Merge pull request #2004 from asvetlik/master

Added fuzzing code and readme.md to explain the fuzzer

roaring/README.md

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+# The Fuzzer
+
+For complete documentation on go-fuzz, please see: https://github.com/dvyukov/go-fuzz
+
+The fuzzer in relation to the roaring package checks the `Bitmap.UnmarshalBinary` function found in `roaring.go`. In order to use the fuzzer, you can follow these steps:
+
+`cd $GOPATH/src/github.com/pilosa/pilosa/roaring`
+
+`go-fuzz-build ./`
+
+You must now make the workdir/corpus directory. This is achieved by:
+
+`mkdir workdir/corpus`
+
+The fuzzer needs some input to start the fuzzing with. Copy some sample Pilosa fragments into the workdir/corpus folder. For example:
+
+`cp ~/.pilosa/my-index/my-field/views/standard/fragments/0 workdir/corpus`
+
+Once you have copied your sample inputs, you are ready to run the fuzzer:
+
+`go-fuzz -bin=roaring-fuzz.zip -workdir=workdir -func=FuzzBitmapUnmarshalBinary`
+
+## Understanding the Fuzzer Output
+
+The fuzzer will output something similar to the follwoing:
+
+`2015/04/25 12:39:53 workers: 8, corpus: 124 (12s ago), crashers: 37, restarts: 1/15, execs: 35342 (2941/sec), cover: 403, uptime: 12s`
+
+The most important part of the output is the `crashers` and `cover`. The crashers records how many combinations were discovered that fail and the cover tells you how much code is being accessed.
+For a complete explanation of the output, please see: https://github.com/dvyukov/go-fuzz.
+
+The fuzzer will document the crashers in a folder labeled "crashers." It will record the fragment and the error that was produced in two separate files within this folder. This is the final product.
+
+Happy Fuzzing!

roaring/fuzzer.go

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+// Copyright 2017 Pilosa Corp.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// +build gofuzz
+
+package roaring
+
+func FuzzBitmapUnmarshalBinary(data []byte) int {
+	b := NewBitmap()
+	err := b.UnmarshalBinary(data)
+	if err != nil {
+		return 0
+	}
+	return 1
+}