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.
Back to contents
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;
Back to contents
本文地址：http://com.8s8s.com/it/it6023.htm