Re: Reading binary files

FROM : John Stiles
DATE : Fri Oct 15 19:30:06 2004

For every different type, you need a different swap function. You use 
SwapLittleLong on little-endian longs; you use SwapLittleDouble on 
little-endian doubles.

http://developer.apple.com/documentation/Cocoa/Reference/Foundation/
ObjC_classic/Functions/FoundationFunctions.html#//apple_ref/doc/uid/
20000055/BCICIDIA


On Oct 15, 2004, at 9:21 AM, Peter Schols wrote:

> Hi,
>
> I'm trying to read the header of a shape (.shp) file (containing 
> geographical information). This works as expected for reading an 
> integer, but it does not work for reading a double. The data is in 
> little endian format. Any ideas what's going on here?
>
> The .shp file is available upon request.
>
> Thanks!
>
> Peter
>
> Peter Schols
> Laboratory of Plant Systematics - K.U.Leuven
> Belgium
>
> ---
>
> - (IBAction)read:(id)sender;
> {
>    NSFileHandle *file;
>    int type;
>    double number;
>
>    file = [NSFileHandle 
> fileHandleForReadingAtPath:@"/Users/mac/Desktop/st12_d00_shp/
> st12_d00.shp"];
>    [file readDataOfLength:32];
>
>    [[file readDataOfLength:4] getBytes:&type];
>    type = NSSwapLittleLongToHost(type);
>    NSLog(@"Type: %d", type);  // The type is correctly reported as 
> being 5
>
>    [[file readDataOfLength:8] getBytes:&number];
>    number = NSSwapLittleLongToHost(number);
>    NSLog(@"Number: %lf", number);  // The Number is reported as 
> being 0.00000 which is not the case
> }
>
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