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get_constant
Langue: en
Version: 8 December 2008 (fedora - 06/07/09)
Section: 3 (Bibliothèques de fonctions)
NAME
get_constant --- retrieve a scalar constant from a dirfile databaseSYNOPSIS
#include <getdata.h>- int get_constant(DIRFILE *dirfile, const char *field_code, gd_type_t return_type, void *data_out);
DESCRIPTION
- The get_constant() function queries a dirfile(5) database specified by dirfile for the CONST scalar field_code. The constant is converted to the data type specified by return_type, and stored in the user-supplied buffer data_out.
The dirfile argument must point to a valid DIRFILE object previously created by a call to dirfile_open(3).
The return_type argument should be one of the following symbols, which indicates the desired return type of the data:
-
- GD_UINT8
- unsigned 8-bit integer
- GD_INT8
- signed 8-bit integer
- GD_UINT16
- unsigned 16-bit integer
- GD_INT16
- signed 16-bit integer
- GD_UINT32
- unsigned 32-bit integer
- GD_INT32
- signed 32-bit integer
- GD_UINT64
- unsigned 64-bit integer
- GD_INT64
- signed 64-bit integer
- GD_FLOAT32~or~GD_FLOAT
- IEEE-754 standard 32-bit single precision floating point number
- GD_FLOAT64~or~GD_DOUBLE
- IEEE-754 standard 64-bit double precision floating point number
- GD_NULL
- the null type: the database is queried as usual, but no data is returned. In this case, data_out is ignored and may be NULL.
The return type of the constant need not be the same as the type of the data stored in the database. Type conversion will be performed as necessary to return the requested type. The argument data_out must point to a valid memory location of sufficient size to hold a value of the return type specified.
RETURN VALUE
On success, get_constant() returns zero. On error, it returns -1 and sets the dirfile error to a non-zero value. Possible error values are:- GD_E_BAD_CODE
- The field specified by field_code was not found in the database.
- GD_E_BAD_DIRFILE
- An invalid dirfile was supplied.
- GD_E_BAD_FIELD_TYPE
- The supplied field_code referred to a field of a type other than CONST. The caller should use getdata(3), or get_string(3) instead.
- GD_E_BAD_TYPE
- An invalid return_type was specified.
- 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 maintainer.
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).
SEE ALSO
dirfile(5), dirfile_open(3), get_constants(3), get_error(3), get_error_string(3), put_constant(3)Contenus ©2006-2024 Benjamin Poulain
Design ©2006-2024 Maxime Vantorre