Snippet - Read StreamReader Contents In Chunks

ArkPhaze · 08-20-2012, 12:57 AM

Here's a cool snippet I came up with to read using a StreamReader in chunks based on an input of how many lines you want to read at a time until the end of the Stream for the file.

Good example usage for where the null coalescing operator in C# comes in nicely as well :ok:

I used the fully fleged StringBuilder just in case we're dealing with a fair bit of lines based on the lnBufferCount for determining the buffer size for the string we're dealing with through the loop.

Code:
private void MainMethod()
{
	using (StreamReader sr = new StreamReader(@"F:\file.txt"))
	{
		string lnBuffer = string.Empty;
		int lnBufferCount = 5;

		//If based on user input:
		if (lnBufferCount < 1) throw new ArgumentException("lnBufferCount cannot be less than 1.");

		while (LinesAvailable(ref lnBuffer, ReadLines(lnBufferCount, sr)))
		{
			MessageBox.Show(lnBuffer);
		}
	}
}

private bool LinesAvailable(ref string lnBuffer, string readLine)
{
	lnBuffer = readLine;
	return !(lnBuffer.StartsWith("\0"));
}

private string ReadLines(int numLines, StreamReader reader)
{
	StringBuilder sb = new StringBuilder();

	Array.ForEach(Enumerable.Range(1, numLines).ToArray(), i => sb.AppendLine(reader.ReadLine() ?? "\0"));
	return sb.ToString();
}

Enjoy

ArkPhaze · 08-20-2012, 01:36 AM

So say we had a file like:

Code:
Name: ArkPhaze
UID: 1234
Group: Regular

Name: Frooxious
UID: 234134
Group: Regular

Name: 1llusion 
UID: 64445
Group: Admin

Name: bluedog.tar.gz
UID: 77777
Group: Admin

Now I can read off the data from this file in chunks of linecounts of 4 in length, which enables me to deal with these string values each time through the loop, and apply my standard action to each:

Code:
Name: ArkPhaze
UID: 1234
Group: Regular

Code:
Name: Frooxious
UID: 234134
Group: Regular

Code:
Name: 1llusion 
UID: 64445
Group: Admin

Code:
Name: bluedog.tar.gz
UID: 77777
Group: Admin

Example: (Using the file above)

Code:
private void MainMethod()
{
	using (StreamReader sr = new StreamReader(@"F:\file.txt"))
	{
		string lnBuffer = string.Empty;
		int lnBufferCount = 4;

		//If based on user input:
		if (lnBufferCount < 1) throw new ArgumentException("lnBufferCount cannot be less than 1.");

		while (LinesAvailable(ref lnBuffer, ReadLines(lnBufferCount, sr)))
		{
			string[] lines = lnBuffer.Split(new char[] {'\n'}, StringSplitOptions.RemoveEmptyEntries);
			string[] data = lines.Take(3).Select(s => s.Split(':')[1].Trim()).ToArray();
			MessageBox.Show(string.Format("The member {0} has a UID of {1} and is in the {2}'s group.", data[0], data[1], data[2]));
		}
	}
}

private bool LinesAvailable(ref string lnBuffer, string readLine)
{
	lnBuffer = readLine;
	return !(lnBuffer.StartsWith("\0"));
}

private string ReadLines(int numLines, StreamReader reader)
{
	StringBuilder sb = new StringBuilder();

	Array.ForEach(Enumerable.Range(1, numLines).ToArray(), i => sb.AppendLine(reader.ReadLine() ?? "\0"));
	return sb.ToString();
}

Result:

You could even have used Regex.

Not too good with Regex, but here's an example:

Code:
Match m = Regex.Match(lnBuffer, @"\bName: (.*?)\r\nUID: (.*?)\r\nGroup: (\w.*?)\r?\n?\b");
MessageBox.Show(string.Format("The member {0} has a UID of {1} and is in the {2}'s group.", m.Groups[1].Value, m.Groups[2].Value, m.Groups[3].Value));

Inside the while loop.