NSData to NString conversion problem - iphone

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.

Related

NSString unichar from int

I have an int value which I obtained from the character 爸, which is 29240. I can convert this number to hex, but I have no clue how to write the chinese character out in an NSString with only the int 29240.
Basically, what I did was:
NSString * s = #"爸";
int a = [s characterAtIndex:0];
NSLog(#"%d", a);
What it gave as output was 29240.
However, I don't know how to create an NSString that just contains 爸 from only the int 29240.
I converted 29240 into binary which gave me 7238, but I can't seem to create a method which allows me to input any integer and NSLog the corresponding character.
I can hard code it in, so that I have
char cString[] = "\u7238";
NSData *data = [NSData dataWithBytes:cString length:strlen(cString)];
NSString *string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(#"result string: %#", string);
But I'm not sure how to do it with any int.
Thanks to anyone who can help me!
To create a string from one (or more) Unicode characters use initWithCharacters:
unichar c = 29240;
NSString *string = [[NSString alloc] initWithCharacters:&c length:1];
NSString uses UTF-16 characters internally, so
this works for all characters in the "Basic Multilingual Plane", i.e. all characters up to U+FFFF. The following code works for arbitrary characters:
uint32_t ch = 0x1F60E;
ch = OSSwapHostToLittleInt32(ch); // To make it byte-order safe
NSString *s1 = [[NSString alloc] initWithBytes:&ch length:4 encoding:NSUTF32LittleEndianStringEncoding];
NSLog(#"%#", s1);
// Output: 😎
Try out this code snippet to get you started in the right direction:
NSString *s = #"0123456789";
for (int i = 0; i < [s length]; i++) {
NSLog(#"Value: %d", [s characterAtIndex:i]);
}
Just pass in the character as an integer:
unichar decimal = 12298;
NSString *charStr = [NSString stringWithFormat:#"%C", decimal];

Adding more variables to NSData for turn-based gaming data encoding

I am making a turn-based game where I have stored an integer variable 'points' into NSData, which is then stored by gamecenter. So far I am doing this as follows:
NSString *newString=[[NSString alloc] initWithFormat: #"%i", points];
NSData *data = [newString dataUsingEncoding:NSUTF8StringEncoding];
I need to store more variables into NSData *data. How can i do this?
I am now aware that you can store 2 integers in the string *newString by:
NSString *newString=[[NSString alloc] initWithFormat: #"%i, %i", points, otherInteger];
However I don't know how I would decode this as the string would be stored as one integer value following on from the last. It might not be the best implementation anyway so any suggestions would be appreciated.
You could do something like this:
// for encoding
int32_t points = ...;
int32_t otherInteger = ...;
NSMutableData *data = [NSMutableData data];
[data appendBytes:&points length:sizeof(int32_t)];
[data appendBytes:&otherInteger length:sizeof(int32_t)];
.
.
.
// for decoding
NSData *data = ...;
int32_t points;
int32_t otherInteger;
int index = 0;
NSRange range;
range = NSMakeRange(index, sizeof(int32_t));
[data getBytes:&points range:range];
index += sizeof(int32_t);
range = NSMakeRange(index, sizeof(int32_t));
[data getBytes:&otherInteger range:range];
index += sizeof(int32_t);
.
.
.

How to read bytes from NSData

Can anyone suggest a method to read bytes from NSData (like read function in #interface NSInputStream : NSStream)
How to read binary bytes in NSData? may help you:
NSString *path = #"…put the path to your file here…";
NSData * fileData = [NSData dataWithContentsOfFile: path];
const char* fileBytes = (const char*)[fileData bytes];
NSUInteger length = [fileData length];
NSUInteger index;
for (index = 0; index<length; index++) {
char aByte = fileBytes[index];
//Do something with each byte
}
You can also create an NSInputStream from an NSData object, if you need the read interface:
NSData *data = ...;
NSInputStream *readData = [[NSInputStream alloc] initWithData:data];
[readData open];
However, you should be aware that initWithData copies the contents of data.
One of the simplest ways is to use NSData getBytes:range:.
NSData *data = ...;
char buffer[numberOfBytes];
[data getBytes:buffer range:NSMakeRange(position, numberOfBytes)];
where position and length is the position you want to read from in NSData and the length is how many bytes you want to read. No need to copy.
Alex already mentioned NSData getBytes:range: but there is also NSData getBytes:length: which starts from the first byte.
NSData *data = ...;
char buffer[numberOfBytes];
[data getBytes:buffer length:numberOfBytes];
May way of doing that..
do not forget to free byte array after usage.
NSData* dat = //your code
NSLog(#"Receive from Peripheral: %#",dat);
NSUInteger len = [dat length];
Byte *bytedata = (Byte*)malloc(len);
[dat getBytes:bytedata length:len];
int p = 0;
while(p < len)
{
printf("%02x",bytedata[p]);
if(p!=len-1)
{
printf("-");
}//printf("%c",bytedata[p]);
p++;
}
printf("\n");
// byte array manipulation
free(bytedata);

Converting NSString, data type expression, to actual NSData

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

how to encode a UInt32 scalar type into a NSData object

I am currently creating this NSData object. I would like to put in sever different objects that are of type NSString and UInt32. I know how to put a NSString into my NSData object, but I don't know how to do this with a UInt32 scalar type.
this is how I do it with a NSString
- (void) constructRequest
{
NSString *mystring = [[NSString alloc] initWithString:[self addMethodName]];
UInt32 protocolInt = [self addProtocolVersion];
NSData* data=[mystring dataUsingEncoding:NSUTF8StringEncoding];
[data writeToFile:#"/Users/imac/Desktop/_dataDump.dat" atomically:YES];
}
So I have figured it out, and instead of just updating my question I will put in the answer so others can see that this question has been answered if they are looking to do something similar.
code is as follows
- (void) constructRequest
{
//NSString *mystring = [[NSString alloc] initWithString:[self addMethodName]];
UInt32 protocolInt = [self addProt];
NSData * data = [[NSData alloc] initWithBytes:&protocolInt length:sizeof(protocolInt)];
//NSData* data=[mystring dataUsingEncoding:NSUTF8StringEncoding];
[data writeToFile:#"/Users/imac/Desktop/_dataDump.dat" atomically:YES];
}
Does it need to be NSData? You could use NSString or NSNumber (both can be saved in a property list).
Your scheme doesn't really distinguish between a 4-byte string and a UInt32, if that matters.
You can use htonl(),htons(), ntohl() and ntohs() to make it endian-safe.
htonl()--"Host to Network Long int" 32Bytes
ntohl()--"Network to Host Long int" 32Bytes
htons()--"Host to Network Short int" 16Bytes
ntohs()--"Network to Host Short int" 16Bytes
Example:
- (void)testExample {
UInt32 length = 0x1a2b3c4d;
NSLog(#"%x", length);
length = htonl(length);
NSLog(#"%x", length);
NSMutableData *data = [[NSMutableData alloc] init];
[data appendBytes:&length length:4];
NSLog(#"%#", data);
}
print:
2015-10-29 15:46:49.224 UPHTTP-iOS[3896:101301] 1a2b3c4d
2015-10-29 15:46:49.224 UPHTTP-iOS[3896:101301] 4d3c2b1a
2015-10-29 15:46:49.224 UPHTTP-iOS[3896:101301] <1a2b3c4d>