gd_bof(3)							      GETDATA								 gd_bof(3)

NAME

       gd_bof -- report the start of data in a field

SYNOPSIS

       #include <getdata.h>

       off_t gd_bof(DIRFILE *dirfile, const char *field_code);

DESCRIPTION

       The gd_bof() function queries a dirfile(5) database specified by dirfile and returns the sample number of the beginning-of-field marker for
       the vector field given by field_code.

       The caller should not assume that the beginning-of-field marker falls on a frame boundary.  The beginning-of-field marker  is  never  nega-
       tive.

       For  a RAW field, the beginning-of-field corresponds to the frame offset of that field (see gd_frameoffset(3)).	The beginning-of-field for
       all other vector field type is the same as the beginning-of-field of whichever of its input fields that starts latest.	The  beginning-of-
       field marker for the special field INDEX is always zero.

       The beginning-of-field marker for a field containing no data is in the same location as, or after, its end-of-field marker (see gd_eof(3)).
       For a RAW field, the difference between the locations of the beginning- and end-of-field markers indicates the number of  samples  of  data
       actually stored on disk.

       The dirfile argument must point to a valid DIRFILE object previously created by a call to gd_open(3).

RETURN VALUE

       Upon successful completion, gd_bof() returns the sample number of the end-of-field marker for the indicated field.  On error, it returns -1
       and sets the dirfile error to a non-zero error value.  Possible error values are:

       GD_E_BAD_CODE
	       The field specified by field_code or one of the fields it uses as input was not found in the database.

       GD_E_BAD_DIRFILE
	       The supplied dirfile was invalid.

       GD_E_BAD_REPR
	       The representation suffix specified in field_code, or in one of its inputs was not recognised.

       GD_E_DIMENSION
	       A scalar field was found where a vector field was expected in the definition of field_code or one of its inputs, or else field_code
	       itself specified a scalar field.

       GD_E_RECURSE_LEVEL
	       Too  many levels of recursion were encountered while trying to resolve field_code.  This usually indicates a circular dependency in
	       field specification in the dirfile.

       The dirfile error may be retrieved by calling gd_error(3).  A descriptive error string for the last error encountered can be obtained  from
       a call to gd_error_string(3).

SEE ALSO

       dirfile(5), dirfile-encoding(5), gd_open(3), gd_eof(3), gd_error(3), gd_error_string(3), gd_nframes(3)

Version 0.7.0							  15 October 2010							 gd_bof(3)