qbytearray.cpp

奇趣公司比较新的qt/emd版本

    QByteArray baunzip;
    int res;
    do {
        baunzip.resize(len);
        res = ::uncompress((uchar*)baunzip.data(), &len,
                            (uchar*)data+4, nbytes-4);

        switch (res) {
        case Z_OK:
            if ((int)len != baunzip.size())
                baunzip.resize(len);
            break;
        case Z_MEM_ERROR:
            qWarning("qUncompress: Z_MEM_ERROR: Not enough memory");
            break;
        case Z_BUF_ERROR:
            len *= 2;
            break;
        case Z_DATA_ERROR:
            qWarning("qUncompress: Z_DATA_ERROR: Input data is corrupted");
            break;
        }
    } while (res == Z_BUF_ERROR);

    if (res != Z_OK)
        baunzip = QByteArray();

    return baunzip;
}
#endif

static inline bool qIsUpper(char c)
{
    return c >= 'A' && c <= 'Z';
}

static inline char qToLower(char c)
{
    if (c >= 'A' && c <= 'Z')
        return c - 'A' + 'a';
    else
        return c;
}

Q_CORE_EXPORT QByteArray::Data QByteArray::shared_null = {Q_ATOMIC_INIT(1), 0, 0, shared_null.array, {0} };
QByteArray::Data QByteArray::shared_empty = { Q_ATOMIC_INIT(1), 0, 0, shared_empty.array, {0} };

/*!
    \class QByteArray
    \brief The QByteArray class provides an array of bytes.

    \ingroup tools
    \ingroup shared
    \ingroup text
    \mainclass
    \reentrant

    QByteArray can be used to store both raw bytes (including '\\0's)
    and traditional 8-bit '\\0'-terminated strings. Using QByteArray
    is much more convenient than using \c{const char *}. Behind the
    scenes, it always ensures that the data is followed by a '\\0'
    terminator, and uses \l{implicit sharing} (copy-on-write) to
    reduce memory usage and avoid needless copying of data.

    In addition to QByteArray, Qt also provides the QString class to
    store string data. For most purposes, QString is the class you
    want to use. It stores 16-bit Unicode characters, making it easy
    to store non-ASCII/non-Latin-1 characters in your application.
    Furthermore, QString is used throughout in the Qt API. The two
    main cases where QByteArray is appropriate are when you need to
    store raw binary data, and when memory conservation is critical
    (e.g. with Qtopia Core).

    One way to initialize a QByteArray is simply to pass a \c{const
    char *} to its constructor. For example, the following code
    creates a byte array of size 5 containing the data "Hello":

    \code
        QByteArray ba("Hello");
    \endcode

    Although the size() is 5, the byte array also maintains an extra
    '\\0' character at the end so that if a function is used that
    asks for a pointer to the underlying data (e.g. a call to
    data()), the data pointed to is guaranteed to be
    '\\0'-terminated.

    QByteArray makes a deep copy of the \c{const char *} data, so you
    can modify it later without experiencing side effects. (If for
    performance reasons you don't want to take a deep copy of the
    character data, use QByteArray::fromRawData() instead.)

    Another approach is to set the size of the array using resize()
    and to initialize the data byte per byte. QByteArray uses 0-based
    indexes, just like C++ arrays. To access the byte at a particular
    index position, you can use operator[](). On non-const byte
    arrays, operator[]() returns a reference to a byte that can be
    used on the left side of an assignment. For example:

    \code
        QByteArray ba;
        ba.resize(5);
        ba[0] = 0x3c;
        ba[1] = 0xb8;
        ba[2] = 0x64;
        ba[3] = 0x18;
        ba[4] = 0xca;
    \endcode

    For read-only access, an alternative syntax is to use at():

    \code
        for (int i = 0; i < ba.size(); ++i) {
            if (ba.at(i) >= 'a' && ba.at(i) <= 'f')
                cout << "Found character in range [a-f]" << endl;
        }
    \endcode

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

    To extract many bytes at a time, use left(), right(), or mid().

    A QByteArray can embed '\\0' bytes. The size() function always
    returns the size of the whole array, including embedded '\\0'
    bytes. If you want to obtain the length of the data up to and
    excluding the first '\\0' character, call qstrlen() on the byte
    array.

    After a call to resize(), newly allocated bytes have undefined
    values. To set all the bytes to a particular value, call fill().

    To obtain a pointer to the actual character data, call data() or
    constData(). These functions return a pointer to the beginning of
    the data. The pointer is guaranteed to remain valid until a
    non-const function is called on the QByteArray. It is also
    guaranteed that the data ends with a '\\0' byte. This '\\0' byte
    is automatically provided by QByteArray and is not counted in
    size().

    QByteArray provides the following basic functions for modifying
    the byte data: append(), prepend(), insert(), replace(), and
    remove(). For example:

    \code
        QByteArray x("and");
        x.prepend("rock ");         // x == "rock and"
        x.append(" roll");          // x == "rock and roll"
        x.replace(5, 3, "&");       // x == "rock & roll"
    \endcode

    The replace() and remove() functions' first two arguments are the
    position from which to start erasing and the number of bytes that
    should be erased.

    When you append() data to a non-empty array, the array will be
    reallocated and the new data copied to it. You can avoid this
    behavior by calling reserve(), which preallocates a certain amount
    of memory. You can also call capacity() to find out how much
    memory QByteArray actually allocated. Data appended to an empty
    array is not copied.

    A frequent requirement is to remove whitespace characters from a
    byte array ('\\n', '\\t', ' ', etc.). If you want to remove
    whitespace from both ends of a QByteArray, use trimmed(). If you
    want to remove whitespace from both ends and replace multiple
    consecutive whitespaces with a single space character within the
    byte array, use simplified().

    If you want to find all occurrences of a particular character or
    substring in a QByteArray, use indexOf() or lastIndexOf(). The
    former searches forward starting from a given index position, the
    latter searches backward. Both return the index position of the
    character or substring if they find it; otherwise, they return -1.
    For example, here's a typical loop that finds all occurrences of a
    particular substring:

    \code
        QByteArray ba("We must be <b>bold</b>, very <b>bold</b>");
        int j = 0;
        while ((j = ba.indexOf("<b>", j)) != -1) {
            cout << "Found <b> tag at index position " << j << endl;
            ++j;
        }
    \endcode

    If you simply want to check whether a QByteArray contains a
    particular character or substring, use contains(). If you want to
    find out how many times a particular character or substring
    occurs in the byte array, use count(). If you want to replace all
    occurrences of a particular value with another, use one of the
    two-parameter replace() overloads.

    QByteArrays can be compared using overloaded operators such as
    operator<(), operator<=(), operator==(), operator>=(), and so on.
    The comparison is based exclusively on the numeric values
    of the characters and is very fast, but is not what a human would
    expect. QString::localeAwareCompare() is a better choice for
    sorting user-interface strings.

    For historical reasons, QByteArray distinguishes between a null
    byte array and an empty byte array. A \e null byte array is a
    byte array that is initialized using QByteArray's default
    constructor or by passing (const char *)0 to the constructor. An
    \e empty byte array is any byte array with size 0. A null byte
    array is always empty, but an empty byte array isn't necessarily
    null:

    \code
        QByteArray().isNull();          // returns true
        QByteArray().isEmpty();         // returns true

        QByteArray("").isNull();        // returns false
        QByteArray("").isEmpty();       // returns true

        QByteArray("abc").isNull();     // returns false
        QByteArray("abc").isEmpty();    // returns false
    \endcode

    All functions except isNull() treat null byte arrays the same as
    empty byte arrays. For example, data() returns a pointer to a
    '\\0' character for a null byte array (\e not a null pointer),
    and QByteArray() compares equal to QByteArray(""). We recommend
    that you always use isEmpty() and avoid isNull().

    \section1 Note on 8-bit Character Comparisons

    In QByteArray, the notion of uppercase and lowercase and of which
    character is greater than or less than another character is
    locale dependent. This affects functions that support a case
    insensitive option or that compare or lowercase or uppercase
    their arguments. Case insensitive operations and comparisons will
    be accurate if both strings contain only ASCII characters. (If \c
    $LC_CTYPE is set, most Unix systems do "the right thing".)
    Functions that this affects include contains(), indexOf(),
    lastIndexOf(), operator<(), operator<=(), operator>(),
    operator>=(), toLower() and toUpper().

    This issue does not apply to QStrings since they represent
    characters using Unicode.

    \sa QString, QBitArray
*/

/*! \fn QByteArray::iterator QByteArray::begin()

    \internal
*/

/*! \fn QByteArray::const_iterator QByteArray::begin() const

    \internal
*/

/*! \fn QByteArray::const_iterator QByteArray::constBegin() const

    \internal
*/

/*! \fn QByteArray::iterator QByteArray::end()

    \internal
*/

/*! \fn QByteArray::const_iterator QByteArray::end() const

    \internal
*/

/*! \fn QByteArray::const_iterator QByteArray::constEnd() const

    \internal
*/

/*! \fn void QByteArray::push_back(const QByteArray &other)

    This function is provided for STL compatibility. It is equivalent
    to append(\a other).
*/

/*! \fn void QByteArray::push_back(const char *str)

    \overload

    Same as append(\a str).
*/

/*! \fn void QByteArray::push_back(char ch)

    \overload

    Same as append(\a ch).
*/

/*! \fn void QByteArray::push_front(const QByteArray &other)

    This function is provided for STL compatibility. It is equivalent
    to prepend(\a other).
*/

/*! \fn void QByteArray::push_front(const char *str)

    \overload

    Same as prepend(\a str).
*/

/*! \fn void QByteArray::push_front(char ch)

    \overload

    Same as prepend(\a ch).
*/

/*! \fn QByteArray::QByteArray(const QByteArray &other)

    Constructs a copy of \a other.

    This operation takes \l{constant time}, because QByteArray is
    \l{implicitly shared}. This makes returning a QByteArray 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 QByteArray::~QByteArray()
    Destroys the byte array.
*/

/*!
    Assigns \a other to this byte array and returns a reference to
    this byte array.
*/
QByteArray &QByteArray::operator=(const QByteArray & other)
{
    Data *x = other.d;
    x->ref.ref();
    x = qAtomicSetPtr(&d, x);
    if (!x->ref.deref())
        qFree(x);
    return *this;
}


/*!
    \overload

    Assigns \a str to this byte array.
*/

QByteArray &QByteArray::operator=(const char *str)
{
    Data *x;
    if (!str) {
        x = &shared_null;
    } else if (!*str) {
        x = &shared_empty;
    } else {
        int len = qstrlen(str);
        if (d->ref != 1 || len > d->alloc || (len < d->size && len < d->alloc >> 1))
            realloc(len);
        x = d;
        memcpy(x->data, str, len + 1); // include null terminator
        x->size = len;
    }
    x->ref.ref();
    x = qAtomicSetPtr(&d, x);
    if (!x->ref.deref())
         qFree(x);
    return *this;
}

/*! \fn int QByteArray::size() const

    Returns the number of bytes in this byte array.

    The last byte in the byte array is at position size() - 1. In
    addition, QByteArray ensures that the byte at position size() is
    always '\\0', so that you can use the return value of data() and
    constData() as arguments to functions that expect
    '\\0'-terminated strings.

    Example:
    \code
        QByteArray ba("Hello");
        int n = ba.size();          // n == 5
        ba.data()[0];               // returns 'H'
        ba.data()[4];               // returns 'o'
        ba.data()[5];               // returns '\0'
    \endcode

    \sa isEmpty(), resize()
*/

/*! \fn bool QByteArray::isEmpty() const

    Returns true if the byte array has size 0; otherwise returns false.

    Example:
    \code
        QByteArray().isEmpty();         // returns true
        QByteArray("").isEmpty();       // returns true
        QByteArray("abc").isEmpty();    // returns false
    \endcode

    \sa size()
*/

/*! \fn int QByteArray::capacity() const

    Returns the maximum number of bytes that can be stored in the
    byte array without forcing a reallocation.

    The sole purpose of this function is to provide a means of fine
    tuning QByteArray's memory usage. In general, you will rarely
    ever need to call this function. If you want to know how many
    bytes are in the byte array, call size().

    \sa reserve(), squeeze()
*/

/*! \fn void QByteArray::reserve(int size)

    Attempts to allocate memory for at least \a size bytes. If you
    know in advance how large the byte array will be, you can call
    this function, and if you call resize() often you are likely to
    get better performance. If \a size is an underestimate, the worst
    that will happen is that the QByteArray will be a bit slower.

    The sole purpose of this function is to provide a means of fine
    tuning QByteArray's memory usage. In general, you will rarely
    ever need to call this function. If you want to change the size
    of the byte array, call resize().

    \sa squeeze(), capacity()
*/

/*! \fn void QByteArray::squeeze()

    Releases any memory not required to store the array's data.

    The sole purpose of this function is to provide a means of fine
    tuning QByteArray's memory usage. In general, you will rarely
    ever need to call this function.

    \sa reserve(), capacity()
*/

/*! \fn QByteArray::operator const char *() const

    Returns a pointer to the data stored in the byte array. The
    pointer can be used to access the bytes that compose the array.
    The data is '\\0'-terminated. The pointer remains valid as long
    as the array isn't reallocated.

    This operator is mostly useful to pass a byte array to a function
    that accepts a \c{const char *}.

    Note: A QByteArray can store any byte values including '\\0's,
    but most functions that take \c{char *} arguments assume that the
    data ends at the first '\\0' they encounter.

    \sa constData()
*/

/*! \fn QByteArray::operator const void *() const

    Returns a void pointer to the data.