michael@0: // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
michael@0: // Use of this source code is governed by a BSD-style license that can be
michael@0: // found in the LICENSE file.
michael@0: 
michael@0: #ifndef BASE_SCOPED_BSTR_WIN_H_
michael@0: #define BASE_SCOPED_BSTR_WIN_H_
michael@0: 
michael@0: #include "base/basictypes.h"  // needed to pick up OS_WIN
michael@0: 
michael@0: #include "base/logging.h"
michael@0: 
michael@0: #include <windows.h>
michael@0: #include <oleauto.h>
michael@0: 
michael@0: // Manages a BSTR string pointer.
michael@0: // The class interface is based on scoped_ptr.
michael@0: class ScopedBstr {
michael@0:  public:
michael@0:   ScopedBstr() : bstr_(NULL) {
michael@0:   }
michael@0: 
michael@0:   // Constructor to create a new BSTR.
michael@0:   // NOTE: Do not pass a BSTR to this constructor expecting ownership to
michael@0:   // be transferred - even though it compiles! ;-)
michael@0:   explicit ScopedBstr(const wchar_t* non_bstr);
michael@0:   ~ScopedBstr();
michael@0: 
michael@0:   // Give ScopedBstr ownership over an already allocated BSTR or NULL.
michael@0:   // If you need to allocate a new BSTR instance, use |allocate| instead.
michael@0:   void Reset(BSTR bstr = NULL);
michael@0: 
michael@0:   // Releases ownership of the BSTR to the caller.
michael@0:   BSTR Release();
michael@0: 
michael@0:   // Creates a new BSTR from a wide string.
michael@0:   // If you already have a BSTR and want to transfer ownership to the
michael@0:   // ScopedBstr instance, call |reset| instead.
michael@0:   // Returns a pointer to the new BSTR, or NULL if allocation failed.
michael@0:   BSTR Allocate(const wchar_t* wide_str);
michael@0: 
michael@0:   // Allocates a new BSTR with the specified number of bytes.
michael@0:   // Returns a pointer to the new BSTR, or NULL if allocation failed.
michael@0:   BSTR AllocateBytes(int bytes);
michael@0: 
michael@0:   // Sets the allocated length field of the already-allocated BSTR to be
michael@0:   // |bytes|.  This is useful when the BSTR was preallocated with e.g.
michael@0:   // SysAllocStringLen or SysAllocStringByteLen (call |AllocateBytes|) and
michael@0:   // then not all the bytes are being used.
michael@0:   // Note that if you want to set the length to a specific number of characters,
michael@0:   // you need to multiply by sizeof(wchar_t).  Oddly, there's no public API to
michael@0:   // set the length, so we do this ourselves by hand.
michael@0:   //
michael@0:   // NOTE: The actual allocated size of the BSTR MUST be >= bytes.
michael@0:   //  That responsibility is with the caller.
michael@0:   void SetByteLen(uint32_t bytes);
michael@0: 
michael@0:   // Swap values of two ScopedBstr's.
michael@0:   void Swap(ScopedBstr& bstr2);
michael@0: 
michael@0:   // Retrieves the pointer address.
michael@0:   // Used to receive BSTRs as out arguments (and take ownership).
michael@0:   // The function DCHECKs on the current value being NULL.
michael@0:   // Usage: GetBstr(bstr.Receive());
michael@0:   BSTR* Receive();
michael@0: 
michael@0:   // Returns number of chars in the BSTR.
michael@0:   uint32_t Length() const;
michael@0: 
michael@0:   // Returns the number of bytes allocated for the BSTR.
michael@0:   uint32_t ByteLength() const;
michael@0: 
michael@0:   operator BSTR() const {
michael@0:     return bstr_;
michael@0:   }
michael@0: 
michael@0:  protected:
michael@0:   BSTR bstr_;
michael@0: 
michael@0:  private:
michael@0:   // Forbid comparison of ScopedBstr types.  You should never have the same
michael@0:   // BSTR owned by two different scoped_ptrs.
michael@0:   bool operator==(const ScopedBstr& bstr2) const;
michael@0:   bool operator!=(const ScopedBstr& bstr2) const;
michael@0:   DISALLOW_COPY_AND_ASSIGN(ScopedBstr);
michael@0: };
michael@0: 
michael@0: // Template class to generate a BSTR from a static wide string
michael@0: // without touching the heap.  Use this class via the StackBstrVar and
michael@0: // StackBstr macros.
michael@0: template <uint32_t string_bytes>
michael@0: class StackBstrT {
michael@0:  public:
michael@0:   // Try to stay as const as we can in an attempt to avoid someone
michael@0:   // using the class incorrectly (e.g. by supplying a variable instead
michael@0:   // of a verbatim string.  We also have an assert in the constructor
michael@0:   // as an extra runtime check since the const-ness only catches one case.
michael@0:   explicit StackBstrT(const wchar_t* const str) {
michael@0:     // The BSTR API uses UINT, but we prefer uint32_t.
michael@0:     // Make sure we'll know about it if these types don't match.
michael@0:     COMPILE_ASSERT(sizeof(uint32_t) == sizeof(UINT), UintToUint32);
michael@0:     COMPILE_ASSERT(sizeof(wchar_t) == sizeof(OLECHAR), WcharToOlechar);
michael@0: 
michael@0:     // You shouldn't pass string pointers to this constructor since
michael@0:     // there's no way for the compiler to calculate the length of the
michael@0:     // string (string_bytes will be equal to pointer size in those cases).
michael@0:     DCHECK(lstrlenW(str) == (string_bytes / sizeof(bstr_.str_[0])) - 1) <<
michael@0:         "not expecting a string pointer";
michael@0:     memcpy(bstr_.str_, str, string_bytes);
michael@0:     bstr_.len_ = string_bytes - sizeof(wchar_t);
michael@0:   }
michael@0: 
michael@0:   operator BSTR() {
michael@0:     return bstr_.str_;
michael@0:   }
michael@0: 
michael@0:  protected:
michael@0:   struct BstrInternal {
michael@0:     uint32_t len_;
michael@0:     wchar_t str_[string_bytes / sizeof(wchar_t)];
michael@0:   } bstr_;
michael@0: };
michael@0: 
michael@0: // Use this macro to generate an inline BSTR from a wide string.
michael@0: // This is about 6 times faster than using the SysAllocXxx functions to
michael@0: // allocate a BSTR and helps with keeping heap fragmentation down.
michael@0: // Example:
michael@0: //  DoBstrStuff(StackBstr(L"This is my BSTR"));
michael@0: // Where DoBstrStuff is:
michael@0: //  HRESULT DoBstrStuff(BSTR bstr) { ... }
michael@0: #define StackBstr(str) \
michael@0:   static_cast<BSTR>(StackBstrT<sizeof(str)>(str))
michael@0: 
michael@0: // If you need a named BSTR variable that's based on a fixed string
michael@0: // (e.g. if the BSTR is used inside a loop or more than one place),
michael@0: // use StackBstrVar to declare a variable.
michael@0: // Example:
michael@0: //   StackBstrVar(L"my_property", myprop);
michael@0: //   for (int i = 0; i < objects.length(); ++i)
michael@0: //     ProcessValue(objects[i].GetProp(myprop));  // GetProp accepts BSTR
michael@0: #define StackBstrVar(str, var) \
michael@0:   StackBstrT<sizeof(str)> var(str)
michael@0: 
michael@0: #endif  // BASE_SCOPED_BSTR_WIN_H_