xenial (3) gd_bof.3.gz

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 negative.

       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_ALLOC
               The library was unable to allocate memory.

       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_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_INTERNAL_ERROR
               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.

       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)