Package ghidra.program.model.data

Class Structure.BitOffsetComparator

java.lang.Object

ghidra.program.model.data.Structure.BitOffsetComparator

All Implemented Interfaces:

java.util.Comparator<java.lang.Object>

Enclosing interface:

Structure

public static class Structure.BitOffsetComparator
extends java.lang.Object
implements java.util.Comparator<java.lang.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

Change	Modifier and Type	Field	Description
NEW	static java.util.Comparator<java.lang.Object>	INSTANCE_BE
NEW	static java.util.Comparator<java.lang.Object>	INSTANCE_LE

Constructor Summary

Constructors

Change	Constructor	Description
BitOffsetComparator(boolean bigEndian)

Method Summary

Change	Modifier and Type	Method	Description
	int	compare(java.lang.Object o1, java.lang.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 Detail

INSTANCE_LE NEW

public static final java.util.Comparator<java.lang.Object> INSTANCE_LE

INSTANCE_BE NEW

public static final java.util.Comparator<java.lang.Object> INSTANCE_BE

Constructor Detail

BitOffsetComparator

public BitOffsetComparator(boolean bigEndian)

Method Detail

compare

public int compare(java.lang.Object o1,
                   java.lang.Object o2)

Specified by:

compare in interface java.util.Comparator<java.lang.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 endianess 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