bQUARKz
f9120e740b
Co-authored-by: Nilton Constantino <nilton.constantino@visma.com> Reviewed-on: #8
71 lines
2.5 KiB
Rust
71 lines
2.5 KiB
Rust
use crate::opcode::OpCode;
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use crate::readwrite::*;
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use std::io::{Cursor, Read};
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/// Represents a disassembled instruction.
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#[derive(Debug, Clone)]
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pub struct Instr {
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/// The absolute address (PC) where this instruction starts in ROM.
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pub pc: u32,
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/// The decoded OpCode.
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pub opcode: OpCode,
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/// The list of operands extracted from the byte stream.
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pub operands: Vec<DisasmOperand>,
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}
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/// Represents an operand decoded from the byte stream.
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#[derive(Debug, Clone)]
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pub enum DisasmOperand {
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U32(u32),
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I32(i32),
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I64(i64),
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F64(f64),
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Bool(bool),
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}
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/// Translates raw ROM bytes back into a human-readable list of instructions.
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///
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/// This is the inverse of the assembly process. It reads the bytes sequentially,
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/// identifies the OpCode, and then reads the correct number of operand bytes
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/// based on the ISA rules.
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pub fn disasm(rom: &[u8]) -> Result<Vec<Instr>, String> {
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let mut instructions = Vec::new();
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let mut cursor = Cursor::new(rom);
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while (cursor.position() as usize) < rom.len() {
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let pc = cursor.position() as u32;
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let op_val = read_u16_le(&mut cursor).map_err(|e| e.to_string())?;
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let opcode = OpCode::try_from(op_val)?;
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let mut operands = Vec::new();
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match opcode {
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OpCode::PushConst | OpCode::PushI32 | OpCode::PushBounded | OpCode::Jmp | OpCode::JmpIfFalse | OpCode::JmpIfTrue
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| OpCode::GetGlobal | OpCode::SetGlobal | OpCode::GetLocal | OpCode::SetLocal
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| OpCode::PopN | OpCode::Syscall | OpCode::GateLoad | OpCode::GateStore | OpCode::Call => {
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let v = read_u32_le(&mut cursor).map_err(|e| e.to_string())?;
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operands.push(DisasmOperand::U32(v));
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}
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OpCode::PushI64 | OpCode::PushF64 => {
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let v = read_i64_le(&mut cursor).map_err(|e| e.to_string())?;
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operands.push(DisasmOperand::I64(v));
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}
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OpCode::PushBool => {
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let mut b_buf = [0u8; 1];
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cursor.read_exact(&mut b_buf).map_err(|e| e.to_string())?;
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operands.push(DisasmOperand::Bool(b_buf[0] != 0));
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}
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OpCode::Alloc => {
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let v1 = read_u32_le(&mut cursor).map_err(|e| e.to_string())?;
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let v2 = read_u32_le(&mut cursor).map_err(|e| e.to_string())?;
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operands.push(DisasmOperand::U32(v1));
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operands.push(DisasmOperand::U32(v2));
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}
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_ => {}
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}
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instructions.push(Instr { pc, opcode, operands });
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}
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Ok(instructions)
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}
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