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,
GENERIC_READ,
0,
0,
OPEN_EXISTING,
0,
0);
}
[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
Console.WriteLine("Contents");
while (fr.Read(buffer, 128) != 0)
{
Console.Write("{0}", e.GetString(buffer));
}
}
}
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