qlistdata.cpp

qt-x11-opensource-src-4.1.4.tar.gz源码

/****************************************************************************
**
** Copyright (C) 1992-2006 Trolltech ASA. All rights reserved.
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** This file may be used under the terms of the GNU General Public
** License version 2.0 as published by the Free Software Foundation
** and appearing in the file LICENSE.GPL included in the packaging of
** this file.  Please review the following information to ensure GNU
** General Public Licensing requirements will be met:
** http://www.trolltech.com/products/qt/opensource.html
**
** If you are unsure which license is appropriate for your use, please
** review the following information:
** http://www.trolltech.com/products/qt/licensing.html or contact the
** sales department at [e-mail].
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** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
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****************************************************************************/

#include "qlist.h"
#include "qtools_p.h"
#include <string.h>

/*
    QList as an array-list combines the easy-of-use of a random
    access interface with fast list operations and the low memory
    management overhead of an array. Accessing elements by index,
    appending, prepending, and removing elements from both the front
    and the back all happen in constant time O(1). Inserting or
    removing elements at random index positions \ai happens in linear
    time, or more precisly in O(min{i,n-i}) <= O(n/2), with n being
    the number of elements in the list.
*/

QListData::Data QListData::shared_null = { Q_ATOMIC_INIT(1), 0, 0, 0, true, { 0 } };

static int grow(int size)
{
    // dear compiler: don't optimize me out.
    volatile int x = qAllocMore(size * sizeof(void *), QListData::DataHeaderSize) / sizeof(void *);
    return x;
}

QListData::Data *QListData::detach()
{
    Q_ASSERT(d->ref != 1);
    Data *x = static_cast<Data *>(qMalloc(DataHeaderSize + d->alloc * sizeof(void *)));
    ::memcpy(x, d, DataHeaderSize + d->alloc * sizeof(void *));
    x->alloc = d->alloc;
    x->ref.init(1);
    x->sharable = true;
    if (!x->alloc)
        x->begin = x->end = 0;

    x = qAtomicSetPtr(&d, x);
    if (!x->ref.deref())
        return x;
    return 0;
}

void QListData::realloc(int alloc)
{
    Q_ASSERT(d->ref == 1);
    d = static_cast<Data *>(qRealloc(d, DataHeaderSize + alloc * sizeof(void *)));
    d->alloc = alloc;
    if (!alloc)
        d->begin = d->end = 0;
}


void **QListData::append()
{
    Q_ASSERT(d->ref == 1);
    if (d->end == d->alloc) {
        int n = d->end - d->begin;
        if (d->begin > 2 * d->alloc / 3) {
            ::memcpy(d->array + n, d->array + d->begin, n * sizeof(void *));
            d->begin = n;
            d->end = n * 2;
        } else {
            realloc(grow(d->alloc + 1));
        }
    }
    return d->array + d->end++;
}

void **QListData::append(const QListData& l)
{
    Q_ASSERT(d->ref == 1);
    int e = d->end;
    int n = l.d->end - l.d->begin;
    if (n) {
        if (e + n > d->alloc)
            realloc(grow(e + l.d->end - l.d->begin));
        ::memcpy(d->array + d->end, l.d->array + l.d->begin, n * sizeof(void*));
        d->end += n;
    }
    return d->array + e;
}

void **QListData::prepend()
{
    Q_ASSERT(d->ref == 1);
    if (d->begin == 0) {
        if (d->end >= d->alloc / 3)
            realloc(grow(d->alloc + 1));

        if (d->end < d->alloc / 3)
            d->begin = d->alloc - 2 * d->end;
        else
            d->begin = d->alloc - d->end;

        ::memmove(d->array + d->begin, d->array, d->end * sizeof(void *));
        d->end += d->begin;
    }
    return d->array + --d->begin;
}

void **QListData::insert(int i)
{
    Q_ASSERT(d->ref == 1);
    if (i <= 0)
        return prepend();
    if (i >= d->end - d->begin)
        return append();

    bool leftward = false;
    int size = d->end - d->begin;

    if (d->begin == 0) {
        if (d->end == d->alloc) {
            // If the array is full, we expand it and move some items rightward
            realloc(grow(d->alloc + 1));
        } else {
            // If there is free space at the end of the array, we move some items rightward
        }
    } else {
        if (d->end == d->alloc) {
            // If there is free space at the beginning of the array, we move some items leftward
            leftward = true;
        } else {
            // If there is free space at both ends, we move as few items as possible
            leftward = (i < size - i);
        }
    }

    if (leftward) {
        --d->begin;
        ::memmove(d->array + d->begin, d->array + d->begin + 1, i * sizeof(void *));
    } else {
        ::memmove(d->array + d->begin + i + 1, d->array + d->begin + i,
                  (size - i) * sizeof(void *));
        ++d->end;
    }
    return d->array + d->begin + i;
}

void QListData::remove(int i)
{
    Q_ASSERT(d->ref == 1);
    i += d->begin;
    if (i - d->begin < d->end - i) {
        if (int offset = i - d->begin)
            ::memmove(d->array + d->begin + 1, d->array + d->begin, offset * sizeof(void *));
        d->begin++;
    } else {
        if (int offset = d->end - i - 1)
            ::memmove(d->array + i, d->array + i + 1, offset * sizeof(void *));
        d->end--;
    }
}

void QListData::remove(int i, int n)
{
    Q_ASSERT(d->ref == 1);
    i += d->begin;
    int middle = i + n/2;
    if (middle - d->begin < d->end - middle) {
        ::memmove(d->array + d->begin + n, d->array + d->begin,
                   (i - d->begin) * sizeof(void*));
        d->begin += n;
    } else {
        ::memmove(d->array + i, d->array + i + n,
                   (d->end - i - n) * sizeof(void*));
        d->end -= n;
    }
}

void QListData::move(int from, int to)
{
    Q_ASSERT(d->ref == 1);
    if (from == to)
        return;

    from += d->begin;
    to += d->begin;
    void *t = d->array[from];

    if (from < to) {
        if (d->end == d->alloc || 3 * (to - from) < 2 * (d->end - d->begin)) {
            ::memmove(d->array + from, d->array + from + 1, (to - from) * sizeof(void *));
        } else {
            // optimization
            if (int offset = from - d->begin)
                ::memmove(d->array + d->begin + 1, d->array + d->begin, offset * sizeof(void *));
            if (int offset = d->end - (to + 1))
                ::memmove(d->array + to + 2, d->array + to + 1, offset * sizeof(void *));
            ++d->begin;
            ++d->end;
            ++to;
        }
    } else {
        if (d->begin == 0 || 3 * (from - to) < 2 * (d->end - d->begin)) {
            ::memmove(d->array + to + 1, d->array + to, (from - to) * sizeof(void *));
        } else {
            // optimization
            if (int offset = to - d->begin)
                ::memmove(d->array + d->begin - 1, d->array + d->begin, offset * sizeof(void *));
            if (int offset = d->end - (from + 1))
                ::memmove(d->array + from, d->array + from + 1, offset * sizeof(void *));
            --d->begin;
            --d->end;
            --to;
        }
    }
    d->array[to] = t;
}

void **QListData::erase(void **xi)
{
    Q_ASSERT(d->ref == 1);
    int i = xi - (d->array + d->begin);
    remove(i);
    return d->array + d->begin + i;
}

/*! \class QList
    \brief The QList class is a template class that provides lists.

    \ingroup tools
    \ingroup shared
    \mainclass
    \reentrant

    QList\<T\> is one of Qt's generic \l{container classes}. It
    stores a list of values and provides fast index-based access as
    well as fast insertions and removals.

    QList\<T\>, QLinkedList\<T\>, and QVector\<T\> provide similar
    functionality. Here's an overview:

    \list
    \i For most purposes, QList is the right class to use. Its
       index-based API is more convenient than QLinkedList's
       iterator-based API, and it is usually faster than
       QVector because of the way it stores its items in
       memory. It also expands to less code in your executable.
    \i If you need a real linked list, with guarantees of \l{constant
       time} insertions in the middle of the list and iterators to
       items rather than indexes, use QLinkedList.
    \i If you want the items to occupy adjacent memory positions,
       use QVector.
    \endlist

    Internally, QList\<T\> is represented as an array of pointers to
    items. (Exceptionally, if T is a pointer type, a basic type of
    the size of a pointer, or one of Qt's \l{shared classes},
    QList\<T\> stores the item directly in the pointer.) For lists
    under a thousand items, this representation allows for very fast
    insertions in the middle, in addition to instantaneous
    index-based access. Furthermore, operations like prepend() and
    append() are very fast, because QList preallocates memory on both
    sides of its internal array.

    Here's an example of a QList that stores integers and
    a QList that stores QDate values:

    \code
        QList<int> integerList;
        QList<QDate> dateList;
    \endcode

    Qt includes a QStringList class that inherits QList\<QString\>
    and adds a few convenience functions, such as QStringList::join()
    and QStringList::find(). (QString::split() creates QStringLists
    from strings.)

    QList stores a list of items. The default constructor creates an
    empty list. To insert items into the list, you can use
    operator<<():

    \code
        QList<QString> list;
        list << "one" << "two" << "three";
        // list: ["one", "two", "three"]
    \endcode

    QList provides these basic functions to add, move, and remove
    items: insert(), replace(), removeAt(), move(), and swap(). In
    addition, it provides the following convenience functions:
    append(), prepend(), removeFirst(), and removeLast().

    QList uses 0-based indexes, just like C++ arrays. To access the
    item at a particular index position, you can use operator[](). On
    non-const lists, operator[]() returns a reference to the item and
    can be used on the left side of an assignment:

    \code
        if (list[0] == "Bob")
            list[0] = "Robert";
    \endcode

    Because QList is implemented as an array of pointers, this
    operation is very fast (\l{constant time}). For read-only access,
    an alternative syntax is to use at():

    \code
        for (int i = 0; i < list.size(); ++i) {
            if (list.at(i) == "Jane")
                cout << "Found Jane at position " << i << endl;
        }
    \endcode

    at() can be faster than operator[](), because it never causes a
    \l{deep copy} to occur.

    A common requirement is to remove an item from a list and do
    something with it. For this, QList provides takeAt(), takeFirst(),
    and takeLast(). Here's a loop that removes the items from a list
    one at a time and calls \c delete on them:

    \code
        QList<QWidget *> list;
        ...
        while (!list.isEmpty())
            delete list.takeFirst();
    \endcode

    Inserting and removing items at either ends of the list is very
    fast (\l{constant time} in most cases), because QList
    preallocates extra space on both sides of its internal buffer to
    allow for fast growth at both ends of the list.

    If you want to find all occurrences of a particular value in a
    list, use indexOf() or lastIndexOf(). The former searches forward
    starting from a given index position, the latter searches
    backward. Both return the index of a matching item if they find
    it; otherwise, they return -1. For example:

    \code
        int i = list.indexOf("Jane");
        if (i != -1)
            cout << "First occurrence of Jane is at position " << i << endl;
    \endcode

    If you simply want to check whether a list contains a particular
    value, use contains(). If you want to find out how many times a
    particular value occurs in the list, use count(). If you want to
    replace all occurrences of a particular value with another, use
    replace().

    QList's value type must be an \l{assignable data type}. This
    covers most data types that are commonly used, but the compiler
    won't let you, for example, store a QWidget as a value; instead,
    store a QWidget *. A few functions have additional requirements;
    for example, indexOf() and lastIndexOf() expect the value type to
    support \c operator==(). These requirements are documented on a
    per-function basis.

    Like the other container classes, QList provides \l{Java-style
    iterators} (QListIterator and QMutableListIterator) and
    \l{STL-style iterators} (QList::const_iterator and
    QList::iterator). In practice, these are rarely used, because
    you can use indexes into the QList. QList is implemented in such
    a way that direct index-based access is just as fast as using
    iterators.

    QList does \e not support inserting, prepending, appending or replacing
    with references to its own values. Doing so will cause your application to
    abort with an error message.

    \sa QListIterator, QMutableListIterator, QLinkedList, QVector
*/

/*!
    \fn QList<T> QList<T>::mid(int pos, int length) const

    Returns a list whose elements are copied from this list,
    starting at position \a pos. If \a length is -1 (the default), all
    elements after \a pos are copied; otherwise \a length elements (or
    all remaining elements if there are less than \a length elements)
    are copied.
*/

/*! \fn QList::QList()

    Constructs an empty list.
*/

/*! \fn QList::QList(const QList<T> &other)

    Constructs a copy of \a other.

    This operation takes \l{constant time}, because QList is
    \l{implicitly shared}. This makes returning a QList 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 QList::~QList()

    Destroys the list. References to the values in the list and all
    iterators of this list become invalid.
*/

/*! \fn QList<T> &QList::operator=(const QList<T> &other)

    Assigns \a other to this list and returns a reference to this
    list.
*/

/*! \fn bool QList::operator==(const QList<T> &other) const

    Returns true if \a other is equal to this list; otherwise returns
    false.

    Two lists are considered equal if they contain the same values in
    the same order.

    This function requires the value type to have an implementation of
    \c operator==().