blob: 456357c32f66d0d47d0cca5c9c51e4416b79ff8f [file] [log] [blame]
// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <stdint.h>
#include <limits>
#include <type_traits>
#include <zircon/assert.h>
namespace affine {
class Transform; // fwd decl for friendship
class Ratio {
enum class Exact { No, Yes };
// Used to indicate overflow/underflow of scaling operations.
static constexpr int64_t kOverflow = std::numeric_limits<int64_t>::max();
static constexpr int64_t kUnderflow = std::numeric_limits<int64_t>::min();
// Reduces the ratio of N/D
// Defined only for uint32_t and uint64_t
template <typename T>
static void Reduce(T* numerator, T* denominator);
// Produces the product two 32 bit ratios. If exact is true, ASSERTs on loss
// of precision.
static void Product(uint32_t a_numerator,
uint32_t a_denominator,
uint32_t b_numerator,
uint32_t b_denominator,
uint32_t* product_numerator,
uint32_t* product_denominator,
Exact exact = Exact::Yes);
// Produces the product of a 32 bit ratio and the int64_t as an int64_t. Returns
// a saturated value (either kOverflow or kUnderflow) on overflow/underflow.
static int64_t Scale(int64_t value, uint32_t numerator, uint32_t denominator);
// Returns the product of the ratios. If exact is true, ASSERTs on loss of
// precision.
static Ratio Product(Ratio a, Ratio b, Exact exact = Exact::Yes) {
uint32_t result_numerator;
uint32_t result_denominator;
Product(a.numerator(), a.denominator(),
b.numerator(), b.denominator(),
&result_numerator, &result_denominator,
return Ratio(result_numerator, result_denominator, NoReduce::Tag);
Ratio() = default;
Ratio(uint32_t numerator, uint32_t denominator)
: numerator_(numerator), denominator_(denominator) {
Reduce(&numerator_, &denominator_);
uint32_t numerator() const { return numerator_; }
uint32_t denominator() const { return denominator_; }
bool invertible() const { return numerator_ != 0; }
Ratio Inverse() const {
return Ratio{denominator_, numerator_, NoReduce::Tag};
int64_t Scale(int64_t value) const {
return Scale(value, numerator_, denominator_);
friend class Transform;
enum class NoReduce { Tag };
Ratio(uint32_t numerator, uint32_t denominator, NoReduce)
: numerator_(numerator), denominator_(denominator) {}
uint32_t numerator_ = 1;
uint32_t denominator_ = 1;
// Tests two ratios for equality.
inline bool operator==(Ratio a, Ratio b) {
return a.numerator() == b.numerator() &&
a.denominator() == b.denominator();
// Tests two ratios for inequality.
inline bool operator!=(Ratio a, Ratio b) { return !(a == b); }
// Returns the ratio of the two ratios.
inline Ratio operator/(Ratio a, Ratio b) {
return Ratio::Product(a, b.Inverse());
// Returns the product of the two ratios.
inline Ratio operator*(Ratio a, Ratio b) {
return Ratio::Product(a, b);
// Returns the product of the rate and the int64_t.
inline int64_t operator*(Ratio a, int64_t b) { return a.Scale(b); }
// Returns the product of the rate and the int64_t.
inline int64_t operator*(int64_t a, Ratio b) { return b.Scale(a); }
// Returns the the int64_t divided by the rate.
inline int64_t operator/(int64_t a, Ratio b) {
return b.Inverse().Scale(a);
} // namespace affine