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

For index and char_index:

• When index exceeds the string length, return string length
• When column exceeds the newline char, return the index of the newline char
• When column by zero, return previous char index

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);

The end of string is considered a character:

use line_column::*;

assert_eq!(index("", 1, 1),             0);
assert_eq!(index("a", 1, 2),            1);
assert_eq!(char_index("", 1, 1),        0);
assert_eq!(char_index("a", 1, 2),       1);
assert_eq!(line_column("", 0),          (1, 1));
assert_eq!(line_column("a", 1),         (1, 2));
assert_eq!(char_line_column("", 0),     (1, 1));
assert_eq!(char_line_column("a", 1),    (1, 2));