Simple calculate lines and columns of str index

Use LF (0x0A) to split newline, also compatible with CRLF (0x0D 0x0A)

Newline char line number is current line

Examples

Byte index to line number:

use line_column::line_column;

assert_eq!(line_column("", 0),       (1, 1));
assert_eq!(line_column("a", 0),      (1, 1));
assert_eq!(line_column("a", 1),      (1, 2));
assert_eq!(line_column("ab", 1),     (1, 2));
assert_eq!(line_column("a\n", 1),    (1, 2));
assert_eq!(line_column("a\n", 2),    (2, 1));
assert_eq!(line_column("a\nb", 2),   (2, 1));
assert_eq!(line_column("a\r\nb", 2), (1, 3));
assert_eq!(line_column("a\r\nb", 3), (2, 1));

Character index to line number:

use line_column::char_line_column;

assert_eq!(char_line_column("", 0),         (1, 1));
assert_eq!(char_line_column("a", 0),        (1, 1));
assert_eq!(char_line_column("a", 1),        (1, 2));
assert_eq!(char_line_column("ab", 1),       (1, 2));
assert_eq!(char_line_column("😀\n", 1),     (1, 2));
assert_eq!(char_line_column("😀\n", 2),     (2, 1));
assert_eq!(char_line_column("😀\n❓", 2),   (2, 1));
assert_eq!(char_line_column("😀\n❓", 2),   (2, 1));

Line number to byte index:

use line_column::index;

assert_eq!(index("", 1, 1), 0);
assert_eq!(index("a", 1, 1), 0);
assert_eq!(index("a", 1, 2), 1);
assert_eq!(index("a\n", 1, 2), 1);
assert_eq!(index("a\n", 2, 1), 2);
assert_eq!(index("a\nx", 2, 2), 3);
assert_eq!(index("你好\n世界", 1, 2), 3); // byte index
assert_eq!(index("你好\n世界", 1, 3), 6);
assert_eq!(index("你好\n世界", 2, 1), 7);

Line number to character index:

use line_column::char_index;

assert_eq!(char_index("", 1, 1),            0);
assert_eq!(char_index("a", 1, 1),           0);
assert_eq!(char_index("你好\n世界", 1, 2),  1);
assert_eq!(char_index("你好\n世界", 1, 3),  2);
assert_eq!(char_index("你好\n世界", 2, 1),  3);