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diff --git a/mozglue/linker/Mappable.h b/mozglue/linker/Mappable.h
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+++ b/mozglue/linker/Mappable.h
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef Mappable_h
+#define Mappable_h
+
+#include <optional>
+#include "mozilla/RefCounted.h"
+#include "Utils.h"
+
+/**
+ * Helper class to mmap plain files.
+ */
+class Mappable : public mozilla::RefCounted<Mappable> {
+ public:
+  MOZ_DECLARE_REFCOUNTED_TYPENAME(Mappable)
+  ~Mappable() {}
+
+  MemoryRange mmap(const void* addr, size_t length, int prot, int flags,
+                   off_t offset);
+
+ private:
+  void munmap(void* addr, size_t length) { ::munmap(addr, length); }
+  /* Limit use of Mappable::munmap to classes that keep track of the address
+   * and size of the mapping. This allows to ignore ::munmap return value. */
+  friend class Mappable1stPagePtr;
+  friend class LibHandle;
+
+ public:
+  /**
+   * Indicate to a Mappable instance that no further mmap is going to happen.
+   */
+  void finalize();
+
+  /**
+   * Returns the maximum length that can be mapped from this Mappable for
+   * offset = 0.
+   */
+  size_t GetLength() const;
+
+  /**
+   * Create a Mappable instance for the given file path.
+   */
+  static Mappable* Create(const char* path);
+
+ protected:
+  explicit Mappable(int fd) : fd(fd) {}
+
+ private:
+  /* File descriptor */
+  std::optional<AutoCloseFD> fd;
+};
+
+#endif /* Mappable_h */