Provide a rangeOfData:options:range: method for pre-4.0 iOS.

NSData+JWUtil.m

//--------------------------------------------------------------------------------
// NSData+JWUtil
// Provide a rangeOfData:options:range: method for pre-4.0 iOS.
//--------------------------------------------------------------------------------
@interface NSData (JWUtil)
- (NSRange)rangeOfDataX:(NSData *)dataToFind options:(NSDataSearchOptions)mask range:(NSRange)searchRange;
@end

//--------------------------------------------------------------------------------
// NSData+JWUtil
// Provide a rangeOfData:options:range: method for pre-4.0 iOS.
//
// Notes:
// 1) [strike]Uses strnstr() to fake it.[/strike] 
//    Now uses a hand-written piece of code to string search
// 2) Tested uploading a 1MB png file & various text files.
//
// Contraindications:
// 1) does not support NSDataSearchBackwards
//--------------------------------------------------------------------------------
@implementation NSData (JWUtil)

- (NSRange)rangeOfDataX:(NSData *)dataToFind options:(NSDataSearchOptions)mask range:(NSRange)searchRange
{
	NSRange notFound = {NSNotFound,0};

	// use native call if available
	if ([self respondsToSelector:@selector(rangeOfData:options:range:)]) {
		return [self rangeOfData:dataToFind options:mask range:searchRange];
	}
	
	// assert if called with backwards flag
	NSAssert((mask&/*NSDataSearchBackwards*/1)==0,
			 @"NSDataSearchBackwards is not supported");
	
	// assert if a >0 location is specified for an anchored search
	NSAssert(searchRange.location==0||(mask&/*NSDataSearchAnchored*/2)==0,
			 @"NSDataAnchoredSearch means searchRange must start at 0.");
	
	// assert on bad search range
	NSAssert(searchRange.location+searchRange.length<=[self length],
			 @"searchRange must be within receiver");
	
	// short circuit if data to find + start of range is longer than data to search
	if (searchRange.location + [dataToFind length]>[self length]) {
		return notFound;
	}
	
	// get a zero-terminated string to search
	NSInteger s2size = [dataToFind length];
	char * s2 = malloc(s2size+1);
	NSAssert(s2!=NULL,@"Copying search string failed to allocate memory.");
	*(s2+s2size) = 0;
	strncpy(s2,[dataToFind bytes],s2size);
	
	// get position and length to search
	NSInteger p = searchRange.location;
	NSInteger n = [self length] - p;
	const char * s1 = [self bytes] + p;

//	// do the search - this doesn't work for zeroes in the string to be searched
//	const char * found = strnstr(s1, s2, n);

	// implement a sort of memnmem()
	const char * s = s1;
	const char * found = NULL;
	while (1) {
		// find first character of search string
		while (*s++!=*s2 && s-s1<n)
			{};
		
		// check if we have the whole string
		const char * u = s-1;
		const char * v = s2;
		while (*u++==*v++ && u-s1<n && v-s2<s2size )
			{};

		// did we get it?
		if (v-s2==s2size) {
			found = s-1;
			break;
		}
		
		// done?
		if (u-s1>n) 
			break;
	}

	// free our zero-terminated copy
	free(s2);
	
	// not found?
	if (found==NULL) {
		return notFound;
	}
	
	// build appropriate range, relative to receiver
	NSRange foundRange;
	foundRange.location = found-s1+p;
	foundRange.length = s2size;
	return foundRange;
}

@end