NSData+percentageOfSimilarityTo.m

//
//  NSData+percentageOfSimilarityTo.m
//  Doublette
//
//  Created by Uli Kusterer on 30.04.05.
//  Copyright 2005 M. Uli Kusterer.
//
//	This software is provided 'as-is', without any express or implied
//	warranty. In no event will the authors be held liable for any damages
//	arising from the use of this software.
//
//	Permission is granted to anyone to use this software for any purpose,
//	including commercial applications, and to alter it and redistribute it
//	freely, subject to the following restrictions:
//
//	   1. The origin of this software must not be misrepresented; you must not
//	   claim that you wrote the original software. If you use this software
//	   in a product, an acknowledgment in the product documentation would be
//	   appreciated but is not required.
//
//	   2. Altered source versions must be plainly marked as such, and must not be
//	   misrepresented as being the original software.
//
//	   3. This notice may not be removed or altered from any source
//	   distribution.
//

#import "NSData+percentageOfSimilarityTo.h"


@implementation NSData (UKpercentageOfSimilarityTo)

-(float)    percentageOfSimilarityTo: (NSData*)otherData
{
    if( [self length] != [otherData length] )
        return 0;
    
    int                 numBytes = [self length], x;
    unsigned char   *   myByte = [self bytes],
                    *   otherByte = [otherData bytes];
    float               difference = 0;
    
    for( x = 0; x < numBytes; x++ )
    {
        difference += fabs((*myByte) -(*otherByte)) / (float)numBytes;
        myByte++; otherByte++;
    }
    
    return 1 -difference;
}

@end