How to find line and column for a n-th byte in a buffer?

Question

I want to find a line number and a column for a particular byte number in a buffer in Neovim. I can get it (sort of) with

local b = 444
local line = vim.fn.byte2line(b)
local line_start = vim.fn.line2byte(line)
local col = b - line_start + 1

But the result will not be correct for multibyte charactes.

How to calculate line and column correctly for a given byte in a buffer?

Answer 1

You can use the charidx() function to convert the byte index to the character index. For example:

    chidx = vim.fn.charidx(vim.fn.getline(line), col)

Answer 2

Use :goto to go to a specific byte. Then can use line() & col()

:goto 444
:echo [line('.'), col('.')]

For more help see:

:h :goto
:h line()
:h col()