DevSpatium.IO.TextReader 0.0.9-alpha

TextReaderWrapper - Reads Text by Specified Pattern

A wrapper on top of the standard System.IO.TextReader, which supports sequential asynchronous reading according to a given pattern, and extracts the required pieces of text.

This reader can be useful for parsing texts of custom predefined formats, for automating manual time-consuming copy-paste tasks, or if you are going to implement some code that should have non-trivial reading logic.

Besides, the reader provides an API for extending its internal operations and the pattern syntax.

Getting Started

The pattern can essentially contain two commands: R and S (leaving all their varieties aside for now). R stands for a Read operation. Such an operation reads characters from the source text, converts them into a single string, and adds the string to the output collection. S, in its turn, stands for a Skip operation, which simply skips the required characters.

Example #1

Input

Hello World

Pattern

// R[5] - read 5 chars
// S.   - skip 1 char
// R>   - read remaining chars
const string pattern = @"R[5] S. R>";

Output

["Hello", "World"]

Example #2

Input

* Apple
* Lemon
* Pear
* Kiwi

Pattern

// S>     - skip line
// S+'* ' - skip * and space
// R>     - read remaining chars in the line
// {2}    - repeat twice
const string pattern = @"(S> S+'* ' R>){2}";

Output

["Lemon", "Kiwi"]

Example #3

Input

* 7:00  Wake-up
* 9:00  At work
* 10:00 Stand-up meeting
* 12:00 Lunch
* 16:00 Yet another meeting
...

Pattern

// S|/rgx/ - skip all characters up to the string that matches the specified regex
// {&R}    - and read the matched string
// S+/\s*/ - skip whitespace
// R>      - read remaining chars in the line
// *       - repeat till the end of the text
const string pattern = @"
(
    S| /\d{1,2}:\d{2}/ {&R}
    S+ /\s*/
    R>
)*
";

Output

[
    "7:00",
    "Wake-up",
    "9:00",
    "At work",
    "10:00",
    "Stand-up meeting",
    "12:00",
    "Lunch",
    "16:00",
    "Yet another meeting",
    ...
]

TextReaderWrapper

This is the "entry-point" class that wraps System.IO.TextReader using the following constructor:

public TextReaderWrapper(System.IO.TextReader underlyingReader)

ReadAsync()

// `pattern` - defines how to read the source text.
// `output` - contains the strings read from the source text.
public async Task ReadAsync(string pattern, ICollection<string> output, CancellationToken cancelToken = default)

const string pattern = @"(R.)*";
const string text = "Lorem ipsum";
var output = new List<string>();
var stringReader = new StringReader(text);
using (var textReaderWrapper = new TextReaderWrapper(stringReader))
{
    textReaderWrapper.ReadAsync(pattern, output).Wait();
}

// output: ["L", "o", "r", "e", "m", " ", "i", "p", "s", "u", "m"]

See more here!