Calculate line and column from character index

CalcLineAndColumn.cs

// Calculates line and column from character index.
(int, int ) CalcLineAndColumn( string text, int pos ) {

    // Count the number of line breaks before pos.
    int line = 0, lastLf = -1;
    int lf = text.IndexOf( '\n' );
    while( lf != -1 && lf < pos ) {
        ++line;
        lastLf = lf;
        lf = text.IndexOf( '\n', lf + 1 );
    }

    // Calculate number of chars since last line break before pos up to pos
    int col = pos - lastLf - 1;

    return (line, col);
}

//------------- TEST -------------

string text = @"AB
C
DE";

for( int i = 0; i < text.Length; ++i ) {

    var (row, col) = CalcLineAndColumn( text, i );
    Console.WriteLine( $"Pos: {i}, Row: {row}, Col: {col}, Char: #{(int)text[i]}" );
}

/* Output:
Pos: 0, Row: 0, Col: 0, Char: #65
Pos: 1, Row: 0, Col: 1, Char: #66
Pos: 2, Row: 0, Col: 2, Char: #13
Pos: 3, Row: 0, Col: 3, Char: #10
Pos: 4, Row: 1, Col: 0, Char: #67
Pos: 5, Row: 1, Col: 1, Char: #13
Pos: 6, Row: 1, Col: 2, Char: #10
Pos: 7, Row: 2, Col: 0, Char: #68
Pos: 8, Row: 2, Col: 1, Char: #69
*/