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py/objmodule: Support delegating failed attr lookups.

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This commit adds generic support for mutable module attributes on built in
modules, by adding support for an optional hook function for module
attribute lookup.  If a module wants to support additional attribute load/
store/delete (beyond what is in the constant, globals dict) then it should
add at the very end of its globals dict MP_MODULE_ATTR_DELEGATION_ENTRY().
This should point to a custom function which will handle any additional
attributes.

The mp_module_generic_attr() function is provided as a helper function for
additional attributes: it requires an array of qstrs (terminated in
MP_QSTRnull) and a corresponding array of objects (with a 1-1 mapping
between qstrs and objects).  If the qstr is found in the array then the
corresponding object is loaded/stored/deleted.

Signed-off-by: Damien George <damien@micropython.org>
This commit is contained in:
Damien George 2021-07-27 00:38:21 +10:00
parent d470c5a5ba
commit 3356b5ef8d
3 changed files with 47 additions and 0 deletions
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6
py/mpconfig.h
View File

@ -822,6 +822,12 @@ typedef double mp_float_t;
#define MICROPY_STREAMS_POSIX_API (0)
#endif
// Whether modules can use MP_MODULE_ATTR_DELEGATION_ENTRY() to delegate failed
// attribute lookups.
#ifndef MICROPY_MODULE_ATTR_DELEGATION
#define MICROPY_MODULE_ATTR_DELEGATION (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_EXTRA_FEATURES)
#endif
// Whether to call __init__ when importing builtin modules for the first time
#ifndef MICROPY_MODULE_BUILTIN_INIT
#define MICROPY_MODULE_BUILTIN_INIT (MICROPY_CONFIG_ROM_LEVEL_AT_LEAST_EXTRA_FEATURES)

36
py/objmodule.c
View File

@ -62,6 +62,21 @@ STATIC void module_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kin
mp_printf(print, "<module '%s'>", module_name);
}
STATIC void module_attr_try_delegation(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
#if MICROPY_MODULE_ATTR_DELEGATION
// Delegate lookup to a module's custom attr method (found in last lot of globals dict).
mp_obj_module_t *self = MP_OBJ_TO_PTR(self_in);
mp_map_t *map = &self->globals->map;
if (map->table[map->alloc - 1].key == MP_OBJ_NEW_QSTR(MP_QSTRnull)) {
((mp_attr_fun_t)MP_OBJ_TO_PTR(map->table[map->alloc - 1].value))(self_in, attr, dest);
}
#else
(void)self_in;
(void)attr;
(void)dest;
#endif
}
STATIC void module_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
mp_obj_module_t *self = MP_OBJ_TO_PTR(self_in);
if (dest[0] == MP_OBJ_NULL) {
@ -74,8 +89,12 @@ STATIC void module_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
elem = mp_map_lookup(&self->globals->map, MP_OBJ_NEW_QSTR(MP_QSTR___getattr__), MP_MAP_LOOKUP);
if (elem != NULL) {
dest[0] = mp_call_function_1(elem->value, MP_OBJ_NEW_QSTR(attr));
} else {
module_attr_try_delegation(self_in, attr, dest);
}
#endif
} else {
module_attr_try_delegation(self_in, attr, dest);
}
} else {
// delete/store attribute
@ -91,6 +110,7 @@ STATIC void module_attr(mp_obj_t self_in, qstr attr, mp_obj_t *dest) {
#endif
{
// can't delete or store to fixed map
module_attr_try_delegation(self_in, attr, dest);
return;
}
}
@ -319,3 +339,19 @@ STATIC void mp_module_call_init(mp_obj_t module_name, mp_obj_t module_obj) {
}
}
#endif
void mp_module_generic_attr(qstr attr, mp_obj_t *dest, const uint16_t *keys, mp_obj_t *values) {
for (size_t i = 0; keys[i] != MP_QSTRnull; ++i) {
if (attr == keys[i]) {
if (dest[0] == MP_OBJ_NULL) {
// load attribute (MP_OBJ_NULL returned for deleted items)
dest[0] = values[i];
} else {
// delete or store (delete stores MP_OBJ_NULL)
values[i] = dest[1];
dest[0] = MP_OBJ_NULL; // indicate success
}
return;
}
}
}

5
py/objmodule.h
View File

@ -28,6 +28,9 @@
#include "py/obj.h"
// Place at the very end of a module's globals_table.
#define MP_MODULE_ATTR_DELEGATION_ENTRY(ptr) { MP_ROM_QSTR(MP_QSTRnull), MP_ROM_PTR(ptr) }
extern const mp_map_t mp_builtin_module_map;
mp_obj_t mp_module_get_loaded_or_builtin(qstr module_name);
@ -35,4 +38,6 @@ mp_obj_t mp_module_get_loaded_or_builtin(qstr module_name);
mp_obj_t mp_module_get_builtin(qstr module_name);
#endif
void mp_module_generic_attr(qstr attr, mp_obj_t *dest, const uint16_t *keys, mp_obj_t *values);
#endif // MICROPY_INCLUDED_PY_OBJMODULE_H