NSData+RSHexDump.m

//
//  NSData+RSHexDump.m
//  RSFoundation
//
//  Created by Daniel Jalkut on 2/14/07.
//  Copyright 2007 Red Sweater Software. All rights reserved.
//
//	Based on code from Dan Wood 
//	http://gigliwood.com/weblog/Cocoa/Better_description_.html
//
//

#import "NSData+RSHexDump.h"

const unsigned int kDefaultMaxBytesToHexDump = 1024;

@implementation NSData ( RSHexDump )

- (NSString *)description{
	return [self descriptionFromOffset:0];
}

- (NSString *)descriptionFromOffset:(int)startOffset{
	return [self descriptionFromOffset:startOffset limitingToByteCount:kDefaultMaxBytesToHexDump];
}

- (NSString *)descriptionFromOffset:(int)startOffset limitingToByteCount:(unsigned int)maxBytes{
	unsigned char *bytes = (unsigned char *)[self bytes];
	NSUInteger stopOffset = [self length];

	// Translate negative offset to positive, by subtracting from end
	if(startOffset < 0) startOffset = [self length] + startOffset;

	// Do we have more data than the caller wants?
	if((stopOffset - startOffset) > maxBytes){
		stopOffset = startOffset + maxBytes;
	}

	// If we're showing a subset, we'll tack in info about that
	NSString* curtailInfo = @"";
	if((startOffset > 0) || (stopOffset < [self length])){
		curtailInfo = [NSString stringWithFormat:@" (showing bytes %d through %d)", startOffset, stopOffset];
	}

	// Start the hexdump out with an overview of the content
	NSMutableString *buf = [NSMutableString stringWithFormat:@"NSData %d bytes%@:\n", [self length], curtailInfo];

	// One row of 16-bytes at a time ...
    NSUInteger i, j;
	for(i = startOffset ; i < stopOffset ; i += 16 ){
		// Show the row in Hex first
		for(j = 0 ; j < 16 ; j++){
			NSUInteger rowOffset = i+j;
            if(rowOffset < stopOffset)	[buf appendFormat:@"%02X ", bytes[rowOffset]];
            else						[buf appendFormat:@"   "];
		}

		// Now show in ASCII
		[buf appendString:@"| "];
		for(j = 0 ; j < 16 ; j++){
			NSUInteger rowOffset = i+j;
			if(rowOffset < stopOffset){
				unsigned char theChar = bytes[rowOffset];
				if(theChar < 32 || theChar > 127) theChar ='.';
				[buf appendFormat:@"%c", theChar];
			}
		}
		// If we're not on the last row, tack on a newline
		if(i+16 < stopOffset) [buf appendString:@"\n"];
	}
	return buf;
}

@end