Add explicit buffer option

README.md

@@ -27,7 +27,9 @@ pull(
 
 this supports all the options that node's [fs.createReadStream](https://nodejs.org/dist/latest-v6.x/docs/api/fs.html#fs_fs_createreadstream_path_options) supports,
 and _also_ this supports a `live: true` property which will keep the stream open and wait for appends
-when it gets to the end.
+when it gets to the end and an explicit `buffer` option where your chunks will be read to.
+Note that if your downstream operations are async you may run into concurrency
+issues with this option. Use at your own risk!
 
 
 ## License(s)
@@ -54,4 +56,3 @@ IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-

index.js

@@ -18,13 +18,13 @@ var Decoder = require('pull-utf8-decoder')
 **/
 module.exports = function(filename, opts) {
   var mode = opts && opts.mode || 0x1B6; // 0666
-  var bufferSize = opts && opts.bufferSize || 1024*64;
+  var bufferSize = opts && (opts.bufferSize || (opts.buffer && opts.buffer.length))  || 1024*64;
   var start = opts && opts.start || 0
   var end = opts && opts.end || Number.MAX_SAFE_INTEGER
   var fd = opts && opts.fd
 
   var ended, closeNext, busy;
-  var _buffer = new Buffer(bufferSize)
+  var _buffer = opts && opts.buffer || new Buffer(bufferSize)
   var live = opts && !!opts.live
   var liveCb, closeCb
   var watcher
@@ -88,7 +88,7 @@ module.exports = function(filename, opts) {
         }
       }
     );
-    _buffer = new Buffer(Math.min(end - start, bufferSize))
+    _buffer = opts && opts.buffer || new Buffer(Math.min(end - start, bufferSize))
   }
 
   function open(cb) {
@@ -168,4 +168,3 @@ module.exports = function(filename, opts) {
   return source
 
 };
-

test/explicit-buffer.js

@@ -0,0 +1,33 @@
+var test = require('tape');
+var pull = require('pull-stream');
+var file = require('..');
+
+var path = require('path');
+var crypto = require('crypto')
+var osenv = require('osenv')
+var fs = require('fs')
+
+var tmpfile = path.join(osenv.tmpdir(), 'test_pull-file_big')
+
+var big = crypto.pseudoRandomBytes(10*1024*1024)
+fs.writeFileSync(tmpfile, big)
+
+function hash (data) {
+  return crypto.createHash('sha256').update(data).digest('hex')
+}
+
+test('large file in explicit buffer', function(t) {
+  var buf = new Buffer(65551) // prime close to 1024 * 64
+  var h = crypto.createHash('sha256')
+
+  pull(
+    file(tmpfile, {buffer: buf}),
+    pull.through(function (chunk) {
+      h.update(chunk)
+    }),
+    pull.onEnd(function(err) {
+      t.equal(hash(big), h.digest('hex'))
+      t.end()
+    })
+  );
+});