This patch adds support of ibs= and obs= to dd.
----
Hideki IWAMOTO  h-iwamoto@kit.hi-ho.ne.jp


--- a/include/usage.h	29 Mar 2004 08:20:08 -0000	1.198
+++ b/include/usage.h	4 Apr 2004 07:15:21 -0000
@@ -309,13 +309,15 @@
 	"64\n"
 
 #define dd_trivial_usage \
-	"[if=FILE] [of=FILE] [bs=N] [count=N] [skip=N]\n" \
-	"\t  [seek=N] [conv=notrunc|noerror|sync]"
+	"[if=FILE] [of=FILE] [ibs=N] [obs=N] [bs=N] [count=N]\n" \
+	"\t  [skip=N] [seek=N] [conv=notrunc|noerror|sync]"
 #define dd_full_usage \
 	"Copy a file, converting and formatting according to options\n\n" \
 	"\tif=FILE\t\tread from FILE instead of stdin\n" \
 	"\tof=FILE\t\twrite to FILE instead of stdout\n" \
-	"\tbs=N\t\tread and write N bytes at a time\n" \
+	"\tibs=N\t\tread N bytes at a time\n" \
+	"\tobs=N\t\twrite N bytes at a time\n" \
+	"\tbs=N\t\tforce ibs=N and obs=N\n" \
 	"\tcount=N\t\tcopy only N input blocks\n" \
 	"\tskip=N\t\tskip N input blocks\n" \
 	"\tseek=N\t\tskip N output blocks\n" \
@@ -323,6 +325,8 @@
 	"\tconv=noerror\tcontinue after read errors\n" \
 	"\tconv=sync\tpad blocks with zeros\n" \
 	"\n" \
+	"If the bs= expr operand is not specified, the input is processed and collected\n" \
+	"into full-sized output blocks until the end of the input is reached.\n" \
 	"Numbers may be suffixed by c (x1), w (x2), b (x512), kD (x1000), k (x1024),\n" \
 	"MD (x1000000), M (x1048576), GD (x1000000000) or G (x1073741824)."
 #define dd_example_usage \
--- a/coreutils/dd.c	30 Jan 2004 22:24:32 -0000	1.55
+++ b/coreutils/dd.c	4 Apr 2004 07:15:21 -0000
@@ -30,6 +30,10 @@
 #include <fcntl.h>
 #include "busybox.h"
 
+#define C_NOERROR	0x0001
+#define C_TRUNC		0x0002
+#define C_SYNC		0x0004
+#define C_TWOBUFS	0x0008
 
 static const struct suffix_mult dd_suffixes[] = {
 	{ "c", 1 },
@@ -51,13 +55,13 @@
 	size_t in_full = 0;
 	size_t in_part = 0;
 	size_t count = -1;
-	size_t bs = 512;
+	size_t ibs = 512;
+	size_t obs = 512;
+	size_t oc = 0;
 	ssize_t n;
 	off_t seek = 0;
 	off_t skip = 0;
-	int sync_flag = FALSE;
-	int noerror = FALSE;
-	int trunc_flag = TRUE;
+	unsigned int dd_flags = C_TWOBUFS | C_TRUNC;
 	int oflag;
 	int ifd;
 	int ofd;
@@ -65,11 +69,18 @@
 	const char *infile = NULL;
 	const char *outfile = NULL;
 	char *buf;
+	char *ibuf;
+	char *obuf;
 
 	for (i = 1; i < argc; i++) {
-		if (strncmp("bs=", argv[i], 3) == 0)
-			bs = bb_xparse_number(argv[i]+3, dd_suffixes);
-		else if (strncmp("count=", argv[i], 6) == 0)
+		if (strncmp("ibs=", argv[i], 4) == 0)
+			ibs = bb_xparse_number(argv[i]+4, dd_suffixes);
+		else if (strncmp("obs=", argv[i], 4) == 0)
+			obs = bb_xparse_number(argv[i]+4, dd_suffixes);
+		else if (strncmp("bs=", argv[i], 3) == 0) {
+			ibs = obs = bb_xparse_number(argv[i]+3, dd_suffixes);
+			dd_flags &= ~C_TWOBUFS;
+		} else if (strncmp("count=", argv[i], 6) == 0)
 			count = bb_xparse_number(argv[i]+6, dd_suffixes);
 		else if (strncmp("seek=", argv[i], 5) == 0)
 			seek = bb_xparse_number(argv[i]+5, dd_suffixes);
@@ -83,13 +94,13 @@
 			buf = argv[i]+5;
 			while (1) {
 				if (strncmp("notrunc", buf, 7) == 0) {
-					trunc_flag = FALSE;
+					dd_flags &= ~C_TRUNC;
 					buf += 7;
 				} else if (strncmp("sync", buf, 4) == 0) {
-					sync_flag = TRUE;
+					dd_flags |= C_SYNC;
 					buf += 4;
 				} else if (strncmp("noerror", buf, 7) == 0) {
-					noerror = TRUE;
+					dd_flags |= C_NOERROR;
 					buf += 7;
 				} else {
 					bb_error_msg_and_die("invalid conversion `%s'", argv[i]+5);
@@ -103,7 +114,12 @@
 			bb_show_usage();
 	}
 
-	buf = xmalloc(bs);
+	ibuf = xmalloc(ibs);
+
+	if (dd_flags & C_TWOBUFS)
+		obuf = xmalloc(obs);
+	else
+		obuf = ibuf;
 
 	if (infile != NULL) {
 		ifd = bb_xopen(infile, O_RDONLY);
@@ -115,7 +131,7 @@
 	if (outfile != NULL) {
 		oflag = O_WRONLY | O_CREAT;
 
-		if (!seek && trunc_flag) {
+		if (!seek && (dd_flags & C_TRUNC)) {
 			oflag |= O_TRUNC;
 		}
 
@@ -123,8 +139,8 @@
 			bb_perror_msg_and_die("%s", outfile);
 		}
 
-		if (seek && trunc_flag) {
-			if (ftruncate(ofd, seek * bs) < 0) {
+		if (seek && (dd_flags & C_TRUNC)) {
+			if (ftruncate(ofd, seek * obs) < 0) {
 				struct stat st;
 
 				if (fstat (ofd, &st) < 0 || S_ISREG (st.st_mode) ||
@@ -139,52 +155,88 @@
 	}
 
 	if (skip) {
-		if (lseek(ifd, skip * bs, SEEK_CUR) < 0) {
-			bb_perror_msg_and_die("%s", infile);
+		if (lseek(ifd, skip * ibs, SEEK_CUR) < 0) {
+			while (skip-- > 0) {
+				n = safe_read(ifd, ibuf, ibs);
+				if (n < 0)
+					bb_perror_msg_and_die("%s", infile);
+				if (n == 0)
+					break;
+			}
 		}
 	}
 
 	if (seek) {
-		if (lseek(ofd, seek * bs, SEEK_CUR) < 0) {
+		if (lseek(ofd, seek * obs, SEEK_CUR) < 0) {
 			bb_perror_msg_and_die("%s", outfile);
 		}
 	}
 
 	while (in_full + in_part != count) {
-		if (noerror) {
+		if (dd_flags & C_NOERROR) {
 			/* Pre-zero the buffer when doing the noerror thing */
-			memset(buf, '\0', bs);
+			memset(ibuf, '\0', ibs);
+		}
+
+		n = safe_read(ifd, ibuf, ibs);
+		if (n == 0) {
+			break;
 		}
-		n = safe_read(ifd, buf, bs);
 		if (n < 0) {
-			if (noerror) {
-				n = bs;
+			if (dd_flags & C_NOERROR) {
+				n = ibs;
 				bb_perror_msg("%s", infile);
 			} else {
 				bb_perror_msg_and_die("%s", infile);
 			}
 		}
-		if (n == 0) {
-			break;
-		}
-		if (n == bs) {
+		if (n == ibs) {
 			in_full++;
 		} else {
 			in_part++;
+			if (dd_flags & C_SYNC) {
+				memset(ibuf + n, '\0', ibs - n);
+				n = ibs;
+			}
 		}
-		if (sync_flag) {
-			memset(buf + n, '\0', bs - n);
-			n = bs;
+
+		if (dd_flags & C_TWOBUFS) {
+			size_t d;
+			char *tmp = ibuf;
+
+			while (n) {
+				d = obs - oc;
+				if (d > n)
+					d = n;
+				memcpy(obuf + oc, tmp, d);
+				n -= d;
+				tmp += d;
+				oc += d;
+				if (oc == obs) {
+					if (bb_full_write(ofd, obuf, obs) < 0) {
+						bb_perror_msg_and_die("%s", outfile);
+					}
+					out_full++;
+					oc = 0;
+				}
+			}
+		} else {
+			if (bb_full_write(ofd, ibuf, n) < 0) {
+				bb_perror_msg_and_die("%s", outfile);
+			}
+			if (n == ibs) {
+				out_full++;
+			} else {
+				out_part++;
+			}
 		}
-		n = bb_full_write(ofd, buf, n);
-		if (n < 0) {
+	}
+
+	if (oc) {
+		if (bb_full_write(ofd, obuf, oc) < 0) {
 			bb_perror_msg_and_die("%s", outfile);
 		}
-		if (n == bs) {
-			out_full++;
-		} else {
-			out_part++;
-		}
+		out_part++;
 	}
 
 	if (close (ifd) < 0) {