libs-base/Documentation/gsdoc/NSFunctions.gsdoc

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<?xml version="1.0"?>
<!DOCTYPE gsdoc PUBLIC "-//GNUstep//DTD gsdoc 0.6.6//EN" "http://www.gnustep.org/gsdoc-0_6_6.xml">
<gsdoc base="NSFunctions" up="Base">
<head>
<title>NSFunctions</title>
<author name="Richard Frith-Macdonald">
<email address="rfm@gnu.org"/>
<url url="http://www.gnustep.org/developers/whoiswho.html"/>
</author>
<author name="Nicola Pero">
<email address="n.pero@mi.flashnet.it"/>
<url url="http://www.gnustep.org/developers/whoiswho.html"/>
</author>
<version>$Revision$</version>
<date>$Date$</date>
</head>
<body>
<chapter>
<heading>Functions</heading>
<section>
<heading>Thread Function</heading>
<function name="GSCurrentThread" type="NSThread*">
<declared>Foundation/NSThread.h</declared>
<desc>
<p>
This function is a GNUstep extension. It pretty much
duplicates the functionality of [NSThread +currentThread]
but is more efficient and is used internally throughout
GNUstep.
</p>
<p>
Returns the current thread. Could perhaps return <code>nil</code>
if executing a thread that was started outside the GNUstep
environment and not registered (this should not happen in a
well-coded application).
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSRegisterCurrentThread" type="BOOL">
<declared>Foundation/NSThread.h</declared>
<desc>
<p>
This function is provided to let threads started by some other
software library register themselves to be used with the
GNUstep system. All such threads should call this function
before attempting to use any GNUstep objects.
</p>
<p>
Returns <code>YES</code> if the thread can be registered,
<code>NO</code> if it is already registered.
</p>
<p>
Sends out a <code>NSWillBecomeMultiThreadedNotification</code>
if the process was not already multithreaded.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSUnregisterCurrentThread" type="void">
<declared>Foundation/NSThread.h</declared>
<desc>
<p>
This function is provided to let threads started by some other
software library unregister themselves from the GNUstep threading
system.
</p>
<p>
Calling this function causes a
<code>NSThreadWillExitNotification</code>
to be sent out, and destroys the GNUstep NSThread object
associated with the thread.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
</section>
<section>
<heading>Debugging Functions - Counting Instances of Classes</heading>
<function name="GSDebugAllocationActive" type="BOOL">
<arg type="BOOL">active</arg>
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. It activates or
deactivates object allocation debugging. Returns the
previous state. You should call this function to activate
allocation debugging before using any of the functions
described in this section. Object allocation debugging
should not affect performance too much, and is very useful
as it allows you to monitor how many objects of each class
your application has allocated. See below for a detailed
description of the info you can get, and why it is useful.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSDebugAllocationCount" type="int">
<arg type="Class">c</arg>
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. Returns the number
of instances of the specified class which are currently
allocated. This number is very important to detect memory
leaks. If you notice that this number is constantly
increasing without apparent reason, it is very likely a
memory leak - you need to check that you are correctly
releasing objects of this class, otherwise when your
application runs for a long time, it will eventually
allocate so many objects as to eat up all your system's
memory ...
</p>
<p>
This function, like the ones below, returns the number of
objects allocated/released from the time when
GSDebugAllocationActive was first called. A negative
number means that in total, there are less objects of this
class allocated now than there were when you called
GSDebugAllocationActive; a positive one means there are
more.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSDebugAllocationPeak" type="int">
<arg type="Class">c</arg>
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. Returns the peak
number of instances of the specified class which have been
concurrently allocated. If this number is very high, it
means at some point in time you had a situation with a
huge number of objects of this class allocated - this is
an indicator that probably at some point in time your
application was using a lot of memory - so you might want
to investigate whether you can prevent this problem by
inserting autorelease pools in your application's
processing loops.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSDebugAllocationTotal" type="int">
<arg type="Class">c</arg>
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. Returns the total
number of instances of the specified class which have been
allocated - basically the number of times you have
allocated an object of this class. If this number is very
high, it means you are creating a lot of objects of this
class; even if you are releasing them correctly, you must
not forget that allocating and deallocating objects is
usually one of the slowest things you can do, so you might
want to consider whether you can reduce the number of
allocations and deallocations that you are doing - for
example, by recycling objects of this class, uniquing
them, and/or using some sort of flyweight pattern. It
might also be possible that you are unnecessarily creating
too many objects of this class. Well - of course some times
there is nothing you can do about it.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSDebugAllocationClassList" type="Class*">
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. Returns a NULL
terminated array listing all the classes for which
statistical information has been collected. Usually, you
call this function, and then loop on all the classes returned,
and for each one you get current, peak and total count by
using GSDebugAllocationCount, GSDebugAllocationPeak and
GSDebugAllocationTotal.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSDebugAllocationList" type="const char*">
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. Returns a newline
separated list of the classes which have instances
allocated, and the instance counts. If the 'changeFlag'
argument is YES then the list gives the number of
instances allocated/deallocated since the function was
last called. This function only returns the current count
of instances (not the peak or total count), but its output
is ready to be displayed or logged.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSDebugAllocationListAll" type="const char*">
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. Returns a newline
separated list of the classes which have had instances
allocated at any point, and the total count of the number
of instances allocated for each class. The difference with
GSDebugAllocationList is that this function returns also
classes which have no objects allocated at the moment, but
which had in the past.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
</section>
<section>
<heading>Debugging Functions - Tracking Instances of Classes</heading>
<function name="GSDebugAllocationActiveRecordingObjects" type="void">
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. It activates
tracking all allocated instances of the specified class
(passed as argument). This tracking can slow your
application down, so you should use it only when you are
into serious debugging. Usually, you will monitor your
application by using the functions GSDebugAllocationList
and similia (see above), which do not slow things down
much and return the number of allocated instances; when
(if) by studying the reports generated by these functions
you have found a leak of objects of a certain class, and
if you can't figure out how to fix it by looking at the
code, you can use this function to start tracking
allocated instances of that class, and the following one
can sometime allow you to list the leaked objects directly.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
<function name="GSDebugAllocationListRecordedObjects" type="NSArray *">
<arg type="Class">c</arg>
<declared>Foundation/NSDebug.h</declared>
<desc>
<p>
This function is a GNUstep extension. Returns an array
containing all the allocated objects of a certain class
which have been recorded (to start the recording, you need
to invoke GSDebugAllocationActiveRecordedObjects).
Presumably, you will immediately call -description on them
to find out the objects you are leaking. The objects are
returned in an array, so until the array is autoreleased,
the objects are not released.
</p>
</desc>
<standards><NotOpenStep/><NotMacOS-X/><GNUstep/></standards>
</function>
</section>
</chapter>
<chapter>
<heading>Types</heading>
<type name="NSRange">
<typespec>
struct { unsigned long location; unsigned long length; }
</typespec>
<declared>Foundation/NSRange.h</declared>
<desc>
<p>
The NSRange type is used to specify ranges of locations,
typically items in an array, characters in a string, and bytes
in a data object.
</p>
<p>
As 'boundary' or 'fencepost' errors are a particularly common
problem in programming, it is important that you understand
how an NSRange works.
</p>
<p>
An NSRange consists of a location and a length. The points
that are considered to lie in a range are the integers from
the location to the location plus the length, so the number
of points in a range is the length of the range plus one.<br />
However, if you consider these points like the marks on a
ruler, you can only store information <strong>between</strong>
points. So the number of items that can be stored in a range
is the length of the range.
</p>
</desc>
<standards><OpenStep/><MacOS-X/><GNUstep/></standards>
</type>
</chapter>
</body>
</gsdoc>