/// <summary>
/// Compares two DBF files.
/// Note: the algorithm relies on the fact that it is only possible to
/// append records to a DBF file (i.e. no inserts in the middle of the
/// file) and it is requires the older file is passed as the first
/// argument.
/// </summary>
/// <param name="oldFilepath">
/// The path to the older DBF file to compare.
/// </param>
/// <param name="newFilepath">
/// The path to the newer DBF file to compare.
/// </param>
/// <returns>
/// The <see cref="IEnumerable{T}"/> of the differences between the two files.
/// </returns>
public static IEnumerable<Diff> Compare(string oldFilepath, string newFilepath)
{
using (var reader1 = new DbfReader(oldFilepath))
using (var reader2 = new DbfReader(newFilepath))
{
//// todo: check compatible schema
var hasMore1 = reader1.Read();
var hasMore2 = reader2.Read();
while (hasMore1 && hasMore2)
{
var record1 = reader1.DbfRecord;
var record2 = reader2.DbfRecord;
var diff = Compare(record1, record2);
switch (diff.Operation)
{
case Operation.Unmodified:
hasMore1 = reader1.Read();
hasMore2 = reader2.Read();
break;
case Operation.Modified:
hasMore1 = reader1.Read();
hasMore2 = reader2.Read();
break;
case Operation.Deleted:
hasMore1 = reader1.Read();
break;
}
if (diff.Operation != Operation.Unmodified)
{
yield return diff;
}
if (hasMore1 || !hasMore2)
{
continue;
}
var index = record1.RecordIndex;
while (reader2.Read())
{
record2 = reader2.DbfRecord;
var columnDiffs = new List<ColumnDiff>();
for (int columnIndex = 0; columnIndex < record1.ColumnCount; ++columnIndex)
{
var columnDiff = new ColumnDiff(columnIndex, record1[columnIndex], record2[columnIndex]);
columnDiffs.Add(columnDiff);
}
yield return new Diff(Operation.Inserted, ++index, columnDiffs);
}
hasMore2 = false;
}
}
}
/// <summary>
/// Compares two DbfRecords.
/// </summary>
/// <param name="record1">
/// The first record to compare.
/// </param>
/// <param name="record2">
/// The second record to compare.
/// </param>
/// <returns>
/// The <see cref="Diff"/> between the two records.
/// </returns>
public static Diff Compare(DbfRecord record1, DbfRecord record2)
{
var data1 = record1.Data;
var data2 = record2.Data;
if (data1.SequenceEqual(data2))
{
return new Diff(Operation.Unmodified, record1.RecordIndex);
}
if (record2.IsDeleted)
{
return new Diff(Operation.Deleted, record1.RecordIndex);
}
var columnDiffs = new List<ColumnDiff>();
var equalCount = 0;
for (var columnIndex = 0; columnIndex < record1.ColumnCount; ++columnIndex)
{
var columnData1 = new ArraySegmentWrapper<byte>(record1.ColumnData(columnIndex));
var columnData2 = new ArraySegmentWrapper<byte>(record2.ColumnData(columnIndex));
if (columnData1.SequenceEqual(columnData2))
{
++equalCount;
}
else
{
var columnDiff = new ColumnDiff(columnIndex, record1[columnIndex], record2[columnIndex]);
columnDiffs.Add(columnDiff);
}
}
if (equalCount == 0)
{
return new Diff(Operation.Deleted, record1.RecordIndex);
}
if (equalCount == record1.ColumnCount)
{
return new Diff(Operation.Unmodified, record1.RecordIndex);
}
return new Diff(Operation.Modified, record1.RecordIndex, columnDiffs);
}
