转载需注明出处：http://blog.youkuaiyun.com/minimicall?viewmode=contents，http://cloudtrade.top
数据读取需要定义一个读者。直接见下面代码：
namespace QuantConnect.Lean.Engine.DataFeeds
{
/********************************************************
* CLASS DEFINITIONS
*********************************************************/
/// <summary>
/// Subscription data reader is a wrapper on the stream reader class to download, unpack and iterate over a data file.
/// 订阅数据的读者是对数据流读取类的一个封装，负责下载、解压、遍历数据
/// </summary>
/// <remarks>The class accepts any subscription configuration and automatically makes it availble to enumerate</remarks>
public class SubscriptionDataReader : IEnumerator<BaseData>
{
/********************************************************
* CLASS PRIVATE VARIABLES
*********************************************************/
/// Source string to create memory stream:
private string _source = "";
///Default true to fillforward for this subscription, take the previous result and continue returning it till the next time barrier.
private bool _isFillForward = true;
///Date of this source file.
private DateTime _date = new DateTime();
///End of stream from the reader
private bool _endOfStream = false;
/// Internal stream reader for processing data line by line:
private IStreamReader _reader = null;
/// All streams done async via web protocols:
private WebClient _web = new WebClient();
/// Configuration of the data-reader:订阅数据的配置
private SubscriptionDataConfig _config;
/// Subscription Securities Access证券
private Security _security;
/// true if we can find a scale factor file for the security of the form: ..\Lean\Data\equity\factor_files\{SYMBOL}.csv
private bool _hasScaleFactors = false;
// Subscription is for a QC type:
private bool _isDynamicallyLoadedData = false;
//Symbol Mapping:
private string _mappedSymbol = "";
/// Location of the datafeed - the type of this data. 数据类型
private readonly DataFeedEndpoint _feedEndpoint;
/// Object Activator - Fast create new instance of "Type":
private readonly Func<object[], object> _objectActivator;
///Create a single instance to invoke all Type Methods:
private readonly BaseData _dataFactory;
/// Remember edge conditions as market enters/leaves open-closed.这是什么鬼
private BaseData _lastBarOfStream = null;
private BaseData _lastBarOutsideMarketHours = null;
//Start finish times of the backtest:
private readonly DateTime _periodStart;
private readonly DateTime _periodFinish;
private readonly FactorFile _factorFile;
private readonly MapFile _mapFile;
// we set the price factor ratio when we encounter a dividend in the factor file
// and on the next trading day we use this data to produce the dividend instance
private decimal? _priceFactorRatio;
// we set the split factor when we encounter a split in the factor file
// and on the next trading day we use this data to produce the split instance
private decimal? _splitFactor;
/********************************************************
* CLASS PUBLIC VARIABLES
*********************************************************/
/// <summary>
/// Last read BaseData object from this type and source
/// 最近一个读取出来的数据
/// </summary>
public BaseData Current
{
get;
private set;
}
/// <summary>
/// Explicit Interface Implementation for Current
/// </summary>
object IEnumerator.Current
{
get { return Current; }
}
/// <summary>
/// Provides a means of exposing extra data related to this subscription.
/// For now we expose dividend data for equities through here
/// 额外数据：提供证券订阅数据额外相关的数据的存储，这里指股息
/// </summary>
/// <remarks>
/// It is currently assumed that whomever is pumping data into here is handling the
/// time syncing issues. Dividends do this through the RefreshSource method
/// </remarks>
public Queue<BaseData> AuxiliaryData { get; private set; }
/// <summary>
/// Save an instance of the previous basedata we generated
/// 上一个数据（比Current更前）
/// </summary>
public BaseData Previous
{
get;
private set;
}
/// <summary>
/// Source has been completed, load up next stream or stop asking for data.
/// </summary>
public bool EndOfStream
{
get
{
return _endOfStream || _reader == null;
}
set
{
_endOfStream = value;
}
}
/********************************************************
* CLASS CONSTRUCTOR
*********************************************************/
/// <summary>
/// Subscription data reader takes a subscription request, loads the type, accepts the data source and enumerate on the results.
/// </summary>
/// <param name="config">Subscription configuration object 订阅配置</param>
/// <param name="security">Security asset 证券</param>
/// <param name="feed">Feed type enum 类型</param>
/// <param name="periodStart">Start date for the data request/backtest 开始时间</param>
/// <param name="periodFinish">Finish date for the data request/backtest 结束时间</param>
public SubscriptionDataReader(SubscriptionDataConfig config, Security security, DataFeedEndpoint feed, DateTime periodStart, DateTime periodFinish)
{
Console.WriteLine("SubscriptionDataReader,SubscriptionDataConfig:<symbol:{0},resolution:{1}>" ,config.Symbol,config.Resolution);
//Save configuration of data-subscription:
_config = config;//配置
AuxiliaryData = new Queue<BaseData>();//额外数据队列
//Save access to fill foward flag:是否向前填充
_isFillForward = config.FillDataForward;
//Save Start and End Dates:起止时间
_periodStart = periodStart;
_periodFinish = periodFinish;
//Save access to securities
_security = security;//证券
_isDynamicallyLoadedData = security.IsDynamicallyLoadedData;//是否动态加载数据
// do we have factor tables?
_hasScaleFactors = FactorFile.HasScalingFactors(config.Symbol);//变换因子
//Save the type of data we'll be getting from the source.数据类型
_feedEndpoint = feed;
//Create the dynamic type-activators:提供一种创建给定类型对象的方法
_objectActivator = ObjectActivator.GetActivator(config.Type);
if (_objectActivator == null)
{//创建失败
Engine.ResultHandler.ErrorMessage("Custom data type '" + config.Type.Name + "' missing parameterless constructor E.g. public " + config.Type.Name + "() { }");
_endOfStream = true;
return;
}
//Create an instance of the "Type":
var userObj = _objectActivator.Invoke(new object[] { });
_dataFactory = userObj as BaseData;
//If its quandl set the access token in data factory:
var quandl = _dataFactory as Quandl;
if (quandl != null)
{
if (!Quandl.IsAuthCodeSet)
{
Quandl.SetAuthCode(Config.Get("quandl-auth-token"));
}
}
//Load the entire factor and symbol mapping tables into memory, we'll start with some defaults
Console.WriteLine("load the entire factor and symbol mapping tables into memory");
_factorFile = new FactorFile(config.Symbol, new List<FactorFileRow>());
_mapFile = new MapFile(config.Symbol, new List<MapFileRow>());
try
{
if (_hasScaleFactors)
{
_factorFile = FactorFile.Read(config.Symbol);
_mapFile = MapFile.Read(config.Symbol);
}
}
catch (Exception err)
{
Log.Error("SubscriptionDataReader(): Fetching Price/Map Factors: " + err.Message);
}
}
/********************************************************
* CLASS METHODS
*********************************************************/
/// <summary>
/// Try and create a new instance of the object and return it using the MoveNext enumeration pattern ("Current" public variable).
/// 试图创建一个实例，付给Current
/// </summary>
/// <remarks>This is a highly called method and should be kept lean as possible.</remarks>
/// <returns>Boolean true on successful move next. Set Current public property.</returns>
public bool MoveNext() {
Console.WriteLine("MoveNext()");
// yield the aux data first附加数据优先
if (AuxiliaryData.Count != 0)
{
Previous = Current;//将现在这个付给Previous
Current = AuxiliaryData.Dequeue();//将这个 附属数据弹出付给Current
Console.WriteLine("AuxiliaryData:symbol:"+Current.Symbol+",price:"+Current.Price);
return true;
}
BaseData instance = null;
var instanceMarketOpen = false;
Log.Debug("SubscriptionDataReader.MoveNext(): Starting MoveNext...");
try
{
//Calls this when no file, first "moveNext()" in refresh source.
if (_endOfStream || _reader == null || _reader.EndOfStream)
{
if (_reader == null)
{
//Handle the 1% of time:: getReader failed e.g. missing day so skip day:
Current = null;
}
else
{
//This is a MoveNext() after reading the last line of file:
_lastBarOfStream = Current;
}
_endOfStream = true;
return false;
}
//Log.Debug("SubscriptionDataReader.MoveNext(): Launching While-InstanceNotNull && not EOS: " + reader.EndOfStream);
//Keep looking until output's an instance:
while (instance == null && !_reader.EndOfStream)
{
//Get the next string line from file, create instance of BaseData:读取一行
var line = _reader.ReadLine();//这个_reader里面其实会调用系统的输入流的readLine()
try
{
instance = _dataFactory.Reader(_config, line, _date, _feedEndpoint);//将字符行变成对象
}
catch (Exception err)
{
//Log.Debug("SubscriptionDataReader.MoveNext(): Error invoking instance: " + err.Message);
Engine.ResultHandler.RuntimeError("Error invoking " + _config.Symbol + " data reader. Line: " + line + " Error: " + err.Message, err.StackTrace);
_endOfStream = true;
continue;
}
if (instance != null)
{
// we care if the market was open at any time over the bar判断是否在开市时间段内
instanceMarketOpen = Exchange.IsOpenDuringBar(instance.Time, instance.EndTime, false);
//Apply custom user data filters:
try
{
if (!_security.DataFilter.Filter(_security, instance))
{
instance = null;
continue;
}
}
catch (Exception err)
{
Log.Error("SubscriptionDataReader.MoveNext(): Error applying filter: " + err.Message);
Engine.ResultHandler.RuntimeError("Runtime error applying data filter. Assuming filter pass: " + err.Message, err.StackTrace);
}
if (instance == null)
{
// REVIEW -- Is this condition heuristically possible?
Log.Trace("SubscriptionDataReader.MoveNext(): Instance null, continuing...");
continue;
}
//Check if we're in date range of the data request
if (instance.Time < _periodStart)//取出的数据不在订阅的数据范围内
{
_lastBarOutsideMarketHours = instance;
instance = null;
continue;
}
if (instance.Time > _periodFinish)//取出的数据比订阅的数据晚
{
// we're done with data from this subscription, finalize the reader
Current = null;
_endOfStream = true;
return false;
}
//Save bar for extended market hours (fill forward).
if (!instanceMarketOpen)
{
_lastBarOutsideMarketHours = instance;
}
//However, if we only want market hours data, don't return yet: Discard and continue looping.
if (!_config.ExtendedMarketHours && !instanceMarketOpen)
{
instance = null;
}
}
}
//Handle edge conditions: First Bar Read:
// -> Use previous bar from yesterday if available
if (Current == null)
{
//Handle first loop where not set yet:
if (_lastBarOfStream == null)
{
//For first bar, fill forward from premarket data where possible
_lastBarOfStream = _lastBarOutsideMarketHours ?? instance;
}
//If current not set yet, set Previous to yesterday/last bar read.
Previous = _lastBarOfStream;
}
else
{
Previous = Current;
}
Current = instance;
//End of Stream: rewind reader to last
if (_reader.EndOfStream && instance == null)
{
//Log.Debug("SubscriptionDataReader.MoveNext(): Reader EOS.");
_endOfStream = true;
if (_isFillForward && Previous != null)
{
//If instance == null, current is null, so clone previous to record the final sample:
Current = Previous.Clone(true);
//When market closes fastforward current bar to the last bar fill forwarded to close time.
Current.Time = _security.Exchange.TimeOfDayClosed(Previous.Time);
// Save the previous bar as last bar before next stream (for fill forwrd).
_lastBarOfStream = Previous;
}
return false;
}
return true;
}
catch (Exception err)
{
Log.Error("SubscriptionDataReader.MoveNext(): " + err.Message);
return false;
}
}
/// <summary>
/// For backwards adjusted data the price is adjusted by a scale factor which is a combination of splits and dividends.
/// This backwards adjusted price is used by default and fed as the current price.
/// </summary>
/// <param name="date">Current date of the backtest.</param>
private void UpdateScaleFactors(DateTime date)
{
switch (_config.DataNormalizationMode)
{
case DataNormalizationMode.Raw:
case DataNormalizationMode.TotalReturn:
return;
case DataNormalizationMode.SplitAdjusted:
_config.PriceScaleFactor = _factorFile.GetSplitFactor(date);
break;
case DataNormalizationMode.Adjusted:
_config.PriceScaleFactor = _factorFile.GetPriceScaleFactor(date);
break;
default:
throw new ArgumentOutOfRangeException();
}
}
/// <summary>
/// Check if this time is open for this subscription.
/// </summary>
/// <param name="time">Date and time we're checking to see if the market is open</param>
/// <returns>Boolean true on market open</returns>
public bool IsMarketOpen(DateTime time)
{
return _security.Exchange.DateTimeIsOpen(time);
}
/// <summary>
/// Gets the associated exchange for this data reader/security
/// </summary>
public SecurityExchange Exchange
{
get { return _security.Exchange; }
}
/// <summary>
/// Check if we're still in the extended market hours
/// </summary>
/// <param name="time">Time to scan</param>
/// <returns>True on extended market hours</returns>
public bool IsExtendedMarketOpen(DateTime time)
{
return _security.Exchange.DateTimeIsExtendedOpen(time);
}
/// <summary>
/// Reset the IEnumeration
/// </summary>
/// <remarks>Not used</remarks>
public void Reset()
{
throw new NotImplementedException("Reset method not implemented. Assumes loop will only be used once.");
}
/// <summary>
/// Fetch and set the location of the data from the user's BaseData factory:
/// </summary>
/// <param name="date">Date of the source file.</param>
/// <returns>Boolean true on successfully retrieving the data</returns>
public bool RefreshSource(DateTime date)
{
//Update the source from the getSource method:
_date = date;
Log.Trace("RefreshSource:"+date);
// if the map file is an empty instance this will always return true
if (!_mapFile.HasData(date))
{
// don't even bother checking the disk if the map files state we don't have ze dataz
return false;
}
// check for dividends and split for this security
CheckForDividend(date);
CheckForSplit(date);
var newSource = "";
//If we can find scale factor files on disk, use them. LiveTrading will aways use 1 by definition
if (_hasScaleFactors)
{
// check to see if the symbol was remapped
_mappedSymbol = _mapFile.GetMappedSymbol(date);
_config.MappedSymbol = _mappedSymbol;
// update our price scaling factors in light of the normalization mode
UpdateScaleFactors(date);
}
//Make sure this particular security is trading today:
if (!_security.Exchange.DateIsOpen(date))
{
_endOfStream = true;
return false;
}
//Choose the new source file, hide the QC source file locations
newSource = GetSource(date);
//When stream over stop looping on this data.
if (newSource == "")
{
_endOfStream = true;
return false;
}
Log.Debug("SubscriptionDataReader.MoveNext(): Source Refresh: " + newSource,1);
if (_source != newSource && newSource != "")
{
//If a new file, reset the EOS flag:
_endOfStream = false;
//Set the new source.
_source = newSource;
//Close out the last source file.
Dispose();
//Load the source:
try
{
Log.Trace("SubscriptionDataReader.RefreshSource(): Created new reader for source: " + _source);
_reader = GetReader(_source);
}
catch (Exception err)
{
Log.Error("SubscriptionDataReader.RefreshSource(): Failed to get reader: " + err.Message);
//Engine.ResultHandler.DebugMessage("Failed to get a reader for the data source. There may be an error in your custom data source reader. Skipping date (" + date.ToShortDateString() + "). Err: " + err.Message);
return false;
}
if (_reader == null)
{
Log.Error("Failed to get StreamReader for data source(" + _source + "), symbol(" + _mappedSymbol + "). Skipping date(" + date.ToShortDateString() + "). Reader is null.");
//Engine.ResultHandler.DebugMessage("We could not find the requested data. This may be an invalid data request, failed download of custom data, or a public holiday. Skipping date (" + date.ToShortDateString() + ").");
if (_isDynamicallyLoadedData)
{
Engine.ResultHandler.ErrorMessage("We could not fetch the requested data. This may not be valid data, or a failed download of custom data. Skipping source (" + _source + ").");
}
return false;
}
//Reset the public properties so we can explicitly set them with lastBar data.
Current = null;
Previous = null;
//99% of time, populate the first "Current". 1% of of time no source file (getReader fails), so
// method sets the Subscription properties as if no data.
try
{
MoveNext();
}
catch (Exception err)
{
throw new Exception("SubscriptionDataReader.RefreshSource(): Could not MoveNext to init stream: " + _source + " " + err.Message + " >> " + err.StackTrace);
}
}
//Success:
return true;
}
/// <summary>
/// Check for dividends and emit them into the aux data queue
/// </summary>
private void CheckForSplit(DateTime date)
{
if (_splitFactor != null)
{
var close = GetRawClose();
var split = new Split(_config.Symbol, date, close, _splitFactor.Value);
AuxiliaryData.Enqueue(split);
_splitFactor = null;
}
decimal splitFactor;
if (_factorFile.HasSplitEventOnNextTradingDay(date, out splitFactor))
{
_splitFactor = splitFactor;
}
}
/// <summary>
/// Check for dividends and emit them into the aux data queue
/// 检查股息，并将它写到附加数据队列中
/// </summary>
private void CheckForDividend(DateTime date)
{
if (_priceFactorRatio != null)
{
var close = GetRawClose();
var dividend = new Dividend(_config.Symbol, date, close, _priceFactorRatio.Value);
// let the config know about it for normalization
_config.SumOfDividends += dividend.Distribution;
AuxiliaryData.Enqueue(dividend);
_priceFactorRatio = null;
}
// check the factor file to see if we have a dividend event tomorrow
decimal priceFactorRatio;
if (_factorFile.HasDividendEventOnNextTradingDay(date, out priceFactorRatio))
{
_priceFactorRatio = priceFactorRatio;
}
}
/// <summary>
/// Un-normalizes the Previous.Value标准化什么鬼值
/// </summary>
private decimal GetRawClose()
{
if (Previous == null) return 0m;
var close = Previous.Value;
switch (_config.DataNormalizationMode)
{
case DataNormalizationMode.Raw:
break;
case DataNormalizationMode.SplitAdjusted:
case DataNormalizationMode.Adjusted:
// we need to 'unscale' the price
close = close/_config.PriceScaleFactor;
break;
case DataNormalizationMode.TotalReturn:
// we need to remove the dividends since we've been accumulating them in the price
close -= _config.SumOfDividends;
break;
default:
throw new ArgumentOutOfRangeException();
}
return close;
}
/// <summary>
/// Using this source URL, download it to our cache and open a local reader.
/// </summary>
/// <param name="source">Source URL for the data:</param>
/// <returns>StreamReader for the data source</returns>
private IStreamReader GetReader(string source)
{
IStreamReader reader = null;
if (_feedEndpoint == DataFeedEndpoint.LiveTrading)
{
// live trading currently always gets a rest endpoint，如果是实时交易，则只能用Rest读取
return new RestSubscriptionStreamReader(source);
}
// determine if we're hitting the file system/backtest
if (_feedEndpoint == DataFeedEndpoint.FileSystem || _feedEndpoint == DataFeedEndpoint.Backtesting)
{
// construct a uri to determine if we have a local or remote file
var uri = new Uri(source, UriKind.RelativeOrAbsolute);
if (uri.IsAbsoluteUri && !uri.IsLoopback)
{//绝对地址切uri的IP不是环回地址，即远端
reader = HandleRemoteSourceFile(source);
}
else
{//本地
reader = HandleLocalFileSource(source);
}
}
// if the reader is already at end of stream, just set to null so we don't try to get data for today
if (reader != null && reader.EndOfStream)
{
reader = null;
}
return reader;
}
/// <summary>
/// Dispose of the Stream Reader and close out the source stream and file connections.
/// 废弃该流
/// </summary>
public void Dispose()
{
if (_reader != null)
{
_reader.Close();
_reader.Dispose();
}
if (_web != null)
{
_web.Dispose();
}
}
/// <summary>
/// Get the source URL string for this datetime from the users GetSource() method in BaseData.
/// 获取这个时间对应的文件URL
/// </summary>
/// <param name="date">DateTime we're requesting.</param>
/// <returns>URL string of the source file</returns>
public string GetSource(DateTime date)
{
var newSource = "";
//Invoke our instance of this method.
if (_dataFactory != null)
{
try
{
newSource = _dataFactory.GetSource(_config, date, _feedEndpoint);
}
catch (Exception err)
{
Log.Error("SubscriptionDataReader.GetSource(): " + err.Message);
Engine.ResultHandler.ErrorMessage("Error getting string source location for custom data source: " + err.Message, err.StackTrace);
}
}
//Return the freshly calculated source URL.
return newSource;
}
/// <summary>
/// Opens up an IStreamReader for a local file source
/// 打开一个本地文件数据流
/// </summary>
private IStreamReader HandleLocalFileSource(string source)
{
if (!File.Exists(source))
{
// the local uri doesn't exist, write an error and return null so we we don't try to get data for today
Log.Trace("SubscriptionDataReader.GetReader(): Could not find QC Data, skipped: " + source);
Engine.ResultHandler.SamplePerformance(_date.Date, 0);
return null;
}
// handles zip or text files压缩文件或者文本文件都可以读取
return new LocalFileSubscriptionStreamReader(source);
}
/// <summary>
/// Opens up an IStreamReader for a remote file source
/// 打开远端文件数据源
/// </summary>
private IStreamReader HandleRemoteSourceFile(string source)
{
// clean old files out of the cache
if (!Directory.Exists(Constants.Cache)) Directory.CreateDirectory(Constants.Cache);
foreach (var file in Directory.EnumerateFiles(Constants.Cache))
{
if (File.GetCreationTime(file) < DateTime.Now.AddHours(-24)) File.Delete(file);//一天前的文件都删除掉
}
try
{
// this will fire up a web client in order to download the 'source' file to the cache
return new RemoteFileSubscriptionStreamReader(source, Constants.Cache);//创建一个远端文件读取流（先下载，后调用本地的读取流）
}
catch (Exception err)
{
Engine.ResultHandler.ErrorMessage("Error downloading custom data source file, skipped: " + source + " Err: " + err.Message, err.StackTrace);
Engine.ResultHandler.SamplePerformance(_date.Date, 0);
return null;
}
}
}
}
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