Motown: Rename Ratio and LinearFunction classes

mojo/services/media/common/cpp/ratio.cc

-// Copyright 2016 The Chromium 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 <limits>
-#include <utility>
-
-#include "mojo/public/cpp/environment/logging.h"
-#include "mojo/services/media/common/cpp/ratio.h"
-
-namespace mojo {
-namespace media {
-
-namespace {
-
-// Calculates the greatest common denominator (factor) of two values.
-template <typename T>
-T BinaryGcd(T a, T b) {
-  if (a == 0) {
-    return b;
-  }
-
-  if (b == 0) {
-    return a;
-  }
-
-  // Remove and count the common factors of 2.
-  uint8_t twos;
-  for (twos = 0; ((a | b) & 1) == 0; ++twos) {
-    a >>= 1;
-    b >>= 1;
-  }
-
-  // Get rid of the non-common factors of 2 in a. a is non-zero, so this
-  // terminates.
-  while ((a & 1) == 0) {
-    a >>= 1;
-  }
-
-  do {
-    // Get rid of the non-common factors of 2 in b. b is non-zero, so this
-    // terminates.
-    while ((b & 1) == 0) {
-      b >>= 1;
-    }
-
-    // Apply the Euclid subtraction method.
-    if (a > b) {
-      std::swap(a, b);
-    }
-
-    b = b - a;
-  } while (b != 0);
-
-  // Multiply in the common factors of two.
-  return a << twos;
-}
-
-// Reduces the ration of *numerator and *denominator.
-template <typename T>
-void ReduceRatio(T* numerator, T* denominator) {
-  MOJO_DCHECK(numerator != nullptr);
-  MOJO_DCHECK(denominator != nullptr);
-  MOJO_DCHECK(*denominator != 0);
-
-  T gcd = BinaryGcd(*numerator, *denominator);
-
-  if (gcd == 0) {
-    *denominator = 1;
-    return;
-  }
-
-  if (gcd == 1) {
-    return;
-  }
-
-  *numerator = *numerator / gcd;
-  *denominator = *denominator / gcd;
-}
-
-template void ReduceRatio<uint64_t>(uint64_t* numerator, uint64_t* denominator);
-template void ReduceRatio<uint32_t>(uint32_t* numerator, uint32_t* denominator);
-
-// Scales a uint64_t value by the ratio of two uint32_t values. If round_up is
-// true, the result is rounded up rather than down. overflow is set to indicate
-// overflow.
-uint64_t ScaleUInt64(uint64_t value,
-                     uint32_t numerator,
-                     uint32_t denominator,
-                     bool round_up,
-                     bool* overflow) {
-  MOJO_DCHECK(denominator != 0u);
-  MOJO_DCHECK(overflow != nullptr);
-
-  constexpr uint64_t kLow32Bits = 0xffffffffu;
-  constexpr uint64_t kHigh32Bits = kLow32Bits << 32u;
-
-  // high and low are the product of the numerator and the high and low halves
-  // (respectively) of value.
-  uint64_t high = numerator * (value >> 32u);
-  uint64_t low = numerator * (value & kLow32Bits);
-  // Ignoring overflow and remainder, the result we want is:
-  // ((high << 32) + low) / denominator.
-
-  // Move the high end of low into the low end of high.
-  high += low >> 32u;
-  low = low & kLow32Bits;
-  // Ignoring overflow and remainder, the result we want is still:
-  // ((high << 32) + low) / denominator.
-
-  // When we divide high by denominator, there'll be a remainder. Make
-  // that the high end of low, which is currently all zeroes.
-  low |= (high % denominator) << 32u;
-
-  // Determine if we need to round up when we're done:
-  round_up = round_up && (low % denominator) != 0;
-
-  // Do the division.
-  high /= denominator;
-  low /= denominator;
-
-  // If high's top 32 bits aren't all zero, we have overflow.
-  if (high & kHigh32Bits) {
-    *overflow = true;
-    return 0;
-  }
-
-  uint64_t result = (high << 32u) | low;
-  if (round_up) {
-    if (result == std::numeric_limits<int64_t>::max()) {
-      *overflow = true;
-      return 0;
-    }
-    ++result;
-  }
-
-  *overflow = false;
-  return result;
-}
-
-}  // namespace
-
-// static
-void Ratio::Reduce(uint32_t* numerator, uint32_t* denominator) {
-  ReduceRatio(numerator, denominator);
-}
-
-// static
-void Ratio::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,
-                    bool exact) {
-  MOJO_DCHECK(a_denominator != 0);
-  MOJO_DCHECK(b_denominator != 0);
-  MOJO_DCHECK(product_numerator != nullptr);
-  MOJO_DCHECK(product_denominator != nullptr);
-
-  uint64_t numerator = static_cast<uint64_t>(a_numerator) * b_numerator;
-  uint64_t denominator = static_cast<uint64_t>(a_denominator) * b_denominator;
-
-  ReduceRatio(&numerator, &denominator);
-
-  if (numerator > std::numeric_limits<uint32_t>::max() ||
-      denominator > std::numeric_limits<uint32_t>::max()) {
-    MOJO_DCHECK(!exact);
-
-    do {
-      numerator >>= 1;
-      denominator >>= 1;
-    } while (numerator > std::numeric_limits<uint32_t>::max() ||
-             denominator > std::numeric_limits<uint32_t>::max());
-
-    if (denominator == 0) {
-      // Product is larger than we can represent. Return the largest value we
-      // can represent.
-      *product_numerator = std::numeric_limits<uint32_t>::max();
-      *product_denominator = 1;
-      return;
-    }
-  }
-
-  *product_numerator = static_cast<uint32_t>(numerator);
-  *product_denominator = static_cast<uint32_t>(denominator);
-}
-
-// static
-int64_t Ratio::Scale(int64_t value, uint32_t numerator, uint32_t denominator) {
-  static constexpr uint64_t abs_of_min_int64 =
-      static_cast<uint64_t>(std::numeric_limits<int64_t>::max()) + 1;
-
-  MOJO_DCHECK(denominator != 0u);
-
-  bool overflow;
-
-  uint64_t abs_result;
-
-  if (value >= 0) {
-    abs_result = ScaleUInt64(static_cast<uint64_t>(value), numerator,
-                             denominator, false, &overflow);
-  } else if (value == std::numeric_limits<int64_t>::min()) {
-    abs_result = ScaleUInt64(abs_of_min_int64, numerator, denominator,
-                             true, &overflow);
-  } else {
-    abs_result = ScaleUInt64(static_cast<uint64_t>(-value), numerator,
-                             denominator, true, &overflow);
-  }
-
-  if (overflow) {
-    return Ratio::kOverflow;
-  }
-
-  // Make sure we won't overflow when we cast to int64_t.
-  if (abs_result > static_cast<uint64_t>(std::numeric_limits<int64_t>::max())) {
-    if (value < 0 && abs_result == abs_of_min_int64) {
-      return std::numeric_limits<int64_t>::min();
-    }
-    return Ratio::kOverflow;
-  }
-
-  return value >= 0 ? static_cast<int64_t>(abs_result)
-                    : -static_cast<int64_t>(abs_result);
-}
-
-}  // namespace media
-}  // namespace mojo