/*
** mruby/numeric.h - Numeric, Integer, Float, Fixnum class
**
** See Copyright Notice in mruby.h
*/

#ifndef MRUBY_NUMERIC_H
#define MRUBY_NUMERIC_H

#include "common.h"

/**
 * Numeric class and it's sub-classes.
 *
 * Integer, Float and Fixnum
 */
MRB_BEGIN_DECL

#define POSFIXABLE(f) ((f) <= MRB_INT_MAX)
#define NEGFIXABLE(f) ((f) >= MRB_INT_MIN)
#define FIXABLE(f) (POSFIXABLE(f) && NEGFIXABLE(f))

MRB_API mrb_value mrb_flo_to_fixnum(mrb_state *mrb, mrb_value val);
MRB_API mrb_value mrb_fixnum_to_str(mrb_state *mrb, mrb_value x, int base);
/* ArgumentError if format string doesn't match /%(\.[0-9]+)?[aAeEfFgG]/ */
MRB_API mrb_value mrb_float_to_str(mrb_state *mrb, mrb_value x, const char *fmt);
MRB_API mrb_float mrb_to_flo(mrb_state *mrb, mrb_value x);

mrb_value mrb_fixnum_plus(mrb_state *mrb, mrb_value x, mrb_value y);
mrb_value mrb_fixnum_minus(mrb_state *mrb, mrb_value x, mrb_value y);
mrb_value mrb_fixnum_mul(mrb_state *mrb, mrb_value x, mrb_value y);
mrb_value mrb_num_div(mrb_state *mrb, mrb_value x, mrb_value y);

#ifndef __has_builtin
  #define __has_builtin(x) 0
#endif

#if (defined(__GNUC__) && __GNUC__ >= 5) ||   \
    (__has_builtin(__builtin_add_overflow) && \
     __has_builtin(__builtin_sub_overflow) && \
     __has_builtin(__builtin_mul_overflow))
# define MRB_HAVE_TYPE_GENERIC_CHECKED_ARITHMETIC_BUILTINS
#endif

// Clang 3.8 and 3.9 have problem compiling mruby in 32-bit mode, when MRB_INT64 is set
// because of missing __mulodi4 and similar functions in its runtime. We need to use custom
// implementation for them.
#ifdef MRB_HAVE_TYPE_GENERIC_CHECKED_ARITHMETIC_BUILTINS
#if defined(__clang__) && (__clang_major__ == 3) && (__clang_minor__ >= 8) && \
    defined(MRB_32BIT) && defined(MRB_INT64)
#undef MRB_HAVE_TYPE_GENERIC_CHECKED_ARITHMETIC_BUILTINS
#endif
#endif

#ifdef MRB_HAVE_TYPE_GENERIC_CHECKED_ARITHMETIC_BUILTINS

#ifndef MRB_WORD_BOXING
# define WBCHK(x) 0
#else
# define WBCHK(x) !FIXABLE(x)
#endif

static inline mrb_bool
mrb_int_add_overflow(mrb_int augend, mrb_int addend, mrb_int *sum)
{
  return __builtin_add_overflow(augend, addend, sum) || WBCHK(*sum);
}

static inline mrb_bool
mrb_int_sub_overflow(mrb_int minuend, mrb_int subtrahend, mrb_int *difference)
{
  return __builtin_sub_overflow(minuend, subtrahend, difference) || WBCHK(*difference);
}

static inline mrb_bool
mrb_int_mul_overflow(mrb_int multiplier, mrb_int multiplicand, mrb_int *product)
{
  return __builtin_mul_overflow(multiplier, multiplicand, product) || WBCHK(*product);
}

#undef WBCHK

#else

#define MRB_UINT_MAKE2(n) uint ## n ## _t
#define MRB_UINT_MAKE(n) MRB_UINT_MAKE2(n)
#define mrb_uint MRB_UINT_MAKE(MRB_INT_BIT)

#define MRB_INT_OVERFLOW_MASK ((mrb_uint)1 << (MRB_INT_BIT - 1 - MRB_FIXNUM_SHIFT))

static inline mrb_bool
mrb_int_add_overflow(mrb_int augend, mrb_int addend, mrb_int *sum)
{
  mrb_uint x = (mrb_uint)augend;
  mrb_uint y = (mrb_uint)addend;
  mrb_uint z = (mrb_uint)(x + y);
  *sum = (mrb_int)z;
  return !!(((x ^ z) & (y ^ z)) & MRB_INT_OVERFLOW_MASK);
}

static inline mrb_bool
mrb_int_sub_overflow(mrb_int minuend, mrb_int subtrahend, mrb_int *difference)
{
  mrb_uint x = (mrb_uint)minuend;
  mrb_uint y = (mrb_uint)subtrahend;
  mrb_uint z = (mrb_uint)(x - y);
  *difference = (mrb_int)z;
  return !!(((x ^ z) & (~y ^ z)) & MRB_INT_OVERFLOW_MASK);
}

static inline mrb_bool
mrb_int_mul_overflow(mrb_int multiplier, mrb_int multiplicand, mrb_int *product)
{
#if MRB_INT_BIT == 32
  int64_t n = (int64_t)multiplier * multiplicand;
  *product = (mrb_int)n;
  return !FIXABLE(n);
#else
  if (multiplier > 0) {
    if (multiplicand > 0) {
      if (multiplier > MRB_INT_MAX / multiplicand) return TRUE;
    }
    else {
      if (multiplicand < MRB_INT_MAX / multiplier) return TRUE;
    }
  }
  else {
    if (multiplicand > 0) {
      if (multiplier < MRB_INT_MAX / multiplicand) return TRUE;
    }
    else {
      if (multiplier != 0 && multiplicand < MRB_INT_MAX / multiplier) return TRUE;
    }
  }
  *product = multiplier * multiplicand;
  return FALSE;
#endif
}

#undef MRB_INT_OVERFLOW_MASK
#undef mrb_uint
#undef MRB_UINT_MAKE
#undef MRB_UINT_MAKE2

#endif

MRB_END_DECL

#endif  /* MRUBY_NUMERIC_H */
