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diff --git a/mozglue/linker/Mappable.h 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 "Zip.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtr.h"
+#include "zlib.h"
+
+/**
+ * Abstract class to handle mmap()ing from various kind of entities, such as
+ * plain files or Zip entries. The virtual members are meant to act as the
+ * equivalent system functions, except mapped memory is always MAP_PRIVATE,
+ * even though a given implementation may use something different internally.
+ */
+class Mappable : public mozilla::RefCounted<Mappable> {
+ public:
+  MOZ_DECLARE_REFCOUNTED_TYPENAME(Mappable)
+  virtual ~Mappable() {}
+
+  virtual MemoryRange mmap(const void* addr, size_t length, int prot, int flags,
+                           off_t offset) = 0;
+
+  enum Kind {
+    MAPPABLE_FILE,
+    MAPPABLE_EXTRACT_FILE,
+    MAPPABLE_DEFLATE,
+    MAPPABLE_SEEKABLE_ZSTREAM
+  };
+
+  virtual Kind GetKind() const = 0;
+
+ private:
+  virtual 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.
+   */
+  virtual void finalize() = 0;
+
+  /**
+   * Returns the maximum length that can be mapped from this Mappable for
+   * offset = 0.
+   */
+  virtual size_t GetLength() const = 0;
+};
+
+/**
+ * Mappable implementation for plain files
+ */
+class MappableFile : public Mappable {
+ public:
+  ~MappableFile() {}
+
+  /**
+   * Create a MappableFile instance for the given file path.
+   */
+  static Mappable* Create(const char* path);
+
+  /* Inherited from Mappable */
+  virtual MemoryRange mmap(const void* addr, size_t length, int prot, int flags,
+                           off_t offset);
+  virtual void finalize();
+  virtual size_t GetLength() const;
+
+  virtual Kind GetKind() const { return MAPPABLE_FILE; };
+
+ protected:
+  explicit MappableFile(int fd) : fd(fd) {}
+
+ private:
+  /* File descriptor */
+  AutoCloseFD fd;
+};
+
+/**
+ * Mappable implementation for deflated stream in a Zip archive
+ * Inflates the complete stream into a cache file.
+ */
+class MappableExtractFile : public MappableFile {
+ public:
+  ~MappableExtractFile() = default;
+
+  /**
+   * Create a MappableExtractFile instance for the given Zip stream. The name
+   * argument is used to create the cache file in the cache directory.
+   */
+  static Mappable* Create(const char* name, Zip* zip, Zip::Stream* stream);
+
+  /* Override finalize from MappableFile */
+  virtual void finalize() {}
+
+  virtual Kind GetKind() const { return MAPPABLE_EXTRACT_FILE; };
+
+ private:
+  /**
+   * AutoUnlinkFile keeps track of a file name and removes (unlinks) the file
+   * when the instance is destroyed.
+   */
+  struct UnlinkFile {
+    void operator()(char* value) {
+      unlink(value);
+      delete[] value;
+    }
+  };
+  typedef mozilla::UniquePtr<char[], UnlinkFile> AutoUnlinkFile;
+
+  MappableExtractFile(int fd, const char* path)
+      : MappableFile(fd), path(path) {}
+
+  /* Extracted file path */
+  mozilla::UniquePtr<const char[]> path;
+};
+
+class _MappableBuffer;
+
+/**
+ * Mappable implementation for deflated stream in a Zip archive.
+ * Inflates the mapped bits in a temporary buffer.
+ */
+class MappableDeflate : public Mappable {
+ public:
+  ~MappableDeflate();
+
+  /**
+   * Create a MappableDeflate instance for the given Zip stream. The name
+   * argument is used for an appropriately named temporary file, and the Zip
+   * instance is given for the MappableDeflate to keep a reference of it.
+   */
+  static Mappable* Create(const char* name, Zip* zip, Zip::Stream* stream);
+
+  /* Inherited from Mappable */
+  virtual MemoryRange mmap(const void* addr, size_t length, int prot, int flags,
+                           off_t offset);
+  virtual void finalize();
+  virtual size_t GetLength() const;
+
+  virtual Kind GetKind() const { return MAPPABLE_DEFLATE; };
+
+ private:
+  MappableDeflate(_MappableBuffer* buf, Zip* zip, Zip::Stream* stream);
+
+  /* Zip reference */
+  RefPtr<Zip> zip;
+
+  /* Decompression buffer */
+  mozilla::UniquePtr<_MappableBuffer> buffer;
+
+  /* Zlib data */
+  z_stream zStream;
+};
+
+#endif /* Mappable_h */