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      1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef BASE_WIN_SCOPED_BSTR_H_
      6 #define BASE_WIN_SCOPED_BSTR_H_
      7 
      8 #include <windows.h>
      9 #include <oleauto.h>
     10 
     11 #include "base/base_export.h"
     12 #include "base/logging.h"
     13 #include "base/strings/string16.h"
     14 
     15 namespace base {
     16 namespace win {
     17 
     18 // Manages a BSTR string pointer.
     19 // The class interface is based on scoped_ptr.
     20 class BASE_EXPORT ScopedBstr {
     21  public:
     22   ScopedBstr() : bstr_(NULL) {
     23   }
     24 
     25   // Constructor to create a new BSTR.
     26   //
     27   // NOTE: Do not pass a BSTR to this constructor expecting ownership to
     28   // be transferred - even though it compiles! ;-)
     29   explicit ScopedBstr(const char16* non_bstr);
     30   ~ScopedBstr();
     31 
     32   // Give ScopedBstr ownership over an already allocated BSTR or NULL.
     33   // If you need to allocate a new BSTR instance, use |allocate| instead.
     34   void Reset(BSTR bstr = NULL);
     35 
     36   // Releases ownership of the BSTR to the caller.
     37   BSTR Release();
     38 
     39   // Creates a new BSTR from a 16-bit C-style string.
     40   //
     41   // If you already have a BSTR and want to transfer ownership to the
     42   // ScopedBstr instance, call |reset| instead.
     43   //
     44   // Returns a pointer to the new BSTR, or NULL if allocation failed.
     45   BSTR Allocate(const char16* str);
     46 
     47   // Allocates a new BSTR with the specified number of bytes.
     48   // Returns a pointer to the new BSTR, or NULL if allocation failed.
     49   BSTR AllocateBytes(size_t bytes);
     50 
     51   // Sets the allocated length field of the already-allocated BSTR to be
     52   // |bytes|.  This is useful when the BSTR was preallocated with e.g.
     53   // SysAllocStringLen or SysAllocStringByteLen (call |AllocateBytes|) and then
     54   // not all the bytes are being used.
     55   //
     56   // Note that if you want to set the length to a specific number of
     57   // characters, you need to multiply by sizeof(wchar_t).  Oddly, there's no
     58   // public API to set the length, so we do this ourselves by hand.
     59   //
     60   // NOTE: The actual allocated size of the BSTR MUST be >= bytes.  That
     61   // responsibility is with the caller.
     62   void SetByteLen(size_t bytes);
     63 
     64   // Swap values of two ScopedBstr's.
     65   void Swap(ScopedBstr& bstr2);
     66 
     67   // Retrieves the pointer address.
     68   // Used to receive BSTRs as out arguments (and take ownership).
     69   // The function DCHECKs on the current value being NULL.
     70   // Usage: GetBstr(bstr.Receive());
     71   BSTR* Receive();
     72 
     73   // Returns number of chars in the BSTR.
     74   size_t Length() const;
     75 
     76   // Returns the number of bytes allocated for the BSTR.
     77   size_t ByteLength() const;
     78 
     79   operator BSTR() const {
     80     return bstr_;
     81   }
     82 
     83  protected:
     84   BSTR bstr_;
     85 
     86  private:
     87   // Forbid comparison of ScopedBstr types.  You should never have the same
     88   // BSTR owned by two different scoped_ptrs.
     89   bool operator==(const ScopedBstr& bstr2) const;
     90   bool operator!=(const ScopedBstr& bstr2) const;
     91   DISALLOW_COPY_AND_ASSIGN(ScopedBstr);
     92 };
     93 
     94 }  // namespace win
     95 }  // namespace base
     96 
     97 #endif  // BASE_SCOPED_BSTR_H_
     98