Shared memory

Hello all,

If you're not on the beach maybe you can give me a little help.
I need to implement shared memory between my application and a helper
tool.
At first I tried CFMessageProts. This works, but if you transport huge
amounts of data the data get all paged out and after a few GB I crash.
Then I tred shmget and friends. This works, but I can get only 1-2 MB of
memory this way. I need at least 8MB and I would prefer no limit atall.
So now I am trying mapping a file but I can't get this to work.
The following bare-bones XCode Carbon application crashes. Please tell
me what is wrong.

Jan.


#include <sys/types.h>
#include <sys/uio.h>
#include <sys/fcntl.h>
#include <sys/mman.h>
#include <unistd.h>

#define kBufferSize 960000

int main( void )
{
char sharedMemPath[] = "/Users/jeschot/Documents/Shared_memory_file_1";

int fd = open( sharedMemPath, O_CREAT+O_WRONLY, 0666 );
Ptr videoBuffer, buffer;
int size;
long x = 10;


printf( "\nfd = %d\n", fd );
if ( fd != -1 )
{ // Set size of shared file by writing to it and closing it
buffer = malloc( kBufferSize );

size = write( fd, buffer, kBufferSize );

close( fd );
free( buffer );
}

fd = open( sharedMemPath, O_WRONLY, 0666 ); // Reopen

printf( "fd = %d\n", fd );

if ( fd != -1 )
{ // Map entire file to memory
videoBuffer = mmap( 0, kBufferSize, PROT_WRITE, MAP_FILE, fd, 0 );
printf( "videoBuffer = 0x%lx", (long)videoBuffer );

if ( -1 == (int)videoBuffer )
{
int error = errno;
fprintf( stderr, "mmap error: %d (0x%08x)\n", error, error );
}
else videoBuffer[0] = x; // Crash
}
printf( "finished" );


return 0;
}