NSData's +dataWithContentsOfFile

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pf - 29 Jun 2005 07:39 GMT

Hi,

I'm considering using Cocoa rather than Carbon...

How do I init an NSData object with data from a file *but* only from x bytes
in with a length of y bytes into the file? I don't want to read the whole
file into one data object then copy x bytes into another NSData object.

NSFile doesn't seem to be what I thought - similar to MFC's CFile...

Thanks,

Paul

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Gregory Weston - 29 Jun 2005 12:05 GMT

In article
<42c24225$0$845$61c65585@uq-127creek-reader-03.brisbane.pipenetworks.com
.au>,

> Hi,
>
[quoted text clipped - 3 lines]
> in with a length of y bytes into the file? I don't want to read the whole
> file into one data object then copy x bytes into another NSData object.

+ (id)dataWithContentsOfMappedFile:(NSString *)path can create an NSData
that simply references the file. So you could...

NSData* theChunk = [[NSData dataWithContentsOfMappedFile:@"foo"]
subdataWithRange:NSMakeRange(theStart, theLength)];

> NSFile doesn't seem to be what I thought - similar to MFC's CFile...

I don't know what NSFile is. NSFileHandle might be what you're looking
for.

NSFileHandle* theFile = [NSFileHandle fileHandleForReadingAtPath:@"foo"];
[theFile seekToFileOffset:theStart];
NSData* theChunk = [theFile readDataOfLength:theLength];

G

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Mac Forum / Programming / Mac Programming / June 2005

NSData's +dataWithContentsOfFile