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< td align = "right" valign = "center" > < img src = "logo32.png" align = "right" width = "64" height = "32" border = "0" > < / td > < / tr > < / table > < h1 align = center > TQDeepCopy Class Reference< / h1 >
< p > The TQDeepCopy class is a template class which ensures that
implicitly shared and explicitly shared classes reference unique
data.
< a href = "#details" > More...< / a >
< p > All the functions in this class are < a href = "threads.html#reentrant" > reentrant< / a > when TQt is built with thread support.< / p >
< p > < tt > #include < < a href = "qdeepcopy-h.html" > ntqdeepcopy.h< / a > > < / tt >
< p > < a href = "qdeepcopy-members.html" > List of all member functions.< / a >
< h2 > Public Members< / h2 >
< ul >
< li class = fn > < a href = "#TQDeepCopy" > < b > TQDeepCopy< / b > < / a > ()< / li >
< li class = fn > < a href = "#TQDeepCopy-2" > < b > TQDeepCopy< / b > < / a > ( const T & t )< / li >
< li class = fn > TQDeepCopy< T> & < a href = "#operator-eq" > < b > operator=< / b > < / a > ( const T & t )< / li >
< li class = fn > < a href = "#operator-T" > < b > operator T< / b > < / a > ()< / li >
< / ul >
< hr > < a name = "details" > < / a > < h2 > Detailed Description< / h2 >
The TQDeepCopy class is a template class which ensures that
< a href = "shclass.html#implicitly-shared" > implicitly shared< / a > and < a href = "shclass.html#explicitly-shared" > explicitly shared< / a > classes reference unique
data.
< p >
< p >
< p > Normally, shared copies reference the same data to optimize memory
use and for maximum speed. In the example below, < tt > s1< / tt > , < tt > s2< / tt > , < tt > s3< / tt > , < tt > s4< / tt > and < tt > s5< / tt > share data.
< p > < pre >
// all 5 strings share the same data
< a href = "tqstring.html" > TQString< / a > s1 = "abcd";
< a href = "tqstring.html" > TQString< / a > s2 = s1;
< a href = "tqstring.html" > TQString< / a > s3 = s2;
< a href = "tqstring.html" > TQString< / a > s4 = s3;
< a href = "tqstring.html" > TQString< / a > s5 = s2;
< / pre >
< p > TQDeepCopy can be used several ways to ensure that an object
references unique, unshared data. In the example below, < tt > s1< / tt > , < tt > s2< / tt > and < tt > s5< / tt > share data, while neither < tt > s3< / tt > nor < tt > s4< / tt > share data.
< pre >
// s1, s2 and s5 share the same data, neither s3 nor s4 are shared
< a href = "tqstring.html" > TQString< / a > s1 = "abcd";
< a href = "tqstring.html" > TQString< / a > s2 = s1;
TQDeepCopy< TQString> s3 = s2; // s3 is a < a href = "shclass.html#deep-copy" > deep copy< / a > of s2
< a href = "tqstring.html" > TQString< / a > s4 = s3; // s4 is a deep copy of s3
< a href = "tqstring.html" > TQString< / a > s5 = s2;
< / pre >
< p > In the example below, < tt > s1< / tt > , < tt > s2< / tt > and < tt > s5< / tt > share data, and < tt > s3< / tt >
and < tt > s4< / tt > share data.
< pre >
// s1, s2 and s5 share the same data, s3 and s4 share the same data
< a href = "tqstring.html" > TQString< / a > s1 = "abcd";
< a href = "tqstring.html" > TQString< / a > s2 = s1;
< a href = "tqstring.html" > TQString< / a > s3 = TQDeepCopy< TQString> ( s2 ); // s3 is a deep copy of s2
< a href = "tqstring.html" > TQString< / a > s4 = s3; // s4 is a < a href = "shclass.html#shallow-copy" > shallow copy< / a > of s3
< a href = "tqstring.html" > TQString< / a > s5 = s2;
< / pre >
< p > TQDeepCopy can also provide safety in multithreaded applications
that use shared classes. In the example below, the variable < tt > global_string< / tt > is used safely since the data contained in < tt > global_string< / tt > is always a deep copy. This ensures that all threads
get a unique copy of the data, and that any assignments to < tt > global_string< / tt > will result in a deep copy.
< p > < pre >
TQDeepCopy< TQString> global_string; // global string data
< a href = "ntqmutex.html" > TQMutex< / a > global_mutex; // mutex to protext global_string
...
void setGlobalString( const < a href = "tqstring.html" > TQString< / a > & str )
{
global_mutex.< a href = "ntqmutex.html#lock" > lock< / a > ();
global_string = str; // global_string is a deep copy of str
global_mutex.< a href = "ntqmutex.html#unlock" > unlock< / a > ();
}
...
void MyThread::run()
{
global_mutex.< a href = "ntqmutex.html#lock" > lock< / a > ();
< a href = "tqstring.html" > TQString< / a > str = global_string; // str is a deep copy of global_string
global_mutex.< a href = "ntqmutex.html#unlock" > unlock< / a > ();
// process the string data
...
// update global_string
setGlobalString( str );
}
< / pre >
< p > < b > Warning:< / b > It is the application developer's responsibility to
protect the object shared across multiple threads.
< p > The examples above use < a href = "tqstring.html" > TQString< / a > , which is an implicitly shared
class. The behavior of TQDeepCopy is the same when using explicitly
shared classes like < a href = "qbytearray.html" > TQByteArray< / a > .
< p > Currently, TQDeepCopy works with the following classes:
< ul >
< li > < a href = "ntqmemarray.html" > TQMemArray< / a > (including subclasses like TQByteArray and < a href = "ntqcstring.html" > TQCString< / a > )
< li > < a href = "tqmap.html" > TQMap< / a >
< li > TQString
< li > < a href = "tqvaluelist.html" > TQValueList< / a > (including subclasses like < a href = "tqstringlist.html" > TQStringList< / a > and < a href = "tqvaluestack.html" > TQValueStack< / a > )
< li > < a href = "tqvaluevector.html" > TQValueVector< / a >
< / ul >
< p > < p > See also < a href = "threads.html" > Thread Support in TQt< / a > , < a href = "shared.html" > Implicitly and Explicitly Shared Classes< / a > , and < a href = "tools.html" > Non-GUI Classes< / a > .
< hr > < h2 > Member Function Documentation< / h2 >
< h3 class = fn > < a name = "TQDeepCopy" > < / a > TQDeepCopy::TQDeepCopy ()
< / h3 >
< p > Constructs an empty instance of type < em > T< / em > .
< h3 class = fn > < a name = "TQDeepCopy-2" > < / a > TQDeepCopy::TQDeepCopy ( const T & t )
< / h3 >
< p > Constructs a < a href = "shclass.html#deep-copy" > deep copy< / a > of < em > t< / em > .
< h3 class = fn > < a name = "operator-T" > < / a > TQDeepCopy::operator T ()
< / h3 >
< p > Returns a < a href = "shclass.html#deep-copy" > deep copy< / a > of the encapsulated data.
< h3 class = fn > < a href = "ntqdeepcopy.html" > TQDeepCopy< / a > < T> & < a name = "operator-eq" > < / a > TQDeepCopy::operator= ( const T & t )
< / h3 >
< p > Assigns a < a href = "shclass.html#deep-copy" > deep copy< / a > of < em > t< / em > .
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