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AutoMemMap.h (2145B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
      3 /* This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #ifndef mozilla_devtools_AutoMemMap_h
      8 #define mozilla_devtools_AutoMemMap_h
      9 
     10 #include <prio.h>
     11 #include "nsIFile.h"
     12 #include "mozilla/Assertions.h"
     13 #include "ErrorList.h"
     14 
     15 namespace mozilla {
     16 namespace devtools {
     17 
     18 // # AutoMemMap
     19 //
     20 // AutoMemMap is an RAII class to manage mapping a file to memory. It is a
     21 // wrapper around managing opening and closing a file and calling PR_MemMap and
     22 // PR_MemUnmap.
     23 //
     24 // Example usage:
     25 //
     26 //     {
     27 //       AutoMemMap mm;
     28 //       if (NS_FAILED(mm.init("/path/to/desired/file"))) {
     29 //          // Handle the error however you see fit.
     30 //         return false;
     31 //       }
     32 //
     33 //       doStuffWithMappedMemory(mm.address());
     34 //     }
     35 //     // The memory is automatically unmapped when the AutoMemMap leaves scope.
     36 class MOZ_RAII AutoMemMap {
     37  // At the time of this writing, this class supports file imports up to
     38  // UINT32_MAX bytes due to limitations in the underlying function PR_MemMap.
     39  uint32_t fileSize;
     40  PRFileDesc* fd;
     41  PRFileMap* fileMap;
     42  void* addr;
     43 
     44  AutoMemMap(const AutoMemMap& aOther) = delete;
     45  void operator=(const AutoMemMap& aOther) = delete;
     46 
     47 public:
     48  explicit AutoMemMap()
     49      : fileSize(0), fd(nullptr), fileMap(nullptr), addr(nullptr) {};
     50  ~AutoMemMap();
     51 
     52  // Initialize this AutoMemMap.
     53  nsresult init(nsIFile* file, int flags = PR_RDONLY, int mode = 0,
     54                PRFileMapProtect prot = PR_PROT_READONLY);
     55 
     56  // Get the size of the memory mapped file.
     57  uint32_t size() const {
     58    MOZ_ASSERT(fd, "Should only call size() if init() succeeded.");
     59    return fileSize;
     60  }
     61 
     62  // Get the mapped memory.
     63  void* address() {
     64    MOZ_ASSERT(addr);
     65    return addr;
     66  }
     67  const void* address() const {
     68    MOZ_ASSERT(addr);
     69    return addr;
     70  }
     71 };
     72 
     73 }  // namespace devtools
     74 }  // namespace mozilla
     75 
     76 #endif  // mozilla_devtools_AutoMemMap_h