/// <summary>
/// Start to read
/// </summary>
/// <param name="offset">How many rows to read</param>
/// <param name="toward">If start from begin or end of file</param>
/// <param name="visualizationType">Set Visualization type</param>
/// <returns></returns>
public TextInfo Read(int offset, OffsetTowards toward, VisulaziationType visualizationType)
{
switch (visualizationType)
{
case VisulaziationType.Rows:
return(ReadRows(offset, toward));
}
return(new TextInfo());
}
private TextInfo ReadRows(int offset, OffsetTowards toward)
{
TextInfo result = new TextInfo();
/*no lines to read*/
if (offset == 0)
{
return(result);
}
using (FileStream fs = new FileStream(FullName, FileMode.Open, FileAccess.Read, FileShare.ReadWrite, 2048, true))
{
List <char> charBuilder = new List <char>(); /*StringBuilder doesn't work with Encoding: example char 𐍈 */
StringBuilder sb = new StringBuilder();
Stopwatch stopWatch = new Stopwatch();
int count = 0;
switch (toward)
{
case OffsetTowards.Downwards:
{
/*tested with utf8 file encoded by notepad-pp; other encoding may not work*/
stopWatch.Start();
var decoder = ReaderEncoding.GetDecoder();
byte[] buffer;
int bufferLength;
fs.Seek(0, SeekOrigin.End);
while (true)
{
bufferLength = 1;
buffer = new byte[1];
/*for variable byte dimension encoding, everytime i read a byte that is
* a part of character and not whole character the decoder return '�' (invalid character)
*/
char[] chars = { '�' }; //� 65533
int iteration = 0;
while (chars.Contains('�'))
{
/*at every iteration that does not produce character, buffer get bigger, up to 4 byte*/
if (iteration > 0)
{
bufferLength = buffer.Length + 1;
byte[] newBuffer = new byte[bufferLength];
Array.Copy(buffer, newBuffer, bufferLength - 1);
buffer = newBuffer;
}
/*there are no characters with more than 4 bytes in utf-8*/
if (iteration > 4)
{
stopWatch.Stop();
result.TimeOfRead = stopWatch.Elapsed;
throw new Exception();
}
/*if all is ok, the last seek return IOError with chars = empty*/
try
{
fs.Seek(-(bufferLength), SeekOrigin.Current);
}
catch
{
chars = new char[] { '\0' };
break;
}
fs.Read(buffer, 0, bufferLength);
var charCount = decoder.GetCharCount(buffer, 0, bufferLength);
chars = new char[charCount];
decoder.GetChars(buffer, 0, bufferLength, chars, 0);
++iteration;
}
/*when i get a char*/
charBuilder.InsertRange(0, chars);
if (chars.Length > 0 && chars[0] == '\n')
{
++count;
}
/*exit when i get the correctly number of line (*last row is in interval)*/
if (count == offset)
{
break;
}
/*the first search goes back, the reading goes on then we come back again, except the last */
try
{
fs.Seek(-(bufferLength), SeekOrigin.Current);
}
catch (Exception)
{
break;
}
}
stopWatch.Stop();
/*everithing must be reversed, but not \0*/
charBuilder.RemoveAt(0);
/*yuppi!*/
result.Text = new string(charBuilder.ToArray());
result.TimeOfRead = stopWatch.Elapsed;
break;
}
case OffsetTowards.Upwards:
{
using (StreamReader sr = new StreamReader(fs, ReaderEncoding))
{
string line;
stopWatch.Start();
while ((line = sr.ReadLine()) != null)
{
sb.AppendLine(line);
if (++count == offset)
{
break;
}
}
stopWatch.Stop();
result.Text = sb.ToString();
result.TimeOfRead = stopWatch.Elapsed;
break;
}
}
}
}/*end outer using*/
return(result);
}
public async Task LoadAsync()
{
/*subfunctions*/
OffsetTowards GetOffset()
{
OffsetTowards result = OffsetTowards.Unselected;
var rdbSelectedButtonFilter = gpbTowards
.Controls
.OfType <RadioButton>()
.Where(r => r.Checked).ToArray();
switch (rdbSelectedButtonFilter.FirstOrDefault()?.Name)
{
case "rdbFilterFirst":
result = OffsetTowards.Upwards;
break;
case "rdbFilterLast":
result = OffsetTowards.Downwards;
break;
default:
break;
}
return(result);
}
/*start*/
/*get info by form*/
await Task.Run(() =>
{
var toward = GetOffset();
string offsetText = (toward == OffsetTowards.Upwards) ? tbxFirstRows.Text : tbxLastRows.Text;
Int32.TryParse(offsetText, out int offset);
/*setting up the down info*/
statusStripEncoding.Items[0].Text = "Encoding: " + _reader.ReaderEncoding.HeaderName;
statusStripEncoding.Items[2].Text = "Info: try to change encoding if the file is not utf-8 and the log is empty or unreadable, the backwards read is guaranteed only with utf-8 encoded file.";
/*start reading*/
TextInfo result = new TextInfo();
var mainForm = (MainForm)this
.Parent
.Parent
.Parent;
/*setting up the last down info*/
mainForm.Invoke(new Action(() =>
{
tsslElaborationTime.Text = "Loading..";
statusStripEncoding.Items[1].Enabled = false;
cbxCompatibility.Enabled = false;
btnCloseTab.Enabled = false;
}));
try
{
result = _reader.Read(offset, toward, VisulaziationType.Rows);
mainForm.Invoke(new Action(() =>
{
/*delete \n in Upwords forward*/
result.Text = result.Text.TrimEnd();
if (cbxCompatibility.Checked)
{
tbxLog.Text = string.Empty;
tbxLog.Visible = false;
tbxLogCompatibility.Text = result.Text.Replace("\n", Environment.NewLine);
}
else
{
tbxLog.Visible = true;
tbxLog.Text = result.Text;
tbxLog.GoEnd();
tbxLogCompatibility.Text = string.Empty;
}
}));
}
/*same encoding of the reader but bad encoded*/
catch
{
MessageBox.Show("An error occurred during the reading of file: "
+ mainForm.Invoke(new Func <string>(() => tsslFullName.Text)),
"Error", MessageBoxButtons.OK, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1, MessageBoxOptions.DefaultDesktopOnly);
mainForm.Invoke(new Action(() =>
{
tbxLog.Text = string.Empty;
tbxLogCompatibility.Text = string.Empty;
BtnCloseTab_Click(null, null);
}));
return;
}
/*setting up the last down info*/
mainForm.Invoke(new Action(() =>
{
tsslElaborationTime.Text = result.TimeOfRead.TotalSeconds.ToString();
statusStripEncoding.Items[1].Enabled = true;
cbxCompatibility.Enabled = true;
btnCloseTab.Enabled = true;
}));
});
}
