers when enough have been accumulated that a number can be constructed; also encode whole numbers to an array of varint style bytes.
+encode whole numbers to an array of [protobuf-style varint bytes](https://developers.google.com/protocol-buffers/docs/encoding#varints) and also decode them.
 
 ```javascript
 var varint = require('varint')
 
 var bytes = varint.encode(300) // === [0xAC, 0x02]
-  , vi = varint()
+varint.decode(bytes) // 300
-
+varint.decode.bytesRead // 2 (the last decode() call required 2 bytes)
-vi.once('data', function(num) {
-  console.log('got', num)
-})
-
-vi.write(bytes[0])
-vi.write(bytes[1]) // "got 300"
-
 ```
 
 ## api
@@ -24,16 +17,22 @@ vi.write(bytes[1]) // "got 300"
 ### varint.encode(num[, output=[], offset=0]) -> array
 
 encodes `num` into either the array given by `offset` or a new array at `offset`
-and returns that array.
+and returns that array filled with integers.
+
+### varint.decode(data[, offset=0]) -> number
+
+decodes `data`, which can be either a buffer or array of integers, from position `offset` or default 0 and returns the decoded original integer.
+
+### varint.decode.bytesRead
 
-### vi = varint() -> EventEmitter
+if you also require the length (number of bytes) that were required to decode the integer you can access it via `varint.decode.bytesRead`. this is an integer property that will tell you the number of bytes that the last .decode() call had to use to decode.
 
-return a new `varint` instance.
+## usage notes
 
-### vi.write(byte) -> undefined
+if you are using this to decode buffers from a streaming source it's up to you to make sure that you send 'complete' buffers into `varint.decode`. the maximum number of bytes that varint will need to decode is 8, so all you have to do is make sure you are sending buffers that are at least 8 bytes long from the point at which you know a varint range begins.
 
-write a byte to the varint. if the byte is "final" (i.e., does not have the bit at `0x80` set),
+for example, if you are reading buffers from a `fs.createReadStream`,
-it will attempt to compile the number and emit it as a `data` event.
+imagine the first buffer contains one full varint range and half of a second one, and the second buffer contains the second half of the second varint range. in order to be safe across the buffer boundaries you'd just have to make sure the buffer you give to `varint.decode` contains the full varint range (8 bytes), otherwise you'll get an error.
 
 # License
 

decode.js

@@ -1,33 +1,24 @@
-module.exports = Decoder
+module.exports = read
 
 var MSB = 0x80
   , REST = 0x7F
 
-
+function read(buf, offset) {
-function Decoder() {
+  var res    = 0
-  this.accum = []
+    , offset = offset || 0
+    , shift  = 0
+    , counter = offset
+    , b
+  
+  do {
+    b = buf[counter++]
+    res += shift < 28
+      ? (b & REST) << shift
+      : (b & REST) * Math.pow(2, shift)
+    shift += 7
+  } while (b >= MSB)
+  
+  read.bytesRead = counter - offset
+  
+  return res
 }
-Decoder.prototype.write = write;
-
-function write(byte) {
-  var msb = byte & MSB
-    , accum = this.accum
-    , len
-    , out
-
-  accum[accum.length] = byte & REST
-  if(msb) {
-    return
-  }
-
-  len = accum.length
-  out = 0
-
-  for(var i = 0; i < len; ++i) {
-    out |= accum[i] << (7 * i)
-  }
-
-  accum.length = 0
-  this.ondata(out)
-  return
-}

encode.js

@@ -14,4 +14,4 @@ function encode(num, out, offset) {
   }
   out[offset] = num
   return out
-}
+}

index.js

@@ -1,22 +1,4 @@
-module.exports = varint
+module.exports = {
-
+    encode: require('./encode.js')
-varint.encode = require('./encode.js');
+  , decode: require('./decode.js')
-
+}
-var EE = require('events').EventEmitter
-  , Decoder = require('./decode.js')
-
-function varint() {
-  var ee = new EE
-    , dec = new Decoder
-
-  dec.ondata = function (item) {
-    ee.emit("data", item)
-  }
-
-  ee.write = function (item) {
-    dec.write(item);
-  }
-
-  return ee
-}
-

package.json

@@ -1,7 +1,7 @@
 {
   "name": "varint",
   "version": "0.0.3",
-  "description": "use msb to create integer values of varying sizes",
+  "description": "protobuf-style varint bytes - use msb to create integer values of varying sizes",
   "main": "index.js",
   "scripts": {
     "test": "node test.js"

test.js

@@ -1,85 +1,72 @@
 var varint = require('./index')
   , test = require('tape')
+  , decode = varint.decode
+  , encode = varint.encode
 
 test('fuzz test', function(assert) {
-  var vi = varint()
+  var expect
-    , expect
     , encoded
 
-  vi.on('data', function(data) {
-    assert.equal(expect, data, 'fuzz test: '+expect.toString(16))
-  })
-
   for(var i = 0, len = 100; i < len; ++i) {
     expect = randint(0x7FFFFFFF)
-    encoded = varint.encode(expect)
+    encoded = encode(expect)
- 
+    var data = decode(encoded)
-    for(var x = 0; x < encoded.length; ++x) {
+    assert.equal(expect, data, 'fuzz test: ' + expect.toString())
-      vi.write(encoded[x])
+    assert.equal(decode.bytesRead, encoded.length)
-    } 
   }
 
   assert.end()
 })
 
 test('test single byte works as expected', function(assert) {
-  var num = [0xAC, 0x02]
+  var buf = new Uint8Array(2)
-  var acc = varint()
+  buf[0] = 172
-
+  buf[1] = 2
-  acc.on('data', function(data) {
+  var data = decode(buf)
-    assert.equal(data, 300, 'should equal 300 every time')
+  assert.equal(data, 300, 'should equal 300')
-  })
+  assert.equal(decode.bytesRead, 2)
-
-  for(var i = 0, len = 10; i < len; ++i) {
-    acc.write(0xAC)
-    acc.write(0x02)
-  }
-
   assert.end()
 })
 
 test('test encode works as expected', function(assert) {
   var out = []
 
-  assert.deepEqual(varint.encode(300), [0xAC, 0x02])
+  assert.deepEqual(encode(300), [0xAC, 0x02])
 
   assert.end()
 })
 
 test('test decode single bytes', function(assert) {
-  var vi = varint()
+  var expected = randint(parseInt('1111111', '2'))
-    , expected = randint(parseInt('1111111', '2'))
+  var buf = new Uint8Array(1)
-
+  buf[0] = expected
-  vi.once('data', function(data) {
+  var data = decode(buf)
-    assert.equal(data, expected)
+  assert.equal(data, expected)
-    assert.end()
+  assert.equal(decode.bytesRead, 1)
-  })
+  assert.end()
-
-  vi.write(expected)
 })
 
 test('test decode multiple bytes with zero', function(assert) {
-  var vi = varint()
+  var expected = randint(parseInt('1111111', '2'))
-    , expected = randint(parseInt('1111111', '2'))
+  var buf = new Uint8Array(2)
-
+  buf[0] = 128
-  vi.once('data', function(data) {
+  buf[1] = expected
-    assert.equal(data, expected << 7)
+  var data = decode(buf)
-    assert.end()
+  assert.equal(data, expected << 7)
-  })
+  assert.equal(decode.bytesRead, 2)
-
+  assert.end()
-  vi.write(0x80)
-  vi.write(expected)
 })
 
 test('encode single byte', function(assert) {
   var expected = randint(parseInt('1111111', '2'))
-  assert.deepEqual(varint.encode(expected), [expected])
+  assert.deepEqual(encode(expected), [expected])
   assert.end()
 })
 
 test('encode multiple byte with zero first byte', function(assert) {
   var expected = 0x0F00
-  assert.deepEqual(varint.encode(expected), [0x80, 0x1E])
+  assert.deepEqual(encode(expected), [0x80, 0x1E])
+  assert.end()
 })
 
 function randint(range) {