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27
28/*!
29\page io-functions.html
30\title File and Datastream Functions
31
32The QIODevice class is the base interface class of all I/O devices in
33\l{Qt Core}.  QIODevice provides both a common implementation and an
34abstract interface for devices that support reading and writing of blocks
35of data. The device can be a memory buffer, a file, or a datastream.
36
37Some subclasses like QFile have been implemented using a memory buffer for
38intermediate storing of data. This speeds up programs by reducing
39read/write operations. Buffering makes functions like \l{QFile::}{getChar()} and
40\l{QFile::}{putChar()} fast, as they can operate on the memory buffer instead of
41directly on the device itself.
42
43The QFile class provides functions for reading from and writing to files.
44A QFile may be used by itself or, more conveniently, with a QTextStream or
45QDataStream.
46
47QBuffer allows you to access a QByteArray using the QIODevice interface.
48The QByteArray is treated just as a standard random-accessed file.
49An example:
50
51\code
52     QBuffer buffer;
53     char ch;
54
55     buffer.open(QBuffer::ReadWrite);
56     buffer.write("Qt rocks!");
57     buffer.seek(0);
58     buffer.getChar(&ch);  // ch == 'Q'
59     buffer.getChar(&ch);  // ch == 't'
60     buffer.getChar(&ch);  // ch == ' '
61     buffer.getChar(&ch);  // ch == 'r'
62\endcode
63
64Call \l{QBuffer::}{open()} to open the buffer. Then call \l{QBuffer::}{write()} or \l{QBuffer::}{putChar()} to write to
65the buffer, and \l{QBuffer::}{read()}, \l{QBuffer::}{readLine()}, \l{QBuffer::}{readAll()}, or \l{QBuffer::}{getChar()} to read from it.
66\l{QBuffer::}{size()} returns the current size of the buffer, and you can seek to arbitrary
67positions in the buffer by calling \l{QBuffer::}{seek()}. When you are done with accessing
68the buffer, call \l{QBuffer::}{close()}.
69
70The QDataStream class provides serialization of binary data to a QIODevice.
71A data stream is a binary stream of encoded information which is 100% inde-
72pendent of the host computer's operating system, CPU or byte order. For
73example, a data stream that is written by a PC under Windows can be read
74by a Sun SPARC running Solaris. You can also use a data stream to read/write
75raw unencoded binary data.
76
77For more details on the datatypes that QDataStream can serialize, see
78\l{Serializing Qt Data Types}.
79
80The QTextStream class provides a convenient interface for reading and
81writing text. QTextStream can operate on a QIODevice, a QByteArray or
82a QString. Using QTextStream's streaming operators, you can conveniently read
83and write words, lines and numbers. It's also common to use QTextStream to
84read console input and write console output.
85
86There are three general ways to use QTextStream when reading text files:
87
88\list
89    \li Chunk by chunk, by calling \l{QBuffer::readLine()}{readLine()} or \l{QBuffer::readAll()}{readAll()}.
90    \li Word by word. QTextStream supports streaming into \l{QString}s, \l{QByteArray}s
91        and char* buffers. Words are delimited by space, and leading white space
92        is automatically skipped.
93    \li Character by character, by streaming into QChar or char types. This
94        method is often used for convenient input handling when parsing files,
95        independent of character encoding and end-of-line semantics. To skip
96        white space, call \l{QTextStream::}{skipWhiteSpace()}.
97\endlist
98
99QByteArray can be used to store both raw bytes (including \c{\0}) and traditional
1008-bit '\\0'-terminated strings. Using QByteArray is much more convenient
101than using const char *. It always ensures that the data is followed by a '\\0'
102terminator, and uses \l{Implicit Sharing}{implicitly shared classes} (copy-on-write)
103to reduce memory usage and avoid needless copying of data.
104
105In addition to QByteArray, Qt also provides the QString class to store string
106data. For most purposes, QString is the most appropriate class to use. It stores
10716-bit Unicode characters. It is, however, a good idea to use QByteArray when you
108need to store raw binary data, and when memory conservation is critical (for
109example, with Qt for Embedded Linux).
110
111*/
112