PerformanceProvider.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.CompilerServices;
using Xamarin.Forms.Internals;

namespace Xamarin.Forms.Build.Tasks
{
	[Preserve(AllMembers = true)]
	internal class PerformanceProvider : IPerformanceProvider
	{
		internal class Statistic
		{
			public readonly List<Tuple<string, long>> StartTimes = new List<Tuple<string, long>>();
			public int CallCount;
			public long TotalTime;
			public bool IsDetail;
		}

		readonly Dictionary<string, Statistic> _Statistics = new Dictionary<string, Statistic>();

		public Dictionary<string, Statistic> Statistics
		{
			get { return _Statistics; }
		}

		public void Clear()
		{
			Statistics.Clear();
		}

		public void Start(string reference, string tag = null, [CallerFilePath] string path = null, [CallerMemberName] string member = null)
		{
			string id = GetId(tag, path, member);

			Statistic stats = GetStat(id);

			if (tag != null)
				stats.IsDetail = true;

			stats.CallCount++;
			stats.StartTimes.Add(new Tuple<string, long>(reference, Stopwatch.GetTimestamp()));
		}

		public void Stop(string reference, string tag = null, [CallerFilePath] string path = null, [CallerMemberName] string member = null)
		{
			string id = GetId(tag, path, member);
			long stop = Stopwatch.GetTimestamp();

			Statistic stats = GetStat(id);

			if (!stats.StartTimes.Any())
				return;

			long start = stats.StartTimes.Single(s => s.Item1 == reference).Item2;
			stats.TotalTime += stop - start;
		}

		public IEnumerable<string> GetStats()
		{
			yield return "ID                                                                                 | Call Count | Total Time | Avg Time";
			foreach (KeyValuePair<string, Statistic> kvp in Statistics.OrderBy(kvp => kvp.Key))
			{
				string key = ShortenPath(kvp.Key);
				double total = TimeSpan.FromTicks(kvp.Value.TotalTime).TotalMilliseconds;
				double avg = total / kvp.Value.CallCount;
				yield return string.Format("{0,-80} | {1,-10} | {2,-10}ms | {3,-8}ms", key, kvp.Value.CallCount, total, avg);
			}
		}

		static string ShortenPath(string path)
		{
			int index = path.IndexOf("Xamarin.Forms.");
			if (index > -1)
				path = path.Substring(index + 14);

			return path;
		}

		static string GetId(string tag, string path, string member)
		{
			return string.Format("{0}:{1}{2}", path, member, (tag != null ? "-" + tag : string.Empty));
		}

		Statistic GetStat(string id)
		{
			Statistic stats;
			if (!Statistics.TryGetValue(id, out stats))
			{
				Statistics[id] = stats = new Statistic();
			}
			return stats;
		}
	}
}