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, 10 insertions, 4 deletions

diff --git a/stmhal/pyexec.c b/stmhal/pyexec.c
index 1563dc8e4..930c1c019 100644
--- a/stmhal/pyexec.c
+++ b/stmhal/pyexec.c
@@ -248,11 +248,12 @@ int pyexec_friendly_repl_process_char(int c) {
             return 0;
         }
 
+        vstr_null_terminate(&repl.line);
         if (!mp_repl_continue_with_input(vstr_str(&repl.line))) {
             goto exec;
         }
 
-        vstr_add_char(&repl.line, '\n');
+        vstr_add_byte(&repl.line, '\n');
         repl.cont_line = true;
         stdout_tx_str("... ");
         readline_note_newline();
@@ -274,8 +275,9 @@ int pyexec_friendly_repl_process_char(int c) {
             return 0;
         }
 
+        vstr_null_terminate(&repl.line);
         if (mp_repl_continue_with_input(vstr_str(&repl.line))) {
-            vstr_add_char(&repl.line, '\n');
+            vstr_add_byte(&repl.line, '\n');
             stdout_tx_str("... ");
             readline_note_newline();
             return 0;
@@ -362,8 +364,12 @@ friendly_repl_reset:
             continue;
         }
 
-        while (mp_repl_continue_with_input(vstr_str(&line))) {
-            vstr_add_char(&line, '\n');
+        for (;;) {
+            vstr_null_terminate(&line);
+            if (!mp_repl_continue_with_input(vstr_str(&line))) {
+                break;
+            }
+            vstr_add_byte(&line, '\n');
             ret = readline(&line, "... ");
             if (ret == CHAR_CTRL_C) {
                 // cancel everything