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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 "Zip.h"
+#include "SeekableZStream.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:
+  /**
+   * Ensures the availability of the memory pages for the page(s) containing
+   * the given address. Returns whether the pages were successfully made
+   * available.
+   */
+  virtual bool ensure(const void *addr) { return true; }
+
+  /**
+   * Indicate to a Mappable instance that no further mmap is going to happen.
+   */
+  virtual void finalize() = 0;
+
+  /**
+   * Shows some stats about the Mappable instance.
+   * Meant for MappableSeekableZStream only.
+   * As Mappables don't keep track of what they are instanciated for, the name
+   * argument is used to make the stats logging useful to the reader. The when
+   * argument is to be used by the caller to give an identifier of the when
+   * the stats call is made.
+   */
+  virtual void stats(const char *when, const char *name) const { }
+
+  /**
+   * 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:
+  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 */
+  zxx_stream zStream;
+};
+
+/**
+ * Mappable implementation for seekable zStreams.
+ * Inflates the mapped bits in a temporary buffer, on demand.
+ */
+class MappableSeekableZStream: public Mappable
+{
+public:
+  ~MappableSeekableZStream();
+
+  /**
+   * Create a MappableSeekableZStream 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 MappableSeekableZStream 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 munmap(void *addr, size_t length);
+  virtual void finalize();
+  virtual bool ensure(const void *addr);
+  virtual void stats(const char *when, const char *name) const;
+  virtual size_t GetLength() const;
+
+  virtual Kind GetKind() const { return MAPPABLE_SEEKABLE_ZSTREAM; };
+private:
+  MappableSeekableZStream(Zip *zip);
+
+  /* Zip reference */
+  RefPtr<Zip> zip;
+
+  /* Decompression buffer */
+  mozilla::UniquePtr<_MappableBuffer> buffer;
+
+  /* Seekable ZStream */
+  SeekableZStream zStream;
+
+  /* Keep track of mappings performed with MappableSeekableZStream::mmap so
+   * that they can be realized by MappableSeekableZStream::ensure.
+   * Values stored in the struct are those passed to mmap */
+  struct LazyMap
+  {
+    const void *addr;
+    size_t length;
+    int prot;
+    off_t offset;
+
+    /* Returns addr + length, as a pointer */
+    const void *end() const {
+      return reinterpret_cast<const void *>
+             (reinterpret_cast<const unsigned char *>(addr) + length);
+    }
+
+    /* Returns offset + length */
+    off_t endOffset() const {
+      return offset + length;
+    }
+
+    /* Returns the offset corresponding to the given address */
+    off_t offsetOf(const void *ptr) const {
+      return reinterpret_cast<uintptr_t>(ptr)
+             - reinterpret_cast<uintptr_t>(addr) + offset;
+    }
+
+    /* Returns whether the given address is in the LazyMap range */
+    bool Contains(const void *ptr) const {
+      return (ptr >= addr) && (ptr < end());
+    }
+  };
+
+  /* List of all mappings */
+  std::vector<LazyMap> lazyMaps;
+
+  /* Array keeping track of which chunks have already been decompressed.
+   * Each value is the number of pages decompressed for the given chunk. */
+  mozilla::UniquePtr<unsigned char[]> chunkAvail;
+
+  /* Number of chunks that have already been decompressed. */
+  mozilla::Atomic<size_t> chunkAvailNum;
+
+  /* Mutex protecting decompression */
+  pthread_mutex_t mutex;
+};
+
+#endif /* Mappable_h */