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The TQIODevice class is the base class of I/O devices. More...
All the functions in this class are reentrant when TQt is built with thread support.
#include <qiodevice.h>
Inherited by TQBuffer, TQFile, TQSocket, and TQSocketDevice.
The TQIODevice class is the base class of I/O devices.
An I/O device represents a medium that one can read bytes from and/or write bytes to. The TQIODevice class is the abstract superclass of all such devices; classes such as TQFile, TQBuffer and TQSocket inherit TQIODevice and implement virtual functions such as write() appropriately.
Although applications sometimes use TQIODevice directly, it is usually better to use TQTextStream and TQDataStream, which provide stream operations on any TQIODevice subclass. TQTextStream provides text-oriented stream functionality (for human-readable ASCII files, for example), whereas TQDataStream deals with binary data in a totally platform-independent manner.
The public member functions in TQIODevice roughly fall into two groups: the action functions and the state access functions. The most important action functions are:
There are also some other, less used, action functions:
The state access are all "get" functions. The TQIODevice subclass calls setState() to update the state, and simple access functions tell the user of the device what the device's state is. Here are the settings, and their associated access functions:
TQIODevice provides numerous pure virtual functions that you need to implement when subclassing it. Here is a skeleton subclass with all the members you are sure to need and some that you will probably need:
class MyDevice : public TQIODevice
{
public:
MyDevice();
~MyDevice();
bool open( int mode );
void close();
void flush();
uint size() const;
int at() const; // non-pure virtual
bool at( int ); // non-pure virtual
bool atEnd() const; // non-pure virtual
int readBlock( char *data, uint maxlen );
int writeBlock( const char *data, uint len );
int readLine( char *data, uint maxlen );
int getch();
int putch( int );
int ungetch( int );
};
The three non-pure virtual functions need not be reimplemented for sequential devices.
See also TQDataStream, TQTextStream, and Input/Output and Networking.
The offset within the device.
This is the position of the data read/write head of the I/O device.
See also size().
Example: distributor/distributor.ui.h.
Reimplemented in TQSocket.
See also size().
Reimplemented in TQSocket.
Reimplemented in TQFile and TQSocket.
Closes the I/O device.
This virtual function must be reimplemented by all subclasses.
See also open().
Example: grapher/grapher.cpp.
Reimplemented in TQFile and TQSocket.
Returns the current I/O device flags setting.
Flags consists of mode flags and state flags.
Flushes an open I/O device.
This virtual function must be reimplemented by all subclasses.
Reimplemented in TQFile and TQSocket.
Reads a single byte/character from the I/O device.
Returns the byte/character read, or -1 if the end of the I/O device has been reached.
This virtual function must be reimplemented by all subclasses.
See also putch() and ungetch().
Reimplemented in TQFile and TQSocket.
Returns TRUE if the device is an asynchronous device; otherwise returns FALSE, i.e. if the device is a synchronous device.
This mode is currently not in use.
See also isSynchronous().
Returns TRUE if the I/O device is a buffered device; otherwise returns FALSE, i.e. the device is a raw device.
See also isRaw().
Returns TRUE if the I/O device is a combined access (both direct and sequential) device; otherwise returns FALSE.
This access method is currently not in use.
Returns TRUE if the I/O device is a direct access device; otherwise returns FALSE, i.e. if the device is a sequential access device.
See also isSequentialAccess().
Returns TRUE if the I/O device state is 0, i.e. the device is not open; otherwise returns FALSE.
See also isOpen().
Returns TRUE if the I/O device has been opened; otherwise returns FALSE.
See also isInactive().
Example: network/networkprotocol/nntp.cpp.
Returns TRUE if the device is a raw device; otherwise returns FALSE, i.e. if the device is a buffered device.
See also isBuffered().
Returns TRUE if the I/O device was opened using IO_ReadWrite mode; otherwise returns FALSE.
See also isReadable() and isWritable().
Returns TRUE if the I/O device was opened using IO_ReadOnly or IO_ReadWrite mode; otherwise returns FALSE.
See also isWritable() and isReadWrite().
Returns TRUE if the device is a sequential access device; otherwise returns FALSE, i.e. if the device is a direct access device.
Operations involving size() and at(int) are not valid on sequential devices.
See also isDirectAccess().
Returns TRUE if the I/O device is a synchronous device; otherwise returns FALSE, i.e. the device is an asynchronous device.
See also isAsynchronous().
Returns TRUE if the I/O device translates carriage-return and linefeed characters; otherwise returns FALSE.
A TQFile is translated if it is opened with the IO_Translate mode flag.
Returns TRUE if the I/O device was opened using IO_WriteOnly or IO_ReadWrite mode; otherwise returns FALSE.
See also isReadable() and isReadWrite().
Returns bits OR'ed together that specify the current operation mode.
These are the flags that were given to the open() function.
The flags are IO_ReadOnly, IO_WriteOnly, IO_ReadWrite, IO_Append, IO_Truncate and IO_Translate.
Opens the I/O device using the specified mode. Returns TRUE if the device was successfully opened; otherwise returns FALSE.
The mode parameter mode must be an OR'ed combination of the following flags.
| Mode flags | Meaning |
|---|---|
| IO_Raw | specifies raw (unbuffered) file access. |
| IO_ReadOnly | opens a file in read-only mode. |
| IO_WriteOnly | opens a file in write-only mode. |
| IO_ReadWrite | opens a file in read/write mode. |
| IO_Append | sets the file index to the end of the file. |
| IO_Truncate | truncates the file. |
| IO_Translate | enables carriage returns and linefeed translation for text files under MS-DOS, Windows and Macintosh. On Unix systems this flag has no effect. Use with caution as it will also transform every linefeed written to the file into a CRLF pair. This is likely to corrupt your file if you write write binary data. Cannot be combined with IO_Raw. |
This virtual function must be reimplemented by all subclasses.
See also close().
Example: grapher/grapher.cpp.
Reimplemented in TQFile and TQSocket.
Writes the character ch to the I/O device.
Returns ch, or -1 if an error occurred.
This virtual function must be reimplemented by all subclasses.
See also getch() and ungetch().
Example: grapher/grapher.cpp.
Reimplemented in TQFile and TQSocket.
Reads at most maxlen bytes from the I/O device into data and returns the number of bytes actually read.
This function should return -1 if a fatal error occurs and should return 0 if there are no bytes to read.
The device must be opened for reading, and data must not be 0.
This virtual function must be reimplemented by all subclasses.
See also writeBlock(), isOpen(), and isReadable().
Example: distributor/distributor.ui.h.
Reimplemented in TQSocket and TQSocketDevice.
Returns the number of bytes read including the terminating '\0', or -1 if an error occurred.
This virtual function can be reimplemented much more efficiently by the most subclasses.
See also readBlock() and TQTextStream::readLine().
Reimplemented in TQFile.
Sets the device index position to 0.
See also at().
Sets the I/O device status to IO_Ok.
See also status().
Used by subclasses to set the device flags to the flags specified.
Used by subclasses to set the device mode to the mode specified.
Used by subclasses to set the device state to the state specified.
Used by subclasses to set the device type to the type specified.
Virtual function that returns the size of the I/O device.
See also at().
Reimplemented in TQFile and TQSocket.
Returns bits OR'ed together that specify the current state.
The flags are: IO_Open.
Subclasses may define additional flags.
Returns the I/O device status.
The I/O device status returns an error code. If open() returns FALSE or readBlock() or writeBlock() return -1, this function can be called to find out the reason why the operation failed.
The status codes are:
| Status code | Meaning |
|---|---|
| IO_Ok | The operation was successful. |
| IO_ReadError | Could not read from the device. |
| IO_WriteError | Could not write to the device. |
| IO_FatalError | A fatal unrecoverable error occurred. |
| IO_OpenError | Could not open the device. |
| IO_ConnectError | Could not connect to the device. |
| IO_AbortError | The operation was unexpectedly aborted. |
| IO_TimeOutError | The operation timed out. |
| IO_UnspecifiedError | An unspecified error happened on close. |
See also resetStatus().
Puts the character ch back into the I/O device and decrements the index position if it is not zero.
This function is normally called to "undo" a getch() operation.
Returns ch, or -1 if an error occurred.
This virtual function must be reimplemented by all subclasses.
Reimplemented in TQFile and TQSocket.
Writes len bytes from data to the I/O device and returns the number of bytes actually written.
This function should return -1 if a fatal error occurs.
This virtual function must be reimplemented by all subclasses.
See also readBlock().
Example: distributor/distributor.ui.h.
Reimplemented in TQBuffer, TQSocket, and TQSocketDevice.
This convenience function is the same as calling writeBlock( data.data(), data.size() ).
This file is part of the TQt toolkit. Copyright © 1995-2007 Trolltech. All Rights Reserved.
| Copyright © 2007 Trolltech | Trademarks | TQt 3.3.8
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