ScanBootImage (Jikes RVM API)

java.lang.Object
- org.jikesrvm.mm.mmtk.ScanBootImage

```
public class ScanBootImage
extends Object
```
Scan the boot image for references using the boot image reference map

Field Summary

Fields
Modifier and Type	Field and Description
`private static int`	`CHUNK_BYTES`
`private static int`	`codeIndex`
`private static boolean`	`DEBUG`
`private static boolean`	`FILTER`
`private static int`	`GUARD_REGION`
`private static int`	`lastOffset`
`private static int`	`LOG_CHUNK_BYTES`
`private static int`	`LONGENCODING_MASK`
`private static int`	`LONGENCODING_OFFSET_BYTES`
`private static int`	`longRefs`
`private static int`	`MAX_RUN`
`private static int`	`oldIndex`
`(package private) static int`	`refs`
`(package private) static int`	`roots`
`private static int`	`RUN_MASK`
`private static int`	`runRefs`
`private static int`	`shortRefs`
`private static int`	`startRefs`

Constructor Summary

Constructors
Constructor and Description

ScanBootImage()

Constructors
Constructor and Description
`ScanBootImage()`

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`private static void`	`addOffset(byte[] code, int offset)` Encode a given offset (distance from the start of the boot image) into the code array.
`private static void`	`checkReference(Address refaddr)` Check that a reference encountered during scanning is valid.
`private static Offset`	`decodeLongEncoding(Address cursor)` Decode a 4-byte encoding, taking a pointer to the first byte of the encoding, and returning the encoded value as an `Offset`
`private static int`	`decodeLongEncoding(byte[] code, int index)` Decode a 4-byte encoding, taking a byte array and an index into it and returning the encoded value as an integer
`private static int`	`encodeLongEncoding(byte[] code, int index, int value)` Encode a 4-byte encoding, taking a byte array, the current index into it, and the value to be encoded.
`static int`	`encodeRMap(byte[] bootImageRMap, byte[] referenceMap, int referenceMapLimit)` Take a bytemap encoding of all references in the boot image, and produce an encoded byte array.
`static void`	`encodingStats()` Print some basic statistics about the encoded references, for debugging purposes.
`private static int`	`getOffset(byte[] code, int index, int lastOffset)` Decode an encoded offset given the coded byte array, and index into it, and the current (last) offset.
`private static boolean`	`isAddressAligned(Address address)` Return true if the given address is address-aligned
`private static boolean`	`isAddressAligned(Offset offset)` Return true if the given offset is address-aligned
`private static void`	`processChunk(Address chunkStart, Address imageStart, Address mapStart, Address mapEnd, TraceLocal trace)` Process a chunk of encoded reference data, enqueuing each reference (optionally filtering them on whether they point outside the boot image).
`static void`	`scanBootImage(TraceLocal trace)` Scan the boot image for object references.

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

- Field Detail
  - DEBUG
```
private static final boolean DEBUG
```
    See Also:
    
    Constant Field Values
  - FILTER
```
private static final boolean FILTER
```
    See Also:
    
    Constant Field Values
  - LOG_CHUNK_BYTES
```
private static final int LOG_CHUNK_BYTES
```
    See Also:
    
    Constant Field Values
  - CHUNK_BYTES
```
private static final int CHUNK_BYTES
```
    See Also:
    
    Constant Field Values
  - LONGENCODING_MASK
```
private static final int LONGENCODING_MASK
```
    See Also:
    
    Constant Field Values
  - RUN_MASK
```
private static final int RUN_MASK
```
    See Also:
    
    Constant Field Values
  - MAX_RUN
```
private static final int MAX_RUN
```
    See Also:
    
    Constant Field Values
  - LONGENCODING_OFFSET_BYTES
```
private static final int LONGENCODING_OFFSET_BYTES
```
    See Also:
    
    Constant Field Values
  - GUARD_REGION
```
private static final int GUARD_REGION
```
    See Also:
    
    Constant Field Values
  - roots
```
static int roots
```
  - refs
```
static int refs
```
  - lastOffset
```
private static int lastOffset
```
  - oldIndex
```
private static int oldIndex
```
  - codeIndex
```
private static int codeIndex
```
  - shortRefs
```
private static int shortRefs
```
  - runRefs
```
private static int runRefs
```
  - longRefs
```
private static int longRefs
```
  - startRefs
```
private static int startRefs
```
- Constructor Detail
  - ScanBootImage
```
public ScanBootImage()
```
- Method Detail
  - scanBootImage
```
public static void scanBootImage(TraceLocal trace)
```
    Scan the boot image for object references. Executed by all GC threads in parallel, with each doing a portion of the boot image.
    
    Parameters:
    
    trace - The trace object to which the roots should be added
  - processChunk
```
private static void processChunk(Address chunkStart,
                                 Address imageStart,
                                 Address mapStart,
                                 Address mapEnd,
                                 TraceLocal trace)
```
    Process a chunk of encoded reference data, enqueuing each reference (optionally filtering them on whether they point outside the boot image).
    
    Parameters:
    
    chunkStart - The address of the first byte of encoded data
    
    imageStart - The address of the start of the boot image
    
    mapStart - The address of the start of the encoded reference map
    
    mapEnd - The address of the end of the encoded reference map
    
    trace - The TraceLocal into which roots should be enqueued.
  - checkReference
```
private static void checkReference(Address refaddr)
```
    Check that a reference encountered during scanning is valid. If the reference is invalid, dump stack and die.
    
    Parameters:
    
    refaddr - The address of the reference in question.
  - isAddressAligned
```
private static boolean isAddressAligned(Offset offset)
```
    Return true if the given offset is address-aligned
    
    Parameters:
    
    offset - the offset to be check
    
    Returns:
    
    true if the offset is address aligned.
  - isAddressAligned
```
private static boolean isAddressAligned(Address address)
```
    Return true if the given address is address-aligned
    
    Parameters:
    
    address - the address to be check
    
    Returns:
    
    true if the address is address aligned.
  - encodeRMap
```
public static int encodeRMap(byte[] bootImageRMap,
                             byte[] referenceMap,
                             int referenceMapLimit)
```
    Take a bytemap encoding of all references in the boot image, and produce an encoded byte array. Return the total length of the encoding.
    
    Parameters:
    
    bootImageRMap - space for the compressed reference map. The map is initially empty and will be filled during execution of this method.
    
    referenceMap - the (uncompressed) reference map for the bootimage
    
    referenceMapLimit - the highest index in the referenceMap that contains a reference
    
    Returns:
    
    the total length of the encoding
  - encodingStats
```
public static void encodingStats()
```
    Print some basic statistics about the encoded references, for debugging purposes.
  - addOffset
```
private static void addOffset(byte[] code,
                              int offset)
```
    Encode a given offset (distance from the start of the boot image) into the code array.
    
    Parameters:
    
    code - A byte array into which the value should be encoded
    
    offset - The offset value to be encoded
  - getOffset
```
private static int getOffset(byte[] code,
                             int index,
                             int lastOffset)
```
    Decode an encoded offset given the coded byte array, and index into it, and the current (last) offset.
    
    Parameters:
    
    code - A byte array containing the encoded value
    
    index - The offset into the code array from which to commence decoding
    
    lastOffset - The current (last) encoded offset
    
    Returns:
    
    The next offset, which is either explicitly encoded in the byte array or inferred from an encoded delta and the last offset.
  - decodeLongEncoding
```
private static Offset decodeLongEncoding(Address cursor)
```
    Decode a 4-byte encoding, taking a pointer to the first byte of the encoding, and returning the encoded value as an Offset
    
    Parameters:
    
    cursor - A pointer to the first byte of encoded data
    
    Returns:
    
    The encoded value as an Offset
  - decodeLongEncoding
```
private static int decodeLongEncoding(byte[] code,
                                      int index)
```
    Decode a 4-byte encoding, taking a byte array and an index into it and returning the encoded value as an integer
    
    Parameters:
    
    code - A byte array containing the encoded value
    
    index - The offset into the code array from which to commence decoding
    
    Returns:
    
    The encoded value as an integer
  - encodeLongEncoding
```
private static int encodeLongEncoding(byte[] code,
                                      int index,
                                      int value)
```
    Encode a 4-byte encoding, taking a byte array, the current index into it, and the value to be encoded.
    
    Parameters:
    
    code - A byte array to contain the encoded value
    
    index - The current offset into the code array
    
    value - The value to be encoded
    
    Returns:
    
    The updated index into the code array

Class ScanBootImage

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

DEBUG

FILTER

LOG_CHUNK_BYTES

CHUNK_BYTES

LONGENCODING_MASK

RUN_MASK

MAX_RUN

LONGENCODING_OFFSET_BYTES

GUARD_REGION

roots

refs

lastOffset

oldIndex

codeIndex

shortRefs

runRefs

longRefs

startRefs

Constructor Detail

ScanBootImage

Method Detail

scanBootImage

processChunk

checkReference

isAddressAligned

isAddressAligned

encodeRMap

encodingStats

addOffset

getOffset

decodeLongEncoding

decodeLongEncoding

encodeLongEncoding