diff options
Diffstat (limited to 'py/obj.h')
| -rw-r--r-- | py/obj.h | 46 |
1 files changed, 29 insertions, 17 deletions
@@ -1,3 +1,8 @@ +// A Micro Python object is a machine word having the following form: +// - xxxx...xxx1 : a small int, bits 1 and above are the value +// - xxxx...xx10 : a qstr, bits 2 and above are the value +// - xxxx...xx00 : a pointer to an mp_obj_base_t (unless a fake object) + // All Micro Python objects are at least this type // It must be of pointer size @@ -10,7 +15,7 @@ typedef machine_const_ptr_t mp_const_obj_t; typedef machine_int_t mp_small_int_t; // Anything that wants to be a Micro Python object must have -// mp_obj_base_t as its first member (except NULL and small ints) +// mp_obj_base_t as its first member (except small ints and qstrs) struct _mp_obj_type_t; struct _mp_obj_base_t { @@ -18,24 +23,31 @@ struct _mp_obj_base_t { }; typedef struct _mp_obj_base_t mp_obj_base_t; -// The NULL object is used to indicate the absence of an object -// It *cannot* be used when an mp_obj_t is expected, except where explicitly allowed - -#define MP_OBJ_NULL ((mp_obj_t)0) - -// The SENTINEL object is used for various internal purposes where one needs -// an object which is unique from all other objects, including MP_OBJ_NULL. - -#define MP_OBJ_SENTINEL ((mp_obj_t)8) - -// The NOT_SUPPORTED object is a return value that indicates an unsupported operation. - -#define MP_OBJ_NOT_SUPPORTED ((mp_obj_t)16) +// These fake objects are used to indicate certain things in arguments or return +// values, and should only be used when explicitly allowed. +// +// - MP_OBJ_NULL : used to indicate the absence of an object. +// - MP_OBJ_NOT_SUPPORTED : a return value that indicates an unsupported operation. +// - MP_OBJ_STOP_ITERATION : used instead of throwing a StopIteration, for efficiency. +// - MP_OBJ_SENTINEL : used for various internal purposes where one needs +// an object which is unique from all other objects, including MP_OBJ_NULL. +// +// For debugging purposes they are all different. For non-debug mode, we alias +// as many as we can to MP_OBJ_NULL because it's cheaper to load/compare 0. + +#if NDEBUG +#define MP_OBJ_NULL ((mp_obj_t)0) +#define MP_OBJ_NOT_SUPPORTED ((mp_obj_t)0) +#define MP_OBJ_STOP_ITERATION ((mp_obj_t)0) +#define MP_OBJ_SENTINEL ((mp_obj_t)4) +#else +#define MP_OBJ_NULL ((mp_obj_t)0) +#define MP_OBJ_NOT_SUPPORTED ((mp_obj_t)4) +#define MP_OBJ_STOP_ITERATION ((mp_obj_t)8) +#define MP_OBJ_SENTINEL ((mp_obj_t)12) +#endif // These macros check for small int, qstr or object, and access small int and qstr values -// - xxxx...xxx1: a small int, bits 1 and above are the value -// - xxxx...xx10: a qstr, bits 2 and above are the value -// - xxxx...xx00: a pointer to an mp_obj_base_t // In SMALL_INT, next-to-highest bits is used as sign, so both must match for value in range #define MP_SMALL_INT_MIN ((mp_small_int_t)(((machine_int_t)WORD_MSBIT_HIGH) >> 1)) |