=== Parent File Block (`PRNT`)

The parent file block provides metadata required to locate the image file from which the current image is derived.
Its primary purpose is to enable hierarchical composition, where non-written sectors in the current image are transparently resolved by referencing their counterparts in the parent image.

All sectors marked as unwritten must be read from the associated parent image, ensuring data completeness and consistency across derivative images.

==== Structure Definition

[source,c]
/* Undefined */

==== Field Descriptions

[cols="2,2,2,6",options="header"]
|===
|Type
|Size
|Name
|Description

|uint32_t
|4 bytes
|identifier
|The parent block identifier, always `PRNT`

|uint32_t
|4 bytes
|length
|The length in bytes of the data following this header.

|GUID
|16 bytes
|parentId
|The unique identifier of the parent.

|uint16_t
|2 bytes
|parentClueLength
|The size in bytes of the clue string following this field.

|String
|N bytes
|parentClue
|A clue, be it a path, filename, UNC, etc., to find the parent. If not valid or not found implementations shall try the directory where the image resides first and the current working directory if not found there.
|===

This block contains metadata essential for locating the corresponding parent image.

All sectors flagged as undumped in the current image must be retrieved from the parent image to ensure completeness.
The parent may also store supplementary blocks—such as media tags or metadata—that are not duplicated in the current image.
However, any correctly defined data blocks or deduplication tables present in this image will override those found in the parent.

A clue field assists implementations in locating the parent, while a unique parent ID confirms its validity.
If the clue fails to resolve the location, the implementation must first scan the directory containing the current image for files with a matching AaruFormat header and expected ID.
If unsuccessful, the fallback should be the current working directory.

If this block is present but the parent image cannot be located, the implementation must terminate the open operation, as reconstructing the complete media content depends on the parent’s data.
