SCP: Add option to write debug output to an in memory circular buffer

scp.c

@@ -576,6 +576,10 @@ FILEREF *sim_log_ref = NULL;                            /* log file file referen
 FILE *sim_deb = NULL;                                   /* debug file */
 FILEREF *sim_deb_ref = NULL;                            /* debug file file reference */
 int32 sim_deb_switches = 0;                             /* debug switches */
+size_t sim_deb_buffer_size = 0;                         /* debug memory buffer size */
+char *sim_deb_buffer = NULL;                            /* debug memory buffer */
+size_t sim_debug_buffer_offset = 0;                     /* debug memory buffer insertion offset */
+size_t sim_debug_buffer_inuse = 0;                      /* debug memory buffer inuse count */
 struct timespec sim_deb_basetime;                       /* debug timestamp relative base time */
 char *sim_prompt = NULL;                                /* prompt string */
 static FILE *sim_gotofile;                              /* the currently open do file */
@@ -1224,6 +1228,13 @@ static const char simh_help[] =
       "5-E\n"
       " The -E switch causes data blob output to also display the data as\n"
       " EBCDIC characters.\n"
+      "5-B\n"
+      " The -B switch causes debug data output to be written to a circular\n"
+      " buffer in memory.   This avoids the potential delays for disk I/O to\n"
+      " and the disk storage that a long running debug might consume.\n"
+      " The size of the circular memory buffer that is used is specified on\n"
+      " the SET DEBUG command line, for example:\n\n"
+      "++SET DEBUG -B <sizeinMB> <debug-destination>\n\n"
 #define HLP_SET_BREAK  "*Commands SET Breakpoints"
       "3Breakpoints\n"
       "+SET BREAK <list>            set breakpoints\n"
@@ -12181,6 +12192,33 @@ size_t debug_line_bufsize = 0;
 size_t debug_line_offset = 0;
 size_t debug_line_count = 0;
 
+static void _debug_fwrite (const char *buf, size_t len)
+{
+size_t move_size;
+
+if (sim_deb_buffer == NULL) {
+    fwrite (buf, 1, len, sim_deb);              /* output now. */
+    return;
+    }
+if ((sim_deb == stdout) && (!sim_is_running))
+    fwrite (buf, 1, len, stdout);               /* output now. */
+while (len > 0) {
+    if (sim_debug_buffer_offset + len <= sim_deb_buffer_size)
+        move_size = len;
+    else
+        move_size = sim_deb_buffer_size - sim_debug_buffer_offset;
+    memcpy (sim_deb_buffer + sim_debug_buffer_offset, buf, move_size);
+    sim_debug_buffer_offset += move_size;
+    if (sim_debug_buffer_offset == sim_deb_buffer_size) {
+        sim_debug_buffer_offset = 0;
+        sim_debug_buffer_inuse = sim_deb_buffer_size;
+        }
+    if (sim_debug_buffer_inuse < sim_deb_buffer_size)
+        sim_debug_buffer_inuse += move_size;
+    len -= move_size;
+    }
+}
+
 /*
  * Optionally filter debug output to summarize duplicate debug lines
  */
@@ -12190,7 +12228,7 @@ char *eol;
 
 if (sim_deb_switches & SWMASK ('F')) {              /* filtering disabled? */
     if (len > 0)
-        fwrite (buf, 1, len, sim_deb);              /* output now. */
+        _debug_fwrite (buf, len);                   /* output now. */
     return;                                         /* done */
     }
 if (debug_line_offset + len + 1 > debug_line_bufsize) {
@@ -12207,20 +12245,20 @@ while ((eol = strchr (debug_line_buf, '\n')) || flush) {
 
     if ((0 != memcmp ("DBG(", debug_line_buf, 4)) || (endprefix == NULL)) {
         if (debug_line_count > 0)
-            fwrite (debug_line_buf_last, 1, strlen (debug_line_buf_last), sim_deb);
+            _debug_fwrite (debug_line_buf_last, strlen (debug_line_buf_last));
         if (debug_line_count > 1) {
             char countstr[32];
 
             sprintf (countstr, "same as above (%d time%s)\r\n", (int)(debug_line_count - 1), ((debug_line_count - 1) != 1) ? "s" : "");
-            fwrite (debug_line_last_prefix, 1, strlen (debug_line_last_prefix), sim_deb);
+            _debug_fwrite (debug_line_last_prefix, strlen (debug_line_last_prefix));
-            fwrite (countstr, 1, strlen (countstr), sim_deb);
+            _debug_fwrite (countstr, strlen (countstr));
             }
         if (flush) {
             linesize = debug_line_offset;
             flush = FALSE;              /* already flushed */
             }
         if (linesize)
-            fwrite (debug_line_buf, 1, linesize, sim_deb);
+            _debug_fwrite  (debug_line_buf, linesize);
         debug_line_count = 0;
         }
     else {
@@ -12239,13 +12277,13 @@ while ((eol = strchr (debug_line_buf, '\n')) || flush) {
                 debug_line_last_prefix[(endprefix - debug_line_buf) + 3] = '\0';
                 }
             else {
-                fwrite (debug_line_buf_last, 1, strlen (debug_line_buf_last), sim_deb);
+                _debug_fwrite (debug_line_buf_last, strlen (debug_line_buf_last));
                 if (debug_line_count > 1) {
                     char countstr[32];
 
                     sprintf (countstr, "same as above (%d time%s)\r\n", (int)(debug_line_count - 1), ((debug_line_count - 1) != 1) ? "s" : "");
-                    fwrite (debug_line_last_prefix, 1, strlen (debug_line_last_prefix), sim_deb);
+                    _debug_fwrite (debug_line_last_prefix, strlen (debug_line_last_prefix));
-                    fwrite (countstr, 1, strlen (countstr), sim_deb);
+                    _debug_fwrite (countstr, strlen (countstr));
                     }
                 debug_line_buf_last_endprefix_offset = endprefix - debug_line_buf;
                 memcpy (debug_line_buf_last, debug_line_buf, linesize);
@@ -12284,6 +12322,7 @@ if (sim_deb == sim_log) {                               /* debug is log */
     return SCPE_OK;
     }
 
+if (!(saved_deb_switches & SWMASK ('B'))) {
     strcpy (saved_debug_filename, sim_logfile_name (sim_deb, sim_deb_ref));
 
     sim_quiet = 1;
@@ -12293,6 +12332,7 @@ sim_set_debon (0, saved_debug_filename);
     sim_deb_basetime = saved_deb_basetime;
     sim_switches = saved_sim_switches;
     sim_quiet = saved_quiet;
+    }
 return SCPE_OK;
 }
 

scp.h

@@ -355,6 +355,10 @@ extern FILEREF *sim_log_ref;                            /* log file file referen
 extern FILE *sim_deb;                                   /* debug file */
 extern FILEREF *sim_deb_ref;                            /* debug file file reference */
 extern int32 sim_deb_switches;                          /* debug display flags */
+extern size_t sim_deb_buffer_size;                      /* debug memory buffer size */
+extern char *sim_deb_buffer;                            /* debug memory buffer */
+extern size_t sim_debug_buffer_offset;                  /* debug memory buffer insertion offset */
+extern size_t sim_debug_buffer_inuse;                   /* debug memory buffer inuse count */
 extern struct timespec sim_deb_basetime;                /* debug base time for relative time output */
 extern DEVICE **sim_internal_devices;
 extern uint32 sim_internal_device_count;

sim_console.c

@@ -138,6 +138,10 @@
 #define nice(n) ({})
 #endif
 
+#ifndef MIN
+#define MIN(a,b)  (((a) <= (b)) ? (a) : (b))
+#endif
+
 /* Forward Declaraations of Platform specific routines */
 
 static t_stat sim_os_poll_kbd (void);
@@ -2222,9 +2226,16 @@ t_stat sim_set_debon (int32 flag, CONST char *cptr)
 char gbuf[CBUFSIZE];
 t_stat r;
 time_t now;
+size_t buffer_size;
 
 if ((cptr == NULL) || (*cptr == 0))                     /* need arg */
     return SCPE_2FARG;
+if (sim_switches & SWMASK ('B')) {
+    cptr = get_glyph_nc (cptr, gbuf, 0);                /* buffer size */
+    buffer_size = (size_t)strtoul (gbuf, NULL, 10);
+    if ((buffer_size == 0) || (buffer_size > 1024))
+        return sim_messagef (SCPE_ARG, "Invalid debug memory buffersize %u MB\n", (unsigned int)buffer_size);
+    }
 cptr = get_glyph_nc (cptr, gbuf, 0);                    /* get file name */
 if (*cptr != 0)                                         /* now eol? */
     return SCPE_2MARG;
@@ -2233,7 +2244,11 @@ r = sim_open_logfile (gbuf, FALSE, &sim_deb, &sim_deb_ref);
 if (r != SCPE_OK)
     return r;
 
-sim_deb_switches = sim_switches;                        /* save debug switches */
+sim_deb_switches = sim_switches & 
+                   (SWMASK ('R') | SWMASK ('P') | 
+                    SWMASK ('T') | SWMASK ('A') | 
+                    SWMASK ('F') | SWMASK ('N') |
+                    SWMASK ('B'));                  /* save debug switches */
 if (sim_deb_switches & SWMASK ('R')) {
     struct tm loc_tm, gmt_tm;
     time_t time_t_now;
@@ -2247,25 +2262,33 @@ if (sim_deb_switches & SWMASK ('R')) {
     if (!(sim_deb_switches & (SWMASK ('A') | SWMASK ('T'))))
         sim_deb_switches |= SWMASK ('T');
     }
-if (!sim_quiet) {
+sim_messagef (SCPE_OK, "Debug output to \"%s\"\n", sim_logfile_name (sim_deb, sim_deb_ref));
-    sim_printf ("Debug output to \"%s\"\n", sim_logfile_name (sim_deb, sim_deb_ref));
 if (sim_deb_switches & SWMASK ('P'))
-        sim_printf ("   Debug messages contain current PC value\n");
+    sim_messagef (SCPE_OK, "   Debug messages contain current PC value\n");
 if (sim_deb_switches & SWMASK ('T'))
-        sim_printf ("   Debug messages display time of day as hh:mm:ss.msec%s\n", sim_deb_switches & SWMASK ('R') ? " relative to the start of debugging" : "");
+    sim_messagef (SCPE_OK, "   Debug messages display time of day as hh:mm:ss.msec%s\n", sim_deb_switches & SWMASK ('R') ? " relative to the start of debugging" : "");
 if (sim_deb_switches & SWMASK ('A'))
-        sim_printf ("   Debug messages display time of day as seconds.msec%s\n", sim_deb_switches & SWMASK ('R') ? " relative to the start of debugging" : "");
+    sim_messagef (SCPE_OK, "   Debug messages display time of day as seconds.msec%s\n", sim_deb_switches & SWMASK ('R') ? " relative to the start of debugging" : "");
 if (sim_deb_switches & SWMASK ('F'))
-        sim_printf ("   Debug messages will not be filtered to summarize duplicate lines\n");
+    sim_messagef (SCPE_OK, "   Debug messages will not be filtered to summarize duplicate lines\n");
 if (sim_deb_switches & SWMASK ('E'))
-        sim_printf ("   Debug messages containing blob data in EBCDIC will display in readable form\n");
+    sim_messagef (SCPE_OK, "   Debug messages containing blob data in EBCDIC will display in readable form\n");
+if (sim_deb_switches & SWMASK ('B'))
+    sim_messagef (SCPE_OK, "   Debug messages will be written to a %u MB circular memory buffer\n", 
+                                (unsigned int)buffer_size);
 time(&now);
 fprintf (sim_deb, "Debug output to \"%s\" at %s", sim_logfile_name (sim_deb, sim_deb_ref), ctime(&now));
 show_version (sim_deb, NULL, NULL, 0, NULL);
-    }
 if (sim_deb_switches & SWMASK ('N'))
     sim_deb_switches &= ~SWMASK ('N');          /* Only process the -N flag initially */
 
+if (sim_deb_switches & SWMASK ('B')) {
+    sim_deb_buffer_size = (size_t)(1024 * 1024 * buffer_size);
+    sim_deb_buffer = realloc (sim_deb_buffer, sim_deb_buffer_size);
+    sim_debug_buffer_offset = sim_debug_buffer_inuse = 0;
+    memset (sim_deb_buffer, 0, sim_deb_buffer_size);
+    }
+
 return SCPE_OK;
 }
 
@@ -2277,6 +2300,25 @@ if (cptr && (*cptr != 0))                               /* now eol? */
     return SCPE_2MARG;
 if (sim_deb == NULL)                                    /* no debug? */
     return SCPE_OK;
+if (sim_deb_switches & SWMASK ('B')) {
+    size_t offset = (sim_debug_buffer_inuse == sim_deb_buffer_size) ? sim_debug_buffer_offset : 0;
+    const char *bufmsg = "Circular Buffer Contents follow here:\n\n";
+
+    fwrite (bufmsg, 1, strlen (bufmsg), sim_deb);
+
+    while (sim_debug_buffer_inuse > 0) {
+        size_t write_size = MIN (sim_deb_buffer_size - offset, sim_debug_buffer_inuse);
+
+        fwrite (sim_deb_buffer + offset, 1, write_size, sim_deb);
+        sim_debug_buffer_inuse -= write_size;
+        offset += write_size;
+        if (offset == sim_deb_buffer_size)
+            offset = 0;
+        }
+    free (sim_deb_buffer);
+    sim_deb_buffer = NULL;
+    sim_deb_buffer_size = sim_debug_buffer_offset = sim_debug_buffer_inuse = 0;
+    }
 sim_close_logfile (&sim_deb_ref);
 sim_deb = NULL;
 sim_deb_switches = 0;