Vital.sandbox - string.packsize

local size = string.packsize(format)

Type	Name	Description
`string`	format	Format string - same format as used in `string.pack`

Type	Name	Description
`int`	size	The size in bytes of the packed string that would result from `string.pack`

Get the size of three packed integers

local size = string.packsize("iii")

engine.print("info", size) --12

Get the size of a packed double

local size = string.packsize("d")

engine.print("info", size) --8

Get the size of a fixed-length string

local size = string.packsize("c10")

engine.print("info", size) --10

Get the size of multiple packed types

local size = string.packsize("ifd")

engine.print("info", size) --16

Get the size with a little endian specifier

local size = string.packsize("<I4")

engine.print("info", size) --4

Get the size of a packed byte

local size = string.packsize("b")

engine.print("info", size) --1

Get the size of a packed short

local size = string.packsize("h")

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

Get the size of a packed long

local size = string.packsize("l")

engine.print("info", size) --8

Get the size of a format with padding

local size = string.packsize("ixxi")

engine.print("info", size) --12

Compare sizes of different integer widths

engine.print("info", "i4:", string.packsize("i4")) --4
engine.print("info", "i8:", string.packsize("i8")) --8

Calculate the buffer size needed for a format

local fmt = "i4i4f"
local bufferSize = string.packsize(fmt)

engine.print("info", "Need", bufferSize, "bytes") --'Need 12 bytes'

Get the size of multiple fixed strings

local size = string.packsize("c5c5c5")

engine.print("info", size) --15

Verify packsize matches the actual packed length

local fmt = "ifd"
local size = string.packsize(fmt)
local packed = string.pack(fmt, 1, 2.5, 3.14)

engine.print("info", #packed == size) --true

Pre-calculate record size for file buffers

local recordFormat = "c32i4i4"
local recordSize = string.packsize(recordFormat)

engine.print("info", "Each record:", recordSize, "bytes")

Calculate a network protocol header size

local headerFormat = ">I2I2I4"
local headerSize = string.packsize(headerFormat)

engine.print("info", "Header size:", headerSize) --8

string.packsize