Burn CDs With ICDBurn

Windows XP and its successor Windows operating systems provide the Image Mastering API (IMAPI) for burning CDs. Starting with IMAPI version 2 (the default for Windows Vista, but also available from Microsoft as an upgrade for Windows XP Service Packs 2 and 3, and Windows 2003 Server), DVDs and Blu-ray media can be burned as well.

The shells of these operating systems provide a Component Object Model (COM) class whose ICDBurn interface (which is based on IMAPI version 1) facilitates CD burning. More specifically, ICDBurn makes it easy to create data CDs (CDs that consist of files and directories). ICDBurn doesn't support the creation of audio CDs.

This article introduces you to ICDBurn by first presenting this COM interface's fundamentals. The article next shows you how to access ICDBurn from the C, C++, and C# languages. Lastly, the article reveals ICDBurn's usefulness via a file-backup utility that lets you select and burn files to one or more CDs.

ICDBurn 101

XP's shell provides a shell folder extension class in shell32.dll. This COM class, identified via globally unique identifier (GUID) fbeb8a05-beee-4442-804e-409d6c4515e9, presents the ICDBurn interface, identified via GUID 3d73a659-e5d0-4d42-afc0-5121ba425c8d. These GUIDs are essential for creating a COM object from the extension class, and for accessing this object via ICDBurn.

ICDBurn exposes three functions:

• HRESULT HasRecordableDrive(BOOL *pfHasRecorder) scans the hardware looking for a CD burning device, and stores a Boolean value in the memory location pointed to by pfHasRecorder to indicate the presence (TRUE) or absence (FALSE) of a CD burner. This function returns S_OK if it succeeds.
• HRESULT GetRecorderDriveLetter(LPWSTR pszDrive, UINT cch) stores the drive letter of the default CD burning device in the memory location pointed to by pszDrive. The drive letter is stored as a string of wide characters in the form x:\, where x is the actual letter. This function returns S_OK if it succeeds.
• HRESULT Burn(HWND hwnd) launches a wizard to guide the user through the burning process, and copies files and directories from a special directory known as the staging area to a writable CD. The passed hwnd argument identifies the parent window for each of the wizard's windows. If this function succeeds, it returns S_OK.

Before the Burn() function can copy the staging area's contents to a CD, a program must copy files and/or directories to this special directory. The program identifies the staging area's location by invoking an appropriate shell function. Although there are several functions from which to choose, I find it convenient to work with SHGetFolderPath(), which has the following C prototype:

HRESULT SHGetFolderPath(HWND hwndOwner,
                        int nFolder,
                        HANDLE hToken,
                        DWORD dwFlags,
                        LPTSTR pszPath);

To retrieve the staging area's location, pass the following arguments to this function: a language-dependent null value to hwndOwner and hToken, constant CSIDL_CDBURN_AREA to nFolder, constant SHGFP_TYPE_CURRENT to dwFlags, and a language-dependent TCHAR array of maximum path length characters to pszPath.

In addition to its three functions, ICDBurn inherits the QueryInterface(), AddRef(), and Release() functions from its IUnknown parent. C and C++ code can ignore the first two functions but must work with Release(), whereas C# code can ignore all three functions because the CLR's COM Interop (discussed later) automatically calls Release() for C# and other .NET languages.