Question

Very basic Question. :(. I have a hex value and trying to accommodate into NSData, and
tried the following.

  unsigned char  bytes [] = {0x0f0121dd06a2d00503040705aa010ba2d0a2d0};
  NSData *data = [NSData dataWithBytes: bytes  length:19];
  NSLog (@" DAta is %@ ", data);

I m getting the following Warning

34:37: warning: integer constant is too large for its type
34: warning: large integer implicitly truncated to unsigned type

Data is printed like:

NSDataExample[36136:707]  DAta is <d028e08c 7fff7f00 00000000 00000000 0008fc>

I m not sure if i m doing it in a right way?. Kindly advice.

Answer 1

You aren’t assigning the char array properly it seems; because it is too large for the type you’re assigning. How about this, as an example:

#import <Foundation/Foundation.h>

int main(int argc, char *argv[]) {
    NSAutoreleasePool *p = [[NSAutoreleasePool alloc] init];

    // your example has longer hex value, truncated here for clarity...
    unsigned char bytes[] = { 0x0F, 0x01, 0x21};
    NSData *data = [NSData dataWithBytes:bytes  length:3];
    NSLog (@" Data is %@ ", data);

    [p release];
}

Prints 2012-11-19 06:40:07.581 Untitled 2[12472:707] Data is <0f0121> to the console

Or, if your hex bytes are in the form of a string, something like this:

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        NSString *hexString = @"0x0f0121dd06a2d00503040705aa010ba2d0a2d0";
        NSMutableData *data = [[NSMutableData alloc] init];
        NSRegularExpression *expression = [NSRegularExpression regularExpressionWithPattern:@"[A-Fa-f0-9]{2}" options:0 error:NULL];
        [expression enumerateMatchesInString:hexString options:0 range:NSMakeRange(0, hexString.length) usingBlock:^(NSTextCheckingResult *result, NSMatchingFlags flags, BOOL *stop) {
            int hex = (int)strtol([[hexString substringWithRange:result.range] UTF8String], NULL, 16);
            printf("hex = %d\n",hex);
            [data appendBytes:&hex length:1];
        }];
        NSLog(@"%s - data = %@",__FUNCTION__,data);
    }
    return 0;
}

Which prints 2012-11-19 06:56:15.753 TestHexStringToBytes[12891:303] main - data = <0f0121dd 06a2d005 03040705 aa010ba2 d0a2d0> to the console.