Image::ExifTool::Fixup(3pm)

NAME
Image::ExifTool::Fixup - Utility to handle pointer fixups

SYNOPSIS
    use Image::ExifTool::Fixup;

    $fixup = Image::ExifTool::Fixup->new;

    # add a new fixup to a pointer at the specified offset in data
    $fixup->AddFixup($offset);

    # add a new Fixup object to the tree
    $fixup->AddFixup($subFixup);

    $fixup->{Start} += $shift1;   # shift pointer offsets and values

    $fixup->{Shift} += $shift2;   # shift pointer values only

    # recursively apply fixups to the specified data
    $fixup->ApplyFixups(\$data);

    $fixup->Dump();               # dump debugging information

    $fixup->IsEmpty();            # return true if no offsets to fix

DESCRIPTION
This module contains the code to keep track of pointers in memory and to shift these pointers as required. It is used by ExifTool to maintain the pointers in image file directories (IFD's).

NOTES
Keeps track of pointers with different byte ordering, and relies on Image::ExifTool::GetByteOrder() to determine the current byte ordering when adding new pointers to a fixup.

Maintains a hierarchical list of fixups so that the whole hierarchy can be shifted by a simple shift at the base. Hierarchy is collapsed to a linear list when ApplyFixups() is called.

AUTHOR
Copyright 2003-2026, Phil Harvey (philharvey66 at gmail.com)

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO
Image::ExifTool(3pm)