I would like to transform NSData to int in Objective-c.
In the following code, "index2" is "15", but "value" is "0".
(NSLog says "15,0".)
To be exact, "value" must be "15".
NSString *index = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSString *index2 = [index stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
int value = [index2 intValue];
NSLog(#"%#,%d",index2,value);
Could you tell me how to solve this problem?
If you want to simply convert nsdata to int try the following.
int theInteger;
[completeData getBytes:&theInteger length:sizeof(theInteger)];
Check this link you might need to read the NSData using a range.
I have a uint_8[] array of characters and I'd like to convert it to an NSString but I'm getting NULL back. What's the proper way to convert between these two types?
// Defined else where as:
uint8_t someValue[8];
someValue is not NULL and contains some valid characters
I've tried:
NSLog(#"converted using CString: %#", [NSString stringWithCString:(char const *)someValue encoding:NSUTF8StringEncoding]);
as well as:
NSMutableData *data = [[NSMutableData alloc] init];
[data appendBytes:someValue length:sizeof(someValue)];
converted = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"converted using NSData: %#", converted);
Using:
[NSString stringWithCString:(char const *)someValue encoding:NSUTF8StringEncoding];
only works if there is a null terminator in the someValue array.
Your other solution doesn't work because sizeof(someValue) does not return the number of characters in the array, it returns the size of the uint8_t pointer.
You can use:
NSUInteger len = ... // the actual number of characters in someValue
NSString *str = [[NSString alloc] initWithBytes:someValue length:len encoding:NSUTF8StringEncoding];
Of course this requires that you know how many characters are really in the array.
Ho Everybody I aam trying to call php script thorugh my iphone application that return me a integer value as serverOutput
NSData *dataURL = [NSData dataWithContentsOfURL: [ NSURL URLWithString: hostStr ]];
NSString *serverOutput = [[NSString alloc] initWithData:dataURL encoding: NSASCIIStringEncoding];
NSInteger * userid = [serverOutput integerValue];
NSLog(#" %d" , userid);
But if my print my serverOutput string it is 2381164503 but my NSLog(#" %d" , userid) prints me 2147483647. I dont know for some reason it is parsing different value :(
First, NSInteger is a primitive type so you shouldn't declare userid as a pointer (by putting the asterisk in front). Second, the value 2381164503 is too big for an NSInteger (max is 2147483647).
Try using a long long instead:
long long userid = [serverOutput longLongValue];
NSLog(#" %lld" , userid); //use %lld instead of %d
Based on this question I wrote a category on NSString to hash NSString instances using SHA1. However, there is something wrong with my implementation. The funny thing is that logging the NSData instance does give the expected hash, but when I want to create an NSString from that NSData instance, I simply get null.
- (NSString *)sha1 {
NSData *dataFromString = [self dataUsingEncoding:NSUTF8StringEncoding];
unsigned char hashed[CC_SHA1_DIGEST_LENGTH];
if ( CC_SHA1([dataFromString bytes], [dataFromString length], hashed) ) {
NSData *dataFromDigest = [NSData dataWithBytes:hashed length:CC_SHA1_DIGEST_LENGTH];
NSString *result = [[NSString alloc] initWithBytes:[dataFromDigest bytes] length:[dataFromDigest length] encoding:NSUTF8StringEncoding];
return result;
} else {
return nil;
}
}
Thanks for the help!
The output of a hash function is just a bare bunch of bytes. You're taking those bytes, and essentially telling NSString that they represent a UTF8-encoded string, which they don't. The resulting NSString is just garbage.
It sounds like what you really want is something like a string of hexadecimal digits that represent the hash value? If so, I believe you'll need to roll this yourself by looping through the dataFromDigest one byte at a time and outputting into a new NSMutableString the right hex digits depending on the byte's value. You can do it yourself or use some code from the web. The comment on this post looks promising.
I'm trying to use the BEncoding ObjC class to decode a .torrent file.
NSData *rawdata = [NSData dataWithContentsOfFile:#"/path/to/the.torrent"];
NSData *torrent = [BEncoding objectFromEncodedData:rawdata];
When I NSLog torrent I get the following:
{
announce = <68747470 3a2f2f74 6f727265 6e742e75 62756e74 752e636f 6d3a3639 36392f61 6e6e6f75 6e6365>;
comment = <5562756e 74752043 44207265 6c656173 65732e75 62756e74 752e636f 6d>;
"creation date" = 1225365524;
info = {
length = 732766208;
name = <7562756e 74752d38 2e31302d 6465736b 746f702d 69333836 2e69736f>;
"piece length" = 524288;
....
How do I convert the name into a NSString? I have tried..
NSData *info = [torrent valueForKey:#"info"];
NSData *name = [info valueForKey:#"name"];
unsigned char aBuffer[[name length]];
[name getBytes:aBuffer length:[name length]];
NSLog(#"File name: %s", aBuffer);
..which retrives the data, but seems to have additional unicode rubbish after it:
File name: ubuntu-8.10-desktop-i386.iso)
I have also tried (from here)..
NSString *secondtry = [NSString stringWithCharacters:[name bytes] length:[name length] / sizeof(unichar)];
..but this seems to return a bunch of random characters:
扵湵畴㠭ㄮⴰ敤歳潴⵰㍩㘸椮潳
The fact the first way (as mentioned in the Apple documentation) returns most of the data correctly, with some additional bytes makes me think it might be an error in the BEncoding library.. but my lack of knowledge about ObjC is more likely to be at fault..
That's an important point that should be re-emphasized I think. It turns out that,
NSString *content = [NSString stringWithUTF8String:[responseData bytes]];
is not the same as,
NSString *content = [[NSString alloc] initWithBytes:[responseData bytes]
length:[responseData length] encoding: NSUTF8StringEncoding];
the first expects a NULL terminated byte string, the second doesn't. In the above two cases content will be NULL in the first example if the byte string isn't correctly terminated.
How about
NSString *content = [[[NSString alloc] initWithData:myData
encoding:NSUTF8StringEncoding] autorelease];
NSData *torrent = [BEncoding objectFromEncodedData:rawdata];
When I NSLog torrent I get the following:
{
⋮
}
That would be an NSDictionary, then, not an NSData.
unsigned char aBuffer[[name length]];
[name getBytes:aBuffer length:[name length]];
NSLog(#"File name: %s", aBuffer);
..which retrives the data, but seems to have additional unicode rubbish after it:
File name: ubuntu-8.10-desktop-i386.iso)
No, it retrieved the filename just fine; you simply printed it incorrectly. %s takes a C string, which is null-terminated; the bytes of a data object are not null-terminated (they are just bytes, not necessarily characters in any encoding, and 0—which is null as a character—is a perfectly valid byte). You would have to allocate one more character, and set the last one in the array to 0:
size_t length = [name length] + 1;
unsigned char aBuffer[length];
[name getBytes:aBuffer length:length];
aBuffer[length - 1] = 0;
NSLog(#"File name: %s", aBuffer);
But null-terminating the data in an NSData object is wrong (except when you really do need a C string). I'll get to the right way in a moment.
I have also tried […]..
NSString *secondtry = [NSString stringWithCharacters:[name bytes] length:[name length] / sizeof(unichar)];
..but this seems to return random Chinese characters:
扵湵畴㠭ㄮⴰ敤歳潴⵰㍩㘸椮潳
That's because your bytes are UTF-8, which encodes one character in (usually) one byte.
unichar is, and stringWithCharacters:length: accepts, UTF-16. In that encoding, one character is (usually) two bytes. (Hence the division by sizeof(unichar): it divides the number of bytes by 2 to get the number of characters.)
So you said “here's some UTF-16 data”, and it went and made characters from every two bytes; each pair of bytes was supposed to be two characters, not one, so you got garbage (which turned out to be mostly CJK ideographs).
You answered your own question pretty well, except that stringWithUTF8String: is simpler than stringWithCString:encoding: for UTF-8-encoded strings.
However, when you have the length (as you do when you have an NSData), it is even easier—and more proper—to use initWithBytes:length:encoding:. It's easier because it does not require null-terminated data; it simply uses the length you already have. (Don't forget to release or autorelease it.)
A nice quick and dirty approach is to use NSString's stringWithFormat initializer to help you out. One of the less-often used features of string formatting is the ability to specify a mximum string length when outputting a string. Using this handy feature allows you to convert NSData into a string pretty easily:
NSData *myData = [self getDataFromSomewhere];
NSString *string = [NSString stringWithFormat:#"%.*s", [myData length], [myData bytes]];
If you want to output it to the log, it can be even easier:
NSLog(#"my Data: %.*s", [myData length], [myData bytes]);
Aha, the NSString method stringWithCString works correctly:
With the bencoding.h/.m files added to your project, the complete .m file:
#import <Foundation/Foundation.h>
#import "BEncoding.h"
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
// Read raw file, and de-bencode
NSData *rawdata = [NSData dataWithContentsOfFile:#"/path/to/a.torrent"];
NSData *torrent = [BEncoding objectFromEncodedData:rawdata];
// Get the file name
NSData *infoData = [torrent valueForKey:#"info"];
NSData *nameData = [infoData valueForKey:#"name"];
NSString *filename = [NSString stringWithCString:[nameData bytes] encoding:NSUTF8StringEncoding];
NSLog(#"%#", filename);
[pool drain];
return 0;
}
..and the output:
ubuntu-8.10-desktop-i386.iso
In cases where I don't have control over the data being transformed into a string, such as reading from the network, I prefer to use NSString -initWithBytes:length:encoding: so that I'm not dependent upon having a NULL terminated string in order to get defined results. Note that Apple's documentation says if cString is not a NULL terminated string, that the results are undefined.
Use a category on NSData:
NSData+NSString.h
#interface NSData (NSString)
- (NSString *)toString;
#end
NSData+NSString.m
#import "NSData+NSString.h"
#implementation NSData (NSString)
- (NSString *)toString
{
Byte *dataPointer = (Byte *)[self bytes];
NSMutableString *result = [NSMutableString stringWithCapacity:0];
NSUInteger index;
for (index = 0; index < [self length]; index++)
{
[result appendFormat:#"0x%02x,", dataPointer[index]];
}
return result;
}
#end
Then just NSLog(#"Data is %#", [nsData toString])"
You can try this. Fine with me.
DLog(#"responeData: %#", [[[NSString alloc] initWithBytes:[data bytes] length:[data length] encoding:NSASCIIStringEncoding] autorelease]);
Sometimes you need to create Base64 encoded string from NSData. For instance, when you create a e-mail MIME. In this case use the following:
#import "NSData+Base64.h"
NSString *string = [data base64EncodedString];
This will work.
NSString *str = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];