qemu-e2k/include/qapi/qmp/qnum.h
Markus Armbruster f90cb2846a qobject: Explain how QNum works, and why
Suggested-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503384739-17207-1-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
[Comment typos fixed]
2017-09-04 13:09:11 +02:00

75 lines
1.9 KiB
C

/*
* QNum Module
*
* Copyright (C) 2009 Red Hat Inc.
*
* Authors:
* Luiz Capitulino <lcapitulino@redhat.com>
* Anthony Liguori <aliguori@us.ibm.com>
* Marc-André Lureau <marcandre.lureau@redhat.com>
*
* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
* See the COPYING.LIB file in the top-level directory.
*/
#ifndef QNUM_H
#define QNUM_H
#include "qapi/qmp/qobject.h"
typedef enum {
QNUM_I64,
QNUM_U64,
QNUM_DOUBLE
} QNumKind;
/*
* QNum encapsulates how our dialect of JSON fills in the blanks left
* by the JSON specification (RFC 7159) regarding numbers.
*
* Conceptually, we treat number as an abstract type with three
* concrete subtypes: floating-point, signed integer, unsigned
* integer. QNum implements this as a discriminated union of double,
* int64_t, uint64_t.
*
* The JSON parser picks the subtype as follows. If the number has a
* decimal point or an exponent, it is floating-point. Else if it
* fits into int64_t, it's signed integer. Else if it fits into
* uint64_t, it's unsigned integer. Else it's floating-point.
*
* Any number can serve as double: qnum_get_double() converts under
* the hood.
*
* An integer can serve as signed / unsigned integer as long as it is
* in range: qnum_get_try_int() / qnum_get_try_uint() check range and
* convert under the hood.
*/
typedef struct QNum {
QObject base;
QNumKind kind;
union {
int64_t i64;
uint64_t u64;
double dbl;
} u;
} QNum;
QNum *qnum_from_int(int64_t value);
QNum *qnum_from_uint(uint64_t value);
QNum *qnum_from_double(double value);
bool qnum_get_try_int(const QNum *qn, int64_t *val);
int64_t qnum_get_int(const QNum *qn);
bool qnum_get_try_uint(const QNum *qn, uint64_t *val);
uint64_t qnum_get_uint(const QNum *qn);
double qnum_get_double(QNum *qn);
char *qnum_to_string(QNum *qn);
QNum *qobject_to_qnum(const QObject *obj);
void qnum_destroy_obj(QObject *obj);
#endif /* QNUM_H */