Find Changes Between Two Files With FixedWidthReader

[shriop]

Here's a random code sample showing the usage of FixedWidthReader
along with how DataStreams can be used to find changes between two
files based on the dependency of the data being sorted on a unique
primary key in the data. It uses the file layout of the products.txt
file from the demo download.

using System;

using DataStreams.Csv;
using DataStreams.FixedWidth;

namespace DiffFiles
{
class Program
{
static void Main(string[] args)
{
using (FixedWidthReader previous = new FixedWidthReader(@"./
products1.txt"))
using (FixedWidthReader current = new FixedWidthReader(@"./
products2.txt"))
using (FixedWidthWriter inserts = new FixedWidthWriter(@"./
inserts.txt"))
using (FixedWidthWriter updates = new FixedWidthWriter(@"./
updates.txt"))
using (FixedWidthWriter deletes = new FixedWidthWriter(@"./
deletes.txt"))
using (CsvWriter log = new CsvWriter(@"./log.csv"))
{
log.Write("unique_key");
log.Write("field");
log.Write("previous");
log.Write("current");
log.EndRecord();

previous.Columns.Add(5, "ProductID");
previous.Columns.Add(35, "ProductName");
previous.Columns.Add(5, "SupplierID");
previous.Columns.Add(5, "CategoryID");
previous.Columns.Add(20, "QuantityPerUnit");
previous.Columns.Add(10, "UnitPrice");
previous.Columns.Add(5, "UnitsInStock");
previous.Columns.Add(5, "UnitsOnOrder");
previous.Columns.Add(5, "ReorderLevel");
previous.Columns.Add(1, "Discontinued");

previous.Columns["ProductID"].Alignment = TextAlignment.Right;
previous.Columns["ProductID"].PaddingChar = '0';
previous.Columns["SupplierID"].Alignment = TextAlignment.Right;
previous.Columns["SupplierID"].PaddingChar = '0';
previous.Columns["CategoryID"].Alignment = TextAlignment.Right;
previous.Columns["CategoryID"].PaddingChar = '0';
previous.Columns["UnitPrice"].Alignment = TextAlignment.Right;
previous.Columns["UnitPrice"].PaddingChar = '0';
previous.Columns["UnitPrice"].MinLength = 1;
previous.Columns["UnitsInStock"].Alignment = TextAlignment.Right;
previous.Columns["UnitsInStock"].PaddingChar = '0';
previous.Columns["UnitsInStock"].MinLength = 1;
previous.Columns["UnitsOnOrder"].Alignment = TextAlignment.Right;
previous.Columns["UnitsOnOrder"].PaddingChar = '0';
previous.Columns["UnitsOnOrder"].MinLength = 1;
previous.Columns["ReorderLevel"].Alignment = TextAlignment.Right;
previous.Columns["ReorderLevel"].PaddingChar = '0';
previous.Columns["ReorderLevel"].MinLength = 1;

inserts.Columns.Add(5, "ProductID");
inserts.Columns.Add(35, "ProductName");
inserts.Columns.Add(5, "SupplierID");
inserts.Columns.Add(5, "CategoryID");
inserts.Columns.Add(20, "QuantityPerUnit");
inserts.Columns.Add(10, "UnitPrice");
inserts.Columns.Add(5, "UnitsInStock");
inserts.Columns.Add(5, "UnitsOnOrder");
inserts.Columns.Add(5, "ReorderLevel");
inserts.Columns.Add(1, "Discontinued");

inserts.Columns["ProductID"].Alignment = TextAlignment.Right;
inserts.Columns["ProductID"].PaddingChar = '0';
inserts.Columns["SupplierID"].Alignment = TextAlignment.Right;
inserts.Columns["SupplierID"].PaddingChar = '0';
inserts.Columns["CategoryID"].Alignment = TextAlignment.Right;
inserts.Columns["CategoryID"].PaddingChar = '0';
inserts.Columns["UnitPrice"].Alignment = TextAlignment.Right;
inserts.Columns["UnitPrice"].PaddingChar = '0';
inserts.Columns["UnitsInStock"].Alignment = TextAlignment.Right;
inserts.Columns["UnitsInStock"].PaddingChar = '0';
inserts.Columns["UnitsOnOrder"].Alignment = TextAlignment.Right;
inserts.Columns["UnitsOnOrder"].PaddingChar = '0';
inserts.Columns["ReorderLevel"].Alignment = TextAlignment.Right;
inserts.Columns["ReorderLevel"].PaddingChar = '0';

current.Columns = previous.Columns;

updates.Columns = inserts.Columns;
deletes.Columns = inserts.Columns;

const string uniqueKey = "ProductID";

bool previousHasMore = previous.ReadRecord();
bool currentHasMore = current.ReadRecord();

while (
previousHasMore ||
currentHasMore)
{
if (!previousHasMore)
{
inserts.WriteRecord(current.Values);
currentHasMore = current.ReadRecord();
}
else if (!currentHasMore)
{
deletes.WriteRecord(previous.Values);
previousHasMore = previous.ReadRecord();
}
else
{
long previousKey = Int64.Parse(previous[uniqueKey]);
long currentKey = Int64.Parse(current[uniqueKey]);

if (previousKey == currentKey)
{
bool hasChanges = false;

for (int i = 0; i < previous.Columns.Count; i++)
{
if (previous[i] != current[i])
{
hasChanges = true;
log.Write(previous[uniqueKey]);
log.Write(previous.Columns.Names[i]);
log.Write(previous[i]);
log.Write(current[i]);
log.EndRecord();
}
}

if (hasChanges)
{
updates.WriteRecord(current.Values);
}

currentHasMore = current.ReadRecord();
previousHasMore = previous.ReadRecord();
}
else if (previousKey < currentKey)
{
deletes.WriteRecord(previous.Values);
previousHasMore = previous.ReadRecord();
}
else // currentKey < previousKey
{
inserts.WriteRecord(current.Values);
currentHasMore = current.ReadRecord();
}
}
} // while (previousHasMore || currentHasMore)
} // using's
} // Main
} // class
} // namespace