diff options
| -rw-r--r-- | utf8.lua | 63 |
1 files changed, 63 insertions, 0 deletions
@@ -1,3 +1,26 @@ +-- utf8.lua - Basic (and unsafe) utf8 string support in plain Lua - public domain +-- +-- Written in 2013 by Matthias Richter (vrld@vrld.org) +-- +-- This software is in the public domain. Where that dedication is not +-- recognized, you are granted a perpetual, irrevokable license to copy and +-- modify this file as you see fit. This software is distributed without any +-- warranty. + +-- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! +-- ALL FUNCTIONS ARE UNSAFE: THEY ASSUME VALID UTF8 INPUT +-- !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! + +-- Generic for iterator. +-- +-- Arguments: +-- s ... The utf8 string. +-- i ... Last byte of the previous codepoint. +-- +-- Returns: +-- k ... Number of the *last* byte of the codepoint. +-- c ... The utf8 codepoint (character). +-- n ... Width/number of bytes of the codepoint. local function iter(s, i) if i >= #s then return end local b, nbytes = s:byte(i+1,i+1), 1 @@ -14,16 +37,40 @@ local function iter(s, i) return i+nbytes, s:sub(i+1,i+nbytes), nbytes end +-- Shortcut to the generic for iterator. +-- +-- Usage: +-- for k, c, n in chars(s) do +-- ... +-- end +-- +-- Meaning of k, c, and n is the same as in iter(s, i). local function chars(s) return iter, s, 0 end +-- Get length in characters of an utf8 string. +-- +-- Arguments: +-- s ... The utf8 string. +-- +-- Returns: +-- n ... Number of utf8 characters in s. local function len(s) -- assumes sane utf8 string: count the number of bytes that is *not* 10xxxxxx local _, c = s:gsub('[^\128-\191]', '') return c end +-- Get substring, same semantics as string.sub(s,i,j). +-- +-- Arguments: +-- s ... The utf8 string. +-- i ... Starting position, may be negative. +-- j ... (optional) Ending position, may be negative. +-- +-- Returns: +-- t ... The substring. local function sub(s, i, j) local l = len(s) j = j or l @@ -40,6 +87,15 @@ local function sub(s, i, j) return table.concat(t) end +-- Split utf8 string in two substrings +-- +-- Arguments: +-- s ... The utf8 string. +-- i ... The position to split, may be negative. +-- +-- Returns: +-- left ... Substring before i. +-- right ... Substring after i. local function split(s, i) local l = len(s) if i < 0 then i = l + i + 1 end @@ -52,6 +108,13 @@ local function split(s, i) return s:sub(1, pos), s:sub(pos+1, -1) end +-- Reverses order of characters in an utf8 string. +-- +-- Arguments: +-- s ... The utf8 string. +-- +-- Returns: +-- t ... The revered string. local function reverse(s) local t = {} for _, c in chars(s) do |