gd_tell—report the position of a Dirfile field I/O pointer
off_t gd_tell(DIRFILE *dirfile, const char *field_code);
The gd_tell() function reports the current position of the I/O pointer of the field field_code in the dirfile(5) database specified by dirfile.
Only RAW fields (and the implicit INDEX field) have field pointers associated with them. Calling gd_tell() on a derived field will report the position of the I/O pointer of the derived field only if all of it's inputs are positioned the same. Otherwise, an error results.
Upon successful completion, gd_tell() returns a non-negative integer indicating the I/O position of the specified field in samples. 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 for input, was not found in the database.
- The supplied dirfile was invalid.
- The specified field or one of its inputs wasn't of vector type.
- The I/O position of a derived field wasn't well defined because its input fields simultaneously read from different places in the same RAW 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 maintainer.
- An error occurred while trying to open or read from a file on disk containing a raw field.
- 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 encoding scheme of a RAW field could not be determined. This may also indicate that the binary file associated with the RAW field could not be found.
- Reading from dirfiles with the encoding scheme of the specified dirfile is not supported by the library. See dirfile-encoding(5) for details on dirfile encoding schemes.
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_tell() function appeared in GetData-0.8.0.
In GetData-0.10.0, the error return from this function changed from −1 to a negative-valued error code.
gd_getdata(3), gd_open(3), gd_putdata(3), gd_seek(3).