Adds qFindFirstSetBit() and qFindLastSetBit().
Two new function families have been added: qFindFirstSetBit() and qFindLastSetBit() for a variety of integer sizes. Fast implementations are included for most platforms. [ChangeLog][QtCore][QtAlgorithms] Added qFindFirstSetBit() and qFindLastSetBit(). Change-Id: I89d9d1637ea26070aee5a60be95be1b51bfc84dc Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Glen Mabey
parent
5e9f7b9579
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125
src/corelib/tools/qalgorithms.h
Normal file → Executable file
125
src/corelib/tools/qalgorithms.h
Normal file → Executable file
@ -584,6 +584,131 @@ Q_DECL_CONST_FUNCTION Q_DECL_CONSTEXPR inline uint qPopulationCount(long unsigne
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#undef QALGORITHMS_USE_BUILTIN_POPCOUNT
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#endif
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Q_DECL_RELAXED_CONSTEXPR inline uint qCountTrailingZeroBits(quint32 v) Q_DECL_NOTHROW
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{
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#if defined(Q_CC_GNU)
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return v ? __builtin_ctz(v) : 32U;
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#else
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// see http://graphics.stanford.edu/~seander/bithacks.html#ZerosOnRightParallel
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unsigned int c = 32; // c will be the number of zero bits on the right
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v &= -signed(v);
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if (v) c--;
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if (v & 0x0000FFFF) c -= 16;
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if (v & 0x00FF00FF) c -= 8;
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if (v & 0x0F0F0F0F) c -= 4;
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if (v & 0x33333333) c -= 2;
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if (v & 0x55555555) c -= 1;
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return c;
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#endif
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}
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Q_DECL_RELAXED_CONSTEXPR inline uint qCountTrailingZeroBits(quint8 v) Q_DECL_NOTHROW
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{
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#if defined(Q_CC_GNU)
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return v ? __builtin_ctz(v) : 8U;
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#else
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unsigned int c = 8; // c will be the number of zero bits on the right
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v &= -signed(v);
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if (v) c--;
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if (v & 0x0000000F) c -= 4;
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if (v & 0x00000033) c -= 2;
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if (v & 0x00000055) c -= 1;
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return c;
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#endif
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}
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Q_DECL_RELAXED_CONSTEXPR inline uint qCountTrailingZeroBits(quint16 v) Q_DECL_NOTHROW
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{
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#if defined(Q_CC_GNU)
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return v ? __builtin_ctz(v) : 16U;
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#else
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unsigned int c = 16; // c will be the number of zero bits on the right
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v &= -signed(v);
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if (v) c--;
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if (v & 0x000000FF) c -= 8;
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if (v & 0x00000F0F) c -= 4;
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if (v & 0x00003333) c -= 2;
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if (v & 0x00005555) c -= 1;
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return c;
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#endif
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}
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Q_DECL_RELAXED_CONSTEXPR inline uint qCountTrailingZeroBits(quint64 v) Q_DECL_NOTHROW
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{
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#if defined(Q_CC_GNU)
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return v ? __builtin_ctzll(v) : 64;
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#else
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quint32 x = static_cast<quint32>(v);
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return x ? qCountTrailingZeroBits(x)
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: 32 + qCountTrailingZeroBits(static_cast<quint32>(v >> 32));
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#endif
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}
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Q_DECL_RELAXED_CONSTEXPR inline uint qCountTrailingZeroBits(unsigned long v) Q_DECL_NOTHROW
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{
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return qCountTrailingZeroBits(QIntegerForSizeof<long>::Unsigned(v));
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}
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Q_DECL_CONSTEXPR inline uint qCountLeadingZeroBits(quint32 v) Q_DECL_NOTHROW
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{
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#if defined(Q_CC_GNU)
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return v ? __builtin_clz(v) : 32U;
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#else
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// Hacker's Delight, 2nd ed. Fig 5-16, p. 102
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v = v | (v >> 1);
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v = v | (v >> 2);
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v = v | (v >> 4);
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v = v | (v >> 8);
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v = v | (v >> 16);
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return qPopulationCount(~v);
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#endif
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}
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Q_DECL_CONSTEXPR inline uint qCountLeadingZeroBits(quint8 v) Q_DECL_NOTHROW
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{
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#if defined(Q_CC_GNU)
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return v ? __builtin_clz(v)-24U : 8U;
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#else
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v = v | (v >> 1);
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v = v | (v >> 2);
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v = v | (v >> 4);
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return qPopulationCount(static_cast<quint8>(~v));
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#endif
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}
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Q_DECL_CONSTEXPR inline uint qCountLeadingZeroBits(quint16 v) Q_DECL_NOTHROW
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{
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#if defined(Q_CC_GNU)
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return v ? __builtin_clz(v)-16U : 16U;
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#else
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v = v | (v >> 1);
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v = v | (v >> 2);
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v = v | (v >> 4);
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v = v | (v >> 8);
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return qPopulationCount(static_cast<quint16>(~v));
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#endif
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}
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Q_DECL_CONSTEXPR inline uint qCountLeadingZeroBits(quint64 v) Q_DECL_NOTHROW
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{
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#if defined(Q_CC_GNU)
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return v ? __builtin_clzll(v) : 64U;
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#else
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v = v | (v >> 1);
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v = v | (v >> 2);
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v = v | (v >> 4);
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v = v | (v >> 8);
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v = v | (v >> 16);
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v = v | (v >> 32);
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return qPopulationCount(~v);
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#endif
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}
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Q_DECL_CONSTEXPR inline uint qCountLeadingZeroBits(unsigned long v) Q_DECL_NOTHROW
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{
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return qCountLeadingZeroBits(QIntegerForSizeof<long>::Unsigned(v));
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}
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QT_WARNING_POP
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QT_END_NAMESPACE
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70
src/corelib/tools/qalgorithms.qdoc
Normal file → Executable file
70
src/corelib/tools/qalgorithms.qdoc
Normal file → Executable file
@ -785,3 +785,73 @@
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\since 5.2
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\overload
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*/
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/*!
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\fn uint qCountTrailingZeroBits(quint8 v)
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\relates <QtAlgorithms>
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\since 5.6
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Returns the number of consecutive zero bits in \a v, when searching from the LSB.
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For example, qCountTrailingZeroBits(1) returns 0 and qCountTrailingZeroBits(8) returns 3.
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*/
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/*!
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\fn uint qCountTrailingZeroBits(quint16 v)
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\relates <QtAlgorithms>
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\since 5.6
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\overload
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*/
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/*!
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\fn uint qCountTrailingZeroBits(quint32 v)
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\relates <QtAlgorithms>
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\since 5.6
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\overload
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*/
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/*!
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\fn uint qCountTrailingZeroBits(quint64 v)
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\relates <QtAlgorithms>
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\since 5.6
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\overload
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*/
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/*!
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\fn uint qCountLeadingZeroBits(quint8 v)
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\relates <QtAlgorithms>
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\since 5.6
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Returns the number of consecutive zero bits in \a v, when searching from the MSB.
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For example, qCountLeadingZeroBits(quint8(1)) returns 7 and
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qCountLeadingZeroBits(quint8(8)) returns 4.
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*/
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/*!
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\fn uint qCountLeadingZeroBits(quint16 v)
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\relates <QtAlgorithms>
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\since 5.6
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Returns the number of consecutive zero bits in \a v, when searching from the MSB.
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For example, qCountLeadingZeroBits(quint16(1)) returns 15 and
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qCountLeadingZeroBits(quint16(8)) returns 12.
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*/
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/*!
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\fn uint qCountLeadingZeroBits(quint32 v)
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\relates <QtAlgorithms>
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\since 5.6
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Returns the number of consecutive zero bits in \a v, when searching from the MSB.
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For example, qCountLeadingZeroBits(quint32(1)) returns 31 and
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qCountLeadingZeroBits(quint32(8)) returns 28.
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*/
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/*!
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\fn uint qCountLeadingZeroBits(quint64 v)
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\relates <QtAlgorithms>
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\since 5.6
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Returns the number of consecutive zero bits in \a v, when searching from the MSB.
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For example, qCountLeadingZeroBits(quint64(1)) returns 63 and
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qCountLeadingZeroBits(quint64(8)) returns 60.
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*/
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107
tests/auto/corelib/tools/qalgorithms/tst_qalgorithms.cpp
Normal file → Executable file
107
tests/auto/corelib/tools/qalgorithms/tst_qalgorithms.cpp
Normal file → Executable file
@ -31,6 +31,7 @@
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**
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****************************************************************************/
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#include "../../../../../src/corelib/tools/qalgorithms.h"
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#include <QtTest/QtTest>
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#include <iostream>
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@ -80,6 +81,24 @@ private slots:
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void popCount32() { popCount_impl<quint32>(); }
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void popCount64() { popCount_impl<quint64>(); }
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void countTrailing08_data() { countTrailing_data_impl(sizeof(quint8 )); }
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void countTrailing16_data() { countTrailing_data_impl(sizeof(quint16)); }
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void countTrailing32_data() { countTrailing_data_impl(sizeof(quint32)); }
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void countTrailing64_data() { countTrailing_data_impl(sizeof(quint64)); }
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void countTrailing08() { countTrailing_impl<quint8 >(); }
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void countTrailing16() { countTrailing_impl<quint16>(); }
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void countTrailing32() { countTrailing_impl<quint32>(); }
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void countTrailing64() { countTrailing_impl<quint64>(); }
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void countLeading08_data() { countLeading_data_impl(sizeof(quint8 )); }
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void countLeading16_data() { countLeading_data_impl(sizeof(quint16)); }
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void countLeading32_data() { countLeading_data_impl(sizeof(quint32)); }
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void countLeading64_data() { countLeading_data_impl(sizeof(quint64)); }
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void countLeading08() { countLeading_impl<quint8 >(); }
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void countLeading16() { countLeading_impl<quint16>(); }
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void countLeading32() { countLeading_impl<quint32>(); }
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void countLeading64() { countLeading_impl<quint64>(); }
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private:
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#if Q_TEST_PERFORMANCE
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void performance();
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@ -87,6 +106,14 @@ private:
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void popCount_data_impl(size_t sizeof_T_Int);
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template <typename T_Int>
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void popCount_impl();
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void countTrailing_data_impl(size_t sizeof_T_Int);
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template <typename T_Int>
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void countTrailing_impl();
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void countLeading_data_impl(size_t sizeof_T_Int);
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template <typename T_Int>
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void countLeading_impl();
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};
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class TestInt
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@ -1084,6 +1111,86 @@ void tst_QAlgorithms::popCount_impl()
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QCOMPARE(qPopulationCount(value), expected);
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}
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void tst_QAlgorithms::countTrailing_data_impl(size_t sizeof_T_Int)
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{
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using namespace QTest;
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addColumn<quint64>("input");
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addColumn<uint>("expected");
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int nibs = sizeof_T_Int*2;
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newRow(("0x"+QByteArray::number(0,16).rightJustified(nibs,'0')).constData()) << Q_UINT64_C(0) << uint(sizeof_T_Int*8);
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for (uint i = 0; i < sizeof_T_Int*8; ++i) {
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const quint64 input = Q_UINT64_C(1) << i;
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newRow(("0x"+QByteArray::number(input,16).rightJustified(nibs,'0')).constData()) << input << i;
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}
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quint64 type_mask;
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if (sizeof_T_Int>=8)
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type_mask = ~Q_UINT64_C(0);
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else
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type_mask = (Q_UINT64_C(1) << (sizeof_T_Int*8))-1;
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// and some random ones:
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for (uint i = 0; i < sizeof_T_Int*8; ++i) {
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for (uint j = 0; j < sizeof_T_Int*3; ++j) { // 3 is arbitrary
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const quint64 r = quint64(qrand()) << 32 | quint32(qrand());
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const quint64 b = Q_UINT64_C(1) << i;
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const quint64 mask = ((~(b-1)) ^ b) & type_mask;
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const quint64 input = (r&mask) | b;
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newRow(("0x"+QByteArray::number(input,16).rightJustified(nibs,'0')).constData()) << input << i;
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}
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}
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}
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template <typename T_Int>
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void tst_QAlgorithms::countTrailing_impl()
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{
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QFETCH(quint64, input);
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QFETCH(uint, expected);
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const T_Int value = static_cast<T_Int>(input);
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QCOMPARE(qCountTrailingZeroBits(value), expected);
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}
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void tst_QAlgorithms::countLeading_data_impl(size_t sizeof_T_Int)
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{
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using namespace QTest;
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addColumn<quint64>("input");
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addColumn<uint>("expected");
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int nibs = sizeof_T_Int*2;
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newRow(("0x"+QByteArray::number(0,16).rightJustified(nibs,'0')).constData()) << Q_UINT64_C(0) << uint(sizeof_T_Int*8);
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for (uint i = 0; i < sizeof_T_Int*8; ++i) {
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const quint64 input = Q_UINT64_C(1) << i;
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newRow(("0x"+QByteArray::number(input,16).rightJustified(nibs,'0')).constData()) << input << uint(sizeof_T_Int*8-i-1);
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}
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// and some random ones:
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for (uint i = 0; i < sizeof_T_Int*8; ++i) {
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for (uint j = 0; j < sizeof_T_Int*3; ++j) { // 3 is arbitrary
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const quint64 r = quint64(qrand()) << 32 | quint32(qrand());
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const quint64 b = Q_UINT64_C(1) << i;
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const quint64 mask = b-1;
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const quint64 input = (r&mask) | b;
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newRow(("0x"+QByteArray::number(input,16).rightJustified(nibs,'0')).constData()) << input << uint(sizeof_T_Int*8-i-1);
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}
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}
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}
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template <typename T_Int>
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void tst_QAlgorithms::countLeading_impl()
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{
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QFETCH(quint64, input);
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QFETCH(uint, expected);
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const T_Int value = static_cast<T_Int>(input);
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QCOMPARE(qCountLeadingZeroBits(value), expected);
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}
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QTEST_APPLESS_MAIN(tst_QAlgorithms)
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#include "tst_qalgorithms.moc"
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