/// <summary>Map file name and offset into statistical data.</summary>
/// <remarks>
/// Map file name and offset into statistical data.
/// <p>
/// The map task is to get the
/// <tt>key</tt>, which contains the file name, and the
/// <tt>value</tt>, which is the offset within the file.
/// The parameters are passed to the abstract method
/// <see cref="IOMapperBase{T}.DoIO(Org.Apache.Hadoop.Mapred.Reporter, string, long)"
/// />
/// , which performs the io operation,
/// usually read or write data, and then
/// <see cref="IOMapperBase{T}.CollectStats(Org.Apache.Hadoop.Mapred.OutputCollector{K, V}, string, long, object)
/// "/>
///
/// is called to prepare stat data for a subsequent reducer.
/// </remarks>
/// <exception cref="System.IO.IOException"/>
public virtual void Map(Text key, LongWritable value, OutputCollector <Text, Text>
output, Reporter reporter)
{
string name = key.ToString();
long longValue = value.Get();
reporter.SetStatus("starting " + name + " ::host = " + hostName);
this.stream = GetIOStream(name);
T statValue = null;
long tStart = Runtime.CurrentTimeMillis();
try
{
statValue = DoIO(reporter, name, longValue);
}
finally
{
if (stream != null)
{
stream.Close();
}
}
long tEnd = Runtime.CurrentTimeMillis();
long execTime = tEnd - tStart;
CollectStats(output, name, execTime, statValue);
reporter.SetStatus("finished " + name + " ::host = " + hostName);
}