#import "MyValueFormatter.h"

unsigned charTo4Bits(char c);

@implementation MyValueFormatter

//Textual representation of cell content

//Ð stringForObjectValue:  

- (NSString *)stringForObjectValue:(id)anObject{

    NSString *resultString;

    if ([anObject isMemberOfClass:[NSData class]])

        resultString = [MyValueFormatter hexStringFromData:(NSData *)anObject];

//  else if ([anObject isMemberOfClass:[NSString class]])

//      resultString = anObject;

//  else /*if ([anObject isMemberOfClass:[NSNumber class]])*/{

//      resultString = [anObject stringValue];

//  }

    return resultString;

}

//Object equivalent to textual representation

//Ð getObjectValue:forString:errorDescription:  

- (BOOL)getObjectValue:(id *)anObject forString:(NSString *)string errorDescription:(NSString **)error{

    NSData *data = [MyValueFormatter dataFromHexString:string];

    if (data != nil){

        *anObject = data;

        return YES;

    } else {

        NSString *errorString = @"unsupported object class";

        *error = errorString;

        return NO;

    };

}

/*

//Ð attributedStringForObjectValue:withDefaultAttributes:  

- (NSAttributedString *)attributedStringForObjectValue:(id)anObject withDefaultAttributes:(NSDictionary *)attributes

//Ð editingStringForObjectValue:  

- (NSString *)editingStringForObjectValue:(id)anObject

//Dynamic cell editing

//Ð isPartialStringValid:newEditingString:errorDescription:  

- (BOOL)isPartialStringValid:(NSString *)partialString newEditingString:(NSString **)newString errorDescription:(NSString **)error

//Ð isPartialStringValid:proposedSelectedRange:originalString:originalSelectedRange:errorDescription:  

- (BOOL)isPartialStringValid:(NSString **)partialStringPtr proposedSelectedRange:(NSRangePointer)proposedSelRangePtr originalString:(NSString *)origString originalSelectedRange:(NSRange)origSelRange errorDescription:(NSString **)error

*/

+ (NSString *)hexStringFromData:(NSData*) dataValue{

    UInt32 byteLength = [dataValue length], byteCounter = 0;

    UInt32 stringLength = (byteLength*2) + 1, stringCounter = 0;

    unsigned char dstBuffer[stringLength];

    unsigned char srcBuffer[byteLength];

    unsigned char *srcPtr = srcBuffer;

    [dataValue getBytes:srcBuffer];

    const unsigned char t[16] = "0123456789ABCDEF";

    for (;byteCounter < byteLength; byteCounter++){

        unsigned src = *srcPtr;

        dstBuffer[stringCounter++] = t[src>>4];

        dstBuffer[stringCounter++] = t[src & 15];

        srcPtr++;

    }

    dstBuffer[stringCounter] = '\0';

    return [NSString stringWithUTF8String:(char*)dstBuffer];

}

+ (NSData *)dataFromHexString:(NSString*) dataValue{

    UInt32 stringLength = [dataValue length];

    UInt32 byteLength = stringLength/2;

    UInt32 byteCounter = 0;

    unsigned char srcBuffer[stringLength];

    [dataValue getCString:(char *)srcBuffer];

    unsigned char *srcPtr = srcBuffer;

    Byte dstBuffer[byteLength];

    Byte *dst = dstBuffer;

    for(;byteCounter < byteLength;){

        unsigned char c = *srcPtr++;

        unsigned char d = *srcPtr++;

        unsigned hi = 0, lo = 0;

        hi = charTo4Bits(c);

        lo = charTo4Bits(d);

        if (hi== 255 || lo == 255){

            //errorCase

            return nil;

        }

        dstBuffer[byteCounter++] = ((hi << 4) | lo);

    }

    return [NSData dataWithBytes:dst length:byteLength];

}

@end

unsigned charTo4Bits(char c){

    unsigned bits = 0;

    if (c > '/' && c<':'){

        bits = c - '0'; 

    } else if (c > '@' && c < 'G'){

        bits = (c- 'A') + 10;

    } else if (c > '`' && c < 'g'){

        bits = (c- 'a') + 10;

    } else {

        bits = 255;

    }

    return bits;

}