/// <summary>
/// Splits big file into some chunks by matching starting characters in each line
/// </summary>
/// <param name="inputFileName">Big file name</param>
/// <param name="chars">Number of starting characters to split by</param>
private void SplitFile(string inputFileName, int chars)
{
var files = new Dictionary <string, FileChunk>(StringComparer.CurrentCulture);
using (var sr = new StreamReader(inputFileName, Encoding))
{
while (sr.Peek() >= 0)
{
var line = sr.ReadLine();
DataItem entry = DataItem.FromString(line);
//The length of the line is less than the current number of characters we split by
//In this cases we add the line to the non-sorted file
if (line.Length < chars)
{
ChunkInfo nameInfo;
if (!chunks.TryGetValue(line, out nameInfo))
{
chunks.Add(line, nameInfo = new ChunkInfo());
}
nameInfo.AddSmallString(line, Encoding);
}
//Otherwise we add the line to the file corresponding to the first char characters of the line
else
{
string start = entry.Text.Substring(0, chars);
FileChunk sfi;
if (!files.TryGetValue(start, out sfi))
{
sfi = new FileChunk(Encoding);
files.Add(start, sfi);
}
sfi.Append(line, Encoding);
}
}
}
//For each of the chunk we check if size of the chunk is still greater than the maxFileSize
foreach (var file in files)
{
file.Value.Close();
//If it is - split to smaller chunks
if (file.Value.Size > maxFileSize)
{
SplitFile(file.Value.FileName, chars + 1);
File.Delete(file.Value.FileName);
}
//Otherwise save it to the dictionary
else
{
SortFile(file.Value.FileName, file.Value.FileName);
ChunkInfo nameInfo;
if (!chunks.TryGetValue(file.Key, out nameInfo))
{
chunks.Add(file.Key, nameInfo = new ChunkInfo());
}
nameInfo.FileName = file.Value.FileName;
}
}
}
/// <summary>
/// Sorts content of the specified file
/// </summary>
/// <param name="inputFileName">File to sort</param>
/// <param name="outputFileName">File to write results to</param>
private void SortFile(string inputFileName, string outputFileName)
{
var info = new FileInfo(inputFileName);
var entries = new List <DataItem>((int)(info.Length / 4L));
using (var sr = new StreamReader(inputFileName, Encoding))
{
while (sr.Peek() >= 0)
{
entries.Add(DataItem.FromString(sr.ReadLine()));
}
}
Sorter.QuicksortParallel(entries, 0, entries.Count - 1, Comparer);
using (var sw = new StreamWriter(outputFileName, false, Encoding))
{
foreach (var entry in entries)
{
sw.WriteLine(entry);
}
}
}
