数组作为c函数参数对c#的混淆

本文关键字：参数 函数 数组 | 更新日期: 2023-09-27 17:52:59

我试图在c#中编写一个类，使用从dll导出，但我遇到了一堆函数有一个数组作为函数参数，我不确定如何处理。下面是一个例子。

如何在c#中使用这个函数?具体如何处理iymdf[]?

函数被调用时发生了什么?

这看起来正确吗?

[DllImport("libsofa.dll")]
public static extern int iauJdcalf(int ndp, double dj1, double dj2, ref int[] iymdf =       new int[4]);

的例子:

int __stdcall iauJdcalf(int ndp, double dj1, double dj2, int iymdf[4])
{
    int j, js;
    double denom, d1, d2, f1, f2, f;
    /* Denominator of fraction (e.g. 100 for 2 decimal places). */
    if ((ndp >= 0) && (ndp <= 9)) {
        j = 0;
        denom = pow(10.0, ndp);
    } else {
        j = 1;
        denom = 1.0;
    }
    /* Copy the date, big then small, and realign to midnight. */
    if (dj1 >= dj2) {
        d1 = dj1;
        d2 = dj2;
    } else {
        d1 = dj2;
        d2 = dj1;
    }
    d2 -= 0.5;
    /* Separate days and fractions. */
    f1 = fmod(d1, 1.0);
    f2 = fmod(d2, 1.0);
    d1 = floor(d1 - f1);
    d2 = floor(d2 - f2);
    /* Round the total fraction to the specified number of places. */
    f = floor((f1+f2)*denom + 0.5) / denom;
    /* Re-assemble the rounded date and re-align to noon. */
    d2 += f + 0.5;
    /* Convert to Gregorian calendar. */
    js = iauJd2cal(d1, d2, &iymdf[0], &iymdf[1], &iymdf[2], &f);
    if (js == 0) {
        iymdf[3] = (int) (f * denom);
    } else {
        j = js;
    }
    /* Return the status. */
    return j;
}

函数文档:

/*
**  - - - - - - - - - -
**   i a u J d c a l f
**  - - - - - - - - - -
**
**  Julian Date to Gregorian Calendar, expressed in a form convenient
**  for formatting messages:  rounded to a specified precision.
**
**  This function is part of the International Astronomical Union's
**  SOFA (Standards Of Fundamental Astronomy) software collection.
**
**  Status:  support function.
**
**  Given:
**     ndp       int      number of decimal places of days in fraction 
**     dj1,dj2   double   dj1+dj2 = Julian Date (Note 1)
**
**  Returned:
**     iymdf     int[4]   year, month, day, fraction in Gregorian
**                        calendar
**
**  Returned (function value):
**               int      status:
**                          -1 = date out of range
**                           0 = OK
**                          +1 = NDP not 0-9 (interpreted as 0)
**
**  Notes:
**
**  1) The Julian Date is apportioned in any convenient way between
**     the arguments dj1 and dj2.  For example, JD=2450123.7 could
**     be expressed in any of these ways, among others:
**
**             dj1            dj2
**
**         2450123.7           0.0       (JD method)
**         2451545.0       -1421.3       (J2000 method)
**         2400000.5       50123.2       (MJD method)
**         2450123.5           0.2       (date & time method)
**
**  2) In early eras the conversion is from the "Proleptic Gregorian
**     Calendar";  no account is taken of the date(s) of adoption of
**     the Gregorian Calendar, nor is the AD/BC numbering convention
**     observed.
**
**  3) Refer to the function iauJd2cal.
**
**  4) NDP should be 4 or less if internal overflows are to be
**     avoided on machines which use 16-bit integers.
**
**  Called:
**     iauJd2cal    JD to Gregorian calendar
**
**  Reference:
** 
**     Explanatory Supplement to the Astronomical Almanac,
**     P. Kenneth Seidelmann (ed), University Science Books (1992),
**     Section 12.92 (p604).
**
**  This revision:  2010 July 27
**
**  SOFA release 2010-12-01
**
**  Copyright (C) 2010 IAU SOFA Board.  See notes at end.
*/

数组作为c函数参数对c#的混淆

从c#声明中删除ref关键字，这是不正确的。您还需要丢失声明中的初始化，这是不支持的语法。在调用之前初始化数组

[DllImport("libsofa.dll")]
public static extern int iauJdcalf(int ndp, double dj1, double dj2, int[] iymdf);
...
    int[] arr = new int[] { 1, 2, 3, 4 };
    int retval = iauJdcalf(1, 2, 3, arr);

您将需要一个标准的函数调用，这取决于您正在做什么。函数定义简单地声明"这些是我的输入"，然后当你调用它时，你必须提供实际的值。不需要重新创建函数def。

[DllImport("libsofa.dll")]
myReturn = iauJdcalf(1, 2.0, 2.0, [1,2,3,4]);

你的函数定义为返回一个int，所以我们用myReturn变量捕获它，当然你需要首先声明它。然后提供一个int型、两个double型和一个数组。您也可以传递这些类型的变量，小心确保您的数组与所需的大小相同。

还有，注意你的指针!如果将一个变量传递给c，它会对函数中定义的局部变量进行复制。如果你给它一个指针，你需要在函数定义中声明它，并且意识到我们现在正在玩指针游戏。

也回答了我自己的问题，我认为会有更多的编组的东西，但是下面的代码给出了一个合理的输出:

    [DllImport("libsofa.dll")]
    public static extern int iauJdcalf(int ndp, double dj1, double dj2,    [MarshalAs(UnmanagedType.LPArray, SizeConst = 4)] int[] iymdf);

以及this:

    [DllImport("libsofa.dll")]
    public static extern int iauJdcalf(int ndp, double dj1, double dj2, int[] iymdf);
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