Dart read json objects from Uneditable large file - dart

Question

i have a large file which that uneditable and i have more jsonObject into that, for example:
{"id":"#123456","v":"1"}
this isn't jsonArray which i can't parse and read it, for example:
String file= new File('file.json').readAsStringSync();
Map<String, dynamic> data = json.decode(file);
you think how can i read this objects from file and show key and values?

Answer 1

Try the following solution. I ended up making a parser for your input format which are returning each parsed JSON object in a Stream.
The parser will not work if any strings in your JSON contains { or }. If that is the case, I can expand the parser so it takes this into account but I don't want to make it more advanced than necessary.
import 'dart:async';
import 'dart:convert';
import 'dart:io';
Future<void> main() async {
final ids = await File('large_file.json')
.openRead()
.transform(const Utf8Decoder())
.transform<dynamic>(JsonObjectTransformer())
.map((dynamic json) => json['id'] as String)
.toList();
print(ids); // [#123456, #123456]
}
class JsonObjectTransformer extends StreamTransformerBase<String, dynamic> {
static final _openingBracketChar = '{'.codeUnitAt(0);
static final _closingBracketChar = '}'.codeUnitAt(0);
#override
Stream<dynamic> bind(Stream<String> stream) async* {
final sb = StringBuffer();
var bracketsCount = 0;
await for (final string in stream) {
for (var i = 0; i < string.length; i++) {
final current = string.codeUnitAt(i);
sb.writeCharCode(current);
if (current == _openingBracketChar) {
bracketsCount++;
}
if (current == _closingBracketChar && --bracketsCount == 0) {
yield json.decode(sb.toString());
sb.clear();
}
}
}
}
}