#!/bin/bash

fast_chr() {
    local __octal
    local __char
    printf -v __octal '%03o' "$1"
    printf -v __char "\\%s" "$__octal"
    REPLY=$__char
}

function unichr {
    local c=$1    # Ordinal of char
    local l=0    # Byte ctr
    local o=63    # Ceiling
    local p=128    # Accum. bits
    local s=''    # Output string
    
    (( c < 0x80 )) && { fast_chr "$c"; echo -n "$REPLY"; return; }

    while (( c > o )); do
        fast_chr $(( t = 0x80 | c & 0x3f ))
        s="$REPLY$s"
        (( c >>= 6, l++, p += o+1, o>>=1 ))
    done
    fast_chr $(( t = p | c ))
    echo -n " $REPLY$s"
}
## test harness
# for (( i=0x2500; i<0x2600; i++ )); do
for (( i=0x0; i<0x20000; i++ )); do
    unichr "$i"
done