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─────Run-Time Library───────────────────────────────────────────────────────
 
/* VLOCK.C: This program locks a block of virtual memory using _vlock,
 * writes to it, loads in a new block with _vload, and then verifies
 * that the contents of the locked block are still accessible. It then
 * unlocks the block with _vunlock.
 */
 
#include <stdio.h>
#include <stdlib.h>
#include <vmemory.h>
 
void main()
{
    int i, flag;
    _vmhnd_t handle1,
             handle2;
    int __far *buffer1;
    int __far *buffer2;
 
    if ( !_vheapinit( 0, _VM_ALLDOS, _VM_XMS | _VM_EMS ) )
    {
        printf( "Could not initialize virtual memory manager. \n" );
        exit( -1 );
    }
 
    if ( ( (handle1 = _vmalloc( 100 * sizeof(int) )) == _VM_NULL ) ||
         ( (handle2 = _vmalloc( 100 * sizeof(int) )) == _VM_NULL )   )
    {
        _vheapterm();
        exit( -1 );
    }
 
    printf( "Two blocks of virtual memory allocated.\n" );
 
    if ( (buffer1 = (int __far *)_vlock( handle1 )) == NULL )
    {
        _vheapterm();
        exit( -1 );
    }
 
    printf( "buffer1 locked: valid until unlocked.\n" );
    for ( i = 0; i < 100; i++ )      // write to buffer1
        buffer1[i] = i;
 
    if ( (buffer2 = (int __far *)_vload( handle2, _VM_DIRTY )) == NULL )
    {
        _vheapterm();
        exit( -1 );
    }
 
    printf( "buffer2 loaded. buffer 1 still valid.\n" );
 
    flag = 0;
    for ( i = 0; i < 100; i++ )
        if ( buffer1[i] != i )
            flag = 1;
 
    if ( !flag )
        printf( "contents of buffer1 verified.\n" );
 
    _vunlock( handle1, _VM_DIRTY );
    _vfree( handle1 );
    _vfree( handle2 );
    _vheapterm();
}
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