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Diffstat (limited to 'ipc/chromium/src/base/scoped_bstr_win.h')
-rw-r--r-- | ipc/chromium/src/base/scoped_bstr_win.h | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/ipc/chromium/src/base/scoped_bstr_win.h b/ipc/chromium/src/base/scoped_bstr_win.h new file mode 100644 index 000000000..86cfb0254 --- /dev/null +++ b/ipc/chromium/src/base/scoped_bstr_win.h @@ -0,0 +1,145 @@ +/* -*- 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_ |