extmod/modbtree: Switch to accepting stream object instead of filename.

Requires "embedded" BerkeleyDB BTree implementation.

extmod/modbtree.c

@@ -31,6 +31,7 @@
 
 #include "py/nlr.h"
 #include "py/runtime.h"
+#include "py/stream.h"
 
 #if MICROPY_PY_BTREE
 
@@ -314,15 +315,20 @@ STATIC const mp_obj_type_t btree_type = {
     .locals_dict = (void*)&btree_locals_dict,
 };
 
+STATIC FILEVTABLE btree_stream_fvtable = {
+    mp_stream_posix_read,
+    mp_stream_posix_write,
+    mp_stream_posix_lseek,
+    mp_stream_posix_fsync
+};
+
 STATIC mp_obj_t mod_btree_open(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
     static const mp_arg_t allowed_args[] = {
         { MP_QSTR_server_side, MP_ARG_KW_ONLY | MP_ARG_BOOL, {.u_bool = false} },
     };
 
-    const char *fname = NULL;
-    if (pos_args[0] != mp_const_none) {
-        fname = mp_obj_str_get_str(pos_args[0]);
-    }
+    // Make sure we got a stream object
+    mp_get_stream_raise(pos_args[0], MP_STREAM_OP_READ | MP_STREAM_OP_WRITE | MP_STREAM_OP_IOCTL);
 
     struct {
         mp_arg_val_t server_side;
@@ -330,7 +336,7 @@ STATIC mp_obj_t mod_btree_open(size_t n_args, const mp_obj_t *pos_args, mp_map_t
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args,
         MP_ARRAY_SIZE(allowed_args), allowed_args, (mp_arg_val_t*)&args);
 
-    DB *db = __bt_open(fname, /*flags*/O_CREAT | O_RDWR, /*mode*/0770, /*openinfo*/NULL, /*dflags*/0);
+    DB *db = __bt_open(pos_args[0], &btree_stream_fvtable, /*openinfo*/NULL, /*dflags*/0);
     if (db == NULL) {
         nlr_raise(mp_obj_new_exception_arg1(&mp_type_OSError, MP_OBJ_NEW_SMALL_INT(errno)));
     }