[英]Convert a C++ struct to C#
我正在编写一个与旧C DLL通信的C#应用程序。 我查看了C DLL的标题,看到了我需要在C#中创建的2个结构:
typedef struct
{
char user_field_name[MAXLENGTH];
WORD user_field_length;
char user_field_contents[80];
char user_field_requested[1];
char user_field_clear[1];
char user_field_attribute[1];
} U_FIELD_STRUCT;
typedef U_FIELD_STRUCT FAR * P_U_FIELD_STRUCT;
typedef struct
{
char user_begin_literal[7];
char user_screen_name[MNFRMSCRNAMELENGTH];
char key_to_be_sent[256];
WORD num_of_user_fields;
U_FIELD_STRUCT user_field[MAXFIELDCOUNT];
char user_end_literal[7];
} USER_FIELD_STRUCT;
在我的C#类中,我写了如下:
public const Int32 MAXLENGTH = 51;
public const Int32 MAXTAGLENGTH = 80;
public const Int32 MNFRMSCRNAMELENGTH = 5;
public const Int32 MAXFIELDCOUNT = 100;
public const Int32 MAXTAGCOUNT = 40;
public const Int32 MAXSCREENCOUNT = 150;
public const Int32 NO_SCREEN_DATA = 99;
[StructLayout(LayoutKind.Sequential, Pack=4, CharSet=CharSet.Ansi)]
public struct U_FIELD_STRUCT
{
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=MAXLENGTH)]
public char [] user_field_name;
public short user_field_length;
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=80)]
public char [] user_field_contents;
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=1)]
public char [] user_field_requested;
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=1)]
public char [] user_field_clear;
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=1)]
public char [] user_field_attribute;
};
[StructLayout(LayoutKind.Sequential, Pack = 4, CharSet = CharSet.Ansi)]
public struct USER_FIELD_STRUCT
{
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=7)]
public char [] user_begin_literal;
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=MNFRMSCRNAMELENGTH)]
public char [] user_screen_name;
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=256)]
public char [] key_to_be_sent;
public short num_of_user_fields;
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=MAXFIELDCOUNT)]
public U_FIELD_STRUCT [] user_field;
[ MarshalAs( UnmanagedType.ByValArray, SizeConst=7)]
public char [] user_end_literal;
};
当我在C#中初始化结构时,我按如下方式执行:
USER_FIELD_STRUCT UserFieldsData = new USER_FIELD_STRUCT();
UserFieldsData.user_begin_literal = new char[7];
UserFieldsData.user_screen_name = new char[MNFRMSCRNAMELENGTH];
UserFieldsData.key_to_be_sent = new char[256];
UserFieldsData.user_field = new U_FIELD_STRUCT[MAXFIELDCOUNT];
UserFieldsData.user_end_literal = new char[7];
for (int i = 0; i < MAXFIELDCOUNT; i++)
{
UserFieldsData.user_field[i].user_field_name = new char[MAXLENGTH];
UserFieldsData.user_field[i].user_field_contents = new char[80];
UserFieldsData.user_field[i].user_field_requested = new char[1];
UserFieldsData.user_field[i].user_field_clear = new char[1];
UserFieldsData.user_field[i].user_field_attribute = new char[1];
}
问题是当我pinvoke我的方法时,我收到一条错误消息(基本上DLL必须验证字符串,并发送一条消息,表明字符串不是它们应该是的)。 所以我安装了VS6,我在调试模式下运行了DLL。 我看了一下我发送的结构,字符串确实有我放入的数据(有些char []没有数据,其他有2个字段的组合。)
例如,如果我设置如下字段的字段:
user_begin_literal=”T0k0a10”
user_end_literal=”T0k0b10”
user_screen_name=”SC00”
当我在VS6中查看对象时:
user_begin_literal=” T0k0a10”
user_end_literal=””
user_screen_name=”SC00”
我弄乱了我的结构设计吗?
在C中,char只有1个字节,但在C#中它是2个字节。
在C#中使用sbyte
映射到C char
(两者都是有符号的8位值),并且ushort
映射到C WORD
(两者都是无符号的16位值)。
如果要将字符串值分配给struct的某个缓冲区,则应将其转换为ASCII(如果本机代码可以处理它,则将其转换为UTF8),然后将字节复制到字段中:
void CopyStringToField(string value, sbyte[] field)
{
int maxLength = field.Length; // or field.Length - 1 if you need room for null terminator
byte[] fieldValue = Encoding.ASCII.GetBytes(value);
if (fieldValue.Length > maxLength)
throw new ArgumentException("string too long for field.");
int length = Math.Min(fieldValue.Length, maxLength);
Array.Copy(fieldValue, 0, field, 0, length);
// zero fill remaining bytes
for (int i = length; i < field.Length; i++)
{
field[i] = 0;
}
}
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