Optimizing ISO file structure

[dma_k]

It would be nice if DT team can implement this (simple in my opinion) feature: before (or during) writing the ISO image, make file entries that refer the same file data to point to the same location in ISO. This functionality is available in UltraISO and PowerISO. It saves size in almost no efforts: one can check file_name+file_size, but I would suggest to check file_size+md5+first_2048_bytes (to capture also renamed files).

I am not sure, if it applies to other formats (NRG).

[Blazkowicz]

Could you post a screenshot or/and describe it a little bit more, don't get what you suggest atm.

[dma_k]

Blazkowicz, everything is very simple. Assume I have two files:

jboss_4.0.1/lib/servlet-api.jar
jboss_4.0.3/lib/servlet-api.jar

that have the same size (and in this case they are binary the same).

When I create ISO from UltraISO with optimization enabled I get the size considerably smaller then with DT (compression is OFF and obviously it is hard to gain sensitive difference over JAR files). I explain this as possibility to create directory entries in ISO pointing to the same data location (like hard links in common filesystems). I know for sure that is possible for ISO structure and may help users in specific cases (which may not be rare), for example, when archiving close version of the same Java application.

You can easily do it with UltraISO or I can create one simple test case and provide you the links for download and analysis.

[Blazkowicz]

These aren't standard ISO files anymore then.
Also for archiving users can use MDS format and activate compression.

[dma_k]

I agree, that this feature may not be standard (I believe that current ISO 9660 format implementations already violate standard in some aspects e.g. long file names and deep directory structures).

I wonder, where can I read the comprehensive information about ISO 9660 which is programmer-oriented (till now I've read ISO Master Documentation and ISO9660 Simplified for DOS/Windows briefly)? Can you point me the paragraph and/or page number, saying that this feature conflicts with specification? What I found in ECMA 119, section 6.5.1:

A File Section may be part of more than one file and may occur more than once in the same file. A File Section may be identified by more than one record in the same or a different directory.