Package ghidra.program.model.data

Class Structure.BitOffsetComparator

java.lang.Object

ghidra.program.model.data.Structure.BitOffsetComparator

All Implemented Interfaces:

Comparator<Object>

Enclosing interface:

Structure

public static class Structure.BitOffsetComparator
extends Object
implements Comparator<Object>

BitOffsetComparator provides ability to compare an normalized bit offset (see getNormalizedBitfieldOffset(int, int, int, int, boolean)) with a DataTypeComponent object. The offset will be considered equal (0) if the component contains the offset. A normalized component bit numbering is used to establish the footprint of each component with an ordinal-based ordering (assumes specific LE/BE allocation rules). Bit offsets for this comparator number the first allocated bit of the structure as 0 and the last allocated bit of the structure as (8 * structLength) - 1. For big-endian bitfields the msb of the bitfield will be assigned the lower bit-number (assumes msb-allocated-first), while little-endian will perform similar numbering assuming byte-swap and bit-reversal of the storage unit (assumes lsb-allocated-first). Both cases result in a normalized view where normalized bit-0 is allocated first.

 
 Example:
    
 Big-Endian (normalized view):
    | . . . . . . . 7 | 8 9 . . . . . . |
    |<--------------------------------->| storage-size (2-bytes)
                        |<--------------| bit-offset (6, lsb position within storage unit)
                    |<--->|               bit-size (3)
                        
 Little-Endian (normalized view, w/ storage byte-swap and bit-reversal):
    | . . . . . . 6 7 | 8 . . . . . . . |
    |------------>|                       bit-offset (6, lsb position within storage unit)
                  |<--->|                 bit-size (3)
 
 

Field Summary

Fields

Modifier and Type	Field	Description
static final Comparator<Object>	INSTANCE_BE
static final Comparator<Object>	INSTANCE_LE

Constructor Summary

Constructors

Constructor	Description
BitOffsetComparator(boolean bigEndian)

Method Summary

Modifier and Type	Method	Description
int	compare(Object o1, Object o2)
static int	getNormalizedBitfieldOffset(int byteOffset, int storageSize, int effectiveBitSize, int bitOffset, boolean bigEndian)	Compute the normalized bit offset of a bitfield relative to the start of a structure.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Comparator

equals, reversed, thenComparing, thenComparing, thenComparing, thenComparingDouble, thenComparingInt, thenComparingLong

Field Details

INSTANCE_LE

public static final Comparator<Object> INSTANCE_LE

INSTANCE_BE

public static final Comparator<Object> INSTANCE_BE

Constructor Details

BitOffsetComparator

public BitOffsetComparator(boolean bigEndian)

Method Details

compare

public int compare(Object o1,
 Object o2)

Specified by:

compare in interface Comparator<Object>

getNormalizedBitfieldOffset

public static int getNormalizedBitfieldOffset(int byteOffset,
 int storageSize,
 int effectiveBitSize,
 int bitOffset,
 boolean bigEndian)

Compute the normalized bit offset of a bitfield relative to the start of a structure. NOTE: This implementation currently relies only on endianness to dictate bit allocation ordering. If future support is added for alternate bitfield packing, this implementation will require modification.

Parameters:

byteOffset - byte offset within structure of storage unit

storageSize - storage unit size (i.e., component length)

effectiveBitSize - size of bitfield in bits

bitOffset - left shift amount for bitfield based upon a big-endian view of the storage unit

bigEndian - true if big-endian packing applies

Returns:

normalized bit-offset