On 12 May '08, at 11:38 PM, Daniel Vollmer wrote:
I'm parsing a rather large text-file (usually >20MB) and in doing so I'm iterating over its lines with [String getParagraphStart::::]. I've found a rather noticeable speed-up in the parsing operation if I create the string in question from an NSData object (created via initWithContentsOfMappedFile) using [String initWithData:encoding:].
It sounds like you're creating a single NSString containing the entire contents of the file, then?
Now to the questions:1) Is this safe if the file in question is being moved / deleted / edited during parsing?
The string initializer you're using copies the data. This might just involve calling -copy on the NSData instead of copying the bytes into a new buffer; I'm not sure.
If the NSString made its own copy of the bytes, then you're totally safe; the data from the mapped file isn't being used at all anymore.
If it's using the bytes in the NSData, you're "mostly" safe. Moving or deleting the mapped file won't break the mapping (a deleted file isn't actually deleted until all open file descriptors close.) A typical "safe-save" won't alter the data either, since it creates a new file and then deletes the old one. The only problem would be if something overwrote the file in place, in which case the overwritten data would suddenly show up in the NSData.
2) Are substrings created from the original string (e.g. substringWithRange etc.) still backed properly after the original string and the NSData object are released?
Yes. Even if the NSString is still using the NSData's contents for its buffer, it retained them, so releasing the NSData won't make it go away until the string is done with it.
—Jens
smime.p7s
Description: S/MIME cryptographic signature
_______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
