/////////////////////////////////////////////////////////////////////////////
// Creation 11/12/2003                                               
// 
// 
//                          LOCKAPIWIN32.C
//                          --------------
// 
// 
// Sylvain MARECHAL - sylvain.marechal1@libertysurf.fr
/////////////////////////////////////////////////////////////////////////////
// 
//	Locks with Win32 API (LockFile())
//	Show that locks doesn't work in the same process
// 
/////////////////////////////////////////////////////////////////////////////
#include <windows.h>
#include <stdio.h>
#include <conio.h>

void main()
{
    HANDLE h1, h2;
    DWORD  dwAccess = GENERIC_READ | GENERIC_WRITE;
    DWORD  dwShare  = FILE_SHARE_READ | FILE_SHARE_WRITE;
    DWORD  dwCreate = OPEN_EXISTING;
    DWORD  dwAtts = FILE_ATTRIBUTE_NORMAL;
    DWORD dwPos, dwPos2, dwPos3, dwLock;
    const char szFile[] = "testlock.txt";

    // Open/create a file
    h1 = CreateFile( szFile, 
	dwAccess, 
	dwShare,
	NULL, 
	CREATE_ALWAYS,//dwCreate, 
	dwAtts, 
	NULL); 
    if( h1 == INVALID_HANDLE_VALUE )
    {
	printf( "Can't open file (%d)\n", GetLastError() );
	exit(1);
    }

    // lock 10 bytes at the end
    dwLock = 10;
    dwPos = SetFilePointer( h1, 0, NULL, FILE_END );
    dwPos2 = SetFilePointer( h1, dwPos + dwLock, NULL, FILE_BEGIN );
    SetEndOfFile( h1 );
    dwPos3 = SetFilePointer( h1, 0, NULL, FILE_END );
    printf( "dwPos=%d, dwPos2=%d, dwPos3=%d\n", dwPos, dwPos2, dwPos3 );
    if( ! LockFile( h1, dwPos, 0, dwPos+dwLock, 0) )
    {
	printf( "First call - Unable to lock the %d octets (Error=%d)\n", dwLock, GetLastError() );
	printf( "Press a key to exit...\n" );
	getch();
	return;
    }

    // Message
    printf( "Press a key to continue ...\n" );
    getch();


    // open the same file for 2° time
    h2 = CreateFile( szFile, 
	dwAccess, 
	dwShare,
	NULL, 
	dwCreate, 
	dwAtts, 
	NULL); 
    if( h2 == INVALID_HANDLE_VALUE)
    {
	printf( "Unable to open '%s' (Error=%d)\n", szFile, GetLastError() );
	return;
    }
    
    // Look if lock is possible
    dwPos = SetFilePointer( h2, 0, NULL, FILE_END );
    if( ! LockFile( h2, 11, 0, 10, 0) )
    {
	printf( "Secon call -Unable to lock the first 10 octets (Error=%d)\n", GetLastError() );
	printf( "Press a key to exit...\n" );
	getch();
	return;
    }
    
    // Message
    printf( "Press a key to continue ...\n" );
    getch();
}