On Mar 1, 2014, at 07:23 , Trygve Inda <[email protected]> wrote:

> The problem is that when there is a very small change (just adding or
> removing one of the files in the package), the system does not save in
> place.
> 
> Rather it reads the previous package file completely, writes out a copy of
> the package (400 MB) and then renames it.
> 
> How can I get it to save in place?

AFAIK, NSDocument never saves in place, and isn’t intended to (for safety 
reasons — what happens if your app crashes after some of the files have been 
updated but not others?).

Instead, it achieves its package performance optimization by hard-linking 
unchanged files in the new (saved) package to files in the old (original) 
package. If your save is taking 40 seconds, that could mean:

— The document is on a file system that doesn’t support hard linking.

— The document is on a file system where hard linking 7500 files takes 40 
seconds.

— You didn’t preserve the original file sub-wrappers from the directory wrapper 
created when the document was opened, so NSDocument thinks all the files have 
changed. Note that it’s undocumented (again, AFAIK) what criteria NSDocument 
uses** to decide when a particular file wrapper represents “no change”, so it’s 
safest to keep the original NSFileWrapper objects from open time until save 
time.



** The most likely possibilities are ‘==’ on file wrappers, ‘isEqual:’ on file 
wrappers, or comparison of mod date and/or size of the actual files, but it 
could be something more obscure.

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