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AK: Change standard casting method of FixedPoint to truncation

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This matches what floats do.

Also fix typo `trunk`->`trunc`
This commit is contained in:
Hendiadyoin1 2023-07-23 19:53:04 +02:00 committed by Andrew Kaster
parent 8526791617
commit 05c959e40b
Notes: sideshowbarker 2024-07-18 05:37:06 +09:00 
Author: https://github.com/Hendiadyoin1
Commit: https://github.com/SerenityOS/serenity/commit/05c959e40b
Pull-request: https://github.com/SerenityOS/serenity/pull/20163
Reviewed-by: https://github.com/DanShaders
3 changed files with 29 additions and 27 deletions
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38
AK/FixedPoint.h
View File

@ -66,19 +66,7 @@ public:
template<Integral I> template<Integral I>
explicit constexpr operator I() const explicit constexpr operator I() const
{ {
I value = m_value >> precision; return trunc().raw() >> precision;
// fract(m_value) >= .5?
if (m_value & (1u << (precision - 1))) {
// fract(m_value) > .5?
if (m_value & (radix_mask >> 2u)) {
// yes: round "up";
value += (m_value > 0 ? 1 : -1);
} else {
// no: round to even;
value += value & 1;
}
}
return value;
} }
static constexpr This create_raw(Underlying value) static constexpr This create_raw(Underlying value)
@ -111,9 +99,23 @@ public:
return *this; return *this;
} }
// Note/FIXME: This uses round to nearest break-tie to even
// Not break-tie away from 0 as the C99's round does
constexpr This round() const constexpr This round() const
{ {
return This { static_cast<Underlying>(*this) }; Underlying value = m_value >> precision;
// fract(m_value) >= .5?
if (m_value & (1u << (precision - 1))) {
// fract(m_value) > .5?
if (m_value & (radix_mask >> 2u)) {
// yes: round "up";
value += (m_value > 0 ? 1 : -1);
} else {
// no: round to even;
value += value & 1;
}
}
return value;
} }
constexpr This floor() const constexpr This floor() const
{ {
@ -124,7 +126,7 @@ public:
return create_raw((m_value & ~radix_mask) return create_raw((m_value & ~radix_mask)
+ (m_value & radix_mask ? 1 << precision : 0)); + (m_value & radix_mask ? 1 << precision : 0));
} }
constexpr This trunk() const constexpr This trunc() const
{ {
return create_raw((m_value & ~radix_mask) return create_raw((m_value & ~radix_mask)
+ ((m_value & radix_mask) + ((m_value & radix_mask)
@ -132,14 +134,14 @@ public:
: 0)); : 0));
} }
constexpr Underlying lround() const { return static_cast<Underlying>(*this); } constexpr Underlying lround() const { return round().raw() >> precision; }
constexpr Underlying lfloor() const { return m_value >> precision; } constexpr Underlying lfloor() const { return m_value >> precision; }
constexpr Underlying lceil() const constexpr Underlying lceil() const
{ {
return (m_value >> precision) return (m_value >> precision)
+ (m_value & radix_mask ? 1 : 0); + (m_value & radix_mask ? 1 : 0);
} }
constexpr Underlying ltrunk() const constexpr Underlying ltrunc() const
{ {
return (m_value >> precision) return (m_value >> precision)
+ ((m_value & radix_mask) + ((m_value & radix_mask)
@ -437,7 +439,7 @@ struct Formatter<FixedPoint<precision, Underlying>> : StandardFormatter {
if constexpr (IsSigned<Underlying>) if constexpr (IsSigned<Underlying>)
is_negative = value < 0; is_negative = value < 0;
i64 integer = value.ltrunk(); i64 integer = value.ltrunc();
constexpr u64 one = static_cast<Underlying>(1) << precision; constexpr u64 one = static_cast<Underlying>(1) << precision;
u64 fraction_raw = value.raw() & (one - 1); u64 fraction_raw = value.raw() & (one - 1);
return builder.put_fixed_point(is_negative, integer, fraction_raw, one, base, upper_case, m_zero_pad, m_use_separator, m_align, m_width.value(), m_precision.value(), m_fill, m_sign_mode, real_number_display_mode); return builder.put_fixed_point(is_negative, integer, fraction_raw, one, base, upper_case, m_zero_pad, m_use_separator, m_align, m_width.value(), m_precision.value(), m_fill, m_sign_mode, real_number_display_mode);

16
Tests/AK/TestFixedPoint.cpp
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@ -41,42 +41,42 @@ TEST_CASE(rounding)
EXPECT_EQ(Type(0.5).round(), Type(0)); EXPECT_EQ(Type(0.5).round(), Type(0));
EXPECT_EQ(Type(0.5).floor(), Type(0)); EXPECT_EQ(Type(0.5).floor(), Type(0));
EXPECT_EQ(Type(0.5).ceil(), Type(1)); EXPECT_EQ(Type(0.5).ceil(), Type(1));
EXPECT_EQ(Type(0.75).trunk(), Type(0)); EXPECT_EQ(Type(0.75).trunc(), Type(0));
EXPECT_EQ(Type(1.5).round(), Type(2)); EXPECT_EQ(Type(1.5).round(), Type(2));
EXPECT_EQ(Type(1.5).floor(), Type(1)); EXPECT_EQ(Type(1.5).floor(), Type(1));
EXPECT_EQ(Type(1.5).ceil(), Type(2)); EXPECT_EQ(Type(1.5).ceil(), Type(2));
EXPECT_EQ(Type(1.25).trunk(), Type(1)); EXPECT_EQ(Type(1.25).trunc(), Type(1));
EXPECT_EQ(Type(-0.5).round(), Type(0)); EXPECT_EQ(Type(-0.5).round(), Type(0));
EXPECT_EQ(Type(-0.5).floor(), Type(-1)); EXPECT_EQ(Type(-0.5).floor(), Type(-1));
EXPECT_EQ(Type(-0.5).ceil(), Type(0)); EXPECT_EQ(Type(-0.5).ceil(), Type(0));
EXPECT_EQ(Type(-0.75).trunk(), Type(0)); EXPECT_EQ(Type(-0.75).trunc(), Type(0));
EXPECT_EQ(Type(-1.5).round(), Type(-2)); EXPECT_EQ(Type(-1.5).round(), Type(-2));
EXPECT_EQ(Type(-1.5).floor(), Type(-2)); EXPECT_EQ(Type(-1.5).floor(), Type(-2));
EXPECT_EQ(Type(-1.5).ceil(), Type(-1)); EXPECT_EQ(Type(-1.5).ceil(), Type(-1));
EXPECT_EQ(Type(-1.25).trunk(), Type(-1)); EXPECT_EQ(Type(-1.25).trunc(), Type(-1));
EXPECT_EQ(Type(0.5).lround(), 0); EXPECT_EQ(Type(0.5).lround(), 0);
EXPECT_EQ(Type(0.5).lfloor(), 0); EXPECT_EQ(Type(0.5).lfloor(), 0);
EXPECT_EQ(Type(0.5).lceil(), 1); EXPECT_EQ(Type(0.5).lceil(), 1);
EXPECT_EQ(Type(0.5).ltrunk(), 0); EXPECT_EQ(Type(0.5).ltrunc(), 0);
EXPECT_EQ(Type(1.5).lround(), 2); EXPECT_EQ(Type(1.5).lround(), 2);
EXPECT_EQ(Type(1.5).lfloor(), 1); EXPECT_EQ(Type(1.5).lfloor(), 1);
EXPECT_EQ(Type(1.5).lceil(), 2); EXPECT_EQ(Type(1.5).lceil(), 2);
EXPECT_EQ(Type(1.5).ltrunk(), 1); EXPECT_EQ(Type(1.5).ltrunc(), 1);
EXPECT_EQ(Type(-0.5).lround(), 0); EXPECT_EQ(Type(-0.5).lround(), 0);
EXPECT_EQ(Type(-0.5).lfloor(), -1); EXPECT_EQ(Type(-0.5).lfloor(), -1);
EXPECT_EQ(Type(-0.5).lceil(), 0); EXPECT_EQ(Type(-0.5).lceil(), 0);
EXPECT_EQ(Type(-0.5).ltrunk(), 0); EXPECT_EQ(Type(-0.5).ltrunc(), 0);
EXPECT_EQ(Type(-1.5).lround(), -2); EXPECT_EQ(Type(-1.5).lround(), -2);
EXPECT_EQ(Type(-1.5).lfloor(), -2); EXPECT_EQ(Type(-1.5).lfloor(), -2);
EXPECT_EQ(Type(-1.5).lceil(), -1); EXPECT_EQ(Type(-1.5).lceil(), -1);
EXPECT_EQ(Type(-1.5).ltrunk(), -1); EXPECT_EQ(Type(-1.5).ltrunc(), -1);
// Check that sRGB TRC curve parameters match the s15fixed16 values stored in Gimp's built-in profile. // Check that sRGB TRC curve parameters match the s15fixed16 values stored in Gimp's built-in profile.
// (This only requires that the FixedPoint<> constructor rounds before truncating to the fixed-point value, // (This only requires that the FixedPoint<> constructor rounds before truncating to the fixed-point value,

2
Userland/Libraries/LibEDID/DMT.cpp
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@ -116,7 +116,7 @@ FixedPoint<16, u32> DMT::MonitorTiming::vertical_frequency_hz() const
u32 DMT::MonitorTiming::refresh_rate_hz() const u32 DMT::MonitorTiming::refresh_rate_hz() const
{ {
return vertical_frequency_hz().ltrunk(); return vertical_frequency_hz().ltrunc();
} }
#ifndef KERNEL #ifndef KERNEL