Lua:registerAssembler

<> Lua API Reference

function registerAssembler(callback) : void

Registers a callback function that is called when Cheat Engine's single-line assembler is invoked to convert an instruction into a list of bytes.

The callback can return a byte table to provide the assembled instruction bytes. Return nil to let another registered assembler callback, or the original x86 assembler, handle the instruction.

Function Parameters

Parameter	Type	Description
callback	Function	The assembler callback to register. It receives the target address and instruction text.

Returns

This function does not return a value.

Callback Parameters

Parameter	Type	Description
address	Integer	The address where the instruction is being assembled.
instruction	String	The single-line assembler instruction text.

Callback Return Value

Return Type	Description
Table	Return a byte table containing the exact bytes to emit for the instruction.
nil	Return nil to let another assembler callback or the original x86 assembler handle the instruction.

Byte Table Format

The returned byte table should contain integer byte values.

1 return {0x90}

This example returns a single NOP byte.

Examples

Register an assembler callback that lets CE handle everything

1 registerAssembler(function(address, instruction)
2   return nil
3 end)

Assemble a custom single-byte instruction

1 registerAssembler(function(address, instruction)
2   if instruction == "customnop" then
3     return {0x90}
4   end
5 
6   return nil
7 end)

Assemble a custom two-byte NOP

1 registerAssembler(function(address, instruction)
2   if instruction == "customnop2" then
3     return {0x66, 0x90}
4   end
5 
6   return nil
7 end)

Normalize the instruction text before comparing

 1 registerAssembler(function(address, instruction)
 2   local text = instruction:lower()
 3   text = text:gsub("^%s+", "")
 4   text = text:gsub("%s+$", "")
 5 
 6   if text == "customnop" then
 7     return {0x90}
 8   end
 9 
10   return nil
11 end)

Use the address parameter

 1 registerAssembler(function(address, instruction)
 2   local text = instruction:lower()
 3 
 4   if text == "addresslowbyte" then
 5     local lowByte = address & 0xff
 6     return {lowByte}
 7   end
 8 
 9   return nil
10 end)

Support a small custom instruction alias

 1 registerAssembler(function(address, instruction)
 2   local text = instruction:lower():gsub("^%s+", ""):gsub("%s+$", "")
 3 
 4   if text == "ret0" then
 5     -- xor eax,eax
 6     -- ret
 7     return {0x31, 0xC0, 0xC3}
 8   end
 9 
10   return nil
11 end)

Use with auto assembler

 1 registerAssembler(function(address, instruction)
 2   if instruction:lower() == "customnop" then
 3     return {0x90}
 4   end
 5 
 6   return nil
 7 end)
 8 
 9 autoAssemble([[
10 customnop
11 ]])

Log unhandled instructions

1 registerAssembler(function(address, instruction)
2   print(string.format("Assembling at %X: %s", address, instruction))
3 
4   return nil
5 end)

Main Pages

Core Lua documentation entry points

◆ Lua
◆ Script Engine

Assembler and Disassembler Related Lua Functions

Auto assembler, disassembly helpers, instruction size lookup, and assembler callbacks

◆ autoAssemble ◆ autoAssembleCheck ◆ disassemble ◆ splitDisassembledString

◆ getInstructionSize ◆ getPreviousOpcode ◆ registerAssembler ◆ unregisterAssembler