I'm looking for an example demonstrating how I can encode and then decode the same string using UTF-8. Encode and then Decode means I want to implement the methods in 2 areas where one can encode it and another is able to decode it.
I have seen the API but I didn't get much success:
stringWithCString:encoding:
stringWithUTF8String:
stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc;
EDITED
I have the string øæ-test-2.txt which I am encoding as follows:
char *s = "øæ-test-2.txt";
NSString *enc = [NSString stringWithCString:s encoding:NSASCIIStringEncoding];
but am getting øæ-test-2.txt as output.
Now I want to get back the original string back i.e. øæ-test-2.txt
EDITED
I am getting øæ-test-2.txt from server and I need øæ-test-2.txt by decoding it. I am able to get the output from the link : http://www.cafewebmaster.com/online_tools/utf_decode
Please try to use the link and you will understand my concern.
It would be highly appreciated if anyone can give some hint, tutorial or point me in the right direction.
Regards
To turn an NSString object into a UTF8 C-string, use UTF8String
char *utf8string = [#"A string with ümläuts" UTF8String];
To turn a UTF8 C-string into an NSString object, use stringWithUTF8String: or initWithUTF8String:
NSString *string = [NSString stringWithUTF8String:utf8string];
Note that NSString objects are implemented as UTF-16, so you can't really have a "UTF-8 NSString" (and the encoding should be treated as an implementation detail, anyway).
Instead of
char *utf8string = [#"A string with ümläuts" UTF8String];
This should be
const char *utf8string = [#"A string with ümläuts" UTF8String];
Otherwise you have an incompatible type issue.
Related
I use the following statement for into to NSString conversion (with a find/replace)
curr_rep_date = [tmpRptDt stringByReplacingOccurrencesOfString:tmpYrVal withString:[NSString stringWithFormat:(tmpCurrYearInt-1)]];
I have declared
int tmpYrVal;
NSMutableString *tmp_dt,*curr_rep_date;
But the program seems to be crashing and the debugger is not giving any hint.
Could someone help me with the issue and what would be the correct usage.
There's a number of problems here.
Firstly, sringByReplacingOcurrancesOfString:withString: is expecting NSStrings as parameters, not ints. That's the reason why it crashes. The method Is attempting to send a message to a primitive type, not an object.
Secondly, you need to use a proper format string for the stringWithFormat: method. This is the same as how NSLog works.
A format string can look like #"some text %d". It would then be followed by a comma separated list of values to be used in place of the % placeholders.
Example:
[NSString stringWithFormat:#"%d", myIntValue];
Will effectively turn your int into a string, as it creates a new string with a format using your int.
You invoked the stringWithFormat - Method without a format string. [NSString stringWithFormat: #"%i", (tmpCurrYearInt-1)] should solve your problem.
You are missing the format
curr_rep_date = [tmpRptDt stringByReplacingOccurrencesOfString:tmpYrVal withString:[NSString stringWithFormat:#"%d", (tmpCurrYearInt-1)]];
Basic int to NSString conversion works like this:
NSString* s = [NSString stringWithFormat:#"%d", intNumber];
I have a web-service running on Windows Azure which returns JSON that I consume in my iPhone app.
Unfortunately, Windows Azure doesn't seem to support the compression of dynamic responses yet (long story) so I decided to get around it by returning an uncompressed JSON package, which contains a compressed (using GZIP) string.
e.g
{"Error":null,"IsCompressed":true,"Success":true,"Value":"vWsAAB+LCAAAAAAAB..etc.."}
... where value is the compressed string of a complex object represented in JSON.
This was really easy to implement on the server, but for the life of me I can't figure out how to decompress a gzipped NSString into an uncompressed NSString, all the examples I can find for zlib etc are dealing with files etc.
Can anyone give me any clues on how to do this? (I'd also be happy for a solution that used deflate as I could change the server-side implementation to use deflate too).
Thanks!!
Steven
Edit 1: Aaah, I see that ASIHTTPRequest is using the following function in it's source code:
//uncompress gzipped data with zlib
+ (NSData *)uncompressZippedData:(NSData*)compressedData;
... and I'm aware that I can convert NSString to NSData, so I'll see if this leads me anywhere!
Edit 2: Unfortunately, the method described in Edit 1 didn't lead me anywhere.
Edit 3: Following the advice below regarding base64 encoding/decoding, I came up with the following code. The encodedGzippedString is as you can guess, a string "Hello, my name is Steven Elliott" which is gzipped and then converted to a base64 string. Unfortunately, the result that prints using NSLog is just blank.
NSString *encodedGzippedString = #"GgAAAB+LCAAAAAAABADtvQdgHEmWJSYvbcp7f0r1StfgdKEIgGATJNiQQBDswYjN5pLsHWlHIymrKoHKZVZlXWYWQMztnbz33nvvvffee++997o7nU4n99//P1xmZAFs9s5K2smeIYCqyB8/fnwfPyK+uE6X2SJPiyZ93eaX+TI9Lcuiatvx/wOwYc0HGgAAAA==";
NSData *decodedGzippedData = [NSData dataFromBase64String:encodedGzippedString];
NSData* unGzippedJsonData = [ASIHTTPRequest uncompressZippedData:decodedGzippedData];
NSString* unGzippedJsonString = [[NSString alloc] initWithData:unGzippedJsonData encoding:NSASCIIStringEncoding];
NSLog(#"Result: %#", unGzippedJsonString);
After all this time, I finally found a solution to this problem!
None of the answers above helped me, as promising as they all looked. In the end, I was able to compress the string on the server with gzip using the chilkat framework for .net ... and then decompress it on the iphone using the chilkat framework for iOS (not yet released, but available if you email the guy directly).
The chilkat framework made this super easy to do so big thumbs up to the developer!
Your "compressed" string is not raw GZIP'd data, it's in some encoding that allows those bytes to be stored in a string-- looks like base-64 or something like it. To get an NSData out of this, you'll need to decode it into the NSData.
If it's really base-64, check out this blog post an accompanying code:
http://cocoawithlove.com/2009/06/base64-encoding-options-on-mac-and.html
which will do what you want.
Once you have an NSData object, the ASIHTTPRequest method will probably do as you like.
This worked for me:
from a string gzipeed, then base64 encoded
to un-gzipped string (all utf8).
#import "base64.h"
#import "NSData+Compression.h"
...
+(NSString *)gunzipBase64StrToStr:(NSString *)stringValue {
//now we decode from Base64
Byte inputData[[stringValue lengthOfBytesUsingEncoding:NSUTF8StringEncoding]];//prepare a Byte[]
[[stringValue dataUsingEncoding:NSUTF8StringEncoding] getBytes:inputData];//get the pointer of the data
size_t inputDataSize = (size_t)[stringValue length];
size_t outputDataSize = EstimateBas64DecodedDataSize(inputDataSize);//calculate the decoded data size
Byte outputData[outputDataSize];//prepare a Byte[] for the decoded data
Base64DecodeData(inputData, inputDataSize, outputData, &outputDataSize);//decode the data
NSData *theData = [[NSData alloc] initWithBytes:outputData length:outputDataSize];//create a NSData object from the decoded data
//NSLog(#"DATA: %# \n",[theData description]);
//And now we gunzip:
theData=[theData gzipInflate];//make bigger==gunzip
return [[NSString alloc] initWithData:theData encoding:NSUTF8StringEncoding];
}
#end
I needed to compress data on the iPhone using Objective-c and decompress on PHP. Here is what I used in XCode 11.5 and iOS 12.4:
iOS Objective-c Compression Decompression Test
Include libcompression.tbd in the Build Phases -> Link Binary With Library. Then include the header.
#include "compression.h"
NSLog(#"START META DATA COMPRESSION");
NSString *testString = #"THIS IS A COMPRESSION TESTTHIS IS A COMPRESSION TESTTHIS IS A COMPRESSION TESTTHIS IS A COMPRESSION TESTTHIS IS A COMPRESSION TESTTHIS IS A COMPRESSION TEST";
NSData *theData = [testString dataUsingEncoding:NSUTF8StringEncoding];
size_t src_size = theData.length;
uint8_t *src_buffer = (uint8_t*)[theData bytes];
size_t dst_size = src_size+4096;
uint8_t *dst_buffer = (uint8_t*)malloc(dst_size);
dst_size = compression_encode_buffer(dst_buffer, dst_size, src_buffer, src_size, NULL, COMPRESSION_ZLIB);
NSLog(#"originalsize:%zu compressed:%zu", src_size, dst_size);
NSData *dataData = [NSData dataWithBytes:dst_buffer length:sizeof(dst_buffer)];
NSString *compressedDataBase64String = [dataData base64EncodedStringWithOptions:0];
NSLog(#"Compressed Data %#", compressedDataBase64String);
NSLog(#"START META DATA DECOMPRESSION");
src_size = compression_decode_buffer(src_buffer, src_size, dst_buffer, dst_size, NULL, COMPRESSION_ZLIB);
NSData *decompressed = [[NSData alloc] initWithBytes:src_buffer length:src_size];
NSString *decTestString;
decTestString = [[NSString alloc] initWithData:decompressed encoding:NSASCIIStringEncoding];
NSLog(#"DECOMPRESSED DATA %#", decTestString);
free(dst_buffer);
On the PHP side I used the following function to decompress the data:
function decompressString($compressed_string) {
//NEED RAW GZINFLATE FOR COMPATIBILITY WITH IOS COMPRESSION_ZLIB WITH IETF RFC 1951
$full_string = gzinflate($compressed_string);
return $full_string;
}
When I fetch the source of any web page, no matter the encoding I use, I always end up with &# - characters (such as © or ®) instead of the actual characters themselves. This goes for foreign characters as well (such as åäö in swedish), which I have to parse from "Å" and such).
I'm using
+stringWithContentsOfUrl: encoding: error;
to fetch the source and have tried several different encodings such as NSUTF8StringEncoding and NSASCIIStringEncoding, but nothing seems to affect the end result string.
Any ideas / tips / solution is greatly appreciated! I'd rather not have to implement the entire ASCII table and replace all occurrances of every character... Thanks in advance!
Regards
I'm using
+stringWithContentsOfUrl: encoding: error;
to fetch the source and have tried several different encodings such as NSUTF8StringEncoding and NSASCIIStringEncoding, but nothing seems to affect the end result string.
You're misunderstanding the purpose of that encoding: argument. The method needs to convert bytes into characters somehow; the encoding tells it what sequences of bytes describe which characters. You need to make sure the encoding matches that of the resource data.
The entity references are an SGML/XML thing. SGML and XML are not encodings; they are markup language syntaxes. stringWithContentsOfURL:encoding:error: and its cousins do not attempt to parse sequences of characters (syntax) in any way, which is what they would have to do to convert one sequence of characters (an entity reference) into a different one (the entity, in practice meaning single character, that is referenced).
You can convert the entity references to un-escaped characters using the CFXMLCreateStringByUnescapingEntities function. It takes a CFString, which an NSString is (toll-free bridging), and returns a CFString, which is an NSString.
Are you sure they originally are not in Å form? Try to view the source code in a browser first.
That really, really sucks. I wanted to convert it directly and the above solution isn't really a good one, so I just wrote my own ascii-table converter (static) class. Works as it should have worked natively (though I have to fill in the ascii table myself...)
Ideas for optimization? ("ASCII" is a static NSDictionary)
#implementation InternetHelper
+(NSString *)HTMLSourceFromUrlWithString:(NSString *)str convertASCII:(BOOL)state
{
NSURL *url = [NSURL URLWithString:str];
NSString *source = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];
if (state)
source = [InternetHelper ConvertASCIICharactersInString:source];
return source;
}
+(NSString *)ConvertASCIICharactersInString:(NSString *)str
{
NSString *ret = [NSString stringWithString:str];
if (!ASCII)
{
NSString *path = [[NSBundle mainBundle] pathForResource:kASCIICharacterTableFilename ofType:kFileFormat];
ASCII = [[NSDictionary alloc] initWithContentsOfFile:path];
}
for (id key in ASCII)
{
ret = [ret stringByReplacingOccurrencesOfString:key withString:[ASCII objectForKey:key]];
}
return ret;
}
#end
NSXMLParserInvalidCharacterError # 9
This is the error I get when I hit a weird character (like quotes copied and pasted from word to the web form, that end up in the feed). The feed I am using is not giving an encoding, and their is no hope for me to get them to change that. This is all I get in the header:
< ?xml version="1.0"?>
< rss version="2.0">
What can I do about illegal characters when parsing feeds? Do I sweep the data prior to the parse? Is there something I am missing in the API? Has anyone dealt with this issue?
NSString *dataString = [[[NSString alloc] initWithData:webData encoding:NSASCIIStringEncoding] autorelease];
NSData *data = [dataString dataUsingEncoding:NSUTF8StringEncoding allowLossyConversion:YES];
NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data];
Fixed my problems...
The NSString -initWithData:encoding: method returns nil if it fails, so you can try one encoding after another until you find one that converts. This doesn't guarantee that you'll convert all the characters correctly, but if your feed source isn't sending you correctly encoded XML, then you'll probably have to live with it.
The basic idea is:
// try the most likely encoding
NSString xmlString = [[NSString alloc] initWithData:xmlData
encoding:NSUTF8StringEncoding];
if (xmlString == nil) {
// try the next likely encoding
xmlString = [[NSString alloc] initWithData:xmlData
encoding:NSWindowsCP1252StringEncoding];
}
if (xmlString == nil) {
// etc...
}
To be generic and robust, you could do the following until successful:
1.) Try the encoding specified in the Content-Type header of the HTTP response (if any)
2.) Check the start of the response data for a byte order mark and if found, try the indicated encoding
3.) Look at the first two bytes; if you find a whitespace character or '<' paired with a nul/zero character, try UTF-16 (similarly, you can check the first four bytes to see if you have UTF-32)
4.) Scan the start of the data looking for the <?xml ... ?> processing instruction and look for encoding='something' inside it; try that encoding.
5.) Try some common encodings. Definitely check Windows Latin-1, Mac Roman, and ISO Latin-1 if your data source is in English.
6.) If none of the above work, you could try removing all bytes greater than 127 (or substitute '?' or another ASCII character) and convert the data using the ASCII encoding.
If you don't have an NSString by this point, you should fail. If you do have an NSString, you should look for the encoding declaration in the <?xml ... ?> processing instruction (if you didn't already in step 4). If it's there, you should convert the NSString back to NSData using that encoding; if it's not there, you should convert back using UTF-8 encoding.
Also, the CFStringConvertIANACharSetNameToEncoding() and CFStringConvertEncodingToNSStringEncoding() functions can help get the NSStringEncoding that goes with the encoding name form the Content-Type header or the <?xml ... ?> processing instruction.
You can also remove that encoding line from xml like this:
int length = str.length >100 ? 100:str.length;
NSString*mystr= [str stringByReplacingOccurrencesOfString:#"encoding=\".*?\""
withString:#""
options:NSRegularExpressionSearch
range:NSMakeRange(0, length)];
im trying to get a call to amazon web service and im stuck on getting the signature, looked at this but i still have a question on it.
using this example what is the
NSData *keyData;
NSData *clearTextData
? what do i need to pass for these two values?
/*
inputs:
NSData *keyData;
NSData *clearTextData
*/
uint8_t digest[CC_SHA1_DIGEST_LENGTH] = {0};
CCHmacContext hmacContext;
CCHmacInit(&hmacContext, kCCHmacAlgSHA1, keyData.bytes, keyData.length);
CCHmacUpdate(&hmacContext, clearTextData.bytes, clearTextData.length);
CCHmacFinal(&hmacContext, digest);
NSData *out = [NSData dataWithBytes:digest length:CC_SHA1_DIGEST_LENGTH]
I just spent like 4 hours Googling and looking for ways to calculate an unkeyed SHA1 on the iPhone that would match the results of the sha1() function in php. Here was the result:
#import <CommonCrypto/CommonDigest.h>
NSString *hashkey = <your data here>;
// PHP uses ASCII encoding, not UTF
const char *s = [hashkey cStringUsingEncoding:NSASCIIStringEncoding];
NSData *keyData = [NSData dataWithBytes:s length:strlen(s)];
// This is the destination
uint8_t digest[CC_SHA1_DIGEST_LENGTH] = {0};
// This one function does an unkeyed SHA1 hash of your hash data
CC_SHA1(keyData.bytes, keyData.length, digest);
// Now convert to NSData structure to make it usable again
NSData *out = [NSData dataWithBytes:digest length:CC_SHA1_DIGEST_LENGTH];
// description converts to hex but puts <> around it and spaces every 4 bytes
NSString *hash = [out description];
hash = [hash stringByReplacingOccurrencesOfString:#" " withString:#""];
hash = [hash stringByReplacingOccurrencesOfString:#"<" withString:#""];
hash = [hash stringByReplacingOccurrencesOfString:#">" withString:#""];
// hash is now a string with just the 40char hash value in it
Hopefully this will help others who are struggling with SHA1 on the iPhone
If you are calling the Amazon web service too look up prices or product details, your Amazon web service key will be disabled and your app will stop working.
Look at the terms of service of the Amazon Web Services, use by mobile clients is strictly disallowed:
https://affiliate-program.amazon.com/gp/advertising/api/detail/agreement.html
I found this out the hard way when my own application had my AWS key disabled in a production app. I had read the TOS, but it was not really there as you can see by the link above to some other obscure detail of use. You wouldn't think the affiliate program would have anything to do with the API, but it does.
You can find details of other apps blocked at this TechCrunch article:
http://www.techcrunch.com/2009/07/07/amazon-killing-mobile-apps-that-use-its-data/
Just giving you a heads up and hopefully saving you a lot of work.
// This is my code used in my Twitter connection, and working well for me.
// KeithF's code was a big help!
//
// This is a category added to NSData.
#implementation NSData (EOUtil)
- (NSData*)dataByHmacSHA1EncryptingWithKey:(NSData*)key
{
void* buffer = malloc(CC_SHA1_DIGEST_LENGTH);
CCHmac(kCCHmacAlgSHA1, [key bytes], [key length], [self bytes], [self length], buffer);
return [NSData dataWithBytesNoCopy:buffer length:CC_SHA1_DIGEST_LENGTH freeWhenDone:YES];
}
#end
Take a look at CocoaCryptoHashing for the SHA1 encoding
I posted one solution to this here, that returns the Base64 encoded data that AWS requests.
Apple's iOS developer library has provided an excellent sample titled CryptoExercise which includes a simple function:
- (NSData *)getHashBytes:(NSData *)plainText" to get a SHA-1 hash.
You can see this
maybe it helps you.