lua-bit

lua-bit is designed for lua binary operation，and there is a Javascript style function charCodeAt accompolished in Lua：

Example

-- 0x0F & 2
bit:_and(0x0F,2)
 
-- 0x0F | 2
bit:_or(0x0F,2)
 
-- 0x0F ^ 2
bit:_xor(0x0F,2)

-- !0x0F 
bit:_not(0x0F)

-- 8<<2( negative number supported if -8<<2)
bit:_lshift(8,2) 【bit:_lshift(-8,2) 】


-- 8>>>2( negative number supported if -8>>>2)
-- >>> take the number as a unsigned value
bit:_frshift(8,2) 【bit:_frshift(-8,2) 】

bit:charCodeAt

The charCodeAt() method returns the numeric Unicode value of the character at the given index (except for unicode codepoints > 0x10000).

special Method

javascript engine using UTF16，characters in Basic Multilingual Plane were the same with unicode, but if the characters were in Supplementary Plane it should use the formula below，usually we encounter Supplementary Plane emoji like (4 byte UTF8 character)

-- formula 1
H = Math.floor((c-0x10000) / 0x400)+0xD800 
L = (c - 0x10000) % 0x400 + 0xDC00

local str 	=	'你好' 
local allBytes = bit:charCodeAt(str)
-- allBytes is a table contain 6 numbers，while one Chinese characters takes 3 bytes
-- if str contains only 1 emoji，it will return a table contains 2 numbers

more details post here http://blog.hellotalk.org/2016/01/16/lua-charCodeAt/

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