c# - C 无符号 `char ** out` 到 C# `byte[]`

Question

这是 libeay32.dll ( openssl project ) 中的函数:

int i2o_ECPublicKey (EC_KEY * key, unsigned char ** out)

如何用C#描述(如果我想获取一个字节[])？

代码:

[DllImport(DLLNAME, CallingConvention = CallingConvention.Cdecl)]
public extern static int i2o_ECPublicKey (IntPtr encKey, StringBuilder outPar);

我不喜欢这个，因为我认为结果是unicode。

回答

        [DllImport(DLLNAME, CallingConvention = CallingConvention.Cdecl)]
        public extern static int i2o_ECPublicKey(IntPtr encKey, ref IntPtr outPar);

        [DllImport(DLLNAME, CallingConvention = CallingConvention.Cdecl)]
        public static extern int i2o_ECPublicKey(IntPtr encKey, int outPar);


        //Pass *out as null for required buffer length.
        int reqLen = i2o_ECPublicKey(k, 0);

        Byte[] outBuf = new Byte[reqLen];
        IntPtr unmanagedOut = Marshal.AllocCoTaskMem(outBuf.Length);
        int res = i2o_ECPublicKey(k, ref unmanagedOut);
        if (res == reqLen)
        {
            unmanagedOut -= reqLen; // because i2o_ECPublicKey add size to unmanagedOut
            Marshal.Copy(unmanagedOut, outBuf, 0, outBuf.Length);
        }
        Marshal.FreeCoTaskMem(unmanagedOut);

Answer 1

我相信手动执行此操作，您需要使用 Marshal.Copy 将数组从非托管内存复制到托管 byte[] 中。 (注意，代码未经测试)。

public extern static int i2o_ECPublicKey (IntPtr encKey, ref IntPtr outPar);

...
//Pass *out as null for required buffer length.
int reqLen = i2o_ECPublicKey(key, null);

Byte[] outBuf = new Byte[reqLen];
IntPtr unmanagedOut = Marshal.AllocCoTaskMem(outBuf.Length);
int res = i2o_ECPublicKey(key, ref unmanagedOut);
if (res == 1) {
    Marshal.Copy(unmanaged, outBuf, 0, outBuf.Length);
}
Marshal.FeeCoTaskMem(unmanagedOut);