如何将C/C++程序转译成Delphi(六)

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#delphi #string #translation #struct #methods #class

博客主要介绍了C语言到Delphi的代码转换，包括字符串和枚举类型。在字符串方面，说明了C语言中字符串是字符数组，以及Delphi中对应声明的差异；在枚举类型上，阐述了两种转换方法及遇到的问题和解决办法。

3.4. Strings

In C, as in Delphi, a string is an array of char types. Often, a string declaration is used in combination with a constant declaration specifying the maximum string length, as the following example shows:

#define RAS_MaxEntryName 256



#define RASENTRYNAMEA struct tagRASENTRYNAMEA



RASENTRYNAMEA



{



  DWORD dwSize;



  CHAR szEntryName[ RAS_MaxEntryName + 1 ];



};

The first line declares a constant RAS_MaxEntryName with the value 256 specifying the maximum length of the string. The lines after it declare a struct (record) which contains a null-terminated string:

CHAR szEntryName[ RAS_MaxEntryName + 1 ];

The Delphi translation:

szEntryName : Array [0..RAS_MaxEntryName] of Char;

Why not Array [0..RAS_MaxEntryName+1] of Char? Recall that a C array starts with 0 and the declaration specifies the number of elements. Thus, Array [0..RAS_MaxEntryName+1] in Delphi is equivalent to [RAS_MaxEntryName+2] in C.

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3.5. Enumerations - Two Methods

Enumerated types can be translated in two ways.

Method 1:

typedef enum _FINDEX_INFO_LEVELS {



FindExInfoStandard,



FindExInfoMaxInfoLevel



} FINDEX_INFO_LEVELS;

This part of a C-header file translates easily to Delphi:

Type



  TFindExInfoLevels = (FindExInfoStandard, 



                       FindExInfoMaxInfoLevel);

The ordinal Value of the item FindExInfoStandard is 0. In Delphi each enumeration starts with 0.

Method 2:

The following C-declaration is more problematic:

typedef enum _ACL_INFORMATION_CLASS {



AclRevisionInformation = 1,



AclSizeInformation



} ACL_INFORMATION_CLASS

The "= 1" in the declaration forces C to start with the ordinal value 1. This is not possible in Delphi.

There are two ways to solve the problem.

Solution a): Declare the enumeration as

TACLInformationClass = (_Fill0, 



                        AclRevisionInformation, 



                        AclSizeInformation);

Solution b): Translate the enumeration as

CONST



  AclRevisionInformation = 1;



  AclSizeInformation = 2;







TYPE



  TACLInformationClass = DWord;

That's no problem for this example. But in C it's possible to specify the ordinal value of each item of the enumeration, for example:

Typedef enum _ENUMEXAMPLE { 



  Item1 = 5,



  Item2 = 10,



} ENUMEXAMPLE;

Using enumeration in Delphi the declaration would have to be done like this:

TEnumExample = (_Fill0, 



                _Fill1, 



                _Fill2, 



                _Fill3, 



                _Fill4, 



                Item1, 



                _Fill6, 



                _Fill7, 



                _Fill8, 



                _Fill9, 



                Item2);

This is hard to read and clumsy to maintain.

This works better:


CONST



  Item1 = 5;



  Item2 = 10;







TYPE



  TEnumExample = DWord;

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