Vital.sandbox - string.unpack

Syntax

local ..., next_pos = string.unpack(format, input, start_at = 1)

Parameters

Type	Name	Description
`string`	format	Format string - same format as used in `string.pack`
`string`	input	Binary string containing packed data
`int`	start_at	Starting position in the string

Returns

Type	Name	Description
`...`	...	Unpacked values
`int`	next_pos	Index of the first unread byte in the string

Examples

Pack and unpack integers

local packed = string.pack("iii", 10, 20, 30)
local a, b, c = string.unpack("iii", packed)

engine.print("info", a, b, c) --10  20  30

Unpack values using position tracking

local packed = string.pack("ii", 100, 200)
local val1, pos = string.unpack("i", packed)
local val2 = string.unpack("i", packed, pos)

engine.print("info", val1, val2) --100  200

Unpack a fixed-size string

local packed = string.pack("c5", "hello")
local str = string.unpack("c5", packed)

engine.print("info", str) --'hello'

Unpack a zero-terminated string

local packed = string.pack("z", "world")
local str, nextPos = string.unpack("z", packed)

engine.print("info", str) --'world'
engine.print("info", nextPos) --7

Unpack mixed types from a binary string

local packed = string.pack("ifd", 42, 3.14, 2.718)
local i, f, d = string.unpack("ifd", packed)

engine.print("info", i, f, d) --42  3.14  2.718

Unpack from a specific position

local packed = string.pack("iii", 1, 2, 3)
local value = string.unpack("i", packed, 5)

engine.print("info", value) --2

Unpack a little endian value

local packed = string.pack("<I4", 0x12345678)
local value = string.unpack("<I4", packed)

engine.print("info", string.format("0x%X", value)) --'0x12345678'

Unpack a big endian value

local packed = string.pack(">I4", 0xABCDEF00)
local value = string.unpack(">I4", packed)

engine.print("info", string.format("0x%X", value)) --'0xABCDEF00'

Unpack raw bytes into characters

local packed = string.pack("BBB", 65, 66, 67)
local b1, b2, b3 = string.unpack("BBB", packed)

engine.print("info", string.char(b1, b2, b3)) --'ABC'

Unpack a double precision float

local packed = string.pack("d", math.pi)
local value = string.unpack("d", packed)

engine.print("info", value) --3.14159...

Unpack struct-like player data

local packed = string.pack("c10i4f", "PlayerName", 100, 99.5)
local name, health, score = string.unpack("c10i4f", packed)

engine.print("info", name, health, score)

Unpack a string with a length prefix

local packed = string.pack("s1", "hello")
local str = string.unpack("s1", packed)

engine.print("info", str) --'hello'

Unpack multiple strings sequentially

local packed = string.pack("zz", "first", "second")
local str1, pos = string.unpack("z", packed)
local str2 = string.unpack("z", packed, pos)

engine.print("info", str1, str2) --'first'  'second'

Unpack a network protocol header

local header = string.pack(">I2I2I4", 1, 2, 1024)
local version, type, length = string.unpack(">I2I2I4", header)

engine.print("info", "Version:", version)
engine.print("info", "Type:", type)
engine.print("info", "Length:", length)

Unpack a boolean stored as a byte

local packed = string.pack("b", 1)
local value = string.unpack("b", packed)
local bool = value ~= 0

engine.print("info", bool) --true

Partially unpack a binary string in two passes

local packed = string.pack("i4i4i4i4", 1, 2, 3, 4)
local a, b, pos = string.unpack("i4i4", packed)
local c, d = string.unpack("i4i4", packed, pos)

engine.print("info", a, b) --1  2
engine.print("info", c, d) --3  4

string.unpack

Syntax

Parameters

Returns

Examples

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