utf8.nvim

missing utf8 module for neovim Lua.

The license for this library is CC0. Feel free to embed and use it. If you find any bugs, I'd appreciate it if you could let me know via PR.

Why?

neovim's Lua is luajit (equivalent to Lua 5.1), so it does not have some of the libraries that recent Lua has.

What is this?

This library provides basic support for UTF-8 encoding. It does not provide any support for Unicode other than the handling of the encoding.

(Citing the official reference manual)

Functions

Global variables are not defined, so call this with require.

local utf8 = require("utf8")

• utf8.char(...)

Receives zero or more integers, converts each one to its corresponding UTF-8 byte sequence and returns a string with the concatenation of all these sequences.

• utf8.charpattern

The pattern (a string, not a function) "[\0-\x7F\xC2-\xF4][\x80-\xBF]*", which matches exactly one UTF-8 byte sequence, assuming that the subject is a valid UTF-8 string.

• utf8.codes(s)

Returns values so that the construction

for p, c in utf8.codes(s) do body end

will iterate over all UTF-8 characters in string s, with p being the position (in bytes) and c the code point of each character. It raises an error if it meets any invalid byte sequence.

• utf8.codepoint(s [, i [, j]])

Returns the code points (as integers) from all characters in s that start between byte position i and j (both included). The default for i is 1 and for j is i. It raises an error if it meets any invalid byte sequence.

• utf8.len(s [, i [, j]])

Returns the number of UTF-8 characters in string s that start between positions i and j (both inclusive). The default for i is 1 and for j is -1. If it finds any invalid byte sequence, returns fail plus the position of the first invalid byte.

• utf8.offset(s, n [, i])

Returns the position (in bytes) where the encoding of the n-th character of s (counting from position i) starts. A negative n gets characters before position i. The default for i is 1 when n is non-negative and #s+1 otherwise, so that utf8.offset(s, -n) gets the offset of the n-th character from the end of the string. If the specified character is neither in the subject nor right after its end, the function returns fail.

As a special case, when n is 0 the function returns the start of the encoding of the character that contains the i-th byte of s.