dd: support iflag=count_bytes

It allows passing amount of bytes in the count=

function                                             old     new   delta
packed_usage                                       33599   33617     +18
static.iflag_words                                    29      41     +12
dd_main                                             1601    1607      +6
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 36/0)               Total: 36 bytes

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 33 insertions, 18 deletions

diff --git a/coreutils/dd.c b/coreutils/dd.c
index 24d7f0b..a243f71 100644
--- a/coreutils/dd.c
+++ b/coreutils/dd.c
@@ -59,7 +59,7 @@
 //usage:       "[if=FILE] [of=FILE] [" IF_FEATURE_DD_IBS_OBS("ibs=N obs=N/") "bs=N] [count=N] [skip=N] [seek=N]\n"
 //usage:	IF_FEATURE_DD_IBS_OBS(
 //usage:       "	[conv=notrunc|noerror|sync|fsync]\n"
-//usage:       "	[iflag=skip_bytes|fullblock|direct] [oflag=seek_bytes|append|direct]"
+//usage:       "	[iflag=skip_bytes|count_bytes|fullblock|direct] [oflag=seek_bytes|append|direct]"
 //usage:	)
 //usage:#define dd_full_usage "\n\n"
 //usage:       "Copy a file with converting and formatting\n"
@@ -82,6 +82,7 @@
 //usage:     "\n	conv=fsync	Physically write data out before finishing"
 //usage:     "\n	conv=swab	Swap every pair of bytes"
 //usage:     "\n	iflag=skip_bytes	skip=N is in bytes"
+//usage:     "\n	iflag=count_bytes	count=N is in bytes"
 //usage:     "\n	oflag=seek_bytes	seek=N is in bytes"
 //usage:     "\n	iflag=direct	O_DIRECT input"
 //usage:     "\n	oflag=direct	O_DIRECT output"
@@ -136,21 +137,22 @@ enum {
 	FLAG_SWAB    = (1 << 4) * ENABLE_FEATURE_DD_IBS_OBS,
 	/* end of conv flags */
 	/* start of input flags */
-	FLAG_IFLAG_SHIFT = 5,
-	FLAG_SKIP_BYTES = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
-	FLAG_FULLBLOCK = (1 << 6) * ENABLE_FEATURE_DD_IBS_OBS,
-	FLAG_IDIRECT = (1 << 7) * ENABLE_FEATURE_DD_IBS_OBS,
+	FLAG_IFLAG_SHIFT   = 5,
+	FLAG_SKIP_BYTES    = (1 << 5) * ENABLE_FEATURE_DD_IBS_OBS,
+	FLAG_COUNT_BYTES   = (1 << 6) * ENABLE_FEATURE_DD_IBS_OBS,
+	FLAG_FULLBLOCK     = (1 << 7) * ENABLE_FEATURE_DD_IBS_OBS,
+	FLAG_IDIRECT       = (1 << 8) * ENABLE_FEATURE_DD_IBS_OBS,
 	/* end of input flags */
 	/* start of output flags */
-	FLAG_OFLAG_SHIFT = 8,
-	FLAG_SEEK_BYTES = (1 << 8) * ENABLE_FEATURE_DD_IBS_OBS,
-	FLAG_APPEND = (1 << 9) * ENABLE_FEATURE_DD_IBS_OBS,
-	FLAG_ODIRECT = (1 << 10) * ENABLE_FEATURE_DD_IBS_OBS,
+	FLAG_OFLAG_SHIFT   = 9,
+	FLAG_SEEK_BYTES    = (1 << 9) * ENABLE_FEATURE_DD_IBS_OBS,
+	FLAG_APPEND        = (1 << 10) * ENABLE_FEATURE_DD_IBS_OBS,
+	FLAG_ODIRECT       = (1 << 11) * ENABLE_FEATURE_DD_IBS_OBS,
 	/* end of output flags */
-	FLAG_TWOBUFS = (1 << 11) * ENABLE_FEATURE_DD_IBS_OBS,
-	FLAG_COUNT   = 1 << 12,
-	FLAG_STATUS_NONE = 1 << 13,
-	FLAG_STATUS_NOXFER = 1 << 14,
+	FLAG_TWOBUFS       = (1 << 12) * ENABLE_FEATURE_DD_IBS_OBS,
+	FLAG_COUNT         = 1 << 13,
+	FLAG_STATUS_NONE   = 1 << 14,
+	FLAG_STATUS_NOXFER = 1 << 15,
 };
 
 static void dd_output_status(int UNUSED_PARAM cur_signal)
@@ -175,8 +177,9 @@ static void dd_output_status(int UNUSED_PARAM cur_signal)
 	//So far we react to it (we print the stats),
 	//status=none only suppresses final, non-USR1 generated status message.
 # endif
-	fprintf(stderr, "%llu bytes (%sB) copied, ",
-			G.total_bytes,
+	fprintf(stderr, /*G.total_bytes < 1024
+				? "%llu bytes copied, " : */ "%llu bytes (%sB) copied, "
+			, G.total_bytes,
 			/* show fractional digit, use suffixes */
 			make_human_readable_str(G.total_bytes, 1, 0)
 	);
@@ -317,7 +320,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
 	static const char conv_words[] ALIGN1 =
 		"notrunc\0""sync\0""noerror\0""fsync\0""swab\0";
 	static const char iflag_words[] ALIGN1 =
-		"skip_bytes\0""fullblock\0""direct\0";
+		"skip_bytes\0""count_bytes\0""fullblock\0""direct\0";
 	static const char oflag_words[] ALIGN1 =
 		"seek_bytes\0append\0""direct\0";
 #endif
@@ -359,6 +362,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
 	/* Partially implemented: */
 	//swab          swap every pair of input bytes: will abort on non-even reads
 		OP_iflag_skip_bytes,
+		OP_iflag_count_bytes,
 		OP_iflag_fullblock,
 		OP_iflag_direct,
 		OP_oflag_seek_bytes,
@@ -551,8 +555,17 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
 			goto die_outfile;
 	}
 
-	while (!(G.flags & FLAG_COUNT) || (G.in_full + G.in_part != count)) {
-		ssize_t n = dd_read(ibuf, ibs);
+	while (1) {
+		ssize_t n = ibs;
+
+		if (G.flags & FLAG_COUNT) {
+			if (count == 0)
+				break;
+			if ((G.flags & FLAG_COUNT_BYTES) && count < ibs)
+				n = count;
+		}
+
+		n = dd_read(ibuf, n);
 		if (n == 0)
 			break;
 		if (n < 0) {
@@ -587,6 +600,7 @@ int dd_main(int argc UNUSED_PARAM, char **argv)
 				p16++;
 			}
 		}
+		count -= (G.flags & FLAG_COUNT_BYTES) ? n : 1;
 		if ((size_t)n == ibs)
 			G.in_full++;
 		else {
diff --git a/testsuite/dd/dd-count-bytes b/testsuite/dd/dd-count-bytes
new file mode 100644
index 0000000..0730cba
--- /dev/null
+++ b/testsuite/dd/dd-count-bytes
@@ -0,0 +1 @@
+test "$(echo I WANT | busybox dd count=3 iflag=count_bytes 2>/dev/null)" = "I W"