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// -*-C++-*-
#ifndef FLOATPROPS_H
#define FLOATPROPS_H
#include <cmath>
#include <cstdint>
#include <cstring>
#include <iostream>
#include <limits>
#include <sstream>
#include <typeinfo>
namespace vecmathlib {
// A structure describing various properties of a floating point
// type. Most properties are already described in numeric_limits, so
// we inherit it.
template<typename real_t>
struct floatprops {
// Some interesting properties are:
// digits
// epsilon
// min_exponent
// max_exponent
};
template<typename int_t>
struct intprops {
};
// Properties of float
template<>
struct floatprops<float>: std::numeric_limits<float> {
typedef float real_t;
typedef int32_t int_t;
typedef uint32_t uint_t;
// Ensure the internal representation is what we expect
static_assert(is_signed, "real_t is not signed");
static_assert(radix==2, "real_t is not binary");
// Ensure the sizes match
static_assert(sizeof(real_t) == sizeof(int_t), "int_t has wrong size");
static_assert(sizeof(real_t) == sizeof(uint_t), "uint_t has wrong size");
// Number of bits in internal representation
static int const bits = 8 * sizeof(real_t);
static int const mantissa_bits = digits - 1;
static int const signbit_bits = 1;
static int const exponent_bits = bits - mantissa_bits - signbit_bits;
static int const exponent_offset = 2 - min_exponent;
static_assert(mantissa_bits + exponent_bits + signbit_bits == bits,
"error in bit counts");
static uint_t const mantissa_mask = (uint_t(1) << mantissa_bits) - 1;
static uint_t const exponent_mask =
((uint_t(1) << exponent_bits) - 1) << mantissa_bits;
static uint_t const signbit_mask = uint_t(1) << (bits-1);
static_assert((mantissa_mask & exponent_mask & signbit_mask) == uint_t(0),
"error in masks");
static_assert((mantissa_mask | exponent_mask | signbit_mask) == ~uint_t(0),
"error in masks");
// Re-interpret bit patterns
static inline real_t as_float(int_t x)
{
// return *(real_t*)&x;
// union { int_t i; real_t r; } ir;
// return ir.i=x, ir.r;
real_t res;
std::memcpy(&res, &x, sizeof res);
return res;
}
static inline int_t as_int(real_t x)
{
// return *(int_t*)&x;
// union { real_t r; int_t i; } ri;
// return ri.r=x, ri.i;
int_t res;
std::memcpy(&res, &x, sizeof res);
return res;
}
// Convert values
static inline real_t convert_float(int_t x) { return real_t(x); }
static inline int_t convert_int(real_t x)
{
static_assert(sizeof std::lrint(x) >= sizeof(int_t),
"lrint() has wrong return type");
long res = std::lrint(x);
if (sizeof std::lrint(x) > sizeof(int_t)) {
if (res < std::numeric_limits<int_t>::min() ||
res > std::numeric_limits<int_t>::max())
{
return std::numeric_limits<int_t>::min();
}
}
return res;
}
};
template<>
struct intprops<floatprops<float>::int_t> {
typedef float real_t;
};
// Properties of double
template<>
struct floatprops<double>: std::numeric_limits<double> {
typedef double real_t;
typedef int64_t int_t;
typedef uint64_t uint_t;
// Ensure the internal representation is what we expect
static_assert(is_signed, "real_t is not signed");
static_assert(radix==2, "real_t is not binary");
// Ensure the sizes match
static_assert(sizeof(real_t) == sizeof(int_t), "int_t has wrong size");
static_assert(sizeof(real_t) == sizeof(uint_t), "uint_t has wrong size");
// Number of bits in internal representation
static int const bits = 8 * sizeof(real_t);
static int const mantissa_bits = digits - 1;
static int const signbit_bits = 1;
static int const exponent_bits = bits - mantissa_bits - signbit_bits;
static int const exponent_offset = 2 - min_exponent;
static_assert(mantissa_bits + exponent_bits + signbit_bits == bits,
"error in bit counts");
static uint_t const mantissa_mask = (uint_t(1) << mantissa_bits) - 1;
static uint_t const exponent_mask =
((uint_t(1) << exponent_bits) - 1) << mantissa_bits;
static uint_t const signbit_mask = uint_t(1) << (bits-1);
static_assert((mantissa_mask & exponent_mask & signbit_mask) == uint_t(0),
"error in masks");
static_assert((mantissa_mask | exponent_mask | signbit_mask) == ~uint_t(0),
"error in masks");
// Re-interpret bit patterns
static inline real_t as_float(int_t x)
{
// return *(real_t*)&x;
// union { int_t i; real_t r; } ir;
// return ir.i=x, ir.r;
real_t res;
std::memcpy(&res, &x, sizeof res);
return res;
}
static inline int_t as_int(real_t x)
{
// return *(int_t*)&x;
// union { real_t r; int_t i; } ri;
// return ri.r=x, ri.i;
int_t res;
std::memcpy(&res, &x, sizeof res);
return res;
}
// Convert values
static inline real_t convert_float(int_t x) { return real_t(x); }
static inline int_t convert_int(real_t x)
{
static_assert(sizeof std::lrint(x) >= sizeof(int_t),
"lrint() has wrong return type");
long res = std::lrint(x);
if (sizeof std::lrint(x) > sizeof(int_t)) {
if (res < std::numeric_limits<int_t>::min() ||
res > std::numeric_limits<int_t>::max())
{
return std::numeric_limits<int_t>::min();
}
}
return res;
}
};
template<>
struct intprops<floatprops<double>::int_t> {
typedef double real_t;
};
} // namespace vecmathlib
#endif // #ifndef FLOATPROPS_H
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