Please any one guide me how to create bytes array from nsdata here is my code for createing nsdata
NSData* data = UIImagePNGRepresentation(img);
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try this answer I think it will help yousalahy– salahy2011-11-05 09:58:09 +00:00Commented Nov 5, 2011 at 9:58
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You read the documentation for NSData. Everything else is just simple C code.Hot Licks– Hot Licks2013-06-30 11:32:21 +00:00Commented Jun 30, 2013 at 11:32
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2 Answers
If you only want to read them, there's a really easy method :
unsigned char *bytes = [data bytes];
If you want to edit the data, there's a method on NSData that does this.
// Make your array to hold the bytes
NSUInteger length = [data length];
unsigned char *bytes = malloc( length * sizeof(unsigned char) );
// Get the data
[data getBytes:bytes length:length];
NB Don't forget - if you're copying the data, you also have to call free(bytes) at some point ;)
1 Comment
Marcin
or this way
UInt8 *bytes = (UInt8 *)[data subdataWithRange:(NSRange){0,length}].bytesHere is fastest way (but pretty danger) to get array:
unsigned char *bytesArray = data.bytes;
NSUInteger lengthOfBytesArray = data.length;
before trying to get byte#100 you should check lengthOfBytesArray like:
if (lengthOfBytesArray > 100 + 1)
{
unsigned char byteWithOffset100 = bytesArray[100];
}
And another safe and more objc-like way:
- (NSArray*) arrayOfBytesFromData:(NSData*) data
{
if (data.length > 0)
{
NSMutableArray *array = [NSMutableArray arrayWithCapacity:data.length];
NSUInteger i = 0;
for (i = 0; i < data.length; i++)
{
unsigned char byteFromArray = data.bytes[i];
[array addObject:[NSValue valueWithBytes:&byteFromArray
objCType:@encode(unsigned char)]];
}
return [NSArray arrayWithArray:array];
}
return nil;
}
1 Comment
johndpope
xcode 6 throws an error for me initialising 'unsigned char' with an expression of incompatible type const void. ... unsigned char byteFromArray = data.bytes[i];