Skip to main content

​
Overview

Opcode: 0x39 Introduced: Frontier (EVM genesis) CODECOPY copies a specified range of the currently executing code to memory.

​
Specification

Stack Input: 
destOffset (memory offset)
offset (code offset)
length (bytes to copy)
Stack Output: 
[]
Gas Cost: 3 + memory expansion + (length / 32) * 3 (rounded up)

​
Behavior

Copies length bytes from executing code at offset to memory at destOffset. Zero-pads if code bounds exceeded.

​
Examples

​
Copy Runtime Code

function getRuntimeCode() public pure returns (bytes memory code) {
    assembly {
        let size := codesize()
        code := mload(0x40)
        mstore(code, size)
        codecopy(add(code, 0x20), 0, size)
        mstore(0x40, add(add(code, 0x20), size))
    }
}

​
CREATE2 Factory

function deploy() public returns (address) {
    bytes memory code;
    assembly {
        let size := codesize()
        code := mload(0x40)
        codecopy(add(code, 0x20), 0, size)
    }
    // Use code for CREATE2
}

​
Gas Cost

Base: 3 gas Memory expansion: Variable Copy cost: 3 gas per 32-byte word

​
Implementation

export function codecopy(frame: FrameType): EvmError | null {
  // Pop destOffset, offset, length
  // Calculate gas (base + memory + copy cost)
  // Copy bytecode to memory
  // See full implementation in codebase

  frame.pc += 1;
  return null;
}

​
References