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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_SCOPED_BSTR_WIN_H_
+#define BASE_SCOPED_BSTR_WIN_H_
+
+#include "base/basictypes.h" // needed to pick up OS_WIN
+
+#include "base/logging.h"
+
+#include <windows.h>
+#include <oleauto.h>
+
+// Manages a BSTR string pointer.
+// The class interface is based on scoped_ptr.
+class ScopedBstr {
+ public:
+ ScopedBstr() : bstr_(NULL) {}
+
+ // Constructor to create a new BSTR.
+ // NOTE: Do not pass a BSTR to this constructor expecting ownership to
+ // be transferred - even though it compiles! ;-)
+ explicit ScopedBstr(const wchar_t* non_bstr);
+ ~ScopedBstr();
+
+ // Give ScopedBstr ownership over an already allocated BSTR or NULL.
+ // If you need to allocate a new BSTR instance, use |allocate| instead.
+ void Reset(BSTR bstr = NULL);
+
+ // Releases ownership of the BSTR to the caller.
+ BSTR Release();
+
+ // Creates a new BSTR from a wide string.
+ // If you already have a BSTR and want to transfer ownership to the
+ // ScopedBstr instance, call |reset| instead.
+ // Returns a pointer to the new BSTR, or NULL if allocation failed.
+ BSTR Allocate(const wchar_t* wide_str);
+
+ // Allocates a new BSTR with the specified number of bytes.
+ // Returns a pointer to the new BSTR, or NULL if allocation failed.
+ BSTR AllocateBytes(int bytes);
+
+ // Sets the allocated length field of the already-allocated BSTR to be
+ // |bytes|. This is useful when the BSTR was preallocated with e.g.
+ // SysAllocStringLen or SysAllocStringByteLen (call |AllocateBytes|) and
+ // then not all the bytes are being used.
+ // Note that if you want to set the length to a specific number of characters,
+ // you need to multiply by sizeof(wchar_t). Oddly, there's no public API to
+ // set the length, so we do this ourselves by hand.
+ //
+ // NOTE: The actual allocated size of the BSTR MUST be >= bytes.
+ // That responsibility is with the caller.
+ void SetByteLen(uint32_t bytes);
+
+ // Swap values of two ScopedBstr's.
+ void Swap(ScopedBstr& bstr2);
+
+ // Retrieves the pointer address.
+ // Used to receive BSTRs as out arguments (and take ownership).
+ // The function DCHECKs on the current value being NULL.
+ // Usage: GetBstr(bstr.Receive());
+ BSTR* Receive();
+
+ // Returns number of chars in the BSTR.
+ uint32_t Length() const;
+
+ // Returns the number of bytes allocated for the BSTR.
+ uint32_t ByteLength() const;
+
+ operator BSTR() const { return bstr_; }
+
+ protected:
+ BSTR bstr_;
+
+ private:
+ // Forbid comparison of ScopedBstr types. You should never have the same
+ // BSTR owned by two different scoped_ptrs.
+ bool operator==(const ScopedBstr& bstr2) const;
+ bool operator!=(const ScopedBstr& bstr2) const;
+ DISALLOW_COPY_AND_ASSIGN(ScopedBstr);
+};
+
+// Template class to generate a BSTR from a static wide string
+// without touching the heap. Use this class via the StackBstrVar and
+// StackBstr macros.
+template <uint32_t string_bytes>
+class StackBstrT {
+ public:
+ // Try to stay as const as we can in an attempt to avoid someone
+ // using the class incorrectly (e.g. by supplying a variable instead
+ // of a verbatim string. We also have an assert in the constructor
+ // as an extra runtime check since the const-ness only catches one case.
+ explicit StackBstrT(const wchar_t* const str) {
+ // The BSTR API uses UINT, but we prefer uint32_t.
+ // Make sure we'll know about it if these types don't match.
+ COMPILE_ASSERT(sizeof(uint32_t) == sizeof(UINT), UintToUint32);
+ COMPILE_ASSERT(sizeof(wchar_t) == sizeof(OLECHAR), WcharToOlechar);
+
+ // You shouldn't pass string pointers to this constructor since
+ // there's no way for the compiler to calculate the length of the
+ // string (string_bytes will be equal to pointer size in those cases).
+ DCHECK(lstrlenW(str) == (string_bytes / sizeof(bstr_.str_[0])) - 1)
+ << "not expecting a string pointer";
+ memcpy(bstr_.str_, str, string_bytes);
+ bstr_.len_ = string_bytes - sizeof(wchar_t);
+ }
+
+ operator BSTR() { return bstr_.str_; }
+
+ protected:
+ struct BstrInternal {
+ uint32_t len_;
+ wchar_t str_[string_bytes / sizeof(wchar_t)];
+ } bstr_;
+};
+
+// Use this macro to generate an inline BSTR from a wide string.
+// This is about 6 times faster than using the SysAllocXxx functions to
+// allocate a BSTR and helps with keeping heap fragmentation down.
+// Example:
+// DoBstrStuff(StackBstr(L"This is my BSTR"));
+// Where DoBstrStuff is:
+// HRESULT DoBstrStuff(BSTR bstr) { ... }
+#define StackBstr(str) static_cast<BSTR>(StackBstrT<sizeof(str)>(str))
+
+// If you need a named BSTR variable that's based on a fixed string
+// (e.g. if the BSTR is used inside a loop or more than one place),
+// use StackBstrVar to declare a variable.
+// Example:
+// StackBstrVar(L"my_property", myprop);
+// for (int i = 0; i < objects.length(); ++i)
+// ProcessValue(objects[i].GetProp(myprop)); // GetProp accepts BSTR
+#define StackBstrVar(str, var) StackBstrT<sizeof(str)> var(str)
+
+#endif // BASE_SCOPED_BSTR_WIN_H_