[英]array as function parameter c to c# confusion
我试图用C#编写一个类,以使用dll的导出功能,但是我遇到了很多函数,这些函数具有数组作为函数参数,我不确定该如何处理。 下面是一个例子。
我将如何在C#函数中使用它? 具体如何处理iymdf []?
调用函数时会发生什么?
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]);
例:
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;
}
功能文档:
/*
** - - - - - - - - - -
** 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.
*/
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。 在进行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);
您将要进行标准的函数调用,具体取决于您在做什么。 函数定义仅声明“这些是我的输入”,然后在调用它时,必须提供实际值。 您无需重新创建函数def。
[DllImport("libsofa.dll")]
myReturn = iauJdcalf(1, 2.0, 2.0, [1,2,3,4]);
您的函数定义为返回一个int,因此我们使用myReturn变量捕获它,您当然需要首先对其进行声明。 然后,我们提供一个int,两个double和一个数组。 您还可以传递这些类型的变量,请注意确保数组的大小与所需大小相同。
另外,注意指针! 如果将变量传递给c,它将复制到函数中定义的局部变量。 如果给它一个指针,则需要在函数定义中声明它,并意识到我们正在玩指针游戏。
太回答我自己的问题了,我认为会涉及到更多的Marshaling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);
以及这个:
[DllImport("libsofa.dll")]
public static extern int iauJdcalf(int ndp, double dj1, double dj2, int[] iymdf);
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