1 files changed, 122 insertions, 0 deletions
diff --git a/1brc.dart b/1brc.dart
new file mode 100644
index 0000000..6e4befc
--- /dev/null
+++ b/1brc.dart
@@ -0,0 +1,122 @@
+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}');
+  });
+}