2/23/2023 0 Comments Vb net getwindowtext stringbuilder![]() ![]() Private static extern UInt32 TestAPIAnsiUsingIntPtr(IntPtr lpBuffer, UInt32 uiSize) The following C# code demonstrates how to use the IntPtr for calling TestAPIAnsi() : I shall demonstrate below both techniques and show how the StringBuilder can make programming life simpler. (including the terminating NULL character). ![]() ![]() Return the number of characters copied. The following is the code listing : UINT _stdcall TestAPIAnsi(/**/ char* lpBuffer, /**/ UINT uSize)Ĭonst char szReturnString = "Hello World" Ĭonst UINT uiStringLength = strlen(szReturnString) The StringBuilder and an Example Usage.Ģ.1 In this section, I will build a test C++ API that takes a string buffer as input, fills it with ANSI character values and then return it to the caller. A typical API like that usually returns an integer value which will indicate the required size of the buffer should it be too small. Throughout this article, I shall call such APIs “buffer-reference APIs”.ġ.6 In such cases, the managed string type is not usable. A managed string cannot have its internal buffer pre-allocated and then passed to unmanaged code to be filled.ġ.7 This is where the StringBuilder comes to the rescue. A StringBuilder behaves very much like a typical C-style character buffer and is particularly useful when used with buffer-reference APIs mentioned in point 1.5.ġ.8 This article aims to demonstrate proper use of the StringBuilder with buffer-reference APIs, including how to use it to receive ANSI and Unicode character strings.Ģ. These APIs each require the calling code to first prepare a buffer large enough to hold the string to be returned. : GetWindowsDirectory(), GetPrivateProfileString(), etc. In essence, these APIs require the buffer to be passed by reference, somewhat like the two scenarios described in the previous point holding true at the same time.ġ.5 Such APIs are plenty to be found. ![]() These buffers are then filled by the APIs and returned to the client. The string parameter is typically declared to be passed to the unmanaged API as an “out” (return) parameter.ġ.4 However, there are APIs which require pre-prepared character buffers to be passed. This buffer is then freed on the managed side after it has been used to create a managed string. A buffer to a C-style string is allocated on the unmanaged API side, filled with character values and then returned to the managed side. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |