private void WriteDataCore(IChannel ch, TextWriter writer, IDataView data,
out string argsLoader, out long count, out int min, out int max, params int[] cols)
{
_host.AssertValue(ch);
ch.AssertValue(writer);
ch.AssertValue(data);
ch.AssertNonEmpty(cols);
// Determine the active columns and whether there is header information.
bool[] active = new bool[data.Schema.ColumnCount];
for (int i = 0; i < cols.Length; i++)
{
ch.Check(0 <= cols[i] && cols[i] < active.Length);
ch.Check(data.Schema.GetColumnType(cols[i]).ItemType.RawKind != 0);
active[cols[i]] = true;
}
bool hasHeader = false;
if (_outputHeader)
{
for (int i = 0; i < cols.Length; i++)
{
if (hasHeader)
{
continue;
}
var type = data.Schema.GetColumnType(cols[i]);
if (!type.IsVector)
{
hasHeader = true;
continue;
}
if (!type.IsKnownSizeVector)
{
continue;
}
var typeNames = data.Schema.GetMetadataTypeOrNull(MetadataUtils.Kinds.SlotNames, cols[i]);
if (typeNames != null && typeNames.VectorSize == type.VectorSize && typeNames.ItemType.IsText)
{
hasHeader = true;
}
}
}
using (var cursor = data.GetRowCursor(i => active[i]))
{
var pipes = new ValueWriter[cols.Length];
for (int i = 0; i < cols.Length; i++)
{
pipes[i] = ValueWriter.Create(cursor, cols[i], _sepChar);
}
// REVIEW: This should be outside the cursor creation.
string header = CreateLoaderArguments(data.Schema, pipes, hasHeader, ch);
argsLoader = header;
if (_outputSchema)
{
WriteSchemaAsComment(writer, header);
}
double rowCount = data.GetRowCount(true) ?? double.NaN;
using (var pch = !_silent ? _host.StartProgressChannel("TextSaver: saving data") : null)
{
long stateCount = 0;
var state = new State(this, writer, pipes, hasHeader);
if (pch != null)
{
pch.SetHeader(new ProgressHeader(new[] { "rows" }), e => e.SetProgress(0, stateCount, rowCount));
}
state.Run(cursor, ref stateCount, out min, out max);
count = stateCount;
if (pch != null)
{
pch.Checkpoint(stateCount);
}
}
}
}