Delphi2005学习笔记2——Using Platform Invoke with Delphi 2005[1]|中文方案文档站(提供各类方案下载,WORD文档下载,范文,案例等)

using platform invoke with delphi 2005 this topic describes the basic techniques of using unmanaged apis from delphi 2005. some of the common mistakes and pitfalls are pointed out, and a quick reference for translating delphi data types is provided. this topic does not attempt to explain the basics of platform invoke or marshaling data. please refer to the links at the end of this topic for more information on platform invoke and marshaling. understanding attributes and how they are used is also highly recommended before reading this document. the win32 api is used for several examples. for further details on the api functions mentioned, please see the windows platform sdk documentation. the following topics are discussed in this section:

calling unmanaged functions
structures
callback functions
passing object references
using com interfaces

calling unmanaged functions when calling unmanaged functions, a managed declaration of the function must be created that represents the unmanaged types. in many cases functions take pointers to data that can be of variable types. one example of such a function is the win32 api function systemparametersinfo that is declared as follows:

bool systemparametersinfo(
  uint uiaction,  // system parameter to retrieve or set
  uint uiparam,   // depends on action to be taken
  pvoid pvparam,  // depends on action to be taken
  uint fwinini    // user profile update option
);

depending on the value of uiaction, pvparam can be one of dozens of different structures or simple data types. since there is no way to represent this with one single managed declaration, multiple overloaded versions of the function must be declared (see borland.vcl.windows.pas), where each overload covers one specific case. the parameter pvparam can also be given the generic declaration intptr . this places the burden of marshaling on the caller, rather than the built in marshaler. note that the data types used in a managed declaration of an unmanaged function must be types that the default marshaler supports. otherwise, the caller must declare the parameter as intptr and be responsible for marshaling the data. data types most data types do not need to be changed, except for pointer and string types. the following table shows commonly used data types, and how to translate them for managed code:

unmanaged data type	managed data type
	input parameter	output parameter
pointer to string (pchar)	string	stringbuilder
untyped parameter/buffer	tbytes	tbytes
pointer to structure (prect)	const trect	var trect
pointer to simple type (pbyte)	const byte	var byte
pointer to array (pinteger)	array of integer	array of integer
pointer to pointer type (^pinteger)	intptr	intptr

Delphi2005学习笔记2——Using Platform Invoke with Delphi 2005[1]

[入库：2005年8月18日] [更新：2007年3月24日]