Trace-based benchmarking via a mojo app.

apps/benchmark/args.cc

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "apps/benchmark/args.h"
+
+#include <algorithm>
+
+#include "base/logging.h"
+#include "base/strings/string_split.h"
+
+namespace benchmark {
+namespace {
+
+bool GetArgValue(const std::vector<std::string>& args,
+                 std::string prefix,
+                 std::string* result) {
+  auto matches = [&prefix](const std::string& s) -> bool {
+    return s.substr(0, prefix.size()) == prefix;
+  };
+  auto it = std::find_if(args.begin(), args.end(), matches);

[jamesr, 2015/08/27 21:12:38]

is there a particular reason to avoid base's command line processing logic here?
this file depends on //base already

doing a full scan through the args list for each lookup will be inefficient if
we have a lot of args. could you parse into a set or map at startup? how general
do you want this to be - i.e. how many things do you expect to be configured via
args?

[ppi, 2015/08/28 12:15:11]

Done and done (switched to base::command_line). Don't know if we grow further
switches, but the code is nicer this way in any case.

+  if (it == args.end())
+    return false;
+  *result = it->substr(prefix.size());
+  return true;
+}
+
+bool GetMeasurement(const std::string& measurement_spec, Measurement* result) {
+  // Measurements are described in the format:
+  // <measurement type>/<event category>/<event name>.
+  std::vector<std::string> parts;
+  base::SplitString(measurement_spec, '/', &parts);
+  if (parts.size() != 3) {
+    LOG(ERROR) << "Could not parse the measurement description.";
+    return false;
+  }
+
+  if (parts[0] == "time_until") {
+    result->type = MeasurementType::TIME_UNTIL;
+  } else if (parts[0] == "avg_duration") {
+    result->type = MeasurementType::AVG_DURATION;
+  } else {
+    LOG(ERROR) << "Could not recognize the measurement type: " << parts[0];
+    return false;
+  }
+
+  result->target_event.category = parts[1];
+  result->target_event.name = parts[2];
+  result->spec = measurement_spec;
+  return true;
+}
+
+}  // namespace
+
+Args::Args() {}
+
+Args::~Args() {}
+
+bool GetArgs(const std::vector<std::string>& input_args, Args* result) {
+  if (!GetArgValue(input_args, "--app=", &result->app)) {
+    LOG(ERROR) << "Could not find the required --app argument.";
+    return false;
+  }
+
+  std::string duration_str;
+  if (!GetArgValue(input_args, "--duration=", &duration_str)) {
+    LOG(ERROR) << "Could not find the required --duration argument.";
+    return false;
+  }
+  result->duration = base::TimeDelta::FromSeconds(std::stoi(duration_str));

[jamesr, 2015/08/27 21:12:38]

what if duration_str doesn't contain a valid int? std::stoi will throw an
exception (crash in our world) if it's not valid. base:: has string->number
converters that do something more reasonable on error, or you could try to
validate if you want to avoid the base code

[ppi, 2015/08/28 12:15:11]

Done (used the converter in base).

+
+  // Every argument that doesn't start with "--" and is not the first argument
+  // (url of the benchmark app) is a measurement to run.
+  bool first = true;
+  for (const std::string& arg : input_args) {
+    if (first) {
+      first = false;
+      continue;
+    }
+    if (arg.substr(0, 2) == "--") {

[jamesr, 2015/08/27 21:12:38]

i believe this crashes if the arg length is 0 or 1 chars, which is probably not
what you want. base:: has a StartsWith
(https://github.com/domokit/mojo/blob/master/base/strings/string_util.h#L328) or
if you want to avoid using that be sure to check the length

[ppi, 2015/08/28 12:15:11]

Done (n/a with switch to base::command_line).

+      continue;
+    }
+    Measurement measurement;
+    if (!GetMeasurement(arg, &measurement)) {
+      return false;
+    }
+    result->measurements.push_back(measurement);
+  }
+  return true;
+}
+
+}  // namespace benchmark