table of contents
gd_eof — find the end of a Dirfile field
off_t gd_eof(DIRFILE *dirfile, const char *field_code);
The gd_eof() function queries a dirfile(5) database specified by dirfile and determines the sample number of the end-of-field marker for the vector field given by field_code. This is effectively the total number of samples available for the field, including any frame offset.
The caller should not assume that this is equivalent (when accounting for the samples-per-frame of the indicated field) to the number of frames in the database returned by gd_nframes(3), nor even that the end-of-field marker falls on a frame boundary.
For a RAW field, the end-of-field marker occurs immediately after the last datum in the data file associated with the field. The special field INDEX has no end-of-field marker.
The end-of-field of a PHASE field is the end-of-field of its input adjusted by the PHASE field's shift. For other vector field types, the end-of-field marker is the smallest end-of-field marker of any of its inputs.
If the end-of-field marker for a field is less than or equal to its beginning-of-field marker (see gd_bof(3)), then that field has no data. For a RAW field, the difference between 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).
Upon successful completion, gd_eof() returns the sample number of the end-of-field marker for the indicated field, which is never negative. On error, it returns a negative-valued error code. Possible error codes are:
- The library was unable to allocate memory.
- The field specified by field_code or one of the fields it uses as input was not found in the database.
- The supplied dirfile was invalid.
- The location of the non-existent end-of-field marker for the special field INDEX was requested, possibly as a result of the field specified by field_code using INDEX as one of its inputs.
- 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.
- 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.
- An I/O error occurred while deterimining the size of the raw data file associated with the field, or one of its input fields.
- 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 size of the decoded data file associated with the specified field or one of its inputs could not be determined, because its encoding scheme was not understood.
- The size of the decoded data file associated with the specified field or one of its inputs could not be determined, because its encoding scheme was not supported.
The error code is also stored in the DIRFILE object and may be retrieved after this function returns by calling gd_error(3). A descriptive error string for the error may be obtained by calling gd_error_string(3).
The gd_eof() function appeared in GetData-0.7.0.
In GetData-0.10.0, the error return from this function changed from -1 to a negative-valued error code.
gd_bof(3), gd_error(3), gd_error_string(3), gd_nframes(3), gd_open(3), dirfile(5), dirfile-encoding(5)
|25 December 2016||Version 0.10.0|