Fix #1882 zlib Update 'availOutBefore' value, and test

lib/zlib.js

@@ -303,7 +303,12 @@ Zlib.prototype._process = function() {
 
     if (availOutAfter === 0) {
       // Not actually done.  Need to reprocess.
+      // Also, update the availInBefore to the availInAfter value,
+      // so that if we have to hit it a third (fourth, etc.) time,
+      // it'll have the correct byte counts.
       inOff += (availInBefore - availInAfter);
+      availInBefore = availInAfter;
+
       var newReq = self._binding.write(self._flush,
                                        chunk,
                                        inOff,

test/simple/test-zlib-from-gzip.js

@@ -0,0 +1,48 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 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.
+
+// test unzipping a file that was created with a non-node gzip lib,
+// piped in as fast as possible.
+
+var common = require('../common.js');
+var assert = require('assert');
+var zlib = require('zlib');
+var path = require('path');
+
+var gunzip = zlib.createGunzip();
+
+var fs = require('fs');
+
+var fixture = path.resolve(common.fixturesDir, 'person.jpg.gz');
+var unzippedFixture = path.resolve(common.fixturesDir, 'person.jpg');
+var outputFile = path.resolve(common.tmpDir, 'person.jpg');
+var expect = fs.readFileSync(unzippedFixture);
+var inp = fs.createReadStream(fixture);
+var out = fs.createWriteStream(outputFile);
+
+inp.pipe(gunzip).pipe(out);
+out.on('close', function() {
+  var actual = fs.readFileSync(outputFile);
+  assert.equal(actual.length, expect.length, 'length should match');
+  for (var i = 0, l = actual.length; i < l; i++) {
+    assert.equal(actual[i], expect[i], 'byte['+i+']');
+  }
+});