gspool_jobpbrk(3) retrieve the page offsets and delimiter string


#include <gspool.h>
#include <stdio.h>

FILE *gspool_jobpbrk(const int fd, const unsigned flags, const slotno_t slotno)

int gspool_jobpbrk(const int fd, const int outfile, int (*func)(int,void*,unsigned), const unsigned flags, const slotno_t slotno)


Unix and GNU/Linux

The function gspool_jobpbrk() is used to retrieve the page break offset file of a job.

fd is a file descriptor previously returned by gspool_open. flags is zero, or "GSPOOL_FLAG_IGNORESEQ" to changes since the job list was last read.

slotno is the slot number corresponding to the job previously returned by functions such as gspool_joblist or gspool_jobfindslot.

The result is a "FILE" pointer which can be used with all standard I/O input functions such as fread(3), fgets(3), getc(3) etc. At the end of the data fclose(3) must be called. For reasons of sychronisation the file should be read to the end before other operations are attempted.

If an error is detected, gspool_jobpbrk returns "NULL" and an error code is placed in the external variable "gspool_dataerror".

If there is no page offset file, probably because the delimiter is set to formfeed, then this isn't really an error, but an error report of "GSPOOL_BAD_PF" will be returned. You can tell whether there is a page file from the "struct apispq" job structure returned by xb_jobread or xb_jobfind. The field "apispq_dflags" has the bit designated by "APISPQ_PAGEFILE" set if there is a page file.

The data is returned in three parts.

struct apipages
This is an instance of the following structure, defined in gspool.h, and described below.
delimiter string
This is the delimiter string itself.
vector of longs
This is a vector of "long"s giving the offsets of the start of each page, including the first page, which is always zero, within the job data (as read by gspool_jobdata).


The second format of the gspool_jobpbrk function is for use by Windows programs, as there is no acceptable equivalent of the pipe(2) construct.

The second argument outfile is (possibly) a file handle to the file from to which the job data is passed as the first argument to func.

The third argument func is a function with the same specifications as "write", indeed it may very well be "write". The main reason for doing it this way is that some versions of Windows do strange things if "write" is invoked from within a DLL.

Other aspects of the interface are similar to the Unix routine, apart from the routine returning zero for success and an error code for failure rather than a "FILE*" or "NULL". For consistency with the Unix version, the external variable "gspool_dataerror" is also assigned any error code returned.

The "struct apipages" structure is as follows:

 struct apipages {
   long delimnum;  /* Number of delimiters */
   long deliml;    /* Length of delimiter string */
   long lastpage;  /* Number of delimiters remaining on last page */


In the event of an error, the external variable "gspool_dataerror" is set to the error code. The Unix version of gspool_jobpbrk returns "NULL". The Windows version returns the error code. Error codes which might be returned are:
Invalid file descriptor
failure writing to network
failure reading from network
job not found
job does not belong to user
sequence error, job may be out of data
Invalid slot number
The job had no page file
There is no memory for the page file


Copyright (c) 2009 Free Software Foundation, Inc. This is free software. You may redistribute copies of it under the terms of the GNU General Public License <>. There is NO WARRANTY, to the extent permitted by law.


John M Collins, Xi Software Ltd.