fetcher.h

#pragma once
 
#include "libmicroemu/internal/fetcher/raw_instr.h"
#include "libmicroemu/internal/fetcher/raw_instr_flags_table.h"
#include "libmicroemu/internal/result.h"
#include "libmicroemu/internal/utils/bit_manip.h"
#include "libmicroemu/types.h"
#include <cstddef>
#include <cstdint>
 
namespace libmicroemu::internal {
 
template <typename TCpuAccessor, typename TBus> class Fetcher {
public:
  static Result<RawInstr> Fetch(TCpuAccessor &cpua, TBus &bus, const me_adr_t pc) {
 
    // make first 16 bit access to fetch instruction
    TRY_ASSIGN(
        instr_l, RawInstr,
        bus.template ReadOrRaise<u16>(cpua, pc, BusExceptionType::kRaiseInstructionBusError));
 
    const u32 opc = Bm32::ExtractBits1R<kFlagsOpCodeLast, kFlagsOpCodeFirst>(instr_l);
 
    // Check if a 32-bit instruction was loaded
    u16 instr_h{0x0U};
    const auto flags = kRawInstrFlagsTable[opc];
 
    if ((flags & static_cast<RawInstrFlagsSet>(RawInstrFlagsMsk::k32Bit)) != 0U) {
      // make the second access
      TRY_ASSIGN(instr_h_im, RawInstr,
                 bus.template ReadOrRaise<u16>(cpua, pc + 2U,
                                               BusExceptionType::kRaiseInstructionBusError));
      instr_h = instr_h_im;
    }
 
    return Ok(RawInstr{instr_l, instr_h, flags});
  }
 
private:
  Fetcher() = delete;

  ~Fetcher() = delete;

  Fetcher &operator=(const Fetcher &r_src) = delete;

  Fetcher(Fetcher &&r_src) = delete;

  Fetcher &operator=(Fetcher &&r_src) = delete;
};
 
} // namespace libmicroemu::internal