From dbd987ab19685876bbc1df4c1d0deac7771221c4 Mon Sep 17 00:00:00 2001
From: Jan Nieuwenhuizen <janneke@gnu.org>
Date: Thu, 23 Mar 2017 18:57:06 +0100
Subject: [PATCH] mescc: Have ungetc remember 2 positions.

* doc/examples/t.c (read_test): Test it.
* doc/examples/mini-mes.c:
* mlibc.c (getchar, ungetc): Support 2 ungetc positions.
* module/mes/libc.mes (getchar, ungetc): Likewise.
---
 mlibc.c             | 11 +++++------
 module/mes/libc.mes | 22 +++++++++++++++-------
 scaffold/mini-mes.c |  2 ++
 scaffold/t.c        | 15 +++++++++++++--
 4 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/mlibc.c b/mlibc.c
index 7d4ebf09..e4442dd8 100644
--- a/mlibc.c
+++ b/mlibc.c
@@ -222,6 +222,7 @@ assert_fail (char* s)
 
 
 int ungetc_char = -1;
+char ungetc_buf[2];
 
 int
 getchar ()
@@ -235,10 +236,8 @@ getchar ()
       i = c;
     }
   else
-    {
-      i = ungetc_char;
-      ungetc_char = -1;
-    }
+    i = ungetc_buf[ungetc_char--];
+
   if (i < 0) i += 256;
   return i;
 }
@@ -246,8 +245,8 @@ getchar ()
 int
 ungetc (int c, int fd)
 {
-  assert (ungetc_char == -1);
-  ungetc_char = c;
+  assert (ungetc_char < 2);
+  ungetc_buf[++ungetc_char] = c;
   return c;
 }
 
diff --git a/module/mes/libc.mes b/module/mes/libc.mes
index 05029875..4f575782 100644
--- a/module/mes/libc.mes
+++ b/module/mes/libc.mes
@@ -56,9 +56,6 @@ strlen (char const* s)
 (define getchar
   (let* ((ast (with-input-from-string
                   "
-int g_stdin;
-int ungetc_char = -1;
-
 #if 0
 int
 getchar ()
@@ -71,6 +68,9 @@ getchar ()
 }
 #endif
 
+int g_stdin = 0;
+int ungetc_char = -1;
+char ungetc_buf[2];
 int
 getchar ()
 {
@@ -84,8 +84,11 @@ getchar ()
     }
   else
     {
-      i = ungetc_char;
-      ungetc_char = -1;
+     //FIXME
+     //i = ungetc_buf[ungetc_char--];
+     i = ungetc_buf[ungetc_char];
+     //ungetc_char--;
+     ungetc_char = ungetc_char - 1;
     }
   if (i < 0) i += 256;
   return i;
@@ -121,8 +124,13 @@ assert_fail (char* s)
 int
 ungetc (int c, int fd)
 {
-  assert (ungetc_char == -1);
-  ungetc_char = c;
+  //FIXME
+  //assert (ungetc_char < 2);
+  assert (ungetc_char == -1 || ungetc_char < 2);
+  //FIXME
+  //ungetc_buf[++ungetc_char] = c;
+  ungetc_char++;
+  ungetc_buf[ungetc_char] = c;
   return c;
 }
 "
diff --git a/scaffold/mini-mes.c b/scaffold/mini-mes.c
index 3abe2615..def353aa 100644
--- a/scaffold/mini-mes.c
+++ b/scaffold/mini-mes.c
@@ -26,6 +26,8 @@
 #if __MESCC__
 //void *g_malloc_base = 0;
 char *g_malloc_base = 0;
+// int ungetc_char = -1;
+// char ungetc_buf[2];
 #endif
 
 #define MES_MINI 1
diff --git a/scaffold/t.c b/scaffold/t.c
index db43cd8e..86ffd739 100644
--- a/scaffold/t.c
+++ b/scaffold/t.c
@@ -147,10 +147,9 @@ get ()
 int
 read_test ()
 {
-  puts ("read test\n");
   char *p = (char*)g_chars;
   int i = 0;
-  puts ("t: read 0123456789\n");
+  puts ("t: read 0123456789\nt: ");
   int c = get ();
   while (i < 10) {
     *p++ = c;
@@ -160,6 +159,18 @@ read_test ()
   }
   puts ("\n");
   if (strcmp (g_chars, "0123456789")) return 1;
+
+  puts ("t: ungetc ('A') == getchar ()\n");
+  ungetc ('A', STDIN);
+  if (getchar () != 'A') return 1;
+  ungetc (0, STDIN);
+  //ungetc ('\1', STDIN);
+  ungetc (1, STDIN);
+  puts ("t: ungetc ();ungetc ();getchar ();getchar ()\n");
+  if (getchar () != 1) return 1;
+  //if (getchar () != '\0') return 1;
+  if (getchar () != 0) return 1;
+
   return 0;
 }