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Bug 1193600 - Add Clamp and IsPowerOfTwo to MFBT. - r=waldo

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This commit is contained in:
Jeff Gilbert 2015-09-04 13:33:10 -07:00
parent 37224500a1
commit cfcb90a7d3
3 changed files with 120 additions and 0 deletions
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32
mfbt/MathAlgorithms.h
View File

@ -500,6 +500,38 @@ RotateRight(const T aValue, uint_fast8_t aShift)
return (aValue >> aShift) | (aValue << (sizeof(T) * CHAR_BIT - aShift));
}
/**
* Returns true if |x| is a power of two.
* Zero is not an integer power of two. (-Inf is not an integer)
*/
template<typename T>
inline bool
IsPowerOfTwo(T x)
{
static_assert(IsUnsigned<T>::value,
"IsPowerOfTwo requires unsigned values");
return x && (x & (x - 1)) == 0;
}
template<typename T>
inline T
Clamp(const T aValue, const T aMin, const T aMax)
{
static_assert(IsIntegral<T>::value,
"Clamp accepts only integral types, so that it doesn't have"
" to distinguish differently-signed zeroes (which users may"
" or may not care to distinguish, likely at a perf cost) or"
" to decide how to clamp NaN or a range with a NaN"
" endpoint.");
MOZ_ASSERT(aMin <= aMax);
if (aValue <= aMin)
return aMin;
if (aValue >= aMax)
return aMax;
return aValue;
}
} /* namespace mozilla */
#endif /* mozilla_MathAlgorithms_h */

87
mfbt/tests/TestMathAlgorithms.cpp Normal file
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@ -0,0 +1,87 @@
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "mozilla/MathAlgorithms.h"
using mozilla::Clamp;
using mozilla::IsPowerOfTwo;
static void
TestClamp()
{
MOZ_RELEASE_ASSERT(Clamp(0, 0, 0) == 0);
MOZ_RELEASE_ASSERT(Clamp(1, 0, 0) == 0);
MOZ_RELEASE_ASSERT(Clamp(-1, 0, 0) == 0);
MOZ_RELEASE_ASSERT(Clamp(0, 1, 1) == 1);
MOZ_RELEASE_ASSERT(Clamp(0, 1, 2) == 1);
MOZ_RELEASE_ASSERT(Clamp(0, -1, -1) == -1);
MOZ_RELEASE_ASSERT(Clamp(0, -2, -1) == -1);
MOZ_RELEASE_ASSERT(Clamp(0, 1, 3) == 1);
MOZ_RELEASE_ASSERT(Clamp(1, 1, 3) == 1);
MOZ_RELEASE_ASSERT(Clamp(2, 1, 3) == 2);
MOZ_RELEASE_ASSERT(Clamp(3, 1, 3) == 3);
MOZ_RELEASE_ASSERT(Clamp(4, 1, 3) == 3);
MOZ_RELEASE_ASSERT(Clamp(5, 1, 3) == 3);
MOZ_RELEASE_ASSERT(Clamp<uint8_t>(UINT8_MAX, 0, UINT8_MAX) == UINT8_MAX);
MOZ_RELEASE_ASSERT(Clamp<uint8_t>(0, 0, UINT8_MAX) == 0);
MOZ_RELEASE_ASSERT(Clamp<int8_t>(INT8_MIN, INT8_MIN, INT8_MAX) == INT8_MIN);
MOZ_RELEASE_ASSERT(Clamp<int8_t>(INT8_MIN, 0, INT8_MAX) == 0);
MOZ_RELEASE_ASSERT(Clamp<int8_t>(INT8_MAX, INT8_MIN, INT8_MAX) == INT8_MAX);
MOZ_RELEASE_ASSERT(Clamp<int8_t>(INT8_MAX, INT8_MIN, 0) == 0);
}
static void
TestIsPowerOfTwo()
{
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(0u));
MOZ_RELEASE_ASSERT( IsPowerOfTwo(1u));
MOZ_RELEASE_ASSERT( IsPowerOfTwo(2u));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(3u));
MOZ_RELEASE_ASSERT( IsPowerOfTwo(4u));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(5u));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(6u));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(7u));
MOZ_RELEASE_ASSERT( IsPowerOfTwo(8u));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(9u));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint8_t(UINT8_MAX/2))); // 127, 0x7f
MOZ_RELEASE_ASSERT( IsPowerOfTwo(uint8_t(UINT8_MAX/2 + 1))); // 128, 0x80
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint8_t(UINT8_MAX/2 + 2))); // 129, 0x81
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint8_t(UINT8_MAX - 1))); // 254, 0xfe
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint8_t(UINT8_MAX))); // 255, 0xff
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint16_t(UINT16_MAX/2))); // 0x7fff
MOZ_RELEASE_ASSERT( IsPowerOfTwo(uint16_t(UINT16_MAX/2 + 1))); // 0x8000
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint16_t(UINT16_MAX/2 + 2))); // 0x8001
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint16_t(UINT16_MAX - 1))); // 0xfffe
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint16_t(UINT16_MAX))); // 0xffff
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint32_t(UINT32_MAX/2)));
MOZ_RELEASE_ASSERT( IsPowerOfTwo(uint32_t(UINT32_MAX/2 + 1)));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint32_t(UINT32_MAX/2 + 2)));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint32_t(UINT32_MAX - 1)));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint32_t(UINT32_MAX)));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint64_t(UINT64_MAX/2)));
MOZ_RELEASE_ASSERT( IsPowerOfTwo(uint64_t(UINT64_MAX/2 + 1)));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint64_t(UINT64_MAX/2 + 2)));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint64_t(UINT64_MAX - 1)));
MOZ_RELEASE_ASSERT(!IsPowerOfTwo(uint64_t(UINT64_MAX)));
}
int
main()
{
TestIsPowerOfTwo();
TestClamp();
return 0;
}

1
mfbt/tests/moz.build
View File

@ -22,6 +22,7 @@ CppUnitTests([
'TestJSONWriter',
'TestMacroArgs',
'TestMacroForEach',
'TestMathAlgorithms',
'TestMaybe',
'TestPair',
'TestRefPtr',