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lparser.py: added support for while loops
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README.md
52
README.md
@ -12,44 +12,46 @@ Lua has a relatively small instruction set (only 38 different opcodes!). This ma
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```sh
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> cat example.lua && luac5.1 -o example.luac example.lua
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pp = "pri" .. "nt"
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i = 0
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if 2 + 2 == 4 then
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_G[pp]("Hello world")
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while i < 10 do
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print(i)
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i = i + 1
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end
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> python main.py example.luac
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example.luac
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==== [[example.lua's constants]] ====
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0: [STRING] pp
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1: [STRING] pri
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2: [STRING] nt
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3: [NUMBER] 4.0
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4: [STRING] _G
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5: [STRING] Hello world
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0: [STRING] i
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1: [NUMBER] 0.0
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2: [NUMBER] 10.0
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3: [STRING] print
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4: [NUMBER] 1.0
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==== [[example.lua's dissassembly]] ====
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[ 0] LOADK : R[0] K[1] ; load "pri" into R[0]
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[ 1] LOADK : R[1] K[2] ; load "nt" into R[1]
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[ 2] CONCAT : R[0] R[0] R[1] ; concat 2 values from R[0] to R[1], store into R[0]
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[ 3] SETGLOBAL : R[0] K[0] ;
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[ 4] EQ : R[0] K[3] K[3] ;
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[ 5] JMP : R[0] R[5] ;
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[ 6] GETGLOBAL : R[0] K[4] ;
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[ 7] GETGLOBAL : R[1] K[0] ;
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[ 8] GETTABLE : R[0] R[0] R[1] ;
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[ 9] LOADK : R[1] K[5] ; load "Hello world" into R[1]
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[ 10] CALL : R[0] R[2] R[1] ;
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[ 11] RETURN : R[0] R[1] R[0] ;
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[ 0] LOADK : R[0] K[1] ; load 0.0 into R[0]
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[ 1] SETGLOBAL : R[0] K[0] ;
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[ 2] GETGLOBAL : R[0] K[0] ;
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[ 3] LT : R[0] R[0] K[2] ;
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[ 4] JMP : R[0] 7 ;
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[ 5] GETGLOBAL : R[0] K[3] ;
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[ 6] GETGLOBAL : R[1] K[0] ;
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[ 7] CALL : R[0] 2 1 ;
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[ 8] GETGLOBAL : R[0] K[0] ;
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[ 9] ADD : R[0] R[0] K[4] ;
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[ 10] SETGLOBAL : R[0] K[0] ;
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[ 11] JMP : R[0] -10 ;
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[ 12] RETURN : R[0] 1 0 ;
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==== [[example.lua's decompiled source]] ====
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pp = "pri" .. "nt"
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if 4.0 == 4.0 then
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_G[pp]("Hello world")
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i = 0.0
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while i < 10.0 do
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print(i)
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i = (i + 1.0)
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end
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```
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46
lparser.py
46
lparser.py
@ -53,11 +53,17 @@ class LuaDecomp:
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self.__startStatement()
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self.__addExpr("local " + self.locals[indx] + " = " + expr)
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def __getInstrAtPC(self, pc: int) -> Instruction:
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if pc < len(self.chunk.instructions):
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return self.chunk.instructions[pc]
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raise Exception("Decompilation failed!")
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def __getNextInstr(self) -> Instruction:
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if self.pc + 1 < len(self.chunk.instructions):
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return self.chunk.instructions[self.pc + 1]
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return None
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raise Exception("Decompilation failed!")
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def __getCurrInstr(self) -> Instruction:
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return self.chunk.instructions[self.pc]
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@ -102,6 +108,30 @@ class LuaDecomp:
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def __emitOperand(self, a: int, b: str, c: str, op: str) -> None:
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self.__setReg(a, "(" + b + op + c + ")")
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def __compJmp(self, op: str):
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instr = self.__getCurrInstr()
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jmpType = "if"
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scopeStart = "then"
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# we need to check if the jmp location has a jump back (if so, it's a while loop)
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jmp = self.__getNextInstr().B + 1
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jmpToInstr = self.__getInstrAtPC(self.pc + jmp)
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if jmpToInstr.opcode == Opcodes.JMP:
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# if this jump jumps back to this compJmp, it's a loop!
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if self.pc + jmp + jmpToInstr.B <= self.pc + 1:
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jmpType = "while"
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scopeStart = "do"
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self.__startStatement()
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if instr.A > 0:
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self.__addExpr("%s not " % jmpType)
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else:
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self.__addExpr("%s " % jmpType)
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self.__addExpr(self.__readRK(instr.B) + op + self.__readRK(instr.C) + " ")
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self.__startScope("%s " % scopeStart, jmp)
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self.pc += 1 # skip next instr
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# 'RK's are special in because can be a register or a konstant. a bitflag is read to determine which
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def __readRK(self, rk: int) -> str:
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if (whichRK(rk)) > 0:
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@ -163,19 +193,11 @@ class LuaDecomp:
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elif instr.opcode == Opcodes.JMP:
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pass
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elif instr.opcode == Opcodes.EQ:
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self.__startStatement()
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if instr.A > 0:
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self.__addExpr("if not ")
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else:
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self.__addExpr("if ")
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self.__addExpr(self.__readRK(instr.B) + " == " + self.__readRK(instr.C) + " ")
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self.__startScope("then ", self.__getNextInstr().B + 1)
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self.pc += 1 # skip next instr
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self.__compJmp(" == ")
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elif instr.opcode == Opcodes.LT:
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self.__emitOperand(instr.A, self.__readRK(instr.B), self.__readRK(instr.C), " < ")
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self.__compJmp(" < ")
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elif instr.opcode == Opcodes.LE:
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self.__emitOperand(instr.A, instr.B, instr.C, " <= ")
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self.__compJmp(" <= ")
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elif instr.opcode == Opcodes.CALL:
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preStr = ""
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callStr = ""
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@ -101,8 +101,8 @@ class Instruction:
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if self.type == InstructionType.ABC:
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# by default, treat them as registers
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A = "R[%d]" % self.A
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B = "R[%d]" % self.B
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C = "R[%d]" % self.C
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B = "%d" % self.B
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C = "%d" % self.C
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# these opcodes have RKs for B & C
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if self.opcode in _RKBCInstr:
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@ -114,7 +114,7 @@ class Instruction:
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regs = "%6s %6s %6s" % (A, B, C)
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elif self.type == InstructionType.ABx or self.type == InstructionType.AsBx:
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A = "R[%d]" % self.A
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B = "R[%d]" % self.B
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B = "%d" % self.B
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if self.opcode in _KBx:
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B = "K[%d]" % self.B
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