restructure string decoding to support iterable use and include benchmarks for UTF-8 decoding.

utils/tests/string_encoding/benchmark_runner.dart

Index: utils/tests/string_encoding/benchmark_runner.dart
diff --git a/utils/tests/string_encoding/benchmark_runner.dart b/utils/tests/string_encoding/benchmark_runner.dart
new file mode 100644
index 0000000000000000000000000000000000000000..873979d190c4a527837b9d7033c6f74522971224
--- /dev/null
+++ b/utils/tests/string_encoding/benchmark_runner.dart
@@ -0,0 +1,459 @@
+// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+/**
+ * The results of a single block of tests (count times run, overall time).
+ */
+class BlockSample {
+  BlockSample(this.count, this.durationNanos);
+  int count;
+  int durationNanos;
+
+  static int _totalCount(List<BlockSample> samples) =>
+      _sum(samples, int (BlockSample s) => s.count);
+
+  static int _totalTime(List<BlockSample> samples) =>
+      _sum(samples, int (BlockSample s) => s.durationNanos);
+
+  static BlockSample _select(List<BlockSample> samples,
+      BlockSample selector(BlockSample a, BlockSample b)) {
+    BlockSample r = null;
+    for (BlockSample s in samples) {
+      r = (r == null) ? s : selector(r, s);
+    }
+    return r;
+  }
+
+  static int _sum(List<BlockSample> samples, int extract(BlockSample s)) {
+    int total = 0;
+    for (BlockSample s in samples) {
+      total += extract(s);
+    }
+    return total;
+  }
+}
+
+/**
+ * Uses sample data to build a performance model for a test. Construct
+ * the model from a set of sample results, and it generates a simple
+ * predivtive model for execution of future requests. It uses
+ * a simple least-squares linear solution to build the model.
+ */
+class PerformanceModel {
+  PerformanceModel.calculate(List<BlockSample> source) {
+    if (0 == source.length) {
+      throw "Missing data exception";
+    } else if (1 == source.length) {
+      overheadNanos = 0;
+      perRequestNanos = source[0].durationNanos / source[0].count;
+    } else {
+      double n = source.length.toDouble();
+      double sumY = BlockSample._totalTime(source).toDouble();
+      double sumXSquared = BlockSample._sum(source,
+          int _(BlockSample s) => s.count * s.count).toDouble();
+      double sumX = BlockSample._totalCount(source).toDouble();
+      double sumXY = BlockSample._sum(source,
+          int _(BlockSample s) => s.durationNanos * s.count).toDouble();
+
+      overheadNanos =
+          ((((sumY * sumXSquared) - (sumX * sumXY)) /
+          ((n * sumXSquared) - (sumX * sumX))) / source.length).toInt();
+
+      perRequestNanos =
+          (((n * sumXY) - (sumX * sumY)) /
+          ((n * sumXSquared) - (sumX * sumX))).toInt();
+    }
+  }
+
+  bool isValid() => overheadNanos >= 0 && perRequestNanos >= 0;
+
+  int overheadNanos;
+  int perRequestNanos;
+  int repsFor(int targetDurationNanos, [int blocksize = -1]) {
+    if (blocksize <= 0) {
+      return ((targetDurationNanos - overheadNanos) / perRequestNanos).toInt();
+    } else {
+      int blockTime = overheadNanos + (blocksize * perRequestNanos);
+      int fullBlocks = targetDurationNanos ~/ blockTime;
+      int extraReps =
+          ((targetDurationNanos - (fullBlocks * blockTime)) - overheadNanos)
+          ~/ perRequestNanos;
+      return ((fullBlocks * blocksize) + extraReps).toInt();
+    }
+  }
+}
+
+/**
+ * Report overall test performance
+ */
+class TestReport {
+  TestReport(this.id, this.desc, this.warmup, this.results) {
+    spaceChar = " ".charCodes()[0];
+  }
+
+  int spaceChar;
+
+  int resultsCount() => BlockSample._totalCount(results);
+
+  int resultsNanos() => BlockSample._totalTime(results);
+
+  int resultsBestNanos() {
+    BlockSample best = bestBlock(results);
+    return best.durationNanos ~/ best.count;
+  }
+
+  int resultsMeanNanos() =>
+      (BlockSample._totalTime(results) /
+      BlockSample._totalCount(results)).toInt();
+
+  int resultsWorstNanos() {
+    BlockSample worst = worstBlock(results);
+    return worst.durationNanos / worst.count;
+  }
+
+  int warmupBestNanos() {
+    BlockSample best = bestBlock(warmup);
+    return best.durationNanos / best.count;
+  }
+
+  int warmupMeanNanos() => _totalTime(warmup) / _totalCount(warmup);
+
+  int warmupWorstNanos() {
+    BlockSample worst = worstBlock(warmup);
+    return worst.durationNanos / worst.count;
+  }
+
+  BlockSample bestBlock(List<BlockSample> samples) {
+    return BlockSample._select(samples,
+          BlockSample selector(BlockSample a, BlockSample b) {
+            return a.durationNanos <= b.durationNanos ? a : b;
+    });
+  }
+
+  BlockSample worstBlock(List<BlockSample> samples) {
+    return BlockSample._select(samples,
+          BlockSample selector(BlockSample a, BlockSample b) {
+      return a.durationNanos >= b.durationNanos ? a : b;
+    });
+  }
+
+  void printReport() {
+    String text = _leftAlign("${id}", 30);
+    String totalCount = _rightAlign(resultsCount().toString(), 10);
+    String totalDurationMs =
+        _rightAlign(_stringifyDoubleAsInt(resultsNanos() / 1E6), 6);
+    String meanDuration =
+       _rightAlign(_stringifyDoubleAsInt(resultsMeanNanos().toDouble()), 8);
+
+    print("${text} total time:${totalDurationMs} ms" +
+        "    iterations:${totalCount}    mean:${meanDuration} ns");
+  }
+
+  void printReportWithThroughput(int sizeBytes) {
+    String text = _leftAlign("${id}", 30);
+    String totalCount = _rightAlign(resultsCount().toString(), 10);
+    String totalDurationMs =
+        _rightAlign(_stringifyDoubleAsInt(resultsNanos() / 1E6), 6);
+    String meanDuration =
+        _rightAlign(_stringifyDoubleAsInt(resultsMeanNanos()), 8);
+
+    int totalBytes = sizeBytes * resultsCount();
+    String mbPerSec = (((1E9 * sizeBytes * resultsCount()) /
+       (1024 * 1024 * resultsNanos()))).toString();
+    print("${text} total time:${totalDurationMs} ms" +
+        "    iterations:${totalCount}" +
+        "    mean:${meanDuration} ns;   ${mbPerSec} MB/sec");
+  }
+
+  String _leftAlign(String s, int width) {
+    List<int> outCodes = [];
+    outCodes.insertRange(0, width, spaceChar);
+    outCodes.setRange(0, Math.min(width, s.length), s.charCodes());
+    return new String.fromCharCodes(outCodes);
+  }
+
+  String _rightAlign(String s, int width) {
+    List<int> outCodes = [];
+    outCodes.insertRange(0, width, spaceChar);
+    outCodes.setRange(Math.max(0, width - s.length), Math.min(width, s.length),
+        s.charCodes());
+    return new String.fromCharCodes(outCodes);
+  }
+
+  static String _stringifyDoubleAsInt(double val) {
+    if (val.isInfinite() || val.isNaN()) {
+      return "NaN";
+    } else {
+      return val.toInt().toString();
+    }
+  }
+
+  String id;
+  String desc;
+  List<BlockSample> warmup;
+  List<BlockSample> results;
+}
+
+class Runner {
+  static bool runTest(String testId) {
+    Options opts = new Options();
+    return opts.arguments.length == 0 ||
+        opts.arguments.some(_(String id) => id == testId);
+  }
+}
+
+/**
+ * Run traditional blocking-style tests. Tests may be run a specified number
+ * of times, or they can be run based on performance to estimate a particular
+ * duration.
+ */
+class BenchmarkRunner extends Runner {
+  static void runCount(String id, String desc, CountTestConfig config,
+      Function test) {
+    if (runTest(id)) {
+      List<BlockSample> warmupSamples = _runTests(test, config._warmup, 1);
+      List<BlockSample> resultSamples = _runTests(test, config._reps, 1);
+      config.reportHandler(
+          new TestReport(id, desc, warmupSamples, resultSamples));
+    }
+  }
+
+  static void runTimed(String id, String desc, TimedTestConfig config,
+      Function test) {
+    if (runTest(id)) {
+      List<BlockSample> warmupSamples = _runTests(test, config._warmup, 1);
+      PerformanceModel model = _calibrate(config._minSampleTimeMs, 16, test);
+      int reps = model.repsFor(1E6 * config._targetTimeMs, config._blocksize);
+      int blocksize = config._blocksize < 0 ? reps : config._blocksize;
+      List<BlockSample> resultSamples = _runTests(test, reps, blocksize);
+      config.reportHandler(
+          new TestReport(id, desc, warmupSamples, resultSamples));
+    }
+  }
+
+  static PerformanceModel _calibrate(int minSampleTimeMs, int maxAttempts,
+      Function test) {
+    PerformanceModel model;
+    int i = 0;
+    do {
+      model = _buildPerformanceModel(minSampleTimeMs, test);
+      i++;
+    } while (i < maxAttempts && !model.isValid());
+    return model;
+  }
+
+  static PerformanceModel _buildPerformanceModel(
+      int minSampleTimeMs, Function test) {
+    int iterations = 1;
+    List<BlockSample> calibrationResults = [];
+    BlockSample calibration = _execBlock(test, iterations);
+    calibrationResults.add(calibration);
+    while (calibration.durationNanos < (1E6 * minSampleTimeMs)) {
+      iterations *= 2;
+      calibration = _execBlock(test, iterations);
+      calibrationResults.add(calibration);
+    }
+    return new PerformanceModel.calculate(calibrationResults);
+  }
+
+  static List<BlockSample> _runTests(Function test, int count, int blocksize) {
+    List<BlockSample> samples = [];
+    for (int rem = count; rem > 0; rem -= blocksize) {
+      BlockSample bs = _execBlock(test, Math.min(blocksize, rem));
+      samples.add(bs);
+    }
+    return samples;
+  }
+
+  static BlockSample _execBlock(Function test, int count) {
+    Stopwatch s = new Stopwatch();
+    s.start();
+    for (int i = 0; i < count; i++) {
+      test();
+    }
+    s.stop();
+    return new BlockSample(count, s.elapsedInUs() * 1000);
+  }
+}
+
+/**
+ * Define CPSTest type.
+ */
+typedef void CPSTest(Function continuation);
+
+typedef void ReportHandler(TestReport r);
+
+/**
+ * Run non-blocking-style using Continuation Passing Style callbacks. Tests may
+ * be run a specified number of times, or they can be run based on performance
+ * to estimate a particular duration.
+ */
+class CPSBenchmarkRunner extends Runner {
+
+  CPSBenchmarkRunner(): _cpsTests = [];
+
+  void addTest(CPSTest test) {
+    _cpsTests.add(test);
+  }
+
+  void runTests([int index = 0, Function continuation = null]) {
+    if (index < _cpsTests.length) {
+      _cpsTests[index](_(){
+        _addToEventQueue(_() => runTests(index + 1, continuation));
+      });
+    } else {
+      if (null != continuation) {
+        _addToEventQueue(_() => continuation());
+      }
+    }
+  }
+
+  List<CPSTest> _cpsTests;
+
+  static void runCount(String id, String desc, CountTestConfig config,
+      CPSTest test, void continuation()) {
+    if (runTest(id)) {
+      _runTests(test, config._warmup, 1, (List<BlockSample> warmupSamples){
+        int blocksize =
+            config._blocksize <= 0 ? config._reps : config._blocksize;
+        _runTests(test, config._reps, blocksize,
+          _(List<BlockSample> resultSamples) {
+            config.reportHandler(
+                new TestReport(id, desc, warmupSamples, resultSamples));
+            continuation();
+          });
+      });
+    } else {
+      continuation();
+    }
+  }
+
+  static void runTimed(String id, String desc, TimedTestConfig config,
+      CPSTest test, void continuation()) {
+    if (runTest(id)) {
+      _runTests(test, config._warmup, 1, (List<BlockSample> warmupSamples){
+        _calibrate(config._minSampleTimeMs, 5, test, (PerformanceModel model){
+          int reps =
+              model.repsFor(1E6 * config._targetTimeMs, config._blocksize);
+          int blocksize =
+              config._blocksize <= 0 ? reps : config._blocksize;
+          _runTests(test, reps, blocksize, (List<BlockSample> results) {
+              config.reportHandler(
+                  new TestReport(id, desc, warmupSamples, results));
+              continuation();
+            });
+        });
+      });
+    } else {
+      continuation();
+    }
+  }
+
+  static void nextTest(Function testLoop, int iteration) {
+    _addToEventQueue(() => testLoop(iteration + 1));
+  }
+
+  static void _calibrate(int minSampleTimeMs, int maxAttempts,
+      CPSTest test, void continuation(PerformanceModel model)) {
+    _buildPerformanceModel(minSampleTimeMs, test, (PerformanceModel model){
+      if (maxAttempts > 1 && !model.isValid()) {
+        _calibrate(minSampleTimeMs, maxAttempts - 1, test, continuation);
+      } else {
+        continuation(model);
+      }
+    });
+  }
+
+  static void _buildPerformanceModel(
+      int minSampleTimeMs, CPSTest test, void continuation(PerformanceModel m),
+          [int iterations = 1, List<BlockSample> calibrationResults = null]) {
+    List<BlockSample> _calibrationResults =
+        null == calibrationResults ? [] : calibrationResults;
+    _runTests(test, iterations, 1000, (List<BlockSample> calibration) {
+      _calibrationResults.addAll(calibration);
+      if (BlockSample._totalTime(calibration) < (1E6 * minSampleTimeMs)) {
+        _buildPerformanceModel(minSampleTimeMs, test, continuation,
+            iterations: iterations * 2,
+            calibrationResults: _calibrationResults);
+      } else {
+        PerformanceModel model =
+            new PerformanceModel.calculate(_calibrationResults);
+        continuation(model);
+      }
+    });
+  }
+
+  static void _runTests(CPSTest test, int reps, int blocksize,
+        void continuation(List<BlockSample> samples),
+        [List<BlockSample> samples = null]) {
+    List<BlockSample> localSamples = (null == samples) ? [] : samples;
+    if (reps > 0) {
+      int blockCount = Math.min(blocksize, reps);
+      _execBlock(test, blockCount, (BlockSample sample){
+        localSamples.add(sample);
+        _addToEventQueue(() =>
+            _runTests(test, reps - blockCount, blocksize,
+                continuation, localSamples));
+      });
+    } else {
+      continuation(localSamples);
+    }
+  }
+
+  static void _execBlock(CPSTest test, int count,
+      void continuation(BlockSample sample)) {
+    Stopwatch s = new Stopwatch();
+    s.start();
+    _innerLoop(test, count, () {
+      s.stop();
+      continuation(new BlockSample(count, s.elapsedInUs() * 1000));
+    });
+  }
+
+  static void _innerLoop(CPSTest test, int remainingCount,
+      Function continuation) {
+    if (remainingCount > 1) {
+      test(() => _innerLoop(test, remainingCount - 1, continuation));
+    } else {
+      continuation();
+    }
+  }
+
+  static void _addToEventQueue(Function action) {
+    new Timer(_(Timer t) => action(), 0);
+  }
+}
+
+class CountTestConfig {
+  CountTestConfig(int this._warmup, int this._reps,
+      [int blocksize = -1, ReportHandler reportHandler = null]) {
+        this._blocksize = blocksize;
+        this._reportHandler = (null == reportHandler) ?
+            _(TestReport r) => r.printReport() : reportHandler;
+      }
+
+  Function _reportHandler;
+  Function get reportHandler() => _reportHandler;
+  int _warmup;
+  int _reps;
+  int _blocksize;
+}
+
+class TimedTestConfig {
+  TimedTestConfig(int this._warmup, int this._targetTimeMs,
+      [int minSampleTimeMs = 100, int blocksize = -1,
+      ReportHandler reportHandler = null]) :
+      this._minSampleTimeMs = minSampleTimeMs,
+      this._blocksize = blocksize {
+    this._reportHandler = (null == reportHandler) ?
+        _(TestReport r) => r.printReport() : reportHandler;
+  }
+
+  Function _reportHandler;
+  Function get reportHandler() => _reportHandler;
+  int _warmup;
+  int _targetTimeMs;
+  int _minSampleTimeMs;
+  int _blocksize;
+}