py: Change vstr so that it doesn't null terminate buffer by default.

This cleans up vstr so that it's a pure "variable buffer", and the user
can decide whether they need to add a terminating null byte.  In most
places where vstr is used, the vstr did not need to be null terminated
and so this patch saves code size, a tiny bit of RAM, and makes vstr
usage more efficient.  When null termination is needed it must be
done explicitly using vstr_null_terminate.

1 files changed, 7 insertions, 3 deletions

diff --git a/py/builtinimport.c b/py/builtinimport.c
index 73bf0b4722..1717c500d9 100644
--- a/py/builtinimport.c
+++ b/py/builtinimport.c
@@ -61,12 +61,14 @@ bool mp_obj_is_package(mp_obj_t module) {
 }
 
 STATIC mp_import_stat_t stat_dir_or_file(vstr_t *path) {
+    vstr_null_terminate(path);
     //printf("stat %s\n", vstr_str(path));
     mp_import_stat_t stat = mp_import_stat(vstr_str(path));
     if (stat == MP_IMPORT_STAT_DIR) {
         return stat;
     }
     vstr_add_str(path, ".py");
+    vstr_null_terminate(path);
     stat = mp_import_stat(vstr_str(path));
     if (stat == MP_IMPORT_STAT_FILE) {
         return stat;
@@ -134,6 +136,7 @@ STATIC void do_load_from_lexer(mp_obj_t module_obj, mp_lexer_t *lex, const char
 
 STATIC void do_load(mp_obj_t module_obj, vstr_t *file) {
     // create the lexer
+    vstr_null_terminate(file);
     mp_lexer_t *lex = mp_lexer_new_from_file(vstr_str(file));
     do_load_from_lexer(module_obj, lex, vstr_str(file));
 }
@@ -263,7 +266,7 @@ mp_obj_t mp_builtin___import__(mp_uint_t n_args, const mp_obj_t *args) {
             // create a qstr for the module name up to this depth
             qstr mod_name = qstr_from_strn(mod_str, i);
             DEBUG_printf("Processing module: %s\n", qstr_str(mod_name));
-            DEBUG_printf("Previous path: %s\n", vstr_str(&path));
+            DEBUG_printf("Previous path: %.*s\n", vstr_len(&path), vstr_str(&path));
 
             // find the file corresponding to the module name
             mp_import_stat_t stat;
@@ -276,7 +279,7 @@ mp_obj_t mp_builtin___import__(mp_uint_t n_args, const mp_obj_t *args) {
                 vstr_add_strn(&path, mod_str + last, i - last);
                 stat = stat_dir_or_file(&path);
             }
-            DEBUG_printf("Current path: %s\n", vstr_str(&path));
+            DEBUG_printf("Current path: %.*s\n", vstr_len(&path), vstr_str(&path));
 
             if (stat == MP_IMPORT_STAT_NO_EXIST) {
                 #if MICROPY_MODULE_WEAK_LINKS
@@ -320,12 +323,13 @@ mp_obj_t mp_builtin___import__(mp_uint_t n_args, const mp_obj_t *args) {
                 }
 
                 if (stat == MP_IMPORT_STAT_DIR) {
-                    DEBUG_printf("%s is dir\n", vstr_str(&path));
+                    DEBUG_printf("%.*s is dir\n", vstr_len(&path), vstr_str(&path));
                     // https://docs.python.org/3/reference/import.html
                     // "Specifically, any module that contains a __path__ attribute is considered a package."
                     mp_store_attr(module_obj, MP_QSTR___path__, mp_obj_new_str(vstr_str(&path), vstr_len(&path), false));
                     vstr_add_char(&path, PATH_SEP_CHAR);
                     vstr_add_str(&path, "__init__.py");
+                    vstr_null_terminate(&path);
                     if (mp_import_stat(vstr_str(&path)) != MP_IMPORT_STAT_FILE) {
                         vstr_cut_tail_bytes(&path, sizeof("/__init__.py") - 1); // cut off /__init__.py
                         mp_warning("%s is imported as namespace package", vstr_str(&path));