Detect CSV delimiter in Objective-C

detectCSVDelimiter.m

#define COMMA ','
#define SEMICOLON ';'
#define COLON ':'
#define TAB '\t'
#define SPACE ' '

BOOL delimiterOrNothing(unichar character) {
	return character == COMMA || character == SEMICOLON || character == COLON || character == TAB || character == SPACE || character == 0;
}

/*
 Detects the delimiter by finding the character that has the same number of occurrences in each line
 If nothing is detected, comma is returned
 
 Criticism:
 - only supports comma, semicolon, colon, tab and space as delimiter
 - works bad with small files
 - not fast
 - loads whole file into memory
 */
unichar detectDelimiterOfCSVString(NSString *content) {
	
	#define COMMA_STR @","
	#define SEMICOLON_STR @";"
	#define COLON_STR @":"
	#define TAB_STR @"\t"
	#define SPACE_STR @" "
	#define ZERO_NMB @0
	
	NSArray *lines = [content componentsSeparatedByString:@"\n"];
	
	// count per line:
	
	/*
	 Array of Sets (one per line)
	 Sets contain number of occurrences of one char in that line with character as key
	 */
	NSMutableArray *linesCounts = [NSMutableArray array];
	
	for (NSString *line in lines) {
	
		NSMutableDictionary *counts = [NSMutableDictionary dictionaryWithDictionary:@{COMMA_STR: ZERO_NMB,
																					  SEMICOLON_STR: ZERO_NMB,
																					  COLON_STR: ZERO_NMB,
																					  TAB_STR: ZERO_NMB,
																					  SPACE_STR: ZERO_NMB}];
		
		NSUInteger length = [line length];
		for (NSUInteger i = 0; i < length; i++) {
			
			unichar lastCharacter = i > 0 ? [line characterAtIndex:i-1] : 0;
			unichar character = [line characterAtIndex:i];
			unichar nextCharacter = i < length-1 ? [line characterAtIndex:i+1] : 0;
			
			BOOL quoteOpened = NO;
			
			if (!quoteOpened && delimiterOrNothing(lastCharacter) && character == DOUBLE_QUOTE) { // opening quote
			
				quoteOpened = YES;
			
			} else if (quoteOpened && character == DOUBLE_QUOTE && delimiterOrNothing(nextCharacter)) { // closing quote
				
				quoteOpened = NO;
				
			} else if (!quoteOpened) { // delimiter
				
				#define INCREMENT_COUNT(_key) counts[_key] = [NSNumber numberWithUnsignedInteger:[counts[_key] unsignedIntegerValue] + 1]
				
				switch (character) {
					case COMMA:
						INCREMENT_COUNT(COMMA_STR);
						break;
					case SEMICOLON:
						INCREMENT_COUNT(SEMICOLON_STR);
						break;
					case COLON:
						INCREMENT_COUNT(COLON_STR);
						break;
					case TAB:
						INCREMENT_COUNT(TAB_STR);
						break;
					case SPACE:
						INCREMENT_COUNT(SPACE_STR);
						break;
					default:
						// skip other chars
						break;
				}
				
			}
			
		}
		
		[linesCounts addObject:counts];
		
	}
	
	// detect possible counts:
	
	/*
	 nil at start
	 value for key is NSNull if excluded
	 */
	NSMutableDictionary *possibleCounts = nil;
	for (NSMutableDictionary *lineCounts in linesCounts) {
		if (!possibleCounts) // if nothing so far
			possibleCounts = lineCounts; // use this to start
		else
			for (NSString *delimiter in lineCounts) // each delimiter
				if (![possibleCounts[delimiter] isKindOfClass:[NSNull class]] && ![lineCounts[delimiter] isEqualToNumber:possibleCounts[delimiter]]) // if not excluded yet and is not equal to so far counts
					possibleCounts[delimiter] = [NSNull null]; // exclude this delimiter
	}
	
	// choose delimiter:
	
	for (NSString *delimiter in possibleCounts) {
		NSNumber *count = possibleCounts[delimiter];
		if (![count isKindOfClass:[NSNull class]] && ![count isEqualToNumber:@0]) { // not NSNull and not @0
			if ([delimiter isEqualToString:COMMA_STR]) return COMMA;
			if ([delimiter isEqualToString:SEMICOLON_STR]) return SEMICOLON;
			if ([delimiter isEqualToString:COLON_STR]) return COLON;
			if ([delimiter isEqualToString:TAB_STR]) return TAB;
			if ([delimiter isEqualToString:SPACE_STR]) return SPACE;
		}
	}
	
	// return default if nothing detected
	return COMMA;
	
}

Note: I'm not very experienced in Objective-C, count per line and detect possible counts could be done in one step.

There's an improved version at https://gist.github.com/luisgerhorst/8715763