MFH

Sponsored by:	The FreeBSD Foundation

5 files changed, 60 insertions, 7 deletions

diff --git a/bin/dd/args.c b/bin/dd/args.c
index 4607d673aa74..27d4a9a36314 100644
--- a/bin/dd/args.c
+++ b/bin/dd/args.c
@@ -66,6 +66,7 @@ static void	f_obs(char *);
 static void	f_of(char *);
 static void	f_seek(char *);
 static void	f_skip(char *);
+static void	f_speed(char *);
 static void	f_status(char *);
 static uintmax_t get_num(const char *);
 static off_t	get_off_t(const char *);
@@ -89,6 +90,7 @@ static const struct arg {
 	{ "oseek",	f_seek,		C_SEEK,	 C_SEEK },
 	{ "seek",	f_seek,		C_SEEK,	 C_SEEK },
 	{ "skip",	f_skip,		C_SKIP,	 C_SKIP },
+	{ "speed",	f_speed,	0,	 0 },
 	{ "status",	f_status,	C_STATUS,C_STATUS },
 };
 
@@ -295,6 +297,13 @@ f_skip(char *arg)
 }
 
 static void
+f_speed(char *arg)
+{
+
+	speed = get_num(arg);
+}
+
+static void
 f_status(char *arg)
 {
 
diff --git a/bin/dd/dd.1 b/bin/dd/dd.1
index 4047cdca57f5..64d1acae11a9 100644
--- a/bin/dd/dd.1
+++ b/bin/dd/dd.1
@@ -32,7 +32,7 @@
 .\"     @(#)dd.1	8.2 (Berkeley) 1/13/94
 .\" $FreeBSD$
 .\"
-.Dd February 4, 2016
+.Dd February 28, 2016
 .Dt DD 1
 .Os
 .Sh NAME
@@ -156,6 +156,10 @@ Otherwise, input data is read and discarded.
 For pipes, the correct number of bytes is read.
 For all other devices, the correct number of blocks is read without
 distinguishing between a partial or complete block being read.
+.It Cm speed Ns = Ns Ar n
+Limit the copying speed to
+.Ar n
+bytes per second.
 .It Cm status Ns = Ns Ar value
 Where
 .Cm value
@@ -325,7 +329,7 @@ appended.
 .El
 .El
 .Pp
-Where sizes are specified, a decimal, octal, or hexadecimal number of
+Where sizes or speed are specified, a decimal, octal, or hexadecimal number of
 bytes is expected.
 If the number ends with a
 .Dq Li b ,
diff --git a/bin/dd/dd.c b/bin/dd/dd.c
index 4c31a5e81260..56f8efef7a53 100644
--- a/bin/dd/dd.c
+++ b/bin/dd/dd.c
@@ -82,6 +82,7 @@ size_t	cbsz;			/* conversion block size */
 uintmax_t files_cnt = 1;	/* # of files to copy */
 const	u_char *ctab;		/* conversion table */
 char	fill_char;		/* Character to fill with if defined */
+size_t	speed = 0;		/* maximum speed, in bytes per second */
 volatile sig_atomic_t need_summary;
 
 int
@@ -276,6 +277,29 @@ getfdtype(IO *io)
 		io->flags |= ISSEEK;
 }
 
+/*
+ * Limit the speed by adding a delay before every block read.
+ * The delay (t_usleep) is equal to the time computed from block
+ * size and the specified speed limit (t_target) minus the time
+ * spent on actual read and write operations (t_io).
+ */
+static void
+speed_limit(void)
+{
+	static double t_prev, t_usleep;
+	double t_now, t_io, t_target;
+
+	t_now = secs_elapsed();
+	t_io = t_now - t_prev - t_usleep;
+	t_target = (double)in.dbsz / (double)speed;
+	t_usleep = t_target - t_io;
+	if (t_usleep > 0)
+		usleep(t_usleep * 1000000);
+	else
+		t_usleep = 0;
+	t_prev = t_now;
+}
+
 static void
 dd_in(void)
 {
@@ -293,6 +317,9 @@ dd_in(void)
 			break;
 		}
 
+		if (speed > 0)
+			speed_limit();
+
 		/*
 		 * Zero the buffer first if sync; if doing block operations,
 		 * use spaces.
diff --git a/bin/dd/extern.h b/bin/dd/extern.h
index 6984f6d3b828..25440ca12881 100644
--- a/bin/dd/extern.h
+++ b/bin/dd/extern.h
@@ -42,6 +42,7 @@ void def_close(void);
 void jcl(char **);
 void pos_in(void);
 void pos_out(void);
+double secs_elapsed(void);
 void summary(void);
 void siginfo_handler(int);
 void terminate(int);
@@ -54,6 +55,7 @@ extern void (*cfunc)(void);
 extern uintmax_t cpy_cnt;
 extern size_t cbsz;
 extern u_int ddflags;
+extern size_t speed;
 extern uintmax_t files_cnt;
 extern const u_char *ctab;
 extern const u_char a2e_32V[], a2e_POSIX[];
diff --git a/bin/dd/misc.c b/bin/dd/misc.c
index eb1227bb5ac6..ea0f8d3d6430 100644
--- a/bin/dd/misc.c
+++ b/bin/dd/misc.c
@@ -54,15 +54,12 @@ __FBSDID("$FreeBSD$");
 #include "dd.h"
 #include "extern.h"
 
-void
-summary(void)
+double
+secs_elapsed(void)
 {
 	struct timespec end, ts_res;
 	double secs, res;
 
-	if (ddflags & C_NOINFO)
-		return;
-
 	if (clock_gettime(CLOCK_MONOTONIC, &end))
 		err(1, "clock_gettime");
 	if (clock_getres(CLOCK_MONOTONIC, &ts_res))
@@ -72,6 +69,20 @@ summary(void)
 	res = ts_res.tv_sec + ts_res.tv_nsec * 1e-9;
 	if (secs < res)
 		secs = res;
+
+	return (secs);
+}
+
+void
+summary(void)
+{
+	double secs;
+
+	if (ddflags & C_NOINFO)
+		return;
+
+	secs = secs_elapsed();
+
 	(void)fprintf(stderr,
 	    "%ju+%ju records in\n%ju+%ju records out\n",
 	    st.in_full, st.in_part, st.out_full, st.out_part);