"introduce msh_move_cursor so we can abstrace backspace"

src/main.c

@@ -19,6 +19,15 @@ MSH_ENTRY_POINT {
 
     while ((out = msh_read_input(buf, &sz, 2048)), out > 0) {
       switch (out) {
+      case 0x7F:
+        if (sz > 0) {
+          msh_move_cursor(1);
+          msh_write(" ", 1);
+          msh_move_cursor(1);
+          buf[sz--] = '\0';
+        }
+
+        break;
         /* Ctrl-C */
       case 0x3:
         msh_print_string("^C\n\r");

src/system/linux/linux.c

@@ -3,16 +3,14 @@
 #include "syscall.h"
 
 #include <linux/kd.h>
-#include <signal.h>
 #include <sys/file.h>
 #include <sys/ioctl.h>
 #include <sys/select.h>
+#include <sys/signal.h>
 #include <sys/stat.h>
 #include <sys/termios.h>
 #include <sys/wait.h>
 
-#include <termios.h>
-
 char msh_path_seperator = '/';
 
 int msh_read_input(char *ptr, SIZE_TYPE *size, SIZE_TYPE n) {
@@ -34,13 +32,6 @@ int msh_read_input(char *ptr, SIZE_TYPE *size, SIZE_TYPE n) {
         return -1;
         break;
         /* backspace */
-      case 127:
-        if (*size <= 0) {
-          return 0;
-        }
-        SYSCALL(write, 1, "\33[D \33[D", 7);
-        *size -= 1;
-        break;
       default:
         break;
       }
@@ -54,11 +45,27 @@ int msh_read_input(char *ptr, SIZE_TYPE *size, SIZE_TYPE n) {
   return ch;
 };
 
+void msh_move_cursor(signed int offset) {
+  int i;
+  char *cmd = "\33[D";
+  if (offset <= 0) {
+    offset &= ~0xffffffff;
+    cmd = "\33[C";
+  }
+  for (i = 0; i < offset; i++) {
+    SYSCALL(write, 1, cmd, 3);
+  }
+};
+
 void msh_write(char *st, SIZE_TYPE size) { SYSCALL(write, 1, st, size); }
 
 int msh_execute(char *cmd, char **args) {
   SIZE_TYPE fork;
 
+  if (*cmd == '\0') {
+    return 0;
+  }
+
   fork = (SIZE_TYPE)SYSCALL(fork, 0);
 
   if (fork == 0) {

src/system/system.h

@@ -59,14 +59,18 @@ void msh_file_read(msh_file *file, char *ptr, SIZE_TYPE n);
 
 /*
  * Read user input into ptr, stopping if it has reached n characters.
- * Also has to handle backspace since erasing characters is system-dependent.
  * RETURNS:
- * -2 = if it ran out of space.
- * -1 = if finished reading
- *  0 < ascii character
+ * * -2 = if it ran out of space.
+ * * -1 = if finished reading
+ * *  0 < ascii character
  */
 int msh_read_input(char *ptr, SIZE_TYPE *size, SIZE_TYPE n);
 
+/*
+ * Move terminal cursor x characters to the right. Pass in negative to go left.
+ */
+void msh_move_cursor(signed int offset);
+
 /* Write characters to terminal. */
 void msh_write(char *st, SIZE_TYPE size);