JavaHeaderConstants (Jikes RVM API)

java.lang.Object
- org.jikesrvm.objectmodel.JavaHeaderConstants

public final class JavaHeaderConstants
extends Object

Constants for the JavaHeader.

See Also:: ObjectModel

Field Summary

Fields
Modifier and Type	Field and Description
`static boolean`	`ADDRESS_BASED_HASHING` This object model supports two schemes for hashcodes: (1) a 10 bit hash code in the object header (2) use the address of the object as its hashcode.
`static int`	`ALIGNMENT_MASK`
`static int`	`ALIGNMENT_VALUE`
`static boolean`	`ALLOWS_LINEAR_SCAN` Can we perform a linear scan?
`static Offset`	`ARRAY_BASE_OFFSET` Offset of first element of an array
`static int`	`ARRAY_LENGTH_BYTES` Number of bytes used to store the array length.
`static Offset`	`ARRAY_LENGTH_OFFSET` Offset of array length from object reference
`static boolean`	`DYNAMIC_HASH_OFFSET` Does this object model place the hash for a hashed and moved object after the data (at a dynamic offset)
`static Offset`	`FIELD_ZERO_OFFSET` Offset of the first field from object reference
`static boolean`	`FORWARDING_PTR_OVERLAYS_TIB` Does this object model use the same header word to contain the TIB and a forwarding pointer?
`static int`	`GC_HEADER_BYTES` Number of bytes used by the GC Header
`static Offset`	`GC_HEADER_OFFSET` Offset of the garbage collection header from the object reference
`static Word`	`HASH_STATE_HASHED`
`static Word`	`HASH_STATE_HASHED_AND_MOVED`
`static Word`	`HASH_STATE_MASK`
`static Word`	`HASH_STATE_UNHASHED`
`static int`	`HASHCODE_BYTES`
`static Offset`	`HASHCODE_OFFSET`
`static int`	`JAVA_HEADER_BYTES` Number of bytes used by the Java Header
`static Offset`	`JAVA_HEADER_OFFSET` Offset of the Java header from the object reference
`static int`	`LOG_MIN_ALIGNMENT`
`static int`	`MISC_HEADER_BYTES` Number of bytes used by the miscellaneous header
`static Offset`	`MISC_HEADER_OFFSET` Offset of the miscellaneous header from the object reference
`static int`	`NUM_AVAILABLE_BITS` How many bits in the header are available for the GC and MISC headers?
`static int`	`OTHER_HEADER_BYTES` Size of GC and miscellaneous headers
`static boolean`	`SEGREGATE_ARRAYS_FOR_LINEAR_SCAN` Do we need to segregate arrays and scalars to do a linear scan?
`static int`	`STATUS_BYTES` Number of bytes indicating an object's status
`static int`	`TIB_BYTES` Number of bytes in object's TIB pointer

Constructor Summary

Constructors
Constructor and Description

JavaHeaderConstants()

Constructors
Constructor and Description
`JavaHeaderConstants()`

Method Summary
- Methods inherited from class java.lang.Object
  clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - TIB_BYTES
```
public static final int TIB_BYTES
```
    Number of bytes in object's TIB pointer
    
    See Also:
    
    Constant Field Values
  - STATUS_BYTES
```
public static final int STATUS_BYTES
```
    Number of bytes indicating an object's status
    
    See Also:
    
    Constant Field Values
  - ALIGNMENT_MASK
```
public static final int ALIGNMENT_MASK
```
    See Also:
    
    Constant Field Values
  - ALIGNMENT_VALUE
```
public static final int ALIGNMENT_VALUE
```
    See Also:
    
    Constant Field Values
  - LOG_MIN_ALIGNMENT
```
public static final int LOG_MIN_ALIGNMENT
```
    See Also:
    
    Constant Field Values
  - ARRAY_LENGTH_BYTES
```
public static final int ARRAY_LENGTH_BYTES
```
    Number of bytes used to store the array length. We use 64 bits for the length on a 64 bit architecture as this makes the other words 8-byte aligned, and the header has to be 8-byte aligned.
    
    See Also:
    
    Constant Field Values
  - JAVA_HEADER_BYTES
```
public static final int JAVA_HEADER_BYTES
```
    Number of bytes used by the Java Header
    
    See Also:
    
    Constant Field Values
  - GC_HEADER_BYTES
```
public static final int GC_HEADER_BYTES
```
    Number of bytes used by the GC Header
  - MISC_HEADER_BYTES
```
public static final int MISC_HEADER_BYTES
```
    Number of bytes used by the miscellaneous header
  - OTHER_HEADER_BYTES
```
public static final int OTHER_HEADER_BYTES
```
    Size of GC and miscellaneous headers
  - ARRAY_LENGTH_OFFSET
```
public static final Offset ARRAY_LENGTH_OFFSET
```
    Offset of array length from object reference
  - FIELD_ZERO_OFFSET
```
public static final Offset FIELD_ZERO_OFFSET
```
    Offset of the first field from object reference
  - JAVA_HEADER_OFFSET
```
public static final Offset JAVA_HEADER_OFFSET
```
    Offset of the Java header from the object reference
  - MISC_HEADER_OFFSET
```
public static final Offset MISC_HEADER_OFFSET
```
    Offset of the miscellaneous header from the object reference
  - GC_HEADER_OFFSET
```
public static final Offset GC_HEADER_OFFSET
```
    Offset of the garbage collection header from the object reference
  - ARRAY_BASE_OFFSET
```
public static final Offset ARRAY_BASE_OFFSET
```
    Offset of first element of an array
  - ADDRESS_BASED_HASHING
```
public static final boolean ADDRESS_BASED_HASHING
```
    This object model supports two schemes for hashcodes: (1) a 10 bit hash code in the object header (2) use the address of the object as its hashcode. In a copying collector, this forces us to add a word to copied objects that have had their hashcode taken.
  - NUM_AVAILABLE_BITS
```
public static final int NUM_AVAILABLE_BITS
```
    How many bits in the header are available for the GC and MISC headers?
  - FORWARDING_PTR_OVERLAYS_TIB
```
public static final boolean FORWARDING_PTR_OVERLAYS_TIB
```
    Does this object model use the same header word to contain the TIB and a forwarding pointer?
    
    See Also:
    
    Constant Field Values
  - DYNAMIC_HASH_OFFSET
```
public static final boolean DYNAMIC_HASH_OFFSET
```
    Does this object model place the hash for a hashed and moved object after the data (at a dynamic offset)
  - ALLOWS_LINEAR_SCAN
```
public static final boolean ALLOWS_LINEAR_SCAN
```
    Can we perform a linear scan?
    
    See Also:
    
    Constant Field Values
  - SEGREGATE_ARRAYS_FOR_LINEAR_SCAN
```
public static final boolean SEGREGATE_ARRAYS_FOR_LINEAR_SCAN
```
    Do we need to segregate arrays and scalars to do a linear scan?
    
    See Also:
    
    Constant Field Values
  - HASH_STATE_UNHASHED
```
public static final Word HASH_STATE_UNHASHED
```
  - HASH_STATE_HASHED
```
public static final Word HASH_STATE_HASHED
```
  - HASH_STATE_HASHED_AND_MOVED
```
public static final Word HASH_STATE_HASHED_AND_MOVED
```
  - HASH_STATE_MASK
```
public static final Word HASH_STATE_MASK
```
  - HASHCODE_BYTES
```
public static final int HASHCODE_BYTES
```
    See Also:
    
    Constant Field Values
  - HASHCODE_OFFSET
```
public static final Offset HASHCODE_OFFSET
```
- Constructor Detail
  - JavaHeaderConstants
```
public JavaHeaderConstants()
```

Class JavaHeaderConstants

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

TIB_BYTES

STATUS_BYTES

ALIGNMENT_MASK

ALIGNMENT_VALUE

LOG_MIN_ALIGNMENT

ARRAY_LENGTH_BYTES

JAVA_HEADER_BYTES

GC_HEADER_BYTES

MISC_HEADER_BYTES

OTHER_HEADER_BYTES

ARRAY_LENGTH_OFFSET

FIELD_ZERO_OFFSET

JAVA_HEADER_OFFSET

MISC_HEADER_OFFSET

GC_HEADER_OFFSET

ARRAY_BASE_OFFSET

ADDRESS_BASED_HASHING

NUM_AVAILABLE_BITS

FORWARDING_PTR_OVERLAYS_TIB

DYNAMIC_HASH_OFFSET

ALLOWS_LINEAR_SCAN

SEGREGATE_ARRAYS_FOR_LINEAR_SCAN

HASH_STATE_UNHASHED

HASH_STATE_HASHED

HASH_STATE_HASHED_AND_MOVED

HASH_STATE_MASK

HASHCODE_BYTES

HASHCODE_OFFSET

Constructor Detail

JavaHeaderConstants