terminal.c's from_backend() no longer calls term_out(), because

term_out() can in turn call ldisc_send() which calls back to
from_backend() when local echo is enabled. This was giving rise to
crazy re-entrancy stuff and stack overflows. Instead from_backend()
deposits its data in a bufchain which term_out() empties the next
time it's called.

[originally from svn r1276]

putty.h

@@ -93,15 +93,6 @@ typedef HDC Context;
 
 GLOBAL int rows, cols, savelines;
 
-#define INBUF_SIZE 2048
-GLOBAL unsigned char inbuf[INBUF_SIZE];
-GLOBAL int inbuf_head;
-
-#define OUTBUF_SIZE 2048
-#define OUTBUF_MASK (OUTBUF_SIZE-1)
-GLOBAL unsigned char outbuf[OUTBUF_SIZE];
-GLOBAL int outbuf_head, outbuf_reap;
-
 GLOBAL int has_focus;
 
 GLOBAL int in_vbell;

scp.c

@@ -375,8 +375,6 @@ int from_backend(int is_stderr, char *data, int datalen)
 	return 0;
     }
 
-    inbuf_head = 0;
-
     /*
      * If this is before the real session begins, just return.
      */

terminal.c

@@ -86,6 +86,7 @@ typedef struct {
 #define incpos(p) ( (p).x == cols ? ((p).x = 0, (p).y++, 1) : ((p).x++, 0) )
 #define decpos(p) ( (p).x == 0 ? ((p).x = cols, (p).y--, 1) : ((p).x--, 0) )
 
+static bufchain inbuf;		       /* terminal input buffer */
 static pos curs;		       /* cursor */
 static pos savecurs;		       /* saved cursor position */
 static int marg_t, marg_b;	       /* scroll margins */
@@ -973,20 +974,38 @@ static void do_osc(void)
  */
 void term_out(void)
 {
-    int c, inbuf_reap;
+    int c, unget;
+    unsigned char localbuf[256], *chars;
+    int nchars = 0;
 
-    /*
-     * Optionally log the session traffic to a file. Useful for
-     * debugging and possibly also useful for actual logging.
-     */
-    if (cfg.logtype == LGTYP_DEBUG)
-	for (inbuf_reap = 0; inbuf_reap < inbuf_head; inbuf_reap++) {
-	    logtraffic((unsigned char) inbuf[inbuf_reap], LGTYP_DEBUG);
+    unget = -1;
+
+    while (nchars > 0 || bufchain_size(&inbuf) > 0) {
+	if (unget == -1) {
+	    if (nchars == 0) {
+		void *ret;
+		bufchain_prefix(&inbuf, &ret, &nchars);
+		if (nchars > sizeof(localbuf))
+		    nchars = sizeof(localbuf);
+		memcpy(localbuf, ret, nchars);
+		bufchain_consume(&inbuf, nchars);
+		chars = localbuf;
+		assert(chars != NULL);
+	    }
+	    c = *chars++;
+	    nchars--;
+
+	    /*
+	     * Optionally log the session traffic to a file. Useful for
+	     * debugging and possibly also useful for actual logging.
+	     */
+	    if (cfg.logtype == LGTYP_DEBUG)
+		logtraffic((unsigned char) &c, LGTYP_DEBUG);
+	} else {
+	    c = unget;
+	    unget = -1;
 	}
 
-    for (inbuf_reap = 0; inbuf_reap < inbuf_head; inbuf_reap++) {
-	c = inbuf[inbuf_reap];
-
 	/* Note only VT220+ are 8-bit VT102 is seven bit, it shouldn't even
 	 * be able to display 8-bit characters, but I'll let that go 'cause
 	 * of i18n.
@@ -1029,7 +1048,7 @@ void term_out(void)
 		  case 4:
 		  case 5:
 		    if ((c & 0xC0) != 0x80) {
-			inbuf_reap--;
+			unget = c;
 			c = UCSERR;
 			utf_state = 0;
 			break;
@@ -2480,7 +2499,6 @@ void term_out(void)
 	    check_selection(curs, cursplus);
 	}
     }
-    inbuf_head = 0;
 }
 
 #if 0
@@ -3358,18 +3376,15 @@ int term_ldisc(int option)
  */
 int from_backend(int is_stderr, char *data, int len)
 {
-    while (len--) {
-	if (inbuf_head >= INBUF_SIZE)
-	    term_out();
-	inbuf[inbuf_head++] = *data++;
-    }
+    bufchain_add(&inbuf, data, len);
 
     /*
-     * We process all stdout/stderr data immediately we receive it,
-     * and don't return until it's all gone. Therefore, there's no
-     * reason at all to return anything other than zero from this
-     * function.
-     * 
+     * term_out() always completely empties inbuf. Therefore,
+     * there's no reason at all to return anything other than zero
+     * from this function, because there _can't_ be a question of
+     * the remote side needing to wait until term_out() has cleared
+     * a backlog.
+     *
      * This is a slightly suboptimal way to deal with SSH2 - in
      * principle, the window mechanism would allow us to continue
      * to accept data on forwarded ports and X connections even
@@ -3379,7 +3394,7 @@ int from_backend(int is_stderr, char *data, int len)
      * portability. So we manage stdout buffering the old SSH1 way:
      * if the terminal processing goes slowly, the whole SSH
      * connection stops accepting data until it's ready.
-     * 
+     *
      * In practice, I can't imagine this causing serious trouble.
      */
     return 0;

window.c

@@ -525,12 +525,6 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
 
     session_closed = FALSE;
 
-    /*
-     * Set up the input and output buffers.
-     */
-    inbuf_head = 0;
-    outbuf_reap = outbuf_head = 0;
-
     /*
      * Prepare the mouse handler.
      */
@@ -660,8 +654,7 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
 		timer_id = 0;
 	    }
 	    HideCaret(hwnd);
-	    if (inbuf_head)
-		term_out();
+	    term_out();
 	    term_update();
 	    ShowCaret(hwnd);
 
@@ -1392,8 +1385,7 @@ static LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
       case WM_TIMER:
 	if (pending_netevent)
 	    enact_pending_netevent();
-	if (inbuf_head)
-	    term_out();
+	term_out();
 	noise_regular();
 	HideCaret(hwnd);
 	term_update();