pack - Packing and unpacking format string

Adapted Air780E Air780EP Air780EPS Air780EQ Air700EAQ Air700EMQ Air700ECQ Air201

Note

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Tip

There are also video tutorials in this library, click this link to view

Example

--[[
 '<' Set to Little Ended 
 '>' Set to Big Endian 
 '=' Size side follows local settings 
 'z' Empty string, 0 bytes
 'a' size_t String, first 4 bytes express length, then N bytes of data
 'A' Specifies the length string, such as A8, which represents 8 bytes of data.
 'f' float, 4 Byte
 'd' double , 8 Byte
 'n' Lua number , 32bit Firmware 4 bytes, 64bit firmware 8 bytes
 'c' char , 1 Byte
 'b' byte = unsigned char  , 1 Byte
 'h' short  , 2 Byte
 'H' unsigned short  , 2 Byte
 'i' int  , 4 Byte
 'I' unsigned int , 4 Byte
 'l' long , 8 Bytes, only 64bit firmware can correctly obtain
 'L' unsigned long , 8 Bytes, only 64bit firmware can correctly obtain
]]

-- Please see the detailed usage demo

pack.unpack( string, format, init)

Unpack String

Parameters

Incoming Value Type	Explanation
string	String to be unpacked
string	Formatting Symbols
int	The default value is 1, which marks where unpacking begins

Return Value

return value type	explanation
int	Position of string marker
any	The first unpacked value may have N return values according to the format value.

Examples

local _,a = pack.unpack(x,">h") --Unpack into short (2 bytes)

---

pack.pack( format, val1, val2, val3, valn )

value of the packed string

Parameters

Incoming Value Type	Explanation
string	format Formatting Symbols
any	First value to pack
any	Second value to pack
any	Second value to pack
any	nth value to be packed

Return Value

return value type	explanation
string	A string containing all the formatting variables

Examples

local data = pack.pack('<h', crypto.crc16("MODBUS", val))
log.info("data", data, data:toHex())

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