gd_bof(3)

NAME
gd_bof — find the start of data in a Dirfile field

SYNOPSIS
#include <getdata.h>

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

DESCRIPTION
The function queries a dirfile(5) database specified by and finds the beginning-of-field marker for the vector field given by

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

For a RAW field, the beginning-of-field corresponds to the frame offset of that field (see The beginning-of-field marker of the special field INDEX is zero.

The beginning-of-field of a PHASE field is the beginning-of-field of its input adjusted by the PHASE field's shift (or zero, if the shift would make it negative). The beginning-of-field for all other vector fields is the the latest beginning-of-field of any of its input fields.

If the beginning-of-field marker of a field is greather than or equal to its end-of-field marker (see then that field contains no data. 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 argument must point to a valid DIRFILE object previously created by a call to

RETURN VALUE
Upon successful completion, returns a non-negative integer which is the sample number of the beginning-of-field marker for the specified field. On error, it returns a negative-valued error code. Possible error codes are: The field specified by or one of the fields it uses as input was not found in the database. The supplied dirfile was invalid. A scalar field was found where a vector field was expected in the definition of or one of its inputs, or else itself specified a scalar field. An internal error occurred in the library while trying to perform the task. This indicates a bug in the library. Please report the incident to the GetData developers. Too many levels of recursion were encountered while trying to resolve This usually indicates a circular dependency in field specification in the dirfile.

The error code is also stored in the DIRFILE object and may be retrieved after this function returns by calling A descriptive error string for the error may be obtained by calling

HISTORY
The function appeared in GetData-0.7.0.

Before GetData-0.10.0, this function could also fail with the error code GD_E_ALLOC.

In GetData-0.10.0, the error return from this function changed from -1 to a negative-valued error code.

SEE ALSO
dirfile(5), dirfile-encoding(5)