[PATCH] Speed up "gdb -tui" output

[Pedro Alves]

On 01/07/2015 07:32 PM, Eli Zaretskii wrote:
> So?  How does this help?  The stderr problem is simple, but what do
> you do with stdout and stdlog?  Especially when tui_file_fputs is
> called one character at a time in most cases.

I'm confused on that the confusion is.  :-)

I think something like this should work.  I'm not really seeing a point
for those fflush(stdout)'s, btw.  Note that tui_stream->ts_filestream is
only ever used in tui_file_isatty; it's never written to.

>From 2b4d8cfb56d67f9eded113a120dc5c18ea3781cc Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Wed, 7 Jan 2015 19:50:48 +0000
Subject: [PATCH] TUI emulate line buffering

when printing to stdout, only refresh the console window when either a
new line is seen or when an explicit flush is requested.
---
 gdb/tui/tui-file.c |  5 +++--
 gdb/tui/tui-io.c   | 53 +++++++++++++++++++++++++++++++++++++++++++++--------
 gdb/tui/tui-io.h   | 10 ++++++++--
 3 files changed, 56 insertions(+), 12 deletions(-)

diff --git a/gdb/tui/tui-file.c b/gdb/tui/tui-file.c
index b32cfa6..932df46 100644
--- a/gdb/tui/tui-file.c
+++ b/gdb/tui/tui-file.c
@@ -178,7 +178,7 @@ tui_file_fputs (const char *linebuffer, struct ui_file *file)
     }
   else
     {
-      tui_puts (linebuffer);
+      tui_puts_file (file, linebuffer);
     }
 }

@@ -239,7 +239,8 @@ tui_file_flush (struct ui_file *file)
     case astring:
       break;
     case afile:
-      fflush (stream->ts_filestream);
+      if (file == tui_stdout)
+	tui_flush_stdout ();
       break;
     }
 }
diff --git a/gdb/tui/tui-io.c b/gdb/tui/tui-io.c
index 233e7a6..e7c5583 100644
--- a/gdb/tui/tui-io.c
+++ b/gdb/tui/tui-io.c
@@ -118,7 +118,7 @@ key_is_command_char (int ch)
 /* #undef TUI_USE_PIPE_FOR_READLINE */

 /* TUI output files.  */
-static struct ui_file *tui_stdout;
+struct ui_file *tui_stdout;
 static struct ui_file *tui_stderr;
 struct ui_out *tui_out;

@@ -148,6 +148,17 @@ static char *tui_rl_saved_prompt;

 static unsigned int tui_handle_resize_during_io (unsigned int);

+static void tui_puts (const char *string);
+
+void
+tui_flush_stdout (void)
+{
+  WINDOW *w;
+
+  w = TUI_CMD_WIN->generic.handle;
+  wrefresh (w);
+}
+
 static void
 tui_putc (char c)
 {
@@ -158,9 +169,13 @@ tui_putc (char c)
   tui_puts (buf);
 }

-/* Print the string in the curses command window.  */
-void
-tui_puts (const char *string)
+/* Print the string in the curses command window.  If LINEBUFFERED,
+   we're printing to stdout, and so like stdio, should only flush when
+   we see a new line.  If LINEBUFFERED is false, we'll flush after
+   printing the whole string.  */
+
+static void
+tui_puts_maybe_buffered (const char *string, int linebuffered)
 {
   static int tui_skip_line = -1;
   char c;
@@ -182,15 +197,36 @@ tui_puts (const char *string)
         }
       else if (c == '\n')
         tui_skip_line = -1;
+
+      if (linebuffered && c == '\n')
+	wrefresh (w);
     }
   getyx (w, TUI_CMD_WIN->detail.command_info.cur_line,
          TUI_CMD_WIN->detail.command_info.curch);
   TUI_CMD_WIN->detail.command_info.start_line
     = TUI_CMD_WIN->detail.command_info.cur_line;

-  /* We could defer the following.  */
-  wrefresh (w);
-  fflush (stdout);
+  if (!linebuffered)
+    wrefresh (w);
+}
+
+/* Print the string in the curses command window, as if printing to
+   stdout.  */
+
+static void
+tui_puts (const char *string)
+{
+  tui_puts_maybe_buffered (string, 1);
+}
+
+/* Print the string in the curses command window.  FILE indicates
+   which file the caller is printing to.  If gdb_stdout, then emulate
+   line buffering.  */
+
+void
+tui_puts_file (struct ui_file *file, const char *string)
+{
+  tui_puts_maybe_buffered (string, file == tui_stdout);
 }

 /* Readline callback.
@@ -279,7 +315,6 @@ tui_redisplay_readline (void)
   TUI_CMD_WIN->detail.command_info.start_line -= height - 1;

   wrefresh (w);
-  fflush(stdout);
 }

 /* Readline callback to prepare the terminal.  It is called once each
@@ -412,6 +447,7 @@ tui_rl_display_match_list (char **matches, int len, int max)

   /* Screen dimension correspond to the TUI command window.  */
   int screenwidth = TUI_CMD_WIN->generic.width;
+  WINDOW *w = TUI_CMD_WIN->generic.handle;

   /* If there are many items, then ask the user if she really wants to
      see them all.  */
@@ -422,6 +458,7 @@ tui_rl_display_match_list (char **matches, int len, int max)
       xsnprintf (msg, sizeof (msg),
 		 "\nDisplay all %d possibilities? (y or n)", len);
       tui_puts (msg);
+      tui_flush_stdout ();
       if (get_y_or_n () == 0)
 	{
 	  tui_puts ("\n");
diff --git a/gdb/tui/tui-io.h b/gdb/tui/tui-io.h
index 8f96cfe..81d4337 100644
--- a/gdb/tui/tui-io.h
+++ b/gdb/tui/tui-io.h
@@ -24,8 +24,13 @@

 struct ui_out;

-/* Print the string in the curses command window.  */
-extern void tui_puts (const char *);
+/* Print the string in the curses command window.  FILE indicates
+   which file the caller is printing to.  If gdb_stdout, then emulate
+   line buffering.  */
+extern void tui_puts_file (struct ui_file *file, const char *string);
+
+/* Flush console output.  */
+extern void tui_flush_stdout (void);

 /* Setup the IO for curses or non-curses mode.  */
 extern void tui_setup_io (int mode);
@@ -41,6 +46,7 @@ extern int tui_getc (FILE *);
    changed the edited text.  */
 extern void tui_redisplay_readline (void);

+extern struct ui_file *tui_stdout;
 extern struct ui_out *tui_out;
 extern struct ui_out *tui_old_uiout;

-- 
1.9.3