NSString+Additions.m

#import "CommonCrypto/CommonDigest.h"

@interface NSString (NSStringAdditions)

- (id) stringByPerformingMD5Checksum;
- (id) stringByEncodingIllegalURLCharacters
- (id) stringByDecodingIllegalURLCharacters

@end

@implementation NSString (NSStringAdditions)

- (id) stringByPerformingMD5Checksum {
	const char *cString = [self UTF8String];
	unsigned char result[CC_MD5_DIGEST_LENGTH];
	CC_MD5( cString, strlen(cString), result);
	return [NSString stringWithFormat:
			@"%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X",
			result[0], result[1], result[2], result[3], result[4], result[5], result[6], result[7],
			result[8], result[9], result[10], result[11], result[12], result[13], result[14], result[15]
	];
}

- (id) stringByEncodingIllegalURLCharacters {
	return [(NSString *)CFURLCreateStringByAddingPercentEscapes( NULL, (CFStringRef)self, NULL, CFSTR( ",;:/?@&$=|^~`\{}[]" ), kCFStringEncodingUTF8 ) autorelease];
}

- (id) stringByDecodingIllegalURLCharacters {
	return [(NSString *)CFURLCreateStringByReplacingPercentEscapes( NULL, (CFStringRef)self, CFSTR( "" ) ) autorelease];
}

@end