SIZE Chunk

See more on Chunks in general.

This states the size of the corresponding file. Without this chunk, you won’t know the size of an extracted file without going through the compressed data. This optional chunk offers a shortcut, at the expence of storing arguably redundant and unnecessary information.

SIZE Chunk structure


The a (correlated), b (subtype), and d (redundant) Flagsmust be set.

The r (range of instances) , p (multi-part) & c, and y (payload specification) flags are all available. The i (instance sizes field is present) flag is always cleared.

The y flag may be present. COMP#70 might be particularly useful.

SIZE-nd has a distinct meaning, documented below.


The Subtype must be set to 66.

Instance Number

The Instance Number matches the Instance Number of the DATA it applies to, as with any a-flagged chunk type.

TIME Chunk Payload

The Payload contains a uintV containing the size of the extracted file.

Usage Notes


SIZE-nd Chunk

SIZE-nd indicates that the specified instances are in a different file in a multi-part archive.

This works the same as with DATA-nd chunks.

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