Package ghidra.program.model.data

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

    • Constructor Summary

      Constructors 
      Constructor Description
      BitOffsetComparator​(boolean bigEndian)  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      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

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

      • INSTANCE_BE

        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