CODEWITHSUNDEEP
jsonflutterhttputf-8character-encoding
viks
viks

Reputation: 21

Flutter - Convert "\x" encoded utf-8 characters to readable String from http.get response

I'm parsing a html page in my flutter app, and somewhere in the middle of that html source has a json string in utf-8 format ( "\x" format).

I'm able to get the html content and then parse to it extract that json object in "\x" utf-8 format to a String var, but I'm not able to convert it to a json to decode it.

I tried printing the ranes of that first 4 letters in that parsed output "\x5B" it printing as 4 separate ints, while the same "\x5B" I statically assigned to a String var and printed the ranes , it only shows one digit. So just wondering how can I decode that extracted String in "\x" format ?

An extract of the code as below:

final response = await http.get(Uri.parse(url)); 

 if (response.statusCode == 200) { 
  var res = utf8.decode(response.bodyBytes);
 
 //gives the starting index of json object in html source 
 int startIndex = res.indexOf('var statData');

 // start and end index of json object in "\x" format 
 int start = res.indexOf("(", startIndex) + 2;
 int end = res.indexOf(");", start) - 1;
 
//extract the json in \x encoded
  String dataJson = res.substring(start,end);

  //now sample code to compare the string, one statically assigned, 
  //another extracted from the html source, to describe the issue I'm having now.
 
  String sample1 = dataJson.substring(0,4));  //extracts "\x5B" from the string
 
 String sample2 = "\x5B";  
 
 print(sample2.runes);  // prints (91)   
 
 print(sample1.ranes);   // prints (92, 120, 53, 66), expectation is to get (91) 
 }

Output :

 I/flutter ( 3437): (91)
 I/flutter ( 3437): (92, 120, 53, 66)

While sample2.runes prints the single character (91)( equivalent ascii is '{' - start of the json)),

The same "\x5B" I extracted from the string not getting decoded as (91), instead it is treated as 4 separate characters, so looks like '\x' extracted string is not treated as utf-8 encode indicator.

I want the sample1.runes also to be {91}, how to approach this ?, where am I going wrong?

Upvotes: 1

Views: 1453

Answers (1)

viks
viks

Reputation: 21

I don't know whether this is the correct way to handle it, but thanks to this post https://stackoverflow.com/a/64699290/17301137 , I was able to resolve it.

Basically It does a regex match of all Hex values after '\x' then replace it to corresponding string return.

final Pattern unicodePattern = new RegExp(r'\\x([0-9A-Fa-f]{2})');
final String newStr = sample1.replaceAllMapped(unicodePattern, (Match unicodeMatch) {
  final int hexCode = int.parse(unicodeMatch.group(1)!, radix: 16);
  final unicode = String.fromCharCode(hexCode);
  return unicode;
});

this is the way I resolved it.

But not sure, whether there any better way to resolve it.

Upvotes: 1

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