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Please review the following information to ** ensure the GNU General Public License version 3.0 requirements will be ** met: http://www.gnu.org/copyleft/gpl.html. ** ** If you are unsure which license is appropriate for your use, please ** contact the sales department at http://qt.nokia.com/contact. ** $QT_END_LICENSE$ ** ****************************************************************************/ #include "qbitarray.h" #include #include #include QT_BEGIN_NAMESPACE /*! \class QBitArray \brief The QBitArray class provides an array of bits. \ingroup tools \ingroup shared \reentrant A QBitArray is an array that gives access to individual bits and provides operators (\link operator&() AND\endlink, \link operator|() OR\endlink, \link operator^() XOR\endlink, and \link operator~() NOT\endlink) that work on entire arrays of bits. It uses \l{implicit sharing} (copy-on-write) to reduce memory usage and to avoid the needless copying of data. The following code constructs a QBitArray containing 200 bits initialized to false (0): \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 0 To initialize the bits to true, either pass \c true as second argument to the constructor, or call fill() later on. QBitArray uses 0-based indexes, just like C++ arrays. To access the bit at a particular index position, you can use operator[](). On non-const bit arrays, operator[]() returns a reference to a bit that can be used on the left side of an assignment. For example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 1 For technical reasons, it is more efficient to use testBit() and setBit() to access bits in the array than operator[](). For example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 2 QBitArray supports \c{&} (\link operator&() AND\endlink), \c{|} (\link operator|() OR\endlink), \c{^} (\link operator^() XOR\endlink), \c{~} (\link operator~() NOT\endlink), as well as \c{&=}, \c{|=}, and \c{^=}. These operators work in the same way as the built-in C++ bitwise operators of the same name. For example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 3 For historical reasons, QBitArray distinguishes between a null bit array and an empty bit array. A \e null bit array is a bit array that is initialized using QBitArray's default constructor. An \e empty bit array is any bit array with size 0. A null bit array is always empty, but an empty bit array isn't necessarily null: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 4 All functions except isNull() treat null bit arrays the same as empty bit arrays; for example, QBitArray() compares equal to QBitArray(0). We recommend that you always use isEmpty() and avoid isNull(). \sa QByteArray, QVector */ /*! \fn QBitArray::QBitArray() Constructs an empty bit array. \sa isEmpty() */ /*! Constructs a bit array containing \a size bits. The bits are initialized with \a value, which defaults to false (0). */ QBitArray::QBitArray(int size, bool value) { if (!size) { d.resize(0); return; } d.resize(1 + (size+7)/8); uchar* c = reinterpret_cast(d.data()); memset(c, value ? 0xff : 0, d.size()); *c = d.size()*8 - size; if (value && size && size % 8) *(c+1+size/8) &= (1 << (size%8)) - 1; } /*! \fn int QBitArray::size() const Returns the number of bits stored in the bit array. \sa resize() */ /*! \fn int QBitArray::count() const Same as size(). */ /*! If \a on is true, this function returns the number of 1-bits stored in the bit array; otherwise the number of 0-bits is returned. */ int QBitArray::count(bool on) const { int numBits = 0; int len = size(); #if 0 for (int i = 0; i < len; ++i) numBits += testBit(i); #else // See http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel const quint8 *bits = reinterpret_cast(d.data()) + 1; while (len >= 32) { quint32 v = quint32(bits[0]) | (quint32(bits[1]) << 8) | (quint32(bits[2]) << 16) | (quint32(bits[3]) << 24); quint32 c = ((v & 0xfff) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f; c += (((v & 0xfff000) >> 12) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f; c += ((v >> 24) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f; len -= 32; bits += 4; numBits += int(c); } while (len >= 24) { quint32 v = quint32(bits[0]) | (quint32(bits[1]) << 8) | (quint32(bits[2]) << 16); quint32 c = ((v & 0xfff) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f; c += (((v & 0xfff000) >> 12) * Q_UINT64_C(0x1001001001001) & Q_UINT64_C(0x84210842108421)) % 0x1f; len -= 24; bits += 3; numBits += int(c); } while (len >= 0) { if (bits[len / 8] & (1 << ((len - 1) & 7))) ++numBits; --len; } #endif return on ? numBits : size() - numBits; } /*! Resizes the bit array to \a size bits. If \a size is greater than the current size, the bit array is extended to make it \a size bits with the extra bits added to the end. The new bits are initialized to false (0). If \a size is less than the current size, bits are removed from the end. \sa size() */ void QBitArray::resize(int size) { if (!size) { d.resize(0); } else { int s = d.size(); d.resize(1 + (size+7)/8); uchar* c = reinterpret_cast(d.data()); if (size > (s << 3)) memset(c + s, 0, d.size() - s); *c = d.size()*8 - size; } } /*! \fn bool QBitArray::isEmpty() const Returns true if this bit array has size 0; otherwise returns false. \sa size() */ /*! \fn bool QBitArray::isNull() const Returns true if this bit array is null; otherwise returns false. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 5 Qt makes a distinction between null bit arrays and empty bit arrays for historical reasons. For most applications, what matters is whether or not a bit array contains any data, and this can be determined using isEmpty(). \sa isEmpty() */ /*! \fn bool QBitArray::fill(bool value, int size = -1) Sets every bit in the bit array to \a value, returning true if successful; otherwise returns false. If \a size is different from -1 (the default), the bit array is resized to \a size beforehand. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 6 \sa resize() */ /*! \overload Sets bits at index positions \a begin up to and excluding \a end to \a value. \a begin and \a end must be a valid index position in the bit array (i.e., 0 <= \a begin <= size() and 0 <= \a end <= size()). */ void QBitArray::fill(bool value, int begin, int end) { while (begin < end && begin & 0x7) setBit(begin++, value); int len = end - begin; if (len <= 0) return; int s = len & ~0x7; uchar *c = reinterpret_cast(d.data()); memset(c + (begin >> 3) + 1, value ? 0xff : 0, s >> 3); begin += s; while (begin < end) setBit(begin++, value); } /*! \fn bool QBitArray::isDetached() const \internal */ /*! \fn void QBitArray::detach() \internal */ /*! \fn void QBitArray::clear() Clears the contents of the bit array and makes it empty. \sa resize(), isEmpty() */ /*! \fn void QBitArray::truncate(int pos) Truncates the bit array at index position \a pos. If \a pos is beyond the end of the array, nothing happens. \sa resize() */ /*! \fn bool QBitArray::toggleBit(int i) Inverts the value of the bit at index position \a i, returning the previous value of that bit as either true (if it was set) or false (if it was unset). If the previous value was 0, the new value will be 1. If the previous value was 1, the new value will be 0. \a i must be a valid index position in the bit array (i.e., 0 <= \a i < size()). \sa setBit(), clearBit() */ /*! \fn bool QBitArray::testBit(int i) const Returns true if the bit at index position \a i is 1; otherwise returns false. \a i must be a valid index position in the bit array (i.e., 0 <= \a i < size()). \sa setBit(), clearBit() */ /*! \fn bool QBitArray::setBit(int i) Sets the bit at index position \a i to 1. \a i must be a valid index position in the bit array (i.e., 0 <= \a i < size()). \sa clearBit(), toggleBit() */ /*! \fn void QBitArray::setBit(int i, bool value) \overload Sets the bit at index position \a i to \a value. */ /*! \fn void QBitArray::clearBit(int i) Sets the bit at index position \a i to 0. \a i must be a valid index position in the bit array (i.e., 0 <= \a i < size()). \sa setBit(), toggleBit() */ /*! \fn bool QBitArray::at(int i) const Returns the value of the bit at index position \a i. \a i must be a valid index position in the bit array (i.e., 0 <= \a i < size()). \sa operator[]() */ /*! \fn QBitRef QBitArray::operator[](int i) Returns the bit at index position \a i as a modifiable reference. \a i must be a valid index position in the bit array (i.e., 0 <= \a i < size()). Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 7 The return value is of type QBitRef, a helper class for QBitArray. When you get an object of type QBitRef, you can assign to it, and the assignment will apply to the bit in the QBitArray from which you got the reference. The functions testBit(), setBit(), and clearBit() are slightly faster. \sa at(), testBit(), setBit(), clearBit() */ /*! \fn bool QBitArray::operator[](int i) const \overload */ /*! \fn bool QBitArray::operator[](uint i) \overload */ /*! \fn bool QBitArray::operator[](uint i) const \overload */ /*! \fn QBitArray::QBitArray(const QBitArray &other) Constructs a copy of \a other. This operation takes \l{constant time}, because QBitArray is \l{implicitly shared}. This makes returning a QBitArray from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), and that takes \l{linear time}. \sa operator=() */ /*! \fn QBitArray &QBitArray::operator=(const QBitArray &other) Assigns \a other to this bit array and returns a reference to this bit array. */ /*! \fn bool QBitArray::operator==(const QBitArray &other) const Returns true if \a other is equal to this bit array; otherwise returns false. \sa operator!=() */ /*! \fn bool QBitArray::operator!=(const QBitArray &other) const Returns true if \a other is not equal to this bit array; otherwise returns false. \sa operator==() */ /*! Performs the AND operation between all bits in this bit array and \a other. Assigns the result to this bit array, and returns a reference to it. The result has the length of the longest of the two bit arrays, with any missing bits (if one array is shorter than the other) taken to be 0. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 8 \sa operator&(), operator|=(), operator^=(), operator~() */ QBitArray &QBitArray::operator&=(const QBitArray &other) { resize(qMax(size(), other.size())); uchar *a1 = reinterpret_cast(d.data()) + 1; const uchar *a2 = reinterpret_cast(other.d.constData()) + 1; int n = other.d.size() -1 ; int p = d.size() - 1 - n; while (n-- > 0) *a1++ &= *a2++; while (p-- > 0) *a1++ = 0; return *this; } /*! Performs the OR operation between all bits in this bit array and \a other. Assigns the result to this bit array, and returns a reference to it. The result has the length of the longest of the two bit arrays, with any missing bits (if one array is shorter than the other) taken to be 0. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 9 \sa operator|(), operator&=(), operator^=(), operator~() */ QBitArray &QBitArray::operator|=(const QBitArray &other) { resize(qMax(size(), other.size())); uchar *a1 = reinterpret_cast(d.data()) + 1; const uchar *a2 = reinterpret_cast(other.d.constData()) + 1; int n = other.d.size() - 1; while (n-- > 0) *a1++ |= *a2++; return *this; } /*! Performs the XOR operation between all bits in this bit array and \a other. Assigns the result to this bit array, and returns a reference to it. The result has the length of the longest of the two bit arrays, with any missing bits (if one array is shorter than the other) taken to be 0. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 10 \sa operator^(), operator&=(), operator|=(), operator~() */ QBitArray &QBitArray::operator^=(const QBitArray &other) { resize(qMax(size(), other.size())); uchar *a1 = reinterpret_cast(d.data()) + 1; const uchar *a2 = reinterpret_cast(other.d.constData()) + 1; int n = other.d.size() - 1; while (n-- > 0) *a1++ ^= *a2++; return *this; } /*! Returns a bit array that contains the inverted bits of this bit array. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 11 \sa operator&(), operator|(), operator^() */ QBitArray QBitArray::operator~() const { int sz = size(); QBitArray a(sz); const uchar *a1 = reinterpret_cast(d.constData()) + 1; uchar *a2 = reinterpret_cast(a.d.data()) + 1; int n = d.size() - 1; while (n-- > 0) *a2++ = ~*a1++; if (sz && sz%8) *(a2-1) &= (1 << (sz%8)) - 1; return a; } /*! \relates QBitArray Returns a bit array that is the AND of the bit arrays \a a1 and \a a2. The result has the length of the longest of the two bit arrays, with any missing bits (if one array is shorter than the other) taken to be 0. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 12 \sa QBitArray::operator&=(), operator|(), operator^() */ QBitArray operator&(const QBitArray &a1, const QBitArray &a2) { QBitArray tmp = a1; tmp &= a2; return tmp; } /*! \relates QBitArray Returns a bit array that is the OR of the bit arrays \a a1 and \a a2. The result has the length of the longest of the two bit arrays, with any missing bits (if one array is shorter than the other) taken to be 0. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 13 \sa QBitArray::operator|=(), operator&(), operator^() */ QBitArray operator|(const QBitArray &a1, const QBitArray &a2) { QBitArray tmp = a1; tmp |= a2; return tmp; } /*! \relates QBitArray Returns a bit array that is the XOR of the bit arrays \a a1 and \a a2. The result has the length of the longest of the two bit arrays, with any missing bits (if one array is shorter than the other) taken to be 0. Example: \snippet doc/src/snippets/code/src_corelib_tools_qbitarray.cpp 14 \sa QBitArray::operator^=(), operator&(), operator|() */ QBitArray operator^(const QBitArray &a1, const QBitArray &a2) { QBitArray tmp = a1; tmp ^= a2; return tmp; } /*! \class QBitRef \reentrant \brief The QBitRef class is an internal class, used with QBitArray. \internal The QBitRef is required by the indexing [] operator on bit arrays. It is not for use in any other context. */ /*! \fn QBitRef::QBitRef (QBitArray& a, int i) Constructs a reference to element \a i in the QBitArray \a a. This is what QBitArray::operator[] constructs its return value with. */ /*! \fn QBitRef::operator bool() const Returns the value referenced by the QBitRef. */ /*! \fn bool QBitRef::operator!() const \internal */ /*! \fn QBitRef& QBitRef::operator= (const QBitRef& v) Sets the value referenced by the QBitRef to that referenced by QBitRef \a v. */ /*! \fn QBitRef& QBitRef::operator= (bool v) \overload Sets the value referenced by the QBitRef to \a v. */ /***************************************************************************** QBitArray stream functions *****************************************************************************/ #ifndef QT_NO_DATASTREAM /*! \relates QBitArray Writes bit array \a ba to stream \a out. \sa \link datastreamformat.html Format of the QDataStream operators \endlink */ QDataStream &operator<<(QDataStream &out, const QBitArray &ba) { quint32 len = ba.size(); out << len; if (len > 0) out.writeRawData(ba.d.constData() + 1, ba.d.size() - 1); return out; } /*! \relates QBitArray Reads a bit array into \a ba from stream \a in. \sa \link datastreamformat.html Format of the QDataStream operators \endlink */ QDataStream &operator>>(QDataStream &in, QBitArray &ba) { ba.clear(); quint32 len; in >> len; if (len == 0) { ba.clear(); return in; } const quint32 Step = 8 * 1024 * 1024; quint32 totalBytes = (len + 7) / 8; quint32 allocated = 0; while (allocated < totalBytes) { int blockSize = qMin(Step, totalBytes - allocated); ba.d.resize(allocated + blockSize + 1); if (in.readRawData(ba.d.data() + 1 + allocated, blockSize) != blockSize) { ba.clear(); in.setStatus(QDataStream::ReadPastEnd); return in; } allocated += blockSize; } int paddingMask = ~((0x1 << (len & 0x7)) - 1); if (paddingMask != ~0x0 && (ba.d.constData()[ba.d.size() - 1] & paddingMask)) { ba.clear(); in.setStatus(QDataStream::ReadCorruptData); return in; } *ba.d.data() = ba.d.size() * 8 - len; return in; } #endif // QT_NO_DATASTREAM /*! \fn DataPtr &QBitArray::data_ptr() \internal */ /*! \typedef QBitArray::DataPtr \internal */ QT_END_NAMESPACE