when copying regular files, look for blocks of zeroes. when we see them,

just lseek ahead to create a sparse file.  saves disk and time.
note this behavior in the man page.
ok? deraadt millert

2 files changed, 31 insertions, 5 deletions

diff --git a/bin/cp/cp.1 b/bin/cp/cp.1
index 3c7a7ac6bc3..66702981e63 100644
--- a/bin/cp/cp.1
+++ b/bin/cp/cp.1
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: cp.1,v 1.25 2004/12/10 10:23:30 jmc Exp $
+.\"	$OpenBSD: cp.1,v 1.26 2007/04/06 06:50:00 tedu Exp $
 .\"	$NetBSD: cp.1,v 1.9 1995/07/25 19:36:45 jtc Exp $
 .\"
 .\" Copyright (c) 1989, 1990, 1993, 1994
@@ -166,6 +166,10 @@ conditions must be fulfilled or both bits are removed.
 .Pp
 Appropriate permissions are required for file creation or overwriting.
 .Pp
+When a file containing large blocks of zero-valued bytes is copied,
+.Nm
+will attempt to create a sparse file.
+.Pp
 Symbolic links are always followed unless the
 .Fl R
 flag is set, in which case symbolic links are not followed, by default.
diff --git a/bin/cp/utils.c b/bin/cp/utils.c
index 7e1185fd48b..fa62660fe76 100644
--- a/bin/cp/utils.c
+++ b/bin/cp/utils.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: utils.c,v 1.26 2004/12/10 10:23:30 jmc Exp $	*/
+/*	$OpenBSD: utils.c,v 1.27 2007/04/06 06:50:00 tedu Exp $	*/
 /*	$NetBSD: utils.c,v 1.6 1997/02/26 14:40:51 cgd Exp $	*/
 
 /*-
@@ -34,7 +34,7 @@
 #if 0
 static char sccsid[] = "@(#)utils.c	8.3 (Berkeley) 4/1/94";
 #else
-static char rcsid[] = "$OpenBSD: utils.c,v 1.26 2004/12/10 10:23:30 jmc Exp $";
+static char rcsid[] = "$OpenBSD: utils.c,v 1.27 2007/04/06 06:50:00 tedu Exp $";
 #endif
 #endif /* not lint */
 
@@ -57,13 +57,26 @@ static char rcsid[] = "$OpenBSD: utils.c,v 1.26 2004/12/10 10:23:30 jmc Exp $";
 int
 copy_file(FTSENT *entp, int dne)
 {
-	static char buf[MAXBSIZE];
+	static char *buf;
+	static char *zeroes;
 	struct stat to_stat, *fs;
 	int ch, checkch, from_fd, rcount, rval, to_fd, wcount;
 #ifdef VM_AND_BUFFER_CACHE_SYNCHRONIZED
 	char *p;
 #endif
 
+	if (!buf) {
+		buf = malloc(MAXBSIZE);
+		if (!buf)
+			err(1, "malloc");
+	}
+	if (!zeroes) {
+		zeroes = malloc(MAXBSIZE);
+		if (!zeroes)
+			err(1, "malloc");
+		memset(zeroes, 0, MAXBSIZE);
+	}
+
 	if ((from_fd = open(entp->fts_path, O_RDONLY, 0)) == -1) {
 		warn("%s", entp->fts_path);
 		return (1);
@@ -136,14 +149,23 @@ copy_file(FTSENT *entp, int dne)
 	} else
 #endif
 	{
+		int skipholes = 0;
+		struct stat tosb;
+		if (!fstat(to_fd, &tosb) && S_ISREG(tosb.st_mode))
+			skipholes = 1;
 		while ((rcount = read(from_fd, buf, MAXBSIZE)) > 0) {
-			wcount = write(to_fd, buf, rcount);
+			if (skipholes && memcmp(buf, zeroes, rcount) == 0)
+				wcount = lseek(to_fd, rcount, SEEK_CUR) == -1 ? -1 : rcount;
+			else
+				wcount = write(to_fd, buf, rcount);
 			if (rcount != wcount || wcount == -1) {
 				warn("%s", to.p_path);
 				rval = 1;
 				break;
 			}
 		}
+		if (skipholes && rcount >= 0)
+			rcount = ftruncate(to_fd, fs->st_size);
 		if (rcount < 0) {
 			warn("%s", entp->fts_path);
 			rval = 1;