Merge branch 'shallow-slice' of https://github.com/geloescht/bl into …

…v1.2-dev

README.md

@@ -87,6 +87,7 @@ bl.pipe(fs.createWriteStream('gibberish.txt'))
   * <a href="#append"><code>bl.<b>append(buffer)</b></code></a>
   * <a href="#get"><code>bl.<b>get(index)</b></code></a>
   * <a href="#slice"><code>bl.<b>slice([ start[, end ] ])</b></code></a>
+  * <a href="#shallowSlice"><code>bl.<b>shallowSlice([ start[, end ] ])</b></code></a>
   * <a href="#copy"><code>bl.<b>copy(dest, [ destStart, [ srcStart [, srcEnd ] ] ])</b></code></a>
   * <a href="#duplicate"><code>bl.<b>duplicate()</b></code></a>
   * <a href="#consume"><code>bl.<b>consume(bytes)</b></code></a>
@@ -135,6 +136,13 @@ Get the length of the list in bytes. This is the sum of the lengths of all of th
 
 If the requested range spans a single internal buffer then a slice of that buffer will be returned which shares the original memory range of that Buffer. If the range spans multiple buffers then copy operations will likely occur to give you a uniform Buffer.
 
+--------------------------------------------------------
+<a name="shallowSlice"></a>
+### bl.shallowSlice([ start, [ end ] ])
+`shallowSlice()` returns a new `BufferList` object containing the bytes within the range specified. Both `start` and `end` are optional and will default to the beginning and end of the list respectively.
+
+No copies will be performed. All buffers in the result share memory with the original list.
+
 --------------------------------------------------------
 <a name="copy"></a>
 ### bl.copy(dest, [ destStart, [ srcStart [, srcEnd ] ] ])

bl.js

@@ -41,7 +41,7 @@ BufferList.prototype._offset = function _offset (offset) {
   if (offset === 0) return [ 0, 0 ]
   for (; i < this._bufs.length; i++) {
     _t = tot + this._bufs[i].length
-    if (offset < _t)
+    if (offset < _t || i == this._bufs.length - 1)
       return [ i, offset - tot ]
     tot = _t
   }
@@ -186,6 +186,30 @@ BufferList.prototype.copy = function copy (dst, dstStart, srcStart, srcEnd) {
   return dst
 }
 
+BufferList.prototype.shallowSlice = function shallowSlice (start, end) {
+  start = start || 0
+  end = end || this.length
+
+  if (start < 0)
+    start += this.length
+  if (end < 0)
+    end += this.length
+
+  var startOffset = this._offset(start)
+    , endOffset = this._offset(end)
+    , buffers = this._bufs.slice(startOffset[0], endOffset[0] + 1)
+
+  if(startOffset[1] != 0)
+    buffers[0] = buffers[0].slice(startOffset[1])
+
+  if(endOffset[1] == 0)
+    buffers.pop()
+  else
+    buffers[buffers.length-1] = buffers[buffers.length-1].slice(0, endOffset[1])
+
+  return new BufferList(buffers)
+}
+
 BufferList.prototype.toString = function toString (encoding, start, end) {
   return this.slice(start, end).toString(encoding)
 }

test/test.js

@@ -552,6 +552,50 @@ tape('copy an interval between two buffers', function (t) {
   t.end()
 })
 
+tape('shallow slice across buffer boundaries', function (t) {
+  var bl = new BufferList(['First', 'Second', 'Third'])
+
+  t.equal(bl.shallowSlice(3, 13).toString(), 'stSecondTh')
+  t.end()
+})
+
+tape('shallow slice within single buffer', function (t) {
+  var bl = new BufferList(['First', 'Second', 'Third'])
+
+  t.equal(bl.shallowSlice(5, 10).toString(), 'Secon')
+  t.end()
+})
+
+tape('shallow slice single buffer', function (t) {
+  t.plan(3)
+  var bl = new BufferList(['First', 'Second', 'Third'])
+
+  t.equal(bl.shallowSlice(0, 5).toString(), 'First')
+  t.equal(bl.shallowSlice(5, 11).toString(), 'Second')
+  t.equal(bl.shallowSlice(11, 16).toString(), 'Third')
+})
+
+tape('shallow slice with negative or omitted indices', function (t) {
+  t.plan(4)
+  var bl = new BufferList(['First', 'Second', 'Third'])
+
+  t.equal(bl.shallowSlice().toString(), 'FirstSecondThird')
+  t.equal(bl.shallowSlice(5).toString(), 'SecondThird')
+  t.equal(bl.shallowSlice(5, -3).toString(), 'SecondTh')
+  t.equal(bl.shallowSlice(-8).toString(), 'ondThird')
+})
+
+tape('shallow slice does not make a copy', function (t) {
+  t.plan(1)
+  var buffers = [new Buffer('First'), new Buffer('Second'), new Buffer('Third')]
+  var bl = (new BufferList(buffers)).shallowSlice(5, -3)
+
+  buffers[1].fill('h')
+  buffers[2].fill('h')
+
+  t.equal(bl.toString(), 'hhhhhhhh')
+})
+
 tape('duplicate', function (t) {
   t.plan(2)