I have a nsdata with bytes :0017c572 528e
now i need to encode this byte using either UTF 8 of Ascii
For this i have used following code in Objective C
NSString *Str = [[NSString alloc] initWithData:value encoding:NSUTF8StringEncoding];
then later on at some point i need to get back the same bytes from Str for this i have used
NSData *aData = [Str dataUsingEncoding:NSUTF8StringEncoding];
NSLog(#"aData:%#", aData);
Now the problem is content of aData is null not 0017c572 528e . how can i do the this operation.
this concept works perfectly if data byte is : 323332
str = 232
aData = 323332
Just print the Str value before the line
NSLog(#"Str = %#",Str);
NSData *aData = [Str dataUsingEncoding:NSUTF8StringEncoding];
It seems the Str variable does not have any value. Then only, it will return null. Please check.
Related
NSString* code = #"\x03\x7e";
const char *cString = [code cStringUsingEncoding:NSUnicodeStringEncoding];
NSData* unicodeData = [NSData dataWithBytes:cString length:strlen(cString)];
NSString* convertedString = [[NSString alloc] initWithData:unicodeData encoding:NSUnicodeStringEncoding];
I’d like the convertedString to be the unicode value of \x03\x7e which is a greek question mark (looks kind of like a semicolon). My converted string ends up just as an empty string…
Any idea how I can do this?
Thanks!
Sample Code:
NSString *code = #"\x03\x7e";
NSData *data = [code dataUsingEncoding:NSUnicodeStringEncoding];
NSString *codeNew = [[NSString alloc] initWithData:data encoding:NSUnicodeStringEncoding];
I had created a SHA256 encoding of the string using the following function,
const char *s=[#"123456" cStringUsingEncoding:NSASCIIStringEncoding];
NSData *keyData=[NSData dataWithBytes:s length:strlen(s)];
uint8_t digest[CC_SHA256_DIGEST_LENGTH]={0};
CC_SHA256(keyData.bytes, keyData.length, digest);
NSData *out=[NSData dataWithBytes:digest length:CC_SHA256_DIGEST_LENGTH];
NSString *hash=[out description];
hash = [hash stringByReplacingOccurrencesOfString:#" " withString:#""];
hash = [hash stringByReplacingOccurrencesOfString:#"<" withString:#""];
hash = [hash stringByReplacingOccurrencesOfString:#">" withString:#""];
NSLog(#"Hash : %#", hash);
It gives me the output : 8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92.
But I need the following output : jZae727K08KaOmKSgOaGzww/XVqGr/PKEgIMkjrcbJI=. It's base64.
How Can I convert the "hex" hash I generated to "base64"?
I had use this website to generate base64 hash : http://www.online-convert.com/result/7bd4c809756b3c16cf9d1939b1e57584
You should not be converting the NSString *hash that you generated from the description to base-64. It is a hex string, not the actual data bytes.
You should go straight from NSData *out to base-64 string, using any of the available base-64 encoders. For example, you can download an implementation from this post, and use it as follows:
const char *s=[#"123456" cStringUsingEncoding:NSASCIIStringEncoding];
NSData *keyData=[NSData dataWithBytes:s length:strlen(s)];
uint8_t digest[CC_SHA256_DIGEST_LENGTH]={0};
CC_SHA256(keyData.bytes, keyData.length, digest);
NSData *out=[NSData dataWithBytes:digest length:CC_SHA256_DIGEST_LENGTH];
// The method below is added in the NSData+Base64 category from the download
NSString *base64 =[out base64EncodedString];
I use this, (mentionned in How do I do base64 encoding on iphone-sdk?)
http://www.imthi.com/blog/programming/iphone-sdk-base64-encode-decode.php
Works well, and easily usable with ARC.
NSString *string1 = #"<616263>";
I want to make this into NSData *data1 = <616263>;
so that when I
NSString *string2 = [[NSString alloc] initWithData:data1 encoding:NSUTF8StringEncoding];
NSLog(#"%#", string2);
Result: abc
would come out
p.s.
<616263>, this is data expression of #"abc"
The trick is converting 616263 to abc. Since you are starting with the ASCII representation of the character codes, you need to convert your NSString to an array of bytes (or your original data source to an array instead of saving it as an NSString in the first place).
NSString *string1 = #"616263";
// Make sure that buffer is big enough!
char sourceChars[7];
[string1 getCString:sourceChars maxLength:7 encoding:NSUTF8StringEncoding];
char destBuffer[3];
char charBuffer[3];
// Loop through sourceChars and convert the ASCII character groups to char's
// NOTE: I assume that these are always two character groupings per your example!
for (int index = 0; index < [string1 length]; index = index + 2) {
// Copy the next two digits into charBuffer
strncpy(charBuffer, &sourceChars[index], 2);
charBuffer[2] = '\0';
// convert charBuffer (ie 61) from hex to decimal
destBuffer[index / 2] = strtol(charBuffer, NULL, 16);
}
// destBuffer is properly formatted: init data1 with it.
NSData *data1 = [NSData dataWithBytes:destBuffer length:[string1 length]/2];
// Test
NSString *string2 = [[NSString alloc] initWithData:data1 encoding:NSUTF8StringEncoding];
NSLog(#"%#", string2); // Prints abc
I'm getting weird NSString value after performing a conversion. For example, I have one byte with value 2 (00000010) that is stored in response. I tried both NSString initWithData and initWithBytes but both return weird symbol (upside down question mark). Here's my code:
NSString *command1 = [[NSString alloc] initWithData:response encoding:NSASCIIStringEncoding];
NSString *command2 = [[NSString alloc] initWithBytes:[response bytes] length:[response length] encoding:NSASCIIStringEncoding];
NSLog(#"command1: %#", command1);
NSLog(#"command2: %#", command2);
Also tried NSUTF8StringEncoding but NSASCIIStringEncoding is correct one because data comes encoded one byte per symbol.
From what I am reading, this is what you want:
NSString *stringWithContentsOfBinaryData(NSData *data)
{
NSMutableString *output;
int len = [data length];
uint8_t *bytes = [data bytes];
for (int i = 0; i < len; i++)
{
[output appendFormat:#"%i", bytes[i]];
}
return output;
}
It just simply converts each byte to it's integer representation and concatenates that into a string.
ASCII is not necessarily the right encoding. ASCII only defines characters between 0x00 and 0x7F. If response is an HTTP response, and the encoding is not specified in the HTTP Content-Type header, the default is ISO-8859-1 for which you should use NSISOLatin1StringEncoding
And it doesn't matter what encoding you use: control characters (0x00 - 0x1F) aren't necessarily printable.
I'm getting an HTML file as NSData and need to extract some parts of it. For that I need to convert it to NSString with UTF8 encoding. The thing is that this conversion fails, probably because the NSData contains bytes that are invalid for UTF8. I have tried to get the byte array of the data and go over it, but each time I come across non ASCII character (hebrew letters for example) I get jibrish.
Help will be appreciated.
UPDATE:
To Gordon - the NSData generated like that:
NSData *theData = [NSURLConnection sendSynchronousRequest:theRequest returningResponse:&theResponse error:&theError];
When I say that the conversion fails I mean that
[[NSString alloc] initWithData:temp encoding:NSUTF8StringEncoding]
returns nil
To Ed - Here is my code (I got the Byte array from NSData, found what I need, and constructed another Byte array from that - turned it to NSData and then attempted to convert it to NSString... sounds kinda complicated...)
-(NSString *)UTF8StringFromData:(NSData *)theData{
Byte *arr = [theData bytes];
NSUInteger begin1 = [self findIndexOf:#"<li>" bArr:arr size:[theData length]]+4;
NSUInteger end1 = [self findIndexOf:#"</li></ol>" bArr:arr size:[theData length]];
Byte *arr1 = (Byte *)malloc(sizeof(Byte)*((end1-begin1+1)));
NSLog(#"%d %d",begin1, end1);
int j = 0;
for (int i = begin1; i < end1; i++){
arr1[j] = arr[i];
j++;
}
arr1[j]='\0';
NSData *temp = [NSData dataWithBytes:arr1 length:j];
return [[NSString alloc] initWithData:temp encoding:NSUTF8StringEncoding];
}
I know this is an old topic but it came up when I was looking for the solution today. I've solved it now so I'm just posting it for others who might run into this page looking for a solution.
Here's what I do in an asynchronous request:
I first store the text encoding name in connection:didReceiveResponse using
encodingName = [[NSString alloc] initWithString:[response textEncodingName]];
Then later in my connectionDidFinishLoading method I used
NSStringEncoding encoding = CFStringConvertEncodingToNSStringEncoding(CFStringConvertIANACharSetNameToEncoding((CFStringRef) encodingName));
NSString *payloadAsString = [[NSString alloc] initWithData:receivedData encoding:encoding];
To Gordon - the NSData generated like that:
NSData *theData = [NSURLConnection sendSynchronousRequest:theRequest returningResponse:&theResponse error:&theError];
When I say that the conversion fails I mean that
[[NSString alloc] initWithData:temp encoding:NSUTF8StringEncoding]
returns nil
To Ed - Here is my code (I got the Byte array from NSData, found what I need, and constructed another Byte array from that - turned it to NSData and then attempted to convert it to NSString... sounds kinda complicated...)
-(NSString *)UTF8StringFromData:(NSData *)theData{
Byte *arr = [theData bytes];
NSUInteger begin1 = [self findIndexOf:#"<li>" bArr:arr size:[theData length]]+4;
NSUInteger end1 = [self findIndexOf:#"</li></ol>" bArr:arr size:[theData length]];
Byte *arr1 = (Byte *)malloc(sizeof(Byte)*((end1-begin1+1)));
NSLog(#"%d %d",begin1, end1);
int j = 0;
for (int i = begin1; i < end1; i++){
arr1[j] = arr[i];
j++;
}
arr1[j]='\0';
NSData *temp = [NSData dataWithBytes:arr1 length:j];
return [[NSString alloc] initWithData:temp encoding:NSUTF8StringEncoding];
}
have you checked the charset= in the HTTP headers and/or the document itself? The most likely reason for the conversion to fail is because the bytes don't represent a valid UTF-8 string.
I'm not sure if you're aware, you don't really need to copy the array to another array before putting it into the new NSData object.
-(NSString *)UTF8StringFromData:(NSData *)theData {
Byte *arr = [theData bytes];
NSUInteger begin1 = [self findIndexOf:#"<li>" bArr:arr size:[theData length]]+4;
NSUInteger end1 = [self findIndexOf:#"</li></ol>" bArr:arr size:[theData length]];
Byte *arr1 = arr + begin1;
NSData *temp = [NSData dataWithBytes:arr1 length:end1 - begin1];
return [[NSString alloc] initWithData:temp encoding:NSUTF8StringEncoding];
}
As for your particular problem, I would try looking through the data manually using the debugger. Put a breakpoint after you have your array (arr1). When you hit it, open up the GDB console and try this:
print (char *)arr1
With your code, it should print out the string you're trying to get. (With the code I gave above, it won't stop after the . It'll just keep going).
If the result is not what you expect, then there's something wrong with the data, or perhaps with your begin1 and end1 boundaries.