put_constant (3) - Linux Man Pages
put_constant: retrieve a scalar constant from a dirfile database
NAMEput_constant --- retrieve a scalar constant from a dirfile database
- int put_constant(DIRFILE *dirfile, const char *field_code, gd_type_t data_type, const void *data_in);
The dirfile argument must point to a valid DIRFILE object previously created by a call to dirfile_open(3).
The data_type argument should be one of the following symbols, which indicates the desired return type of the data:
- unsigned 8-bit integer
- signed (two's complement) 8-bit integer
- unsigned 16-bit integer
- signed (two's complement) 16-bit integer
- unsigned 32-bit integer
- signed (two's complement) 32-bit integer
- unsigned 64-bit integer
- signed (two's complement) 64-bit integer
- IEEE-754 standard 32-bit single precision floating point number
- IEEE-754 standard 64-bit double precision floating point number
The data type of the supplied value need not be the same as the type of the storage type of the constant in the database. Type conversion will be performed as necessary to return the requested type. The argument data_out must point to valid data type of the specified type.
Because constant values are stored in the dirfile metadata, the new value of field_code won't be written to disk until the dirfile metadata is flushed with dirfile_metaflush(3), or until the dirfile is closed.
RETURN VALUEOn success, put_constant() returns zero. On error, it returns -1 and sets the dirfile error to a non-zero value. Possible error values are:
- The field specified by field_code was not found in the database.
- An invalid dirfile was supplied.
- The supplied field_code referred to a field of type other than CONST. The caller should use putdata(3), or put_string(3) instead.
- The representation suffix specified in field_code was not recognised.
- An invalid data_type was specified.
- 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.
- The fragment containing the constant was protected from change. The dirfile error may be retrieved by calling get_error(3). A descriptive error string for the last error encountered may be obtained from a call to get_error_string(3).