X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/e3e281ccf9d8777d0df98ddd644720573e0343d1..1d28cc061677bd07d9bed48dd84bd5c590247043:/src/src/debug.c

diff --git a/src/src/debug.c b/src/src/debug.c
index 92cad6d48..44ad763e1 100644
--- a/src/src/debug.c
+++ b/src/src/debug.c
@@ -2,9 +2,10 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
+/* Copyright (c) The Exim Maintainers 2015 - 2022 */
 /* Copyright (c) University of Cambridge 1995 - 2018 */
-/* Copyright (c) The Exim Maintainers 2015 - 2021 */
 /* See the file NOTICE for conditions of use and distribution. */
+/* SPDX-License-Identifier: GPL-2.0-or-later */
 
 
 #include "exim.h"
@@ -13,6 +14,8 @@ static uschar  debug_buffer[2048];
 static uschar *debug_ptr = debug_buffer;
 static int     debug_prefix_length = 0;
 
+static unsigned pretrigger_writeoff;
+static unsigned pretrigger_readoff;
 
 
 const uschar * rc_names[] = {		/* Mostly for debug output */
@@ -318,8 +321,41 @@ if (debug_ptr[-1] == '\n')
       }
     }
 
-  fprintf(debug_file, "%s", CS debug_buffer);
-  fflush(debug_file);
+  if (debug_pretrigger_buf)
+    {
+    int needed = Ustrlen(debug_buffer)+1, avail;
+    char c;
+
+    if (needed > debug_pretrigger_bsize)
+      needed = debug_pretrigger_bsize;
+    if ((avail = pretrigger_readoff - pretrigger_writeoff) <= 0)
+      avail += debug_pretrigger_bsize;
+
+    /* We have a pretrigger set up, trigger not yet hit. Copy the line(s) to the
+    pretrig buffer, dropping earlier lines if needed but truncating this line if
+    the pbuf is maxed out.  In the PTB the lines are NOT nul-terminated. */
+
+    while (avail < needed)
+      do
+	{
+	avail++;
+        c = debug_pretrigger_buf[pretrigger_readoff];
+	if (++pretrigger_readoff >= debug_pretrigger_bsize) pretrigger_readoff = 0;
+	}
+      while (c && c != '\n' && pretrigger_readoff != pretrigger_writeoff);
+
+    needed--;
+    for (int i = 0; needed; i++, needed--)
+      {
+      debug_pretrigger_buf[pretrigger_writeoff] = debug_buffer[i];
+      if (++pretrigger_writeoff >= debug_pretrigger_bsize) pretrigger_writeoff = 0;
+      }
+    }
+  else
+    {
+    fprintf(debug_file, "%s", CS debug_buffer);
+    fflush(debug_file);
+    }
   debug_ptr = debug_buffer;
   debug_prefix_length = 0;
   }
@@ -410,4 +446,54 @@ else
 }
 
 
+/**************************************************************/
+/* Pretrigger handling for debug.  The debug_printf implementation
+diverts output to a circular buffer if the buffer is set up.
+The routines here set up the buffer, and unload it to file (and release it).
+What ends up in the buffer is subject to the usual debug_selector. */
+
+void
+debug_pretrigger_setup(const uschar * size_string)
+{
+long size = Ustrtol(size_string, NULL, 0);
+if (size > 0)
+  {
+  unsigned bufsize = MIN(size, 16384);
+
+  dtrigger_selector |= BIT(DTi_pretrigger);
+  if (debug_pretrigger_buf) store_free(debug_pretrigger_buf);
+  debug_pretrigger_buf = store_malloc((size_t)(debug_pretrigger_bsize = bufsize));
+  pretrigger_readoff = pretrigger_writeoff = 0;
+  }
+}
+
+void
+debug_trigger_fire(void)
+{
+int nbytes;
+
+if (!debug_pretrigger_buf) return;
+
+if (debug_file && (nbytes = pretrigger_writeoff - pretrigger_readoff) != 0)
+  if (nbytes > 0)
+    fwrite(debug_pretrigger_buf + pretrigger_readoff, 1, nbytes, debug_file);
+  else
+    {
+    fwrite(debug_pretrigger_buf + pretrigger_readoff, 1,
+      debug_pretrigger_bsize - pretrigger_readoff, debug_file);
+    fwrite(debug_pretrigger_buf, 1, pretrigger_writeoff, debug_file);
+    }
+
+debug_pretrigger_discard();
+}
+
+void
+debug_pretrigger_discard(void)
+{
+if (debug_pretrigger_buf) store_free(debug_pretrigger_buf);
+debug_pretrigger_buf = NULL;
+dtrigger_selector = 0;
+}
+
+
 /* End of debug.c */