This is the long-awaited import of top into the base system (actually,

the src/contrib/top part right now).  This tools is simply too system-
dependant to maintain it in the ports collection.

1 files changed, 1129 insertions, 0 deletions

diff --git a/contrib/top/display.c b/contrib/top/display.c
new file mode 100644
index 0000000..0769e3f
--- /dev/null
+++ b/contrib/top/display.c
@@ -0,0 +1,1129 @@
+/*
+ *  Top users/processes display for Unix
+ *  Version 3
+ *
+ *  This program may be freely redistributed,
+ *  but this entire comment MUST remain intact.
+ *
+ *  Copyright (c) 1984, 1989, William LeFebvre, Rice University
+ *  Copyright (c) 1989, 1990, 1992, William LeFebvre, Northwestern University
+ */
+
+/*
+ *  This file contains the routines that display information on the screen.
+ *  Each section of the screen has two routines:  one for initially writing
+ *  all constant and dynamic text, and one for only updating the text that
+ *  changes.  The prefix "i_" is used on all the "initial" routines and the
+ *  prefix "u_" is used for all the "updating" routines.
+ *
+ *  ASSUMPTIONS:
+ *        None of the "i_" routines use any of the termcap capabilities.
+ *        In this way, those routines can be safely used on terminals that
+ *        have minimal (or nonexistant) terminal capabilities.
+ *
+ *        The routines are called in this order:  *_loadave, i_timeofday,
+ *        *_procstates, *_cpustates, *_memory, *_message, *_header,
+ *        *_process, u_endscreen.
+ */
+
+#include "os.h"
+#include <ctype.h>
+#include <time.h>
+
+#include "screen.h"		/* interface to screen package */
+#include "layout.h"		/* defines for screen position layout */
+#include "display.h"
+#include "top.h"
+#include "top.local.h"
+#include "boolean.h"
+#include "machine.h"		/* we should eliminate this!!! */
+#include "utils.h"
+
+#ifdef DEBUG
+FILE *debug;
+#endif
+
+/* imported from screen.c */
+extern int overstrike;
+
+static int lmpid = 0;
+static int last_hi = 0;		/* used in u_process and u_endscreen */
+static int lastline = 0;
+static int display_width = MAX_COLS;
+
+#define lineindex(l) ((l)*display_width)
+
+char *printable();
+
+/* things initialized by display_init and used thruout */
+
+/* buffer of proc information lines for display updating */
+char *screenbuf = NULL;
+
+static char **procstate_names;
+static char **cpustate_names;
+static char **memory_names;
+
+static int num_procstates;
+static int num_cpustates;
+static int num_memory;
+
+static int *lprocstates;
+static int *lcpustates;
+static int *lmemory;
+
+static int *cpustate_columns;
+static int cpustate_total_length;
+
+static enum { OFF, ON, ERASE } header_status = ON;
+
+static int string_count();
+static void summary_format();
+static void line_update();
+
+int display_resize()
+
+{
+    register int lines;
+
+    /* first, deallocate any previous buffer that may have been there */
+    if (screenbuf != NULL)
+    {
+	free(screenbuf);
+    }
+
+    /* calculate the current dimensions */
+    /* if operating in "dumb" mode, we only need one line */
+    lines = smart_terminal ? screen_length - Header_lines : 1;
+
+    /* we don't want more than MAX_COLS columns, since the machine-dependent
+       modules make static allocations based on MAX_COLS and we don't want
+       to run off the end of their buffers */
+    display_width = screen_width;
+    if (display_width >= MAX_COLS)
+    {
+	display_width = MAX_COLS - 1;
+    }
+
+    /* now, allocate space for the screen buffer */
+    screenbuf = (char *)malloc(lines * display_width);
+    if (screenbuf == (char *)NULL)
+    {
+	/* oops! */
+	return(-1);
+    }
+
+    /* return number of lines available */
+    /* for dumb terminals, pretend like we can show any amount */
+    return(smart_terminal ? lines : Largest);
+}
+
+int display_init(statics)
+
+struct statics *statics;
+
+{
+    register int lines;
+    register char **pp;
+    register int *ip;
+    register int i;
+
+    /* call resize to do the dirty work */
+    lines = display_resize();
+
+    /* only do the rest if we need to */
+    if (lines > -1)
+    {
+	/* save pointers and allocate space for names */
+	procstate_names = statics->procstate_names;
+	num_procstates = string_count(procstate_names);
+	lprocstates = (int *)malloc(num_procstates * sizeof(int));
+
+	cpustate_names = statics->cpustate_names;
+	num_cpustates = string_count(cpustate_names);
+	lcpustates = (int *)malloc(num_cpustates * sizeof(int));
+	cpustate_columns = (int *)malloc(num_cpustates * sizeof(int));
+
+	memory_names = statics->memory_names;
+	num_memory = string_count(memory_names);
+	lmemory = (int *)malloc(num_memory * sizeof(int));
+
+	/* calculate starting columns where needed */
+	cpustate_total_length = 0;
+	pp = cpustate_names;
+	ip = cpustate_columns;
+	while (*pp != NULL)
+	{
+	    if ((i = strlen(*pp++)) > 0)
+	    {
+		*ip++ = cpustate_total_length;
+		cpustate_total_length += i + 8;
+	    }
+	}
+    }
+
+    /* return number of lines available */
+    return(lines);
+}
+
+i_loadave(mpid, avenrun)
+
+int mpid;
+double *avenrun;
+
+{
+    register int i;
+
+    /* i_loadave also clears the screen, since it is first */
+    clear();
+
+    /* mpid == -1 implies this system doesn't have an _mpid */
+    if (mpid != -1)
+    {
+	printf("last pid: %5d;  ", mpid);
+    }
+
+    printf("load averages");
+
+    for (i = 0; i < 3; i++)
+    {
+	printf("%c %5.2f",
+	    i == 0 ? ':' : ',',
+	    avenrun[i]);
+    }
+    lmpid = mpid;
+}
+
+u_loadave(mpid, avenrun)
+
+int mpid;
+double *avenrun;
+
+{
+    register int i;
+
+    if (mpid != -1)
+    {
+	/* change screen only when value has really changed */
+	if (mpid != lmpid)
+	{
+	    Move_to(x_lastpid, y_lastpid);
+	    printf("%5d", mpid);
+	    lmpid = mpid;
+	}
+
+	/* i remembers x coordinate to move to */
+	i = x_loadave;
+    }
+    else
+    {
+	i = x_loadave_nompid;
+    }
+
+    /* move into position for load averages */
+    Move_to(i, y_loadave);
+
+    /* display new load averages */
+    /* we should optimize this and only display changes */
+    for (i = 0; i < 3; i++)
+    {
+	printf("%s%5.2f",
+	    i == 0 ? "" : ", ",
+	    avenrun[i]);
+    }
+}
+
+i_timeofday(tod)
+
+time_t *tod;
+
+{
+    /*
+     *  Display the current time.
+     *  "ctime" always returns a string that looks like this:
+     *  
+     *	Sun Sep 16 01:03:52 1973
+     *      012345678901234567890123
+     *	          1         2
+     *
+     *  We want indices 11 thru 18 (length 8).
+     */
+
+    if (smart_terminal)
+    {
+	Move_to(screen_width - 8, 0);
+    }
+    else
+    {
+	fputs("    ", stdout);
+    }
+#ifdef DEBUG
+    {
+	char *foo;
+	foo = ctime(tod);
+	fputs(foo, stdout);
+    }
+#endif
+    printf("%-8.8s\n", &(ctime(tod)[11]));
+    lastline = 1;
+}
+
+static int ltotal = 0;
+static char procstates_buffer[128];
+
+/*
+ *  *_procstates(total, brkdn, names) - print the process summary line
+ *
+ *  Assumptions:  cursor is at the beginning of the line on entry
+ *		  lastline is valid
+ */
+
+i_procstates(total, brkdn)
+
+int total;
+int *brkdn;
+
+{
+    register int i;
+
+    /* write current number of processes and remember the value */
+    printf("%d processes:", total);
+    ltotal = total;
+
+    /* put out enough spaces to get to column 15 */
+    i = digits(total);
+    while (i++ < 4)
+    {
+	putchar(' ');
+    }
+
+    /* format and print the process state summary */
+    summary_format(procstates_buffer, brkdn, procstate_names);
+    fputs(procstates_buffer, stdout);
+
+    /* save the numbers for next time */
+    memcpy(lprocstates, brkdn, num_procstates * sizeof(int));
+}
+
+u_procstates(total, brkdn)
+
+int total;
+int *brkdn;
+
+{
+    static char new[128];
+    register int i;
+
+    /* update number of processes only if it has changed */
+    if (ltotal != total)
+    {
+	/* move and overwrite */
+#if (x_procstate == 0)
+	Move_to(x_procstate, y_procstate);
+#else
+	/* cursor is already there...no motion needed */
+	/* assert(lastline == 1); */
+#endif
+	printf("%d", total);
+
+	/* if number of digits differs, rewrite the label */
+	if (digits(total) != digits(ltotal))
+	{
+	    fputs(" processes:", stdout);
+	    /* put out enough spaces to get to column 15 */
+	    i = digits(total);
+	    while (i++ < 4)
+	    {
+		putchar(' ');
+	    }
+	    /* cursor may end up right where we want it!!! */
+	}
+
+	/* save new total */
+	ltotal = total;
+    }
+
+    /* see if any of the state numbers has changed */
+    if (memcmp(lprocstates, brkdn, num_procstates * sizeof(int)) != 0)
+    {
+	/* format and update the line */
+	summary_format(new, brkdn, procstate_names);
+	line_update(procstates_buffer, new, x_brkdn, y_brkdn);
+	memcpy(lprocstates, brkdn, num_procstates * sizeof(int));
+    }
+}
+
+/*
+ *  *_cpustates(states, names) - print the cpu state percentages
+ *
+ *  Assumptions:  cursor is on the PREVIOUS line
+ */
+
+static int cpustates_column;
+
+/* cpustates_tag() calculates the correct tag to use to label the line */
+
+char *cpustates_tag()
+
+{
+    register char *use;
+
+    static char *short_tag = "CPU: ";
+    static char *long_tag = "CPU states: ";
+
+    /* if length + strlen(long_tag) >= screen_width, then we have to
+       use the shorter tag (we subtract 2 to account for ": ") */
+    if (cpustate_total_length + (int)strlen(long_tag) - 2 >= screen_width)
+    {
+	use = short_tag;
+    }
+    else
+    {
+	use = long_tag;
+    }
+
+    /* set cpustates_column accordingly then return result */
+    cpustates_column = strlen(use);
+    return(use);
+}
+
+i_cpustates(states)
+
+register int *states;
+
+{
+    register int i = 0;
+    register int value;
+    register char **names = cpustate_names;
+    register char *thisname;
+
+    /* print tag and bump lastline */
+    printf("\n%s", cpustates_tag());
+    lastline++;
+
+    /* now walk thru the names and print the line */
+    while ((thisname = *names++) != NULL)
+    {
+	if (*thisname != '\0')
+	{
+	    /* retrieve the value and remember it */
+	    value = *states++;
+
+	    /* if percentage is >= 1000, print it as 100% */
+	    printf((value >= 1000 ? "%s%4.0f%% %s" : "%s%4.1f%% %s"),
+		   i++ == 0 ? "" : ", ",
+		   ((float)value)/10.,
+		   thisname);
+	}
+    }
+
+    /* copy over values into "last" array */
+    memcpy(lcpustates, states, num_cpustates * sizeof(int));
+}
+
+u_cpustates(states)
+
+register int *states;
+
+{
+    register int value;
+    register char **names = cpustate_names;
+    register char *thisname;
+    register int *lp;
+    register int *colp;
+
+    Move_to(cpustates_column, y_cpustates);
+    lastline = y_cpustates;
+    lp = lcpustates;
+    colp = cpustate_columns;
+
+    /* we could be much more optimal about this */
+    while ((thisname = *names++) != NULL)
+    {
+	if (*thisname != '\0')
+	{
+	    /* did the value change since last time? */
+	    if (*lp != *states)
+	    {
+		/* yes, move and change */
+		Move_to(cpustates_column + *colp, y_cpustates);
+		lastline = y_cpustates;
+
+		/* retrieve value and remember it */
+		value = *states;
+
+		/* if percentage is >= 1000, print it as 100% */
+		printf((value >= 1000 ? "%4.0f" : "%4.1f"),
+		       ((double)value)/10.);
+
+		/* remember it for next time */
+		*lp = *states;
+	    }
+	}
+
+	/* increment and move on */
+	lp++;
+	states++;
+	colp++;
+    }
+}
+
+z_cpustates()
+
+{
+    register int i = 0;
+    register char **names = cpustate_names;
+    register char *thisname;
+    register int *lp;
+
+    /* show tag and bump lastline */
+    printf("\n%s", cpustates_tag());
+    lastline++;
+
+    while ((thisname = *names++) != NULL)
+    {
+	if (*thisname != '\0')
+	{
+	    printf("%s    %% %s", i++ == 0 ? "" : ", ", thisname);
+	}
+    }
+
+    /* fill the "last" array with all -1s, to insure correct updating */
+    lp = lcpustates;
+    i = num_cpustates;
+    while (--i >= 0)
+    {
+	*lp++ = -1;
+    }
+}
+
+/*
+ *  *_memory(stats) - print "Memory: " followed by the memory summary string
+ *
+ *  Assumptions:  cursor is on "lastline"
+ *                for i_memory ONLY: cursor is on the previous line
+ */
+
+char memory_buffer[MAX_COLS];
+
+i_memory(stats)
+
+int *stats;
+
+{
+    fputs("\nMemory: ", stdout);
+    lastline++;
+
+    /* format and print the memory summary */
+    summary_format(memory_buffer, stats, memory_names);
+    fputs(memory_buffer, stdout);
+}
+
+u_memory(stats)
+
+int *stats;
+
+{
+    static char new[MAX_COLS];
+
+    /* format the new line */
+    summary_format(new, stats, memory_names);
+    line_update(memory_buffer, new, x_mem, y_mem);
+}
+
+/*
+ *  *_message() - print the next pending message line, or erase the one
+ *                that is there.
+ *
+ *  Note that u_message is (currently) the same as i_message.
+ *
+ *  Assumptions:  lastline is consistent
+ */
+
+/*
+ *  i_message is funny because it gets its message asynchronously (with
+ *	respect to screen updates).
+ */
+
+static char next_msg[MAX_COLS + 5];
+static int msglen = 0;
+/* Invariant: msglen is always the length of the message currently displayed
+   on the screen (even when next_msg doesn't contain that message). */
+
+i_message()
+
+{
+    while (lastline < y_message)
+    {
+	fputc('\n', stdout);
+	lastline++;
+    }
+    if (next_msg[0] != '\0')
+    {
+	standout(next_msg);
+	msglen = strlen(next_msg);
+	next_msg[0] = '\0';
+    }
+    else if (msglen > 0)
+    {
+	(void) clear_eol(msglen);
+	msglen = 0;
+    }
+}
+
+u_message()
+
+{
+    i_message();
+}
+
+static int header_length;
+
+/*
+ *  *_header(text) - print the header for the process area
+ *
+ *  Assumptions:  cursor is on the previous line and lastline is consistent
+ */
+
+i_header(text)
+
+char *text;
+
+{
+    header_length = strlen(text);
+    if (header_status == ON)
+    {
+	putchar('\n');
+	fputs(text, stdout);
+	lastline++;
+    }
+    else if (header_status == ERASE)
+    {
+	header_status = OFF;
+    }
+}
+
+/*ARGSUSED*/
+u_header(text)
+
+char *text;		/* ignored */
+
+{
+    if (header_status == ERASE)
+    {
+	putchar('\n');
+	lastline++;
+	clear_eol(header_length);
+	header_status = OFF;
+    }
+}
+
+/*
+ *  *_process(line, thisline) - print one process line
+ *
+ *  Assumptions:  lastline is consistent
+ */
+
+i_process(line, thisline)
+
+int line;
+char *thisline;
+
+{
+    register char *p;
+    register char *base;
+
+    /* make sure we are on the correct line */
+    while (lastline < y_procs + line)
+    {
+	putchar('\n');
+	lastline++;
+    }
+
+    /* truncate the line to conform to our current screen width */
+    thisline[display_width] = '\0';
+
+    /* write the line out */
+    fputs(thisline, stdout);
+
+    /* copy it in to our buffer */
+    base = smart_terminal ? screenbuf + lineindex(line) : screenbuf;
+    p = strecpy(base, thisline);
+
+    /* zero fill the rest of it */
+    memzero(p, display_width - (p - base));
+}
+
+u_process(line, newline)
+
+int line;
+char *newline;
+
+{
+    register char *optr;
+    register int screen_line = line + Header_lines;
+    register char *bufferline;
+
+    /* remember a pointer to the current line in the screen buffer */
+    bufferline = &screenbuf[lineindex(line)];
+
+    /* truncate the line to conform to our current screen width */
+    newline[display_width] = '\0';
+
+    /* is line higher than we went on the last display? */
+    if (line >= last_hi)
+    {
+	/* yes, just ignore screenbuf and write it out directly */
+	/* get positioned on the correct line */
+	if (screen_line - lastline == 1)
+	{
+	    putchar('\n');
+	    lastline++;
+	}
+	else
+	{
+	    Move_to(0, screen_line);
+	    lastline = screen_line;
+	}
+
+	/* now write the line */
+	fputs(newline, stdout);
+
+	/* copy it in to the buffer */
+	optr = strecpy(bufferline, newline);
+
+	/* zero fill the rest of it */
+	memzero(optr, display_width - (optr - bufferline));
+    }
+    else
+    {
+	line_update(bufferline, newline, 0, line + Header_lines);
+    }
+}
+
+u_endscreen(hi)
+
+register int hi;
+
+{
+    register int screen_line = hi + Header_lines;
+    register int i;
+
+    if (smart_terminal)
+    {
+	if (hi < last_hi)
+	{
+	    /* need to blank the remainder of the screen */
+	    /* but only if there is any screen left below this line */
+	    if (lastline + 1 < screen_length)
+	    {
+		/* efficiently move to the end of currently displayed info */
+		if (screen_line - lastline < 5)
+		{
+		    while (lastline < screen_line)
+		    {
+			putchar('\n');
+			lastline++;
+		    }
+		}
+		else
+		{
+		    Move_to(0, screen_line);
+		    lastline = screen_line;
+		}
+
+		if (clear_to_end)
+		{
+		    /* we can do this the easy way */
+		    putcap(clear_to_end);
+		}
+		else
+		{
+		    /* use clear_eol on each line */
+		    i = hi;
+		    while ((void) clear_eol(strlen(&screenbuf[lineindex(i++)])), i < last_hi)
+		    {
+			putchar('\n');
+		    }
+		}
+	    }
+	}
+	last_hi = hi;
+
+	/* move the cursor to a pleasant place */
+	Move_to(x_idlecursor, y_idlecursor);
+	lastline = y_idlecursor;
+    }
+    else
+    {
+	/* separate this display from the next with some vertical room */
+	fputs("\n\n", stdout);
+    }
+}
+
+display_header(t)
+
+int t;
+
+{
+    if (t)
+    {
+	header_status = ON;
+    }
+    else if (header_status == ON)
+    {
+	header_status = ERASE;
+    }
+}
+
+/*VARARGS2*/
+new_message(type, msgfmt, a1, a2, a3)
+
+int type;
+char *msgfmt;
+caddr_t a1, a2, a3;
+
+{
+    register int i;
+
+    /* first, format the message */
+    (void) sprintf(next_msg, msgfmt, a1, a2, a3);
+
+    if (msglen > 0)
+    {
+	/* message there already -- can we clear it? */
+	if (!overstrike)
+	{
+	    /* yes -- write it and clear to end */
+	    i = strlen(next_msg);
+	    if ((type & MT_delayed) == 0)
+	    {
+		type & MT_standout ? standout(next_msg) :
+		                     fputs(next_msg, stdout);
+		(void) clear_eol(msglen - i);
+		msglen = i;
+		next_msg[0] = '\0';
+	    }
+	}
+    }
+    else
+    {
+	if ((type & MT_delayed) == 0)
+	{
+	    type & MT_standout ? standout(next_msg) : fputs(next_msg, stdout);
+	    msglen = strlen(next_msg);
+	    next_msg[0] = '\0';
+	}
+    }
+}
+
+clear_message()
+
+{
+    if (clear_eol(msglen) == 1)
+    {
+	putchar('\r');
+    }
+}
+
+readline(buffer, size, numeric)
+
+char *buffer;
+int  size;
+int  numeric;
+
+{
+    register char *ptr = buffer;
+    register char ch;
+    register char cnt = 0;
+    register char maxcnt = 0;
+
+    /* allow room for null terminator */
+    size -= 1;
+
+    /* read loop */
+    while ((fflush(stdout), read(0, ptr, 1) > 0))
+    {
+	/* newline means we are done */
+	if ((ch = *ptr) == '\n')
+	{
+	    break;
+	}
+
+	/* handle special editing characters */
+	if (ch == ch_kill)
+	{
+	    /* kill line -- account for overstriking */
+	    if (overstrike)
+	    {
+		msglen += maxcnt;
+	    }
+
+	    /* return null string */
+	    *buffer = '\0';
+	    putchar('\r');
+	    return(-1);
+	}
+	else if (ch == ch_erase)
+	{
+	    /* erase previous character */
+	    if (cnt <= 0)
+	    {
+		/* none to erase! */
+		putchar('\7');
+	    }
+	    else
+	    {
+		fputs("\b \b", stdout);
+		ptr--;
+		cnt--;
+	    }
+	}
+	/* check for character validity and buffer overflow */
+	else if (cnt == size || (numeric && !isdigit(ch)) ||
+		!isprint(ch))
+	{
+	    /* not legal */
+	    putchar('\7');
+	}
+	else
+	{
+	    /* echo it and store it in the buffer */
+	    putchar(ch);
+	    ptr++;
+	    cnt++;
+	    if (cnt > maxcnt)
+	    {
+		maxcnt = cnt;
+	    }
+	}
+    }
+
+    /* all done -- null terminate the string */
+    *ptr = '\0';
+
+    /* account for the extra characters in the message area */
+    /* (if terminal overstrikes, remember the furthest they went) */
+    msglen += overstrike ? maxcnt : cnt;
+
+    /* return either inputted number or string length */
+    putchar('\r');
+    return(cnt == 0 ? -1 : numeric ? atoi(buffer) : cnt);
+}
+
+/* internal support routines */
+
+static int string_count(pp)
+
+register char **pp;
+
+{
+    register int cnt;
+
+    cnt = 0;
+    while (*pp++ != NULL)
+    {
+	cnt++;
+    }
+    return(cnt);
+}
+
+static void summary_format(str, numbers, names)
+
+char *str;
+int *numbers;
+register char **names;
+
+{
+    register char *p;
+    register int num;
+    register char *thisname;
+    register int useM = No;
+
+    /* format each number followed by its string */
+    p = str;
+    while ((thisname = *names++) != NULL)
+    {
+	/* get the number to format */
+	num = *numbers++;
+
+	/* display only non-zero numbers */
+	if (num > 0)
+	{
+	    /* is this number in kilobytes? */
+	    if (thisname[0] == 'K')
+	    {
+		/* yes: format it as a memory value */
+		p = strecpy(p, format_k(num));
+
+		/* skip over the K, since it was included by format_k */
+		p = strecpy(p, thisname+1);
+	    }
+	    else
+	    {
+		p = strecpy(p, itoa(num));
+		p = strecpy(p, thisname);
+	    }
+	}
+
+	/* ignore negative numbers, but display corresponding string */
+	else if (num < 0)
+	{
+	    p = strecpy(p, thisname);
+	}
+    }
+
+    /* if the last two characters in the string are ", ", delete them */
+    p -= 2;
+    if (p >= str && p[0] == ',' && p[1] == ' ')
+    {
+	*p = '\0';
+    }
+}
+
+static void line_update(old, new, start, line)
+
+register char *old;
+register char *new;
+int start;
+int line;
+
+{
+    register int ch;
+    register int diff;
+    register int newcol = start + 1;
+    register int lastcol = start;
+    char cursor_on_line = No;
+    char *current;
+
+    /* compare the two strings and only rewrite what has changed */
+    current = old;
+#ifdef DEBUG
+    fprintf(debug, "line_update, starting at %d\n", start);
+    fputs(old, debug);
+    fputc('\n', debug);
+    fputs(new, debug);
+    fputs("\n-\n", debug);
+#endif
+
+    /* start things off on the right foot		    */
+    /* this is to make sure the invariants get set up right */
+    if ((ch = *new++) != *old)
+    {
+	if (line - lastline == 1 && start == 0)
+	{
+	    putchar('\n');
+	}
+	else
+	{
+	    Move_to(start, line);
+	}
+	cursor_on_line = Yes;
+	putchar(ch);
+	*old = ch;
+	lastcol = 1;
+    }
+    old++;
+	
+    /*
+     *  main loop -- check each character.  If the old and new aren't the
+     *	same, then update the display.  When the distance from the
+     *	current cursor position to the new change is small enough,
+     *	the characters that belong there are written to move the
+     *	cursor over.
+     *
+     *	Invariants:
+     *	    lastcol is the column where the cursor currently is sitting
+     *		(always one beyond the end of the last mismatch).
+     */
+    do		/* yes, a do...while */
+    {
+	if ((ch = *new++) != *old)
+	{
+	    /* new character is different from old	  */
+	    /* make sure the cursor is on top of this character */
+	    diff = newcol - lastcol;
+	    if (diff > 0)
+	    {
+		/* some motion is required--figure out which is shorter */
+		if (diff < 6 && cursor_on_line)
+		{
+		    /* overwrite old stuff--get it out of the old buffer */
+		    printf("%.*s", diff, &current[lastcol-start]);
+		}
+		else
+		{
+		    /* use cursor addressing */
+		    Move_to(newcol, line);
+		    cursor_on_line = Yes;
+		}
+		/* remember where the cursor is */
+		lastcol = newcol + 1;
+	    }
+	    else
+	    {
+		/* already there, update position */
+		lastcol++;
+	    }
+		
+	    /* write what we need to */
+	    if (ch == '\0')
+	    {
+		/* at the end--terminate with a clear-to-end-of-line */
+		(void) clear_eol(strlen(old));
+	    }
+	    else
+	    {
+		/* write the new character */
+		putchar(ch);
+	    }
+	    /* put the new character in the screen buffer */
+	    *old = ch;
+	}
+	    
+	/* update working column and screen buffer pointer */
+	newcol++;
+	old++;
+	    
+    } while (ch != '\0');
+
+    /* zero out the rest of the line buffer -- MUST BE DONE! */
+    diff = display_width - newcol;
+    if (diff > 0)
+    {
+	memzero(old, diff);
+    }
+
+    /* remember where the current line is */
+    if (cursor_on_line)
+    {
+	lastline = line;
+    }
+}
+
+/*
+ *  printable(str) - make the string pointed to by "str" into one that is
+ *	printable (i.e.: all ascii), by converting all non-printable
+ *	characters into '?'.  Replacements are done in place and a pointer
+ *	to the original buffer is returned.
+ */
+
+char *printable(str)
+
+char *str;
+
+{
+    register char *ptr;
+    register char ch;
+
+    ptr = str;
+    while ((ch = *ptr) != '\0')
+    {
+	if (!isprint(ch))
+	{
+	    *ptr = '?';
+	}
+	ptr++;
+    }
+    return(str);
+}