njb_get_file(3)

NAME

NJB_Get_File - upload a copy of a file from the NJB to the

host

LIBRARY

libnjb

SYNOPSIS

#include <sys/types.h> #include <libnjb.h>
extern int njb_error
int  NJB_Get_File (njb_t *njb, u_int32_t fileid, u_int32_t
size, const char *path, XferCallback *callback, void *data)

DESCRIPTION

This function uploads a datafile from the NJB (without

deleting it from the NJB) and saves it to the filename specified

by *path. Data files are not music tracks, but general data

storage containers on the jukebox.

The desired datafile's file ID is stored in fileid. Note

that the calling program must also know the size of the file to

be transferred, and sent in the size parameter. Both the

datafile ID and the file size can be found in the datafile tag

for the desired datafile, as returned by NJB_Get_Datafile_Tag

(3). Generally, the calling program should fetch (and cache) the

complete datafile list from the NJB, so that all of this informa

tion is readily available.

For reliability, the datafile is first downloaded to a

temporary directory (see NJB_Get_TmpDir(3)) before being copied

into place. By default, the temporary directory is /tmp, but it

can be changed by the NJB_Set_TmpDir(3) function.

The callback parameter is a pointed to a callback func

tion, as described in NJB_Get_File(3).

The data parameter is a pointer to user data of any kind

that the user of the library wants to associate with this trans

fer. This pointer is used for example when accessing several dif

ferent jukeboxes from withing one program. The XferCallback will

also be delivering this pointer to the target routine for deref

erencing. If this parameter is not used (in for example single

device, single-threaded programs) it may be set to NULL.

RETURN VALUES

If the transfer is successful, 0 is returned. Otherwise,

-1 is returned and njb_error is set as follows:

EO_ABORTED

The transfer was aborted by the user (the call

back function returned -1).

EO_BADSTATUS

A non-zero status was returned by the NJB during

the file transfer.

EO_CANTMOVE

The transferred datafile could not be moved from

the temporary directory to the specified location (see the *path

parameter).

EO_NOMEM There was not enough memory to allocate the file

transfer buffer.

EO_NULLTMP

The temporary directory is undefined (a NULL

pointer).

EO_RDSHORT

The NJB sent fewer bytes than expected on the

bulk data pipe.

EO_TMPFILE

The temporary transfer file could not be created

in the temporary directory.

EO_USBBLK An I/O error occurred on the bulk data pipe.

EO_USBCTL An I/O error occurred on the control pipe.

EO_WRFILE An error occurred while writing to the temporary

transfer file.

EO_XFERDENIED

The NJB returned a non-zero status when the file

transfer was requested. The datafile may be write protected, or

the given track ID may not exist.

EO_XFERERROR

The NJB returned a non-zero status when the host

requested verification of the file transfer.

SEE ALSO

NJB_Get_TmpDir(3), NJB_Get_Datafile_Tag(3), NJB_Set_Tm

pDir(3), XferCallback(3)

January 2003

NJB_GET_FILE(3)