Enable dirty buffer detection in mg.

Emulate the emacs behavior: after suspend/resume, buffer switch,
or at save time, warn (prompt) the user if the file has been modified
on disk in the interim.
This has already saved my butt numerous times.
ok phessler

9 files changed, 160 insertions, 24 deletions

diff --git a/usr.bin/mg/buffer.c b/usr.bin/mg/buffer.c
index 9d7b89e3af0..64761e58106 100644
--- a/usr.bin/mg/buffer.c
+++ b/usr.bin/mg/buffer.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: buffer.c,v 1.67 2007/05/28 17:52:17 kjell Exp $	*/
+/*	$OpenBSD: buffer.c,v 1.68 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -22,10 +22,14 @@ extern int globalwd;
 int
 togglereadonly(int f, int n)
 {
+	int s;
+
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (!(curbp->b_flag & BFREADONLY))
 		curbp->b_flag |= BFREADONLY;
 	else {
-		curbp->b_flag &=~ BFREADONLY;
+		curbp->b_flag &= ~BFREADONLY;
 		if (curbp->b_flag & BFCHG)
 			ewprintf("Warning: Buffer was modified");
 	}
@@ -572,7 +576,7 @@ bclear(struct buffer *bp)
 
 /*
  * Display the given buffer in the given window. Flags indicated
- * action on redisplay.
+ * action on redisplay. Update modified flag so insert loop can check it.
  */
 int
 showbuffer(struct buffer *bp, struct mgwin *wp, int flags)
@@ -580,6 +584,10 @@ showbuffer(struct buffer *bp, struct mgwin *wp, int flags)
 	struct buffer	*obp;
 	struct mgwin	*owp;
 
+	/* Ensure file has not been modified elsewhere */
+	if (fchecktime(bp) != TRUE)
+		bp->b_flag |= BFDIRTY;
+
 	if (wp->w_bufp == bp) {	/* Easy case! */
 		wp->w_flag |= flags;
 		wp->w_dotp = bp->b_dotp;
@@ -798,3 +806,23 @@ error:
 	return (FALSE);
 }
 
+/*
+ * Ensures a buffer has not been modified elsewhere.
+ * Returns TRUE if it has NOT. FALSE or ABORT otherwise
+ */
+int
+checkdirty(struct buffer *bp)
+{
+	int s;
+	
+	if ((bp->b_flag & (BFDIRTY | BFIGNDIRTY)) == BFDIRTY) {
+		if ((s = eyorn("File changed on disk; really edit the buffer"))
+		    != TRUE)
+			return (s);
+		bp->b_flag &= ~BFDIRTY;
+		bp->b_flag |= BFIGNDIRTY;
+	}
+
+	return (TRUE);
+}
+	
diff --git a/usr.bin/mg/def.h b/usr.bin/mg/def.h
index f26d46a2505..542a07c084e 100644
--- a/usr.bin/mg/def.h
+++ b/usr.bin/mg/def.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: def.h,v 1.106 2008/06/14 08:39:30 kjell Exp $	*/
+/*	$OpenBSD: def.h,v 1.107 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -272,7 +272,8 @@ struct buffer {
 #endif
 #define BFOVERWRITE 0x08		/* overwrite mode		 */
 #define BFREADONLY  0x10		/* read only mode		 */
-
+#define BFDIRTY     0x20		/* Buffer was modified elsewhere */
+#define BFIGNDIRTY  0x40		/* Ignore modifications */
 /*
  * This structure holds information about recent actions for the Undo command.
  */
@@ -404,6 +405,7 @@ int		 usebuffer(int, int);
 int		 notmodified(int, int);
 int		 popbuftop(struct buffer *);
 int		 getbufcwd(char *, size_t);
+int		 checkdirty(struct buffer *);
 
 /* display.c */
 int		vtresize(int, int, int);
@@ -424,6 +426,7 @@ void		 free_file_list(struct list *);
 
 /* fileio.c */
 int		 ffropen(const char *, struct buffer *);
+void		 ffstat(struct buffer *);
 int		 ffwopen(const char *, struct buffer *);
 int		 ffclose(struct buffer *);
 int		 ffputbuf(struct buffer *);
@@ -434,6 +437,8 @@ char		*startupfile(char *);
 int		 copy(char *, char *);
 struct list	*make_file_list(char *);
 int		 fisdir(const char *);
+int		 fchecktime(struct buffer *);
+int		 fupdstat(struct buffer *);
 
 /* kbd.c X */
 int		 do_meta(int, int);
diff --git a/usr.bin/mg/file.c b/usr.bin/mg/file.c
index cf4b744de35..6f3f87f7d78 100644
--- a/usr.bin/mg/file.c
+++ b/usr.bin/mg/file.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: file.c,v 1.67 2008/06/18 17:13:53 kjell Exp $	*/
+/*	$OpenBSD: file.c,v 1.68 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -212,7 +212,7 @@ readin(char *fname)
 	if (bclear(curbp) != TRUE)
 		return (TRUE);
 	/* Clear readonly. May be set by autoexec path */
-	curbp->b_flag &=~ BFREADONLY;
+	curbp->b_flag &= ~BFREADONLY;
 	if ((status = insertfile(fname, fname, TRUE)) != TRUE) {
 		ewprintf("File is not readable: %s", fname);
 		return (FALSE);
@@ -566,6 +566,14 @@ buffsave(struct buffer *bp)
 		return (FALSE);
 	}
 
+	/* Ensure file has not been modified elsewhere */
+	/* We don't use the ignore flag here */
+	if (fchecktime(bp) != TRUE) {
+		if ((s = eyesno("File has changed on disk since last save. "
+		    "Save anyway")) != TRUE)
+			return (s);
+	}
+	
 	if (makebackup && (bp->b_flag & BFBAK)) {
 		s = fbackupfile(bp->b_fname);
 		/* hard error */
@@ -632,6 +640,7 @@ writeout(struct buffer *bp, char *fn)
 	} else
 		/* ignore close error if it is a write error */
 		(void)ffclose(bp);
+	(void)fupdstat(bp);
 	return (s == FIOSUC);
 }
 
diff --git a/usr.bin/mg/fileio.c b/usr.bin/mg/fileio.c
index 2f6e8f56856..1f4c40c8fdb 100644
--- a/usr.bin/mg/fileio.c
+++ b/usr.bin/mg/fileio.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: fileio.c,v 1.81 2007/11/27 16:22:14 martynas Exp $	*/
+/*	$OpenBSD: fileio.c,v 1.82 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -8,8 +8,8 @@
 #include "def.h"
 
 
-#include <sys/stat.h>
 #include <sys/types.h>
+#include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 #include <sys/wait.h>
@@ -31,8 +31,6 @@ static FILE	*ffp;
 int
 ffropen(const char *fn, struct buffer *bp)
 {
-	struct stat	statbuf;
-
 	if ((ffp = fopen(fn, "r")) == NULL) {
 		if (errno == ENOENT)
 			return (FIOFNF);
@@ -43,13 +41,44 @@ ffropen(const char *fn, struct buffer *bp)
 	if (fisdir(fn) == TRUE)
 		return (FIODIR);
 
-	if (bp && fstat(fileno(ffp), &statbuf) == 0) {
+	ffstat(bp);
+	
+	return (FIOSUC);
+}
+
+/*
+ * Update stat/dirty info
+ */
+void
+ffstat(struct buffer *bp)
+{
+	struct stat	sb;
+
+	if (bp && fstat(fileno(ffp), &sb) == 0) {
 		/* set highorder bit to make sure this isn't all zero */
-		bp->b_fi.fi_mode = statbuf.st_mode | 0x8000;
-		bp->b_fi.fi_uid = statbuf.st_uid;
-		bp->b_fi.fi_gid = statbuf.st_gid;
+		bp->b_fi.fi_mode = sb.st_mode | 0x8000;
+		bp->b_fi.fi_uid = sb.st_uid;
+		bp->b_fi.fi_gid = sb.st_gid;
+		bp->b_fi.fi_mtime = sb.st_mtimespec;
+		/* Clear the ignore flag */
+		bp->b_flag &= ~(BFIGNDIRTY | BFDIRTY);
 	}
+}
 
+/*
+ * Update the status/dirty info. If there is an error,
+ * there's not a lot we can do.
+ */
+int
+fupdstat(struct buffer *bp)
+{
+	if ((ffp = fopen(bp->b_fname, "r")) == NULL) {
+		if (errno == ENOENT)
+			return (FIOFNF);
+		return (FIOERR);
+	}
+	ffstat(bp);
+	ffclose(bp);
 	return (FIOSUC);
 }
 
@@ -559,3 +588,24 @@ fisdir(const char *fname)
 
 	return (FALSE);
 }
+
+/*
+ * Check the mtime of the supplied filename.
+ * Return TRUE if last mtime matches, FALSE if not,
+ * If the stat fails, return TRUE and try the save anyway
+ */
+int
+fchecktime(struct buffer *bp)
+{
+	struct stat sb;
+
+	if (stat(bp->b_fname, &sb) == -1)
+		return (TRUE);
+
+	if (bp->b_fi.fi_mtime.tv_sec != sb.st_mtimespec.tv_sec ||
+	    bp->b_fi.fi_mtime.tv_nsec != sb.st_mtimespec.tv_nsec)
+		return (FALSE);
+
+	return (TRUE);
+	
+}
diff --git a/usr.bin/mg/line.c b/usr.bin/mg/line.c
index ac600887381..4d0565e0afe 100644
--- a/usr.bin/mg/line.c
+++ b/usr.bin/mg/line.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: line.c,v 1.44 2006/12/24 01:20:53 kjell Exp $	*/
+/*	$OpenBSD: line.c,v 1.45 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -142,7 +142,10 @@ linsert_str(const char *s, int n)
 	struct line	*lp1;
 	struct mgwin	*wp;
 	RSIZE	 i;
-	int	 doto;
+	int	 doto, k;
+
+	if ((k = checkdirty(curbp)) != TRUE)
+		return (k);
 
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read only");
@@ -233,10 +236,14 @@ linsert(int n, int c)
 	struct mgwin	*wp;
 	RSIZE	 i;
 	int	 doto;
+	int s;
 
 	if (!n)
 		return (TRUE);
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
+	
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read only");
 		return (FALSE);
@@ -388,6 +395,10 @@ lnewline_at(struct line *lp1, int doto)
 int
 lnewline(void)
 {
+	int s;
+
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read only");
 		return (FALSE);
@@ -414,7 +425,10 @@ ldelete(RSIZE n, int kflag)
 	size_t		 len;
 	char		*sv;
 	int		 end;
+	int		 s;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read only");
 		return (FALSE);
@@ -497,7 +511,10 @@ ldelnewline(void)
 {
 	struct line	*lp1, *lp2, *lp3;
 	struct mgwin	*wp;
+	int s;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read only");
 		return (FALSE);
@@ -571,7 +588,10 @@ int
 lreplace(RSIZE plen, char *st)
 {
 	RSIZE	rlen;	/* replacement length		 */
+	int s;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read only");
 		return (FALSE);
diff --git a/usr.bin/mg/region.c b/usr.bin/mg/region.c
index 751f63fea7f..78555084453 100644
--- a/usr.bin/mg/region.c
+++ b/usr.bin/mg/region.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: region.c,v 1.26 2008/06/10 23:23:53 kjell Exp $	*/
+/*	$OpenBSD: region.c,v 1.27 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -98,6 +98,8 @@ lowerregion(int f, int n)
 	struct region	 region;
 	int	 loffs, c, s;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read-only");
 		return (FALSE);
@@ -139,6 +141,8 @@ upperregion(int f, int n)
 	struct region	  region;
 	int	  loffs, c, s;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read-only");
 		return (FALSE);
@@ -261,6 +265,8 @@ prefixregion(int f, int n)
 	int	 nline;
 	int	 s;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read-only");
 		return (FALSE);
diff --git a/usr.bin/mg/sysdef.h b/usr.bin/mg/sysdef.h
index 4df4e805a8c..6b7561442b3 100644
--- a/usr.bin/mg/sysdef.h
+++ b/usr.bin/mg/sysdef.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sysdef.h,v 1.15 2006/08/01 22:16:03 jason Exp $	*/
+/*	$OpenBSD: sysdef.h,v 1.16 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -26,4 +26,5 @@ struct fileinfo {
 	uid_t		fi_uid;
 	gid_t		fi_gid;
 	mode_t		fi_mode;
+	struct timespec	fi_mtime;	/* Last modified time */
 };
diff --git a/usr.bin/mg/tty.c b/usr.bin/mg/tty.c
index 49169052153..f803cc7a7ed 100644
--- a/usr.bin/mg/tty.c
+++ b/usr.bin/mg/tty.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tty.c,v 1.29 2008/06/11 00:03:49 tobias Exp $	*/
+/*	$OpenBSD: tty.c,v 1.30 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -127,6 +127,11 @@ ttinit(void)
 void
 ttreinit(void)
 {
+	/* check if file was modified while we were gone */
+	if (fchecktime(curbp) != TRUE) {
+		curbp->b_flag |= BFDIRTY;
+	}
+
 	if (enter_ca_mode)
 		/* enter application mode */
 		putpad(enter_ca_mode, 1);
diff --git a/usr.bin/mg/word.c b/usr.bin/mg/word.c
index 9489120f10a..c18b620e672 100644
--- a/usr.bin/mg/word.c
+++ b/usr.bin/mg/word.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: word.c,v 1.14 2006/05/28 23:30:16 kjell Exp $	*/
+/*	$OpenBSD: word.c,v 1.15 2008/09/15 16:11:35 kjell Exp $	*/
 
 /* This file is in the public domain. */
 
@@ -68,9 +68,11 @@ forwword(int f, int n)
 int
 upperword(int f, int n)
 {
-	int	c;
+	int	c, s;
 	RSIZE	size;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read-only");
 		return (FALSE);
@@ -108,9 +110,11 @@ upperword(int f, int n)
 int
 lowerword(int f, int n)
 {
-	int	c;
+	int	c, s;
 	RSIZE	size;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read-only");
 		return (FALSE);
@@ -149,9 +153,11 @@ lowerword(int f, int n)
 int
 capword(int f, int n)
 {
-	int	c;
+	int	c, s;
 	RSIZE	size;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read-only");
 		return (FALSE);
@@ -228,7 +234,10 @@ delfword(int f, int n)
 	RSIZE		 size;
 	struct line	*dotp;
 	int		 doto;
+	int s;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read-only");
 		return (FALSE);
@@ -279,7 +288,10 @@ int
 delbword(int f, int n)
 {
 	RSIZE	size;
+	int s;
 
+	if ((s = checkdirty(curbp)) != TRUE)
+		return (s);
 	if (curbp->b_flag & BFREADONLY) {
 		ewprintf("Buffer is read-only");
 		return (FALSE);