How to get free bytes and total bytes for volumes

FROM : Marc Lohse
DATE : Fri Jan 04 11:33:04 2008

I am trying to read the free bytes for a volume before trying to copy
some files to it. Shouldn't be a big problem (even to a newbie - as i am
one)
but NSFileManager does not provide methods that do the job. Googling a bit
i found out that i have to use some Carbon file manager functions. BUT
that does not give me correct values (i think). When using this code:

- (unsigned long long) getVolumeTotalBytesForPath: (NSString *) path
{
    [path retain];
    SInt16 vRefNum = [self _getVolumeNumberForPath: path];
    unsigned long long returnValue = 0;
    OSErr osErr;
 
    FSVolumeInfo info;
    osErr = FSGetVolumeInfo (vRefNum, 0, NULL, kFSVolInfoSizes, &info,
NULL, NULL);
 
    if (osErr == noErr) {
        returnValue = info.totalBytes;
    } else {
        NSLog(@"Could not retrive total byte size. Error: %i", osErr);
        returnValue = 0;
    }
 
    [path release];
    return returnValue;
}

- (unsigned long long) getVolumeFreeBytesForPath: (NSString *) path
{
    [path retain];
    SInt16 vRefNum = [self _getVolumeNumberForPath: path];
    unsigned long long returnValue = 0;
    OSErr osErr;
 
    FSVolumeInfo info;
    osErr = FSGetVolumeInfo (vRefNum, 0, NULL, kFSVolInfoSizes, &info,
NULL, NULL);
 
    if (osErr == noErr) {
        returnValue = info.freeBytes;
    } else {
        NSLog(@"Could not retrive free bytes. Error: %i", osErr);
        returnValue = 0;
    }
 
    [path release];
    return returnValue;
}

- (SInt16) _getVolumeNumberForPath: (NSString *) path
{
    [path retain];
 
    FSRef pathRef; 
 
    // why do i have to cast the fileSystemRepresentation to UInt8* anyway?
    // according to a thread from 2003 this should not be necessary
    FSPathMakeRef((UInt8*)[path fileSystemRepresentation], &pathRef, NULL);
     
    OSErr osErr;
 
    FSCatalogInfo catInfo;
    osErr = FSGetCatalogInfo(&pathRef, kFSCatInfoVolume, &catInfo, NULL,
NULL, NULL);
 
    SInt16 returnValue = 0;
 
    if(osErr == noErr) {
        returnValue = catInfo.volume;
    }
 
    [path release];
    return returnValue;
}


[...]

NSLog(@"Total volume size: %i bytes", [self getVolumeTotalBytesForPath:
@"/Users/marc/Desktop"]);
NSLog(@"Free volume size: %i bytes", [self getVolumeFreeBytesForPath:
@"/Users/marc/Desktop"]);


i get something like 3 free bytes and 18 total bytes using a path
on my PowerBook's harddrive which has 80GB total and 12GB free
space. In the documentation for FSVolumeInfo it says :

[...]
UInt64 totalBytes;
UInt64 freeBytes;
[...]

so using an unsigned long long as the returnValue should be fine.
i realized, though,  that the relation of free bytes to total bytes
actually more or less fits: 12 GB is roughly 1/6 of 80GB and the same is
true for 3 and 18. I am lost and i fear that i am probably making some
stupid mistake...