Pointers and Declarative Pinning : Pointer Unsafe « Language Basics « C# / C Sharp

Pointers and Declarative Pinning

A Programmer's Introduction to C# (Second Edition)
by Eric Gunnerson

Publisher: Apress  L.P.
ISBN: 1-893115-62-3
// 31 - Interop\Calling Native DLL Functions\Pointers and Declarative Pinning
// copyright 2000 Eric Gunnerson
// file=ReadFileUnsafe.cs
// compile with: csc /unsafe ReadFileUnsafe.cs
using System;
using System.Runtime.InteropServices;
using System.Text;

class FileRead
    const uint GENERIC_READ = 0x80000000;
    const uint OPEN_EXISTING = 3;
    int handle;
    public FileRead(string filename)
        // opens the existing file
        handle = CreateFile(    filename,
    [DllImport("kernel32", SetLastError=true)]
    static extern int CreateFile(
    string filename,
    uint desiredAccess,
    uint shareMode,
    uint attributes,        // really SecurityAttributes pointer
    uint creationDisposition,
    uint flagsAndAttributes,
    uint templateFile);
    [DllImport("kernel32", SetLastError=true)]
    static extern unsafe bool ReadFile(
    int hFile,
    void* lpBuffer, 
    int nBytesToRead,
    int* nBytesRead,
    int overlapped);
    public unsafe int Read(byte[] buffer, int count)
        int n = 0;
        fixed (byte* p = buffer) 
            ReadFile(handle, p, count, &n, 0);
        return n;
public class PointersandDeclarativePinning
    public static void Main(string[] args)
        FileRead fr = new FileRead(args[0]);
        byte[] buffer = new byte[128];
        ASCIIEncoding e = new ASCIIEncoding();
        // loop through, read until done
        while (fr.Read(buffer, 128) != 0)
            Console.Write("{0}", e.GetString(buffer));


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