如何在内存映射文件中编写包含字符串值的结构? [英] How to write a structure that contains a string value in Memory Mapped File?

问题描述

亲爱的先生，

我创建了以下结构:-

 [StructLayout(LayoutKind.Explicit)]
        public struct Valuess  // as a Union
        {
            [FieldOffset(0)]
            public long lval;
            [FieldOffset(0)]
            public double rval;
            [FieldOffset(12)]
            [MarshalAs(UnmanagedType.AsAny)]
            public byte[] cval;
        };
        public struct SMDATA
        {
            public int type;
            public double AvgVal;
            public double MeanVal;
            public short projectLimoStatus;
            public short SystemLimoStatus;
            public short TestLimoStatus;
            public Valuess Val;  // object of above union
        }

推荐答案

你好Sandeep Tiwari，

Hello Sandeep Tiwari,

1.问题在于，如果"cval"不正确，则返回"0".如果是一个byte []，则必须在"Valuess"中指定其大小.结构，例如:

1. The problem is that if "cval" is a byte[], its size must be specified in the "Valuess" structure, e.g. :

[StructLayout(LayoutKind.Explicit)]
public struct Valuess  // as a Union
{
    [FieldOffset(0)]
    public long lval;
    [FieldOffset(0)]
    public double rval;
    [FieldOffset(12)]
    [MarshalAs(UnmanagedType.ByValArray, SizeConst = 11)]
    public byte[] cval;
};

1.1在以上对值"的定义中，"cval"是指是一个11字节的嵌入式数组.

1.1 In the above definition for "Valuess", "cval" is an embedded array of 11 bytes.

2.如您所愿，"cval"为了实际上包含一个字符串，您还可以指定"cval"作为值"内部的嵌入字符串结构，例如:

2. As you intend "cval" to actually contain a string, you may also specify "cval" as an embedded string inside the "Valuess" structure, e.g. :

[StructLayout(LayoutKind.Explicit)]
public struct Valuess  // as a Union
{
    [FieldOffset(0)]
    public long lval;
    [FieldOffset(0)]
    public double rval;
    [FieldOffset(12)]
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst=11)]
    public string cval;
};

2.1在上面的示例中，"cval"表示是"Valuess"内部的嵌入字符串.长度为11个字符(包括结尾的NULL字符)的结构.

2.1 In the above example, "cval" is an embedded string inside the "Valuess" structure of size 11 characters long (including the terminating NULL character).

3.您还可以指定"cval"是C风格字符串的指针，例如:

3. You may also specify that "cval" be a pointer to a C-style string, e.g. :

[StructLayout(LayoutKind.Explicit)]
public struct Valuess  // as a Union
{
    [FieldOffset(0)]
    public long lval;
    [FieldOffset(0)]
    public double rval;
    [FieldOffset(12)]
    [MarshalAs(UnmanagedType.LPStr)]
    public string cval;
};

-生物学.

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