Strings and numbers

Arithmetic and comparison are Lua operators, compiled to IntOp and the *Cmp family; width and sign are attributes of the type, so there is no Int64Cmp to write. A literal past 32 bits is a 64-bit int, which compares through System::Int64Op, as LogicLib’s L< does, because makensis refuses Int64Cmp for a 32-bit target. It cannot be computed with. There are no floats.

NSIS	Installua
StrCpy	assignment: x = y
StrCmpS	==, which is case-sensitive — the reversal that bites hardest
StrCmp	string.lower(a) == b, which folds to one case-insensitive compare
StrLen	string.len(s) → int
IntOp	+ - * / % // & | ~ << >>
IntCmp / Int64Cmp / IntPtrCmp and the unsigned forms	< <= > >= == ~=
IntFmt / Int64Fmt	string.format

The string adapters

Each compiles to NSIS instructions and StrFunc macros — the ${Using:StrFunc} lines are collected and emitted for you.

Installua	Notes
string.len(s) → int	counts UTF-16 code units
string.sub(s, i[, j]) → string	negative indices follow Lua, not NSIS, except that one reaching before the start gives ""
string.find(s, needle) → int	0 when absent, where Lua says nil; case-sensitive, as Lua’s is
string.lower(s) / string.upper(s) → string
string.format(fmt, value) → string	IntFmt, so one integer and one of %c %d %i %u %x %X

func("majorOf", function(version)
  local dot = string.find(version, ".")
  return string.sub(version, 1, dot - 1)
end)

The math adapters

NSIS has no instruction for these, so each compiles to a compare and a branch. They matter for the type as much as the value: a check like if n > 0 does not make n non-negative for the positions that need one, such as sleep, and these are how a script says so.

Installua	Non-negative when
math.abs(n) → int	always
math.max(a, b, …) → int	any argument is, so math.max(n, 0)
math.min(a, b, …) → int	every argument is

func("pause", function(ini)
  local seconds = tonumber(readIniStr(ini, "Settings", "Autoclose"))
  sleep(math.max(seconds, 0) * 1000)
end)

Arithmetic shift

Lua’s >> fills with zeros, so it compiles to NSIS’s >>>. NSIS’s >> copies the sign bit instead, and Installua writes it as Lua 5.2 did: bit32.arshift(x, n) → IntOp $d x >> n. So bit32.arshift(-8, 1) is -4, where -8 >> 1 is 2147483644.

Casts

Every NSIS value is already a string, so tostring and tonumber emit no code. They change what the compiler lets a value be passed to, and nothing else.

Installua	Takes	Notes
tostring(v) → string	int, string	concatenation already accepts an int: "step " .. i needs no cast
tonumber(s) → int	string, int	NSIS’s reading, not Lua’s: "abc" is 0, "0x10" is 16, "010" is 8

A bool is refused by both, because it is stored as 1 or 0 and Lua’s tostring(true) is "true".

local count = tonumber(readEnvStr("RETRIES")) + 1
messageBox(tostring(count))

ExpandEnvStrings / ReadEnvStr

NSIS	Installua
ReadEnvStr	readEnvStr(name) → string
ExpandEnvStrings	expandEnvStrings(string) → string

NSIS has no instruction that writes a variable. setEnv(name, value) is SetEnvironmentVariable through the System plugin. It changes the installer’s own environment, so a program the installer starts afterwards inherits it, and nothing outside the installer sees it:

setEnv("NSISDIR", EXEDIR .. "/nsis")
exec('"' .. EXEDIR .. '/nsis/makensis.exe" build.nsi')

ReadMemory

Usage readMemory(address, size) → string

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