#include "dpssfs/dpssfs.h" 

int dpssOpen(char *filename, int flags, int modes )

Create a DPSS descriptor for DPSS read/write calls.

Documentation

This call sets up connections to the DPSS. Its interface is similar to the UNIX system call open(). At present, there are no valid "modes," so the third argument to this call should be 0.

dpssOpen() relies on the appropriate  DPSS and (if necessary) DPSS server hosts to have been set. This happens automatically but the defaults can be overridden by either environmental variables or dpssSetHosts().

dpssOpen() returns a DPSSFS descriptor (0-63) on success or -1 on error. If the call fails, an error message should be available via  dpssPerror().

Unlike the UNIX file system, it is an error to try to open a file for reading if the file does not already exist. 

The underlying DPSS communications library is still quite verbose when errors occur. It will be muted in a future release.

WARNING: if the filename already exists on the DPSS, and you open a new file with mode (O_WRONLY | O_CREAT) using the same name, the previous file will be overwritten. Since the DPSS currently has a flat name space, you must be careful not to overwrite existing data.

Examples:

	if (dpssInit() != DPSSFS_OK)
	{   
		dpssPerror("dpssInit()")
		exit(-1);
 	}
	if ((dpssfd = dpssOpen(dpss_url, O_RDONLY, 0)) < 0)
	{
		dpssPerror("dpssOpen()");
		exit(-1);
	}

OR:

	if ((dpssfd = dpssOpen(dpss_url, O_WRONLY, 0)) < 0)
	{ 
		dpssPerror("dpssOpen()");
		exit(-1);
	}

or, to overwrite existing files with the same name:

	if ((dpssfd = dpssOpen(dpss_url, O_WRONLY | O_CREAT, 0)) < 0)
	{ 
		dpssPerror("dpssOpen()");
		exit(-1);
	}

Valid filename formats:

 filename
/path/filename
x-dpss://masterhost/filename
x-dpss://masterhost/setid
 
To be added soon (if needed):
x-dpss://masterhost:port/filename
x-dpss://masterhost:port/setid

Returns:

a dpss descriptor if successful, -1 if error occurred.

Parameters:

filename -  name of the file to open on the DPSS. This can be just a simple name, or a URL.

flags -  currently supported flags are O_RDONLY, O_WRONLY, O_CREAT.

Our view of the other flags follows:

    O_RDWR         Coming soon.
    O_APPEND       To be implemented in future revs.
    O_TRUNC        To be implemented if demand warrants.
    O_NDELAY       Not applicable to DPSSFS lib.
    O_NONBLOCK     Not applicable to DPSSFS lib.
    O_SYNC         Not applicable to DPSSFS lib.
    O_NOCTTY       Not applicable to DPSSFS lib.

mode - this arguement is ignored. It is present so the the API matches the UNIX open call.
 
Author:
Gary Hoo

---

DPSS API Home Page