console,editor: Filter out non-printable characters

stage23/lib/libc.h

@@ -2,6 +2,10 @@
 #define __LIB__LIBC_H__
 
 #include <stddef.h>
+#include <stdbool.h>
+
+bool isprint(int c);
+bool isspace(int c);
 
 int toupper(int c);
 int tolower(int c);

stage23/lib/libc.s2.c

@@ -4,6 +4,14 @@
 #include <stdbool.h>
 #include <lib/blib.h>
 
+bool isprint(int c) {
+    return c >= ' ' && c <= '~';
+}
+
+bool isspace(int c) {
+    return (c >= '\t' && c <= 0xD) || c == ' ';
+}
+
 int toupper(int c) {
     if (c >= 'a' && c <= 'z') {
         return c - 0x20;

stage23/lib/readline.c

@@ -317,7 +317,7 @@ void readline(const char *orig_str, char *buf, size_t limit) {
                 term_write((uintptr_t)"\n", 1);
                 goto out;
             default: {
-                if (strlen(buf) < limit - 1) {
+                if (strlen(buf) < limit - 1 && isprint(c)) {
                     for (size_t j = strlen(buf); ; j--) {
                         buf[j+1] = buf[j];
                         if (j == i)

stage23/menu.c

@@ -463,12 +463,14 @@ refresh:
             return NULL;
         default:
             if (strlen(buffer) < EDITOR_MAX_BUFFER_SIZE - 1) {
-                for (size_t i = strlen(buffer); ; i--) {
+                if (isprint(c) || c == '\n') {
-                    buffer[i+1] = buffer[i];
+                    for (size_t i = strlen(buffer); ; i--) {
-                    if (i == cursor_offset)
+                        buffer[i+1] = buffer[i];
-                        break;
+                        if (i == cursor_offset)
+                            break;
+                    }
+                    buffer[cursor_offset++] = c;
                 }
-                buffer[cursor_offset++] = c;
             } else {
                 display_overflow_error = true;
             }