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import 'dart:collection';
import 'dart:convert';
import 'dart:io';
import 'dart:isolate';
final newLine = 10;
final semiColon = 59;
final minus = 45;
class Result {
double total = 0;
double? min = null;
double? max = null;
double count = 0;
void incrementCount() {
this.count += 1;
}
void addToTotal(double value) {
this.total += value;
}
void processMin(double value) {
if (this.min == null || this.min! > value) {
this.min = value;
}
}
void processMax(double value) {
if (this.max == null || this.max! < value) {
this.max = value;
}
}
double avg() {
return (this.total / this.count);
}
}
final Map<String, Result> res =
SplayTreeMap<String, Result>((a, b) => a.compareTo(b));
void main() async {
final file = File('measurements.txt').openSync();
final fileSize = file.lengthSync();
final maxLineLength = 106;
final threadCount = Platform.numberOfProcessors;
final chunkSize = fileSize ~/ threadCount;
final offsets = <int>[];
int offset = 0;
for (int i = 0; i < threadCount; i++) {
offsets.add(offset);
offset += chunkSize;
if (offset >= fileSize) {
break;
}
file.setPositionSync(offset);
var line = file.readSync(maxLineLength);
offset += line.indexOf(newLine) + 1;
}
final processor =
List<Future<Map<String, Result>>>.generate(offsets.length, (int i) {
var end = offsets.length == i + 1 ? fileSize : offsets[i + 1];
return Isolate.run(() => processChunk(offsets[i], end));
});
for (var res in await Future.wait(processor)) {
addResults(res);
}
printResults();
}
void addResults(Map<String, Result> results) {
results.forEach((key, val) {
res.putIfAbsent(key, () => new Result())
..addToTotal(val.total)
..processMin(val.min!)
..processMax(val.max!)
..count += val.count;
});
}
Future<Map<String, Result>> processChunk(int start, int end) async {
final res = new HashMap<String, Result>();
final file = File("measurements.txt");
List<int> buffer = List<int>.filled(106, 0);
String line = '';
int ct = 0;
List<String> split;
await for (var chunk in file.openRead(start, end)) {
for (var b in chunk) {
if (b != newLine) {
buffer[ct] = b;
ct++;
} else {
line = utf8.decode(buffer.take(ct).toList());
split = line.split(';');
var value = double.parse(split[1]);
res.putIfAbsent(split[0], () => new Result())
..addToTotal(value!)
..processMin(value)
..processMax(value)
..incrementCount();
ct = 0;
}
}
}
return res;
}
void printResults() {
res.forEach((key, value) {
print('$key;${value.min};${value.avg().toStringAsFixed(1)};${value.max}');
});
}
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