lua2hcb_compiler

This tool compiles a Lua 5.3-looking decompiler output back into HCB bytecode.

It targets the practical subset used by the current rfvp/hcb decompiler pipeline:

• Top-level function NAME(...) ... end
• Structured control flow: if/elseif/else/end, while/do/end, break
• Function calls and syscalls
• No closures/upvalues, no vararg, no multi-return

In addition to structured if/while, the compiler also supports the decompiler's __pc-dispatcher form:

local __pc = 0
while true do
  if __pc == 0 then
    ...
    if S0 == 0 then
      __pc = 2
    else
      __pc = 1
    end
  elseif __pc == 1 then
    ...
    __pc = 2
  else
    return
  end
end

Pure local declarations such as local S0, S1, S2 are accepted and ignored.

Important IR convention

This compiler assumes the input Lua is decompiler IR style (stack-machine reconstruction), e.g.

• S0 = 123 means “push 123”
• S1 = (S1 == S2) means “compare top two values and push the result”
• __ret = Foo(...) means “call Foo; return value is available via __ret / push_return”

The if/while conditions are treated as the same style used previously in the CFG/state-machine form:

• if S0 ~= 0 then / while S0 ~= 0 do: jz is used to branch on zero
• if S0 == 0 then / while S0 == 0 do: layout is inverted (still uses jz)

Strings / encoding

All C-strings in HCB are stored as:

• 1-byte length including the trailing NUL
• bytes of the string followed by \0

This applies to:

• push_string immediates inside code
• game_title and syscall names inside sysdesc

Encoding is controlled by nls in YAML (ShiftJIS, UTF-8, GB18030).

YAML meta format

example:

nls: ShiftJIS
sys_desc_offset: 0          # ignored (recomputed)
entry_point: 0              # ignored (recomputed from function entry_point())
non_volatile_global_count: 1915
volatile_global_count: 1990
custom_syscall_count: 0
game_mode: 7
game_title: "..."
syscall_count: 148          # optional; validated if present
syscalls:
  0:   { args: 2,  name: AudioLoad }
  1:   { args: 2,  name: AudioPlay }
  ...
  147: { args: 1,  name: WindowMode }

syscalls may also be provided as a YAML list (legacy), but the map form is recommended.

The difference from Lua 5.3

Build

cargo build --release

Usage

./target/release/lua2hcb --meta meta.yml --lua script.lua -o script.hcb

The tool always uses function entry_point() as the entry.