从C#到F#:从F#调用的外部函数中的固定数组和Stringbuilder

Question

我正在尝试从F#访问外部DLL函数.这个让我真的很汗.

C头是:

ext_def(int32) swe_calc_ut(double tjd_ut, int32 ipl, int32 iflag, 
double *xx, char *serr);

我相应地在F#中导入了它:

extern int32 ext_swe_calc_ut(double tjd_ut, int32 ipl, int32 iflag, double *xx, StringBuilder serr);

问题是阵列部分.我尝试了来自F#Powerpack的PinnedArray,但是呼叫仍然失败.char数组可能没问题,即使我无法检查,因为调用失败了.

到目前为止它是:

open System
open System.Runtime.InteropServices
open System.Text
open Microsoft.FSharp.NativeInterop

#r "FSharp.PowerPack.dll" 
#nowarn "51"

module Sweph =

    [<DllImport(@"swedll32.dll", CharSet = CharSet.Ansi, EntryPoint = "swe_calc_ut")>]
    extern int32 ext_swe_calc_ut(double tjd_ut, int32 ipl, int32 iflag, double *xx, StringBuilder serr);
    /// <param name="jdnr">Julian day</param>
    /// <returns>Array with 6 doubles: 0:longitude, 1:latitude, 2:distance,3:speel in longitude, 
    ///          4: speed in latitude, 5: speed in distance </returns>


let ar: double array = Array.zeroCreate 6
let argx = PinnedArray.of_array ar

printfn "  ar: %A" ar

// This fails with a "FileLoadException"
printfn "ar: %A" argx

// Details of FileLoadException:
(*

"FSharp.Core,Version = 2.0.0.0,Culture = neutral,PublicKeyToken = b03f5f7f11d50a3a"不匹配程序集(Ausnahme von HRESULT:0x80131040)*)

// However, if I leave the printfn for argx out, code continues and does not display this error again.

let sb = new StringBuilder(50)          // Vgl. Expert F#, S. 515

Console.ReadKey(true)


// Application crashes here:
let ret_calc = Sweph.ext_swe_calc_ut(4700.0,1,1,argx.Ptr,sb)

程序在此时崩溃(控制台窗口消失,在调试中,它只是跳回到第一行.

我知道我可以使用"use"代替"let"和"let argx = PinnedArray.of_array ar",但编译器不会因为顶部的模块声明而让我拥有它.

C#中有一个实现,如下所示:

    public static double[] getPlanet(int ipl, double jdnr) {
        //   String ephePath = "Q:\\sweph\\";
        //   Sweph.setEphePath(ephePath);
        double[] xx2 = new double[8];
        double[] xx = new double[6];
        String serr = "";
        int iflag = Constants.SEFLG_SPEED;
        long iflgret = ext_swe_calc_ut(jdnr, ipl, iflag, xx, serr);
        for (int i = 0; i < 6; i++) { 
            xx2[i] = xx[i]; 
        }
        iflag = Constants.SEFLG_SWIEPH | Constants.SEFLG_SPEED | Constants.SEFLG_EQUATORIAL;
        iflgret = ext_swe_calc_ut(jdnr, ipl, iflag, xx, serr);
        xx2[6] = xx[0];
        xx2[7] = xx[1];

        return xx2;
    }

也许整个问题都会回到FileLoad异常(即使它没有在dll调用中显示) - 可能是因为FSharp Powerpack？

非常感谢你的帮助.

Answer 1

这是我的猜测，基于 C 类型签名和我找到的函数文档。它可以编译，但你必须告诉我它是否真的有效，因为我没有swedll32.dll程序集。另外，我的代码不需要 F# Powerpack 程序集。

编辑：只需阅读 @kvb 的答案下的评论 - 他建议我在代码中包含相同的内容，即[<MarshalAs(...)>]具有SizeConst属性集的属性。我还加上了[<Out>]，因为最后两个参数是作为返回值的；IIRC，它也会影响编组行为。

编辑 2：根据 @wolfgang 的报告，ExactSpelling = true从属性中删除了。MarshalAs

[<DllImport(@"swedll32.dll",
    CharSet = CharSet.Ansi,
    EntryPoint = "swe_calc_ut")>]
extern int32 swe_calc_ut (
    float tjd_ut,
    int32 ipl,
    int32 flag,
    [<Out; MarshalAs(UnmanagedType.LPArray, SizeConst = 6)>]
    float[] xx,
    [<Out; MarshalAs(UnmanagedType.LPStr, SizeConst = 256)>]
    System.Text.StringBuilder serr)

// Wrapper function for swe_calc_ut
let swe_calc_ut_wrapper (tjd_ut, ipl, flag) =
    let positions = Array.zeroCreate 6
    let errorSB = System.Text.StringBuilder (256)
    let result = swe_calc_ut (tjd_ut, ipl, flag, positions, errorSB)
    if result < 0 then
        // Error
        Choice2Of2 (result, errorSB.ToString ())
    else
        Choice1Of2 positions