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Two Questions on NSStrings <-> bytes

Hello,

I'm still learning on byte writing stuff. Not sure why it's been so difficult for me. Though I can code web apps, VR tools and scripts galore, simple byte-level writing is a mental roadblock. :) Here are two questions that have stumped me...

1. One of the specs I'm coding for requires a Big Endian 8-bit hex value -- meant to be the length of a C-String. So, I tried the following...

			// value is 20

int8_t chapterURLSizeValue = [chapURLLengthNumber intValue];
NSString *test = [NSString stringWithFormat:@"% x",chapterURLSizeValue];
NSLog(@"test string: %@", test);
CFIndex lhsLen = [test length];
UniChar *lhsBuf = malloc(lhsLen * sizeof(UniChar));
[test getCharacters:lhsBuf];
data3 = [NSMutableData dataWithCapacity:1];
[data3 appendBytes:&lhsBuf length:1];
free(lhsBuf);
NSLog(@"Data 3: %@", data3);

	Result...
		 test string: 14
		 Data 3: <e0>

In other words, I'm getting the byte value of the string. How do I get that hex NSString to a literal byte array? Would there be a better way to get a 8-bit hex value from an NSNumber?


2. The C-string measured above is meant to come from a url stored in an NSString in a NSDictionary. To get the byte array I tried the following...

// string is http://www.apple.com
NSString *chapterURL = [resourceDict objectForKey:@"url"];
const char *cChapterURL = [chapterURL cStringUsingEncoding: [NSString defaultCStringEncoding]];
[data3 appendBytes:&cChapterURL length:strlen(cChapterURL)];

	Result...
		50628816 00000005 00000000 a0110090 01000000

Very much incorrect. What would the proper way to get a c-string from a URL in an NSString?

Overall, does anyone know of a tome that would be useful is learning byte-level writing and data conversion at that level?

thanks for any direction,

Jaime Magiera
Sensory Research
http://www.sensoryresearch.net




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