Qore Programming Language  0.8.11
 All Classes Files Functions Variables Typedefs Enumerations Enumerator Macros Groups Pages
Public Member Functions | List of all members
QoreTypeSafeReferenceHelper Class Reference

helper class to manage variable references passed to functions and class methods, stack only, cannot be dynamically allocated More...

#include <QoreTypeSafeReferenceHelper.h>

Public Member Functions

DLLEXPORT QoreTypeSafeReferenceHelper (const ReferenceNode *ref, ExceptionSink *xsink)
 initializes the object and tries to get the pointer to the pointer of the lvalue expression target More...
 
DLLEXPORT QoreTypeSafeReferenceHelper (const ReferenceNode *ref, AutoVLock &vl, ExceptionSink *xsink)
 initializes the object and tries to get the pointer to the pointer of the lvalue expression target More...
 
DLLEXPORT ~QoreTypeSafeReferenceHelper ()
 destroys the object
 
DLLEXPORT int assign (AbstractQoreNode *val)
 assigns a value to the reference, assumes the reference is valid More...
 
DLLEXPORT int assign (AbstractQoreNode *val, ExceptionSink *xsink)
 assigns a value to the reference, assumes the reference is valid More...
 
DLLEXPORT int assignBigInt (int64 v)
 assigns an integer value to the reference More...
 
DLLEXPORT int assignFloat (double v)
 assigns an integer value to the reference More...
 
DLLEXPORT qore_type_t getType () const
 returns the type of the reference's value More...
 
DLLEXPORT const char * getTypeName () const
 returns the type name of the reference's value More...
 
DLLEXPORT AbstractQoreNodegetUnique (ExceptionSink *xsink)
 returns a pointer to the value with a unique reference count (so it can be updated in place), assumes the reference is valid More...
 
DLLEXPORT const AbstractQoreNodegetValue () const
 returns a constant pointer to the reference's value More...
 
DLLEXPORT operator bool () const
 returns true if the reference is valid, false if not More...
 
DLLEXPORT void swap (QoreTypeSafeReferenceHelper &other)
 swaps the values of two references
 

Detailed Description

helper class to manage variable references passed to functions and class methods, stack only, cannot be dynamically allocated

Takes care of safely accessing ReferenceNode objects, for example when they are passed as arguments to a builtin function or method. Locks are automatically acquired in the constructor if necessary and released in the destructor. The constructor could raise a Qore-language exception if there is a deadlock acquiring any locks to access the ReferenceNode's value as given by the lvalue expression, so the object should be checked for this state right after the constructor as in the following example:

const AbstractQoreNode *p = get_param(params, 0);
if (p && p->getType() == NT_REFERENCE) {
const ReferenceNode *r = reinterpret_cast<const ReferenceNode *>(p);
// a deadlock exception occurred accessing the reference's value pointer
if (!ref)
return 0;
// more code to access the reference
}

Constructor & Destructor Documentation

DLLEXPORT QoreTypeSafeReferenceHelper::QoreTypeSafeReferenceHelper ( const ReferenceNode ref,
ExceptionSink xsink 
)

initializes the object and tries to get the pointer to the pointer of the lvalue expression target

Parameters
refthe ReferenceNode to use
xsinkQore-language exceptions raised will be added here (for example, a deadlock accessing the object)
DLLEXPORT QoreTypeSafeReferenceHelper::QoreTypeSafeReferenceHelper ( const ReferenceNode ref,
AutoVLock vl,
ExceptionSink xsink 
)

initializes the object and tries to get the pointer to the pointer of the lvalue expression target

Parameters
refthe ReferenceNode to use
vlthis argument is ignored in this deprecated version of the function
xsinkQore-language exceptions raised will be added here (for example, a deadlock accessing the object)
Deprecated:
the AutoVLock argument is ignored in this deprecated version

Member Function Documentation

DLLEXPORT int QoreTypeSafeReferenceHelper::assign ( AbstractQoreNode val)

assigns a value to the reference, assumes the reference is valid

Parameters
valthe value to assign (must be already referenced for the assignment)
Returns
0 if there was no error and the variable was assigned, -1 if a Qore-language exception occured dereferencing the current value, in this case no assignment was made and the reference count for val is dereferenced automatically by the QoreTypeSafeReferenceHelper object
Note
you must check that the reference is valid before calling this function
// if the reference is not valid, then return
if (!rh)
return;
// make the assignment (if the assignment fails, the value will be dereferenced automatically)
rh.assign(val->refSelf());
DLLEXPORT int QoreTypeSafeReferenceHelper::assign ( AbstractQoreNode val,
ExceptionSink xsink 
)

assigns a value to the reference, assumes the reference is valid

Parameters
valthe value to assign (must be already referenced for the assignment)
xsinkthis argument is ignored; the ExceptionSink argument used in the constructor is used instead
Returns
0 if there was no error and the variable was assigned, -1 if a Qore-language exception occured dereferencing the current value, in this case no assignment was made and the reference count for val is dereferenced automatically by the QoreTypeSafeReferenceHelper object
Note
you must check that the reference is valid before calling this function
// if the reference is not valid, then return
if (!rh)
return;
// make the assignment (if the assignment fails, the value will be dereferenced automatically)
rh.assign(val->refSelf());
Deprecated:
use QoreTypeSafeReferenceHelper::assign(AbstractQoreNode *val) instead
DLLEXPORT int QoreTypeSafeReferenceHelper::assignBigInt ( int64  v)

assigns an integer value to the reference

Parameters
vthe value to assign
Returns
0 if there was no error and the variable was assigned, -1 if a Qore-language exception occured dereferencing the current value, in this case no assignment was made
DLLEXPORT int QoreTypeSafeReferenceHelper::assignFloat ( double  v)

assigns an integer value to the reference

Parameters
vthe value to assign
Returns
0 if there was no error and the variable was assigned, -1 if a Qore-language exception occured dereferencing the current value, in this case no assignment was made
DLLEXPORT qore_type_t QoreTypeSafeReferenceHelper::getType ( ) const

returns the type of the reference's value

Returns
the type of the reference's value
DLLEXPORT const char* QoreTypeSafeReferenceHelper::getTypeName ( ) const

returns the type name of the reference's value

Returns
the type name of the reference's value
DLLEXPORT AbstractQoreNode* QoreTypeSafeReferenceHelper::getUnique ( ExceptionSink xsink)

returns a pointer to the value with a unique reference count (so it can be updated in place), assumes the reference is valid

Parameters
xsinkrequired for the call to AbstractQoreNode::deref()
Returns
a pointer to the reference's value with a unique reference count (so it can be modified), or 0 if the value was 0 to start with or if a Qore-language exception was raised
Note
you must check that the reference is valid before calling this function
take care to only call this function on types where the AbstractQoreNode::realCopy() function has a valid implementation (on all value types suitable for in-place modification this function has a valid implementation), as in debugging builds other types will abort(); in non-debugging builds this function will simply do nothing
// if the reference is not valid, then return
if (!rh)
return;
// get the unique value
AbstractQoreNode *val = rh.getUnique(xsink);
// if a Qore-language exception was raised, then return
if (*xsink)
return;
DLLEXPORT const AbstractQoreNode* QoreTypeSafeReferenceHelper::getValue ( ) const

returns a constant pointer to the reference's value

Returns
the value of the lvalue reference (may be 0)
DLLEXPORT QoreTypeSafeReferenceHelper::operator bool ( ) const

returns true if the reference is valid, false if not

false will only be returned if a Qore-language exception was raised in the constructor


The documentation for this class was generated from the following file: