Returns the position (in bytes) where the encoding of the n-th codepoint of s (counting from byte position i) starts. A negative n gets characters before position i. The default for i is 0 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 nil.
Returns the position (in bytes) where the encoding of the n-th codepoint of s (counting from byte position i) starts. A negative n gets characters before position i. The default for i is 0 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 nil.