include/qapi/qmp/qnum.h

   1 /*
   2  * QNum Module
   3  *
   4  * Copyright (C) 2009 Red Hat Inc.
   5  *
   6  * Authors:
   7  *  Luiz Capitulino <lcapitulino@redhat.com>
   8  *  Anthony Liguori <aliguori@us.ibm.com>
   9  *  Marc-André Lureau <marcandre.lureau@redhat.com>
  10  *
  11  * This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
  12  * See the COPYING.LIB file in the top-level directory.
  13  */
  14
  15 #ifndef QNUM_H
  16 #define QNUM_H
  17
  18 #include "qapi/qmp/qobject.h"
  19
  20 typedef enum {
  21     QNUM_I64,
  22     QNUM_U64,
  23     QNUM_DOUBLE
  24 } QNumKind;
  25
  26 /*
  27  * QNum encapsulates how our dialect of JSON fills in the blanks left
  28  * by the JSON specification (RFC 8259) regarding numbers.
  29  *
  30  * Conceptually, we treat number as an abstract type with three
  31  * concrete subtypes: floating-point, signed integer, unsigned
  32  * integer.  QNum implements this as a discriminated union of double,
  33  * int64_t, uint64_t.
  34  *
  35  * The JSON parser picks the subtype as follows.  If the number has a
  36  * decimal point or an exponent, it is floating-point.  Else if it
  37  * fits into int64_t, it's signed integer.  Else if it fits into
  38  * uint64_t, it's unsigned integer.  Else it's floating-point.
  39  *
  40  * Any number can serve as double: qnum_get_double() converts under
  41  * the hood.
  42  *
  43  * An integer can serve as signed / unsigned integer as long as it is
  44  * in range: qnum_get_try_int() / qnum_get_try_uint() check range and
  45  * convert under the hood.
  46  */
  47 struct QNum {
  48     struct QObjectBase_ base;
  49     QNumKind kind;
  50     union {
  51         int64_t i64;
  52         uint64_t u64;
  53         double dbl;
  54     } u;
  55 };
  56
  57 QNum *qnum_from_int(int64_t value);
  58 QNum *qnum_from_uint(uint64_t value);
  59 QNum *qnum_from_double(double value);
  60
  61 bool qnum_get_try_int(const QNum *qn, int64_t *val);
  62 int64_t qnum_get_int(const QNum *qn);
  63
  64 bool qnum_get_try_uint(const QNum *qn, uint64_t *val);
  65 uint64_t qnum_get_uint(const QNum *qn);
  66
  67 double qnum_get_double(QNum *qn);
  68
  69 char *qnum_to_string(QNum *qn);
  70
  71 #endif /* QNUM_H */