com.sun.squawk
Class Address

java.lang.Object
  com.sun.squawk.Address

public final class Address
extends Object

The Address class is used to abstract machine addresses. It is used instead of 'int' or 'Object' for coding clarity and machine-portability (it can map to 32 bit and 64 bit integral types).

Variables of type Address will never be updated if they correspond with an object that may be moved by the garbage collector. As such, they should never appear in code that may have a collection occur in between the definition and use of the variable. In general, variables of type address should not be used outside of the garbage collector.

This class is known specially by the translator as a SQUAWKPRIMITIVE and programming with it requires adhering to the restrictions implied by this attribute. Some of these constraints are imposed to keep the job of the translator simple. All of these constraints are currently enforced by the translator. The constraints are:

• A local variable slot allocated by javac for a Squawk primitive variable must never be used for a value of any other type (including a different Squawk primitive type). This is required as the translator cannot currently de-multiplex reference type slots into disjoint typed slots. This restriction on javac is achieved by declaring all Squawk primitive local variables at the outer most scope (as javac using lexical based scoping for register allocation liveness).
• A Squawk primitive value of type T cannot be assigned to or compared with values of any other type (including null) than T.
• A Squawk primitive value of type T cannot be passed as a parameter values of any other type than T. For example, you cannot call T.toString(), or String.valueOf(T). The methods of the classes NativeUnsafe and GC have a special permission to allow Squawk primitive values to passed in place of parameters of type Object.

Only the public methods of this class which do not override any of the methods in java.lang.Object will be available in a non-hosted environment. The translator replaces any calls to these methods to native method calls.

This mechanism was largely inspired by the VM_Address class in the Jikes RVM.

fromPrimitive

public static Address fromPrimitive(int value)
                             throws NativePragma

Casts a word expressed as the appropriate Java primitive type for the platform (i.e. int or long) into a value of type Address.

Parameters:

value - an address expressed as an int or long

Returns:

the canonical Address instance for value

Throws:

NativePragma

fromObject

public static Address fromObject(Object object)
                          throws NativePragma

Casts an object reference to an address.

Parameters:

object - the object reference to cast

Returns:

the object reference as an address

Throws:

NativePragma

zero

public static Address zero()
                    throws NativePragma

Gets the canonical Address representation of null.

Returns:

the canonical Address representation of null

Throws:

NativePragma

max

public static Address max()
                   throws NativePragma

Gets the largest possible machine address.

Returns:

the largest possible machine address

Throws:

NativePragma

toObject

public Object toObject()
                throws NativePragma

Casts this address to an object reference.

Returns:

this address as an object reference

Throws:

NativePragma

toUWord

public UWord toUWord()
              throws NativePragma

Casts this address to a UWord.

Returns:

this address as a UWord

Throws:

NativePragma

add

public Address add(int offset)
            throws NativePragma

Adds a 32 bit offset to this address and return the resulting address.

Parameters:

offset - the offset to add

Returns:

the result of adding offset to this address

Throws:

NativePragma

sub

public Address sub(int offset)
            throws NativePragma

Subtracts a 32 bit offset to this address and return the resulting address.

Parameters:

offset - the offset to subract

Returns:

the result of subtracting offset to this address

Throws:

NativePragma

addOffset

public Address addOffset(Offset offset)
                  throws NativePragma

Adds a 32 or 64 bit offset to this address and return the resulting address.

Parameters:

offset - the offset to add

Returns:

the result of adding offset to this address

Throws:

NativePragma

subOffset

public Address subOffset(Offset offset)
                  throws NativePragma

Subtracts a 32 or 64 bit offset to this address and return the resulting address.

Parameters:

offset - the offset to subract

Returns:

the result of subtracting offset to this address

Throws:

NativePragma

or

public Address or(UWord word)
           throws NativePragma

Logically OR a word with this address.

Parameters:

word - the word to OR this address with

Returns:

the result of the OR operation

Throws:

NativePragma

and

public Address and(UWord word)
            throws NativePragma

Logically AND a word with this address.

Parameters:

word - the word to AND this address with

Returns:

the result of the AND operation

Throws:

NativePragma

diff

public Offset diff(Address address2)
            throws NativePragma

Calculates the offset between this address an another address.

Parameters:

address2 - the address to compare this address with

Returns:

the offset that must be applied to this address to get address2

Throws:

NativePragma

isZero

public boolean isZero()
               throws NativePragma

Determines if this address is null.

Returns:

true if this address is null

Throws:

NativePragma

isMax

public boolean isMax()
              throws NativePragma

Determines if this address is equals to max.

Returns:

true if this address is equals to max

Throws:

NativePragma

eq

public boolean eq(Address address2)
           throws NativePragma

Determines if this address is equal to a given address.

Parameters:

address2 - the address to compare this address against

Returns:

true if this address is equal to address2

Throws:

NativePragma

ne

public boolean ne(Address address2)
           throws NativePragma

Determines if this address is not equal to a given address.

Parameters:

address2 - the address to compare this address against

Returns:

true if this address is not equal to address2

Throws:

NativePragma

lo

public boolean lo(Address address2)
           throws NativePragma

Determines if this address is lower than a given address.

Parameters:

address2 - the address to compare this address against

Returns:

true if this address is lower than or equals to address2

Throws:

NativePragma

loeq

public boolean loeq(Address address2)
             throws NativePragma

Determines if this address is lower than or equal to a given address.

Parameters:

address2 - the address to compare this address against

Returns:

true if this address is lower than or equal to address2

Throws:

NativePragma

hi

public boolean hi(Address address2)
           throws NativePragma

Determines if this address is higher than a given address.

Parameters:

address2 - the address to compare this address against

Returns:

true if this address is higher than address2

Throws:

NativePragma

hieq

public boolean hieq(Address address2)
             throws NativePragma

Determines if this address is higher than or equal to a given address.

Parameters:

address2 - the address to compare this address against

Returns:

true if this address is higher than or equal to address2

Throws:

NativePragma

roundUp

public Address roundUp(int alignment)
                throws NativePragma

Rounds this address up based on a given alignment.

Parameters:

alignment - this address is rounded up to be a multiple of this value

Returns:

the new address

Throws:

NativePragma

roundUpToWord

public Address roundUpToWord()
                      throws NativePragma

Rounds this address up to a machine word boundary.

Returns:

the new address

Throws:

NativePragma

roundDown

public Address roundDown(int alignment)
                  throws NativePragma

Rounds this address down based on a given alignment.

Parameters:

alignment - this address is rounded down to be a multiple of this value

Returns:

the new address

Throws:

NativePragma

roundDownToWord

public Address roundDownToWord()
                        throws NativePragma

Rounds this address down to a machine word boundary.

Returns:

the new address

Throws:

NativePragma

hashCode

public int hashCode()
             throws HostedPragma

Gets a hashcode value for this address which is just the address itself.

Overrides:

hashCode in class Object

Returns:

the value of this address

Throws:

HostedPragma

See Also:

Object.equals(java.lang.Object), Hashtable

toString

public String toString()
                throws HostedPragma

Gets a string representation of this address.

Overrides:

toString in class Object

Returns:

String

Throws:

HostedPragma