py: Fix memoryview referencing so it retains ptr to original buffer.
This way, if original parent object is GC'd, the memoryview still points
to the underlying buffer data so that buffer is not GC'd.
diff --git a/py/objarray.c b/py/objarray.c
index 0fc6b07..2d210d9 100644
--- a/py/objarray.c
+++ b/py/objarray.c
@@ -39,12 +39,32 @@
#if MICROPY_PY_ARRAY || MICROPY_PY_BUILTINS_BYTEARRAY || MICROPY_PY_BUILTINS_MEMORYVIEW
+// About memoryview object: We want to reuse as much code as possible from
+// array, and keep the memoryview object 4 words in size so it fits in 1 GC
+// block. Also, memoryview must keep a pointer to the base of the buffer so
+// that the buffer is not GC'd if the original parent object is no longer
+// around (we are assuming that all memoryview'able objects return a pointer
+// which points to the start of a GC chunk). Given the above constraints we
+// do the following:
+// - typecode high bit is set if the buffer is read-write (else read-only)
+// - free is the offset in elements to the first item in the memoryview
+// - len is the length in elements
+// - items points to the start of the original buffer
+// Note that we don't handle the case where the original buffer might change
+// size due to a resize of the original parent object.
+
+// make (& TYPECODE_MASK) a null operation if memorview not enabled
+#if MICROPY_PY_BUILTINS_MEMORYVIEW
+#define TYPECODE_MASK (0x7f)
+#else
+#define TYPECODE_MASK (~(mp_uint_t)1)
+#endif
+
typedef struct _mp_obj_array_t {
mp_obj_base_t base;
mp_uint_t typecode : 8;
// free is number of unused elements after len used elements
// alloc size = len + free
- // for memoryview, free=0 is read-only, free=1 is read-write
mp_uint_t free : (8 * sizeof(mp_uint_t) - 8);
mp_uint_t len; // in elements
void *items;
@@ -187,7 +207,7 @@
// test if the object can be written to
if (mp_get_buffer(args[0], &bufinfo, MP_BUFFER_RW)) {
- self->free = 1; // used to indicate writable buffer
+ self->typecode |= 0x80; // used to indicate writable buffer
}
return self;
@@ -210,7 +230,7 @@
mp_buffer_info_t rhs_bufinfo;
array_get_buffer(lhs_in, &lhs_bufinfo, MP_BUFFER_READ);
if (!mp_get_buffer(rhs_in, &rhs_bufinfo, MP_BUFFER_READ)) {
- return mp_const_false;
+ return mp_const_false;
}
return MP_BOOL(mp_seq_cmp_bytes(op, lhs_bufinfo.buf, lhs_bufinfo.len, rhs_bufinfo.buf, rhs_bufinfo.len));
}
@@ -259,7 +279,7 @@
"only slices with step=1 (aka None) are supported"));
}
mp_obj_array_t *res;
- int sz = mp_binary_get_size('@', o->typecode, NULL);
+ int sz = mp_binary_get_size('@', o->typecode & TYPECODE_MASK, NULL);
assert(sz > 0);
if (0) {
// dummy
@@ -267,8 +287,8 @@
} else if (o->base.type == &mp_type_memoryview) {
res = m_new_obj(mp_obj_array_t);
*res = *o;
+ res->free += slice.start;
res->len = slice.stop - slice.start;
- res->items += slice.start * sz;
#endif
} else {
res = array_new(o->typecode, slice.stop - slice.start);
@@ -278,18 +298,21 @@
#endif
} else {
mp_uint_t index = mp_get_index(o->base.type, o->len, index_in, false);
- if (value == MP_OBJ_SENTINEL) {
- // load
- return mp_binary_get_val_array(o->typecode, o->items, index);
- } else {
- // store
- #if MICROPY_PY_BUILTINS_MEMORYVIEW
- if (o->base.type == &mp_type_memoryview && o->free == 0) {
- // read-only memoryview
+ #if MICROPY_PY_BUILTINS_MEMORYVIEW
+ if (o->base.type == &mp_type_memoryview) {
+ index += o->free;
+ if (value != MP_OBJ_SENTINEL && (o->typecode & 0x80) == 0) {
+ // store to read-only memoryview
return MP_OBJ_NULL;
}
- #endif
- mp_binary_set_val_array(o->typecode, o->items, index, value);
+ }
+ #endif
+ if (value == MP_OBJ_SENTINEL) {
+ // load
+ return mp_binary_get_val_array(o->typecode & TYPECODE_MASK, o->items, index);
+ } else {
+ // store
+ mp_binary_set_val_array(o->typecode & TYPECODE_MASK, o->items, index, value);
return mp_const_none;
}
}
@@ -298,15 +321,19 @@
STATIC mp_int_t array_get_buffer(mp_obj_t o_in, mp_buffer_info_t *bufinfo, mp_uint_t flags) {
mp_obj_array_t *o = o_in;
+ int sz = mp_binary_get_size('@', o->typecode & TYPECODE_MASK, NULL);
+ bufinfo->buf = o->items;
+ bufinfo->len = o->len * sz;
+ bufinfo->typecode = o->typecode & TYPECODE_MASK;
#if MICROPY_PY_BUILTINS_MEMORYVIEW
- if (o->base.type == &mp_type_memoryview && o->free == 0 && (flags & MP_BUFFER_WRITE)) {
- // read-only memoryview
- return 1;
+ if (o->base.type == &mp_type_memoryview) {
+ if ((o->typecode & 0x80) == 0 && (flags & MP_BUFFER_WRITE)) {
+ // read-only memoryview
+ return 1;
+ }
+ bufinfo->buf += (mp_uint_t)o->free * sz;
}
#endif
- bufinfo->buf = o->items;
- bufinfo->len = o->len * mp_binary_get_size('@', o->typecode, NULL);
- bufinfo->typecode = o->typecode;
return 0;
}
@@ -392,13 +419,14 @@
typedef struct _mp_obj_array_it_t {
mp_obj_base_t base;
mp_obj_array_t *array;
+ mp_uint_t offset;
mp_uint_t cur;
} mp_obj_array_it_t;
STATIC mp_obj_t array_it_iternext(mp_obj_t self_in) {
mp_obj_array_it_t *self = self_in;
if (self->cur < self->array->len) {
- return mp_binary_get_val_array(self->array->typecode, self->array->items, self->cur++);
+ return mp_binary_get_val_array(self->array->typecode & TYPECODE_MASK, self->array->items, self->offset + self->cur++);
} else {
return MP_OBJ_STOP_ITERATION;
}
@@ -413,10 +441,14 @@
STATIC mp_obj_t array_iterator_new(mp_obj_t array_in) {
mp_obj_array_t *array = array_in;
- mp_obj_array_it_t *o = m_new_obj(mp_obj_array_it_t);
+ mp_obj_array_it_t *o = m_new0(mp_obj_array_it_t, 1);
o->base.type = &array_it_type;
o->array = array;
- o->cur = 0;
+ #if MICROPY_PY_BUILTINS_MEMORYVIEW
+ if (array->base.type == &mp_type_memoryview) {
+ o->offset = array->free;
+ }
+ #endif
return o;
}