imprecise mark and sweep native memory leak detector

libmemunreachable uses an imprecise mark and sweep pass over all memory
allocated by jemalloc in order to find unreachable allocations.

Bug: 27208635
Change-Id: Ia70bbf31f5b40ff71dab28cfd6cd06c5ef01a2d4
(cherry picked from commit bcb4ed3eaa92d23949d4ab33dbf1b2604bba8a18)
diff --git a/libmemunreachable/ScopedPipe.h b/libmemunreachable/ScopedPipe.h
new file mode 100644
index 0000000..9beef9a
--- /dev/null
+++ b/libmemunreachable/ScopedPipe.h
@@ -0,0 +1,81 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#ifndef LIBMEMUNREACHABLE_SCOPED_PIPE_H_
+#define LIBMEMUNREACHABLE_SCOPED_PIPE_H_
+
+#include <unistd.h>
+
+#include "log.h"
+
+class ScopedPipe {
+ public:
+  ScopedPipe() : pipefd_{-1, -1} {
+    int ret = pipe2(pipefd_, O_CLOEXEC);
+    if (ret < 0) {
+      LOG_ALWAYS_FATAL("failed to open pipe");
+    }
+  }
+  ~ScopedPipe() {
+    Close();
+  }
+
+  ScopedPipe(ScopedPipe&& other) {
+    SetReceiver(other.ReleaseReceiver());
+    SetSender(other.ReleaseSender());
+  }
+
+  ScopedPipe& operator = (ScopedPipe&& other) {
+    SetReceiver(other.ReleaseReceiver());
+    SetSender(other.ReleaseSender());
+    return *this;
+  }
+
+  void CloseReceiver() {
+    close(ReleaseReceiver());
+  }
+
+  void CloseSender() {
+    close(ReleaseSender());
+  }
+
+  void Close() {
+    CloseReceiver();
+    CloseSender();
+  }
+
+  int Receiver() { return pipefd_[0]; }
+  int Sender() { return pipefd_[1]; }
+
+  int ReleaseReceiver() {
+    int ret = Receiver();
+    SetReceiver(-1);
+    return ret;
+  }
+
+  int ReleaseSender() {
+    int ret = Sender();
+    SetSender(-1);
+    return ret;
+  }
+
+ private:
+  void SetReceiver(int fd) { pipefd_[0] = fd; };
+  void SetSender(int fd) { pipefd_[1] = fd; };
+
+  int pipefd_[2];
+};
+#endif