com.sun.squawk
Class GC

java.lang.Object
  com.sun.squawk.GC

All Implemented Interfaces:

GlobalStaticFields

public class GC
extends Object
implements GlobalStaticFields

Pure static class that handles object creation and GC control and monitoring. The particular GC implementation used is a subclass of GarbageCollector. Many of the "public" methods of this class are actually "suite-private". See the file "squawk.library.properties" for the list of exported methods.

getCollector

public static GarbageCollector getCollector()

Gets a reference to the installed collector.

Returns:

a reference to the installed collector

roundUpToWord

public static int roundUpToWord(int value)
                         throws ForceInlinedPragma

Rounds up a 32 bit value to the next word boundry.

Parameters:

value - the value to round up

Returns:

the result

Throws:

ForceInlinedPragma

getBytesAllocatedSinceLastGC

public static int getBytesAllocatedSinceLastGC()

Get the number of bytes allocated since the last GC. May be inaccurate during a copyObjectGraph operation.

Returns:

bytes

inRam

public static boolean inRam(Object object)
                     throws ForceInlinedPragma

Determines if a given object is in RAM.

Parameters:

object - the object to test

Returns:

true if object is an instance in RAM

Throws:

ForceInlinedPragma

inRam

public static boolean inRam(Address start,
                            Address end)

Determines if any part of the range is in RAM.

Parameters:

start -

end -

Returns:

true if any part of the range start..end overlaps with the heap

setGCEnabled

public static boolean setGCEnabled(boolean newState)

Enable or disable the garbage collector.

Parameters:

newState - the new abled/disabled state of the garbage collector

Returns:

the garbage collector's state before this call

isGCEnabled

public static boolean isGCEnabled()

Is Garnage collection enabled?

Returns:

true if GC enabled.

isSafeToSwitchThreads

public static boolean isSafeToSwitchThreads()

Test to see if this is a safe time to switch threads.

Returns:

true if it is

calculateOopMapSizeInBytes

public static int calculateOopMapSizeInBytes(int size)

Calculates the size (in bytes) of an oop map that will have a bit for every word in a memory of a given size.

Parameters:

size - the size (in bytes) of the memory that the oop map will describe

Returns:

the size (in bytes) of an oop map that will have a bit for every word in a memory region of size size bytes

getKlass

public static Klass getKlass(Object object)
                      throws ForceInlinedPragma

Get the class of an object.

Parameters:

object - the object

Returns:

its class

Throws:

ForceInlinedPragma

getArrayLength

public static int getArrayLength(Object array)
                          throws ForceInlinedPragma

Get the length of an array.

Parameters:

array - the array

Returns:

the length in elements of the array

Throws:

ForceInlinedPragma

arraycopy

public static void arraycopy(Object src,
                             int srcPos,
                             Object dst,
                             int dstPos,
                             int lth)

Copy data from one array to another.

Parameters:

src - the source array

srcPos - the start position in the source array

dst - the destination array

dstPos - the start position in the destination array

lth - number of elements to copy

stringcopy

public static void stringcopy(Object src,
                              int srcPos,
                              Object dst,
                              int dstPos,
                              int lth)

Copy data from one string to another.

Parameters:

src - the source string

srcPos - the start position in the source string

dst - the destination string

dstPos - the start position in the destination string

lth - number of characters to copy

makeEightBitString

public static String makeEightBitString(Object oop)

Change the type of the given object to com.sun.squawk.StringOfBytes.

Parameters:

oop - the object

Returns:

the converted object

makeSixteenBitString

public static String makeSixteenBitString(Object oop)

Change the type of the given object to java.lang.String.

Parameters:

oop - the object

Returns:

the converted object

getHashCode

public static int getHashCode(Object object)

Get the hashcode for an object.

Parameters:

object - the object the hashcode is needed for.

Returns:

the hashcode

freeMemory

public static long freeMemory()

Returns the amount of free memory in the system. Calling the gc method may result in increasing the value returned by freeMemory.

Returns:

an approximation to the total amount of memory currently available for future allocated objects, measured in bytes.

totalMemory

public static long totalMemory()

Returns the total amount of RAM memory in the Squawk Virtual Machine. The value returned by this method may vary over time, depending on the host environment.

Note that the amount of memory required to hold an object of any given type may be implementation-dependent.

Returns:

the total amount of memory currently available for current and future objects, measured in bytes.

getPartialCount

public static int getPartialCount()

Returns the number of partial-heap collections.

Returns:

the count of partial-heap collections.

getFullCount

public static int getFullCount()

Returns the number of full-heap collections.

Returns:

the count of full-heap collections.

getTotalCount

public static int getTotalCount()

Returns the total number of garbage collections that have been performed by the VM.

Returns:

the total count of collections.

initHeapStats

public static void initHeapStats()

Pre-create all data structures used in heap stats, so heap walking won't allocate more memory.

allObjectsFromDo

public static void allObjectsFromDo(Object startObj,
                                    DoBlock doBlock)

Perform doBlock with all objects starting from startObject.

Parameters:

startObj - the object to start walking from , or null

doBlock - callback to perform on each object

printHeapStats

public static void printHeapStats(Object startObj,
                                  boolean printInstances)

Do actual heap walk, from start object, or whole heap is startObj is null. Count how many instances, and how many bytes are used, by all objects that are the same aage or youngre than startObj. Print out statistics of each class that has at least one instance in the set found in the heap walk. Statistics are NOT sorted.

Parameters:

startObj - the object to start walking from , or null

printInstances - if true, print information about each object before printing statistics