Optimize install(1) a bit.

Currently, "install -s -S" behaviour is inefficient for upgrade.
First it finds that destination file already exists and copies
source file to temporary file. Then it calls strip(1)
with name of temporary file as single agrument and our strip(1) creates
another temporary file in the /tmp (or TMPDIR) making another copy
that is finally copied to DESTDIR third time.

Meantime, strip(1) has an option "-o dst" to specify destination
so install(1) is allowed to skip initial copying from obj to DESTDIR.
This change makes it do so.

Take a look at https://reviews.freebsd.org/D25551 for details
and efficiency numbers (in short: upto 32% gained for installword).

MFC after:		1 month
Differential Revision:	https://reviews.freebsd.org/D25551

usr.bin/xinstall/xinstall.c

@@ -147,7 +147,7 @@ static void	install_dir(char *);
 static void	metadata_log(const char *, const char *, struct timespec *,
 		    const char *, const char *, off_t);
 static int	parseid(const char *, id_t *);
-static void	strip(const char *);
+static int	strip(const char *, const char *, char **);
 static int	trymmap(int);
 static void	usage(void);
 
@@ -767,12 +767,13 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 {
 	struct stat from_sb, temp_sb, to_sb;
 	struct timespec tsb[2];
-	int devnull, files_match, from_fd, serrno, target;
+	int devnull, files_match, from_fd, serrno, stripped, target;
 	int tempcopy, temp_fd, to_fd;
 	char backup[MAXPATHLEN], *p, pathbuf[MAXPATHLEN], tempfile[MAXPATHLEN];
 	char *digestresult;
 
-	files_match = 0;
+	digestresult = NULL;
+	files_match = stripped = 0;
 	from_fd = -1;
 	to_fd = -1;
 
@@ -858,19 +859,24 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 				(void)printf("install: %s -> %s\n",
 				    from_name, to_name);
 		}
-		if (!devnull)
+		if (!devnull) {
-			digestresult = copy(from_fd, from_name, to_fd,
+			if (dostrip)
-			     tempcopy ? tempfile : to_name, from_sb.st_size);
+			    stripped = strip(tempcopy ? tempfile : to_name,
-		else
+					     from_name, &digestresult);
-			digestresult = NULL;
+			else
+			    digestresult = copy(from_fd, from_name, to_fd,
+				tempcopy ? tempfile : to_name, from_sb.st_size);
+		}
 	}
 
 	if (dostrip) {
-		strip(tempcopy ? tempfile : to_name);
+		if (!stripped)
+			(void)strip(tempcopy ? tempfile : to_name, NULL,
+			    &digestresult);
 
 		/*
-		 * Re-open our fd on the target, in case we used a strip
+		 * Re-open our fd on the target, in case
-		 * that does not work in-place -- like GNU binutils strip.
+		 * we did not strip in-place.
 		 */
 		close(to_fd);
 		to_fd = open(tempcopy ? tempfile : to_name, O_RDONLY, 0);
@@ -1057,7 +1063,9 @@ install(const char *from_name, const char *to_name, u_long fset, u_int flags)
 
 /*
  * compare --
- *	compare two files; non-zero means files differ
+ *	Compare two files; non-zero means files differ.
+ *	Compute digest and return its address in *dresp
+ *	unless it points to pre-computed digest.
  */
 static int
 compare(int from_fd, const char *from_name __unused, size_t from_len,
@@ -1066,15 +1074,17 @@ compare(int from_fd, const char *from_name __unused, size_t from_len,
 {
 	char *p, *q;
 	int rv;
-	int done_compare;
+	int do_digest, done_compare;
 	DIGEST_CTX ctx;
 
 	rv = 0;
 	if (from_len != to_len)
 		return 1;
 
+	do_digest = (digesttype != DIGEST_NONE && dresp != NULL &&
+			*dresp == NULL);
 	if (from_len <= MAX_CMP_SIZE) {
-		if (dresp != NULL)
+		if (do_digest)
 			digest_init(&ctx);
 		done_compare = 0;
 		if (trymmap(from_fd) && trymmap(to_fd)) {
@@ -1090,7 +1100,7 @@ compare(int from_fd, const char *from_name __unused, size_t from_len,
 			}
 
 			rv = memcmp(p, q, from_len);
-			if (dresp != NULL)
+			if (do_digest)
 				digest_update(&ctx, p, from_len);
 			munmap(p, from_len);
 			munmap(q, from_len);
@@ -1117,7 +1127,8 @@ compare(int from_fd, const char *from_name __unused, size_t from_len,
 						rv = 1;	/* out of sync */
 				} else
 					rv = 1;		/* read failure */
-				digest_update(&ctx, buf1, n1);
+				if (do_digest)
+					digest_update(&ctx, buf1, n1);
 			}
 			lseek(from_fd, 0, SEEK_SET);
 			lseek(to_fd, 0, SEEK_SET);
@@ -1125,7 +1136,7 @@ compare(int from_fd, const char *from_name __unused, size_t from_len,
 	} else
 		rv = 1;	/* don't bother in this case */
 
-	if (dresp != NULL) {
+	if (do_digest) {
 		if (rv == 0)
 			*dresp = digest_end(&ctx, NULL);
 		else
@@ -1298,13 +1309,16 @@ copy(int from_fd, const char *from_name, int to_fd, const char *to_name,
 
 /*
  * strip --
- *	use strip(1) to strip the target file
+ *	Use strip(1) to strip the target file.
+ *	Just invoke strip(1) on to_name if from_name is NULL,
+ *	else try to run "strip -o to_name -- from_name" and return 0 on failure.
+ *	Return 1 on success and assign result of digest_file(to_name) to *dresp.
  */
-static void
+static int
-strip(const char *to_name)
+strip(const char *to_name, const char *from_name, char **dresp)
 {
 	const char *stripbin;
-	const char *args[3];
+	const char *args[6];
 	pid_t pid;
 	int error, status;
 
@@ -1312,8 +1326,16 @@ strip(const char *to_name)
 	if (stripbin == NULL)
 		stripbin = "strip";
 	args[0] = stripbin;
-	args[1] = to_name;
+	if (from_name == NULL) {
-	args[2] = NULL;
+		args[1] = to_name;
+		args[2] = NULL;
+	} else {
+		args[1] = "-o";
+		args[2] = to_name;
+		args[3] = "--";
+		args[4] = from_name;
+		args[5] = NULL;
+	}
 	error = posix_spawnp(&pid, stripbin, NULL, NULL,
 	    __DECONST(char **, args), environ);
 	if (error != 0) {
@@ -1329,9 +1351,14 @@ strip(const char *to_name)
 	}
 	if (status != 0) {
 		(void)unlink(to_name);
+		if (from_name != NULL)
+			return (0);
 		errx(EX_SOFTWARE, "strip command %s failed on %s",
 		    stripbin, to_name);
 	}
+	if (dresp != NULL)
+		*dresp = digest_file(to_name);
+	return (1);
 }
 
 /*