text: #ifndef Py_CPYTHON_CODE_H
  #  error "this header file must not be included directly"
  #endif
  
  typedef uint16_t _Py_CODEUNIT;
  
  #ifdef WORDS_BIGENDIAN
  #  define _Py_OPCODE(word) ((word) >> 8)
  #  define _Py_OPARG(word) ((word) & 255)
  #else
  #  define _Py_OPCODE(word) ((word) & 255)
  #  define _Py_OPARG(word) ((word) >> 8)
  #endif
  
  typedef struct _PyOpcache _PyOpcache;
  
  /* Bytecode object */
  struct PyCodeObject {
      PyObject_HEAD
      int co_argcount;            /* #arguments, except *args */
      int co_posonlyargcount;     /* #positional only arguments */
      int co_kwonlyargcount;      /* #keyword only arguments */
      int co_nlocals;             /* #local variables */
      int co_stacksize;           /* #entries needed for evaluation stack */
      int co_flags;               /* CO_..., see below */
      int co_firstlineno;         /* first source line number */
      PyObject *co_code;          /* instruction opcodes */
      PyObject *co_consts;        /* list (constants used) */
      PyObject *co_names;         /* list of strings (names used) */
      PyObject *co_varnames;      /* tuple of strings (local variable names) */
      PyObject *co_freevars;      /* tuple of strings (free variable names) */
      PyObject *co_cellvars;      /* tuple of strings (cell variable names) */
      /* The rest aren't used in either hash or comparisons, except for co_name,
         used in both. This is done to preserve the name and line number
         for tracebacks and debuggers; otherwise, constant de-duplication
         would collapse identical functions/lambdas defined on different lines.
      */
      Py_ssize_t *co_cell2arg;    /* Maps cell vars which are arguments. */
      PyObject *co_filename;      /* unicode (where it was loaded from) */
      PyObject *co_name;          /* unicode (name, for reference) */
      PyObject *co_lnotab;        /* string (encoding addr<->lineno mapping) See
                                     Objects/lnotab_notes.txt for details. */
      void *co_zombieframe;       /* for optimization only (see frameobject.c) */
      PyObject *co_weakreflist;   /* to support weakrefs to code objects */
      /* Scratch space for extra data relating to the code object.
         Type is a void* to keep the format private in codeobject.c to force
         people to go through the proper APIs. */
      void *co_extra;
  
      /* Per opcodes just-in-time cache
       *
       * To reduce cache size, we use indirect mapping from opcode index to
       * cache object:
       *   cache = co_opcache[co_opcache_map[next_instr - first_instr] - 1]
       */
  
      // co_opcache_map is indexed by (next_instr - first_instr).
      //  * 0 means there is no cache for this opcode.
      //  * n > 0 means there is cache in co_opcache[n-1].
      unsigned char *co_opcache_map;
      _PyOpcache *co_opcache;
      int co_opcache_flag;  // used to determine when create a cache.
      unsigned char co_opcache_size;  // length of co_opcache.
  };
  
  /* Masks for co_flags above */
  #define CO_OPTIMIZED    0x0001
  #define CO_NEWLOCALS    0x0002
  #define CO_VARARGS      0x0004
  #define CO_VARKEYWORDS  0x0008
  #define CO_NESTED       0x0010
  #define CO_GENERATOR    0x0020
  /* The CO_NOFREE flag is set if there are no free or cell variables.
     This information is redundant, but it allows a single flag test
     to determine whether there is any extra work to be done when the
     call frame it setup.
  */
  #define CO_NOFREE       0x0040
  
  /* The CO_COROUTINE flag is set for coroutine functions (defined with
     ``async def`` keywords) */
  #define CO_COROUTINE            0x0080
  #define CO_ITERABLE_COROUTINE   0x0100
  #define CO_ASYNC_GENERATOR      0x0200
  
  /* bpo-39562: These constant values are changed in Python 3.9
     to prevent collision with compiler flags. CO_FUTURE_ and PyCF_
     constants must be kept unique. PyCF_ constants can use bits from
     0x0100 to 0x10000. CO_FUTURE_ constants use bits starting at 0x20000. */
  #define CO_FUTURE_DIVISION      0x20000
  #define CO_FUTURE_ABSOLUTE_IMPORT 0x40000 /* do absolute imports by default */
  #define CO_FUTURE_WITH_STATEMENT  0x80000
  #define CO_FUTURE_PRINT_FUNCTION  0x100000
  #define CO_FUTURE_UNICODE_LITERALS 0x200000
  
  #define CO_FUTURE_BARRY_AS_BDFL  0x400000
  #define CO_FUTURE_GENERATOR_STOP  0x800000
  #define CO_FUTURE_ANNOTATIONS    0x1000000
  
  /* This value is found in the co_cell2arg array when the associated cell
     variable does not correspond to an argument. */
  #define CO_CELL_NOT_AN_ARG (-1)
  
  /* This should be defined if a future statement modifies the syntax.
     For example, when a keyword is added.
  */
  #define PY_PARSER_REQUIRES_FUTURE_KEYWORD
  
  #define CO_MAXBLOCKS 20 /* Max static block nesting within a function */
  
  PyAPI_DATA(PyTypeObject) PyCode_Type;
  
  #define PyCode_Check(op) Py_IS_TYPE(op, &PyCode_Type)
  #define PyCode_GetNumFree(op) (PyTuple_GET_SIZE((op)->co_freevars))
  
  /* Public interface */
  PyAPI_FUNC(PyCodeObject *) PyCode_New(
          int, int, int, int, int, PyObject *, PyObject *,
          PyObject *, PyObject *, PyObject *, PyObject *,
          PyObject *, PyObject *, int, PyObject *);
  
  PyAPI_FUNC(PyCodeObject *) PyCode_NewWithPosOnlyArgs(
          int, int, int, int, int, int, PyObject *, PyObject *,
          PyObject *, PyObject *, PyObject *, PyObject *,
          PyObject *, PyObject *, int, PyObject *);
          /* same as struct above */
  
  /* Creates a new empty code object with the specified source location. */
  PyAPI_FUNC(PyCodeObject *)
  PyCode_NewEmpty(const char *filename, const char *funcname, int firstlineno);
  
  /* Return the line number associated with the specified bytecode index
     in this code object.  If you just need the line number of a frame,
     use PyFrame_GetLineNumber() instead. */
  PyAPI_FUNC(int) PyCode_Addr2Line(PyCodeObject *, int);
  
  /* for internal use only */
  typedef struct _addr_pair {
          int ap_lower;
          int ap_upper;
  } PyAddrPair;
  
  /* Update *bounds to describe the first and one-past-the-last instructions in the
     same line as lasti.  Return the number of that line.
  */
  PyAPI_FUNC(int) _PyCode_CheckLineNumber(PyCodeObject* co,
                                          int lasti, PyAddrPair *bounds);
  
  /* Create a comparable key used to compare constants taking in account the
   * object type. It is used to make sure types are not coerced (e.g., float and
   * complex) _and_ to distinguish 0.0 from -0.0 e.g. on IEEE platforms
   *
   * Return (type(obj), obj, ...): a tuple with variable size (at least 2 items)
   * depending on the type and the value. The type is the first item to not
   * compare bytes and str which can raise a BytesWarning exception. */
  PyAPI_FUNC(PyObject*) _PyCode_ConstantKey(PyObject *obj);
  
  PyAPI_FUNC(PyObject*) PyCode_Optimize(PyObject *code, PyObject* consts,
                                        PyObject *names, PyObject *lnotab);
  
  
  PyAPI_FUNC(int) _PyCode_GetExtra(PyObject *code, Py_ssize_t index,
                                   void **extra);
  PyAPI_FUNC(int) _PyCode_SetExtra(PyObject *code, Py_ssize_t index,
                                   void *extra);
  