using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;

namespace POSV.Utils
{
    public class SharedLibrary
    {
        [System.Runtime.InteropServices.DllImport("kernel32" , SetLastError = true , CharSet = System.Runtime.InteropServices.CharSet.Unicode)]
        protected static extern IntPtr LoadLibrary(string lpFileName);

        [System.Runtime.InteropServices.DllImport("kernel32" , CharSet = System.Runtime.InteropServices.CharSet.Ansi , ExactSpelling = true , SetLastError = true)]
        protected static extern IntPtr GetProcAddress(IntPtr hModule , string procName);

        [System.Runtime.InteropServices.DllImport("kernel32" , SetLastError = true)]
        [return: System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.Bool)]
        protected static extern bool FreeLibrary(IntPtr hModule);


        private IntPtr _IntPtr;
        public SharedLibrary(String path)
        {
            _IntPtr = LoadLibrary(path);
        }

        ~SharedLibrary()
        {
            FreeLibrary(_IntPtr);
        }

        //将要执行的函数转换为委托
        public Delegate Invoke(string procName , Type t)
        {
            IntPtr ptr = GetProcAddress(_IntPtr , procName);
            return (Delegate)Marshal.GetDelegateForFunctionPointer(ptr , t);
        }
        
    }
}