dj(1): statistics now track hard seeks

docs/dj.1

@@ -41,10 +41,6 @@ with a skip offset of 1 skips one byte into the input and reads from the second
 byte onwards. A programmer may think of a file as a zero-indexed array of
 bytes; in this analogy, the offset given is the index of the byte at which to
 start reading or writing.
-
-Seeks and skips aren\(cqt counted in the output statistics because they're
-guaranteed to succeed (or the utility will exit unsuccessfully, before it has
-written any data).
 .\"
 .SH OPTIONS
 
@@ -185,9 +181,20 @@ option is specified, this could make written data nonsensical.
 
 Existing files are not truncated on ouput and are instead overwritten.
 
-Many lowercase options have capitalized variants and vice-versa which can be
-confusing. Capitalized options tend to affect output or are more intense
-versions of lowercase options.
+The options
+.B -b
+and
+.B -B
+could be confused for each other, and so could
+.B -s
+and
+.BR -S .
+The lowercase option affects input and the capitalized option affects output.
+
+The skipped or sought bytes while processing irregular files, such as streams,
+are reported in the diagnostic output, because they were actually read or
+written. This is as opposed to bytes skipped while processing regular files,
+which are not reported.
 .\"
 .SH RATIONALE
 
@@ -208,3 +215,4 @@ Copyright \(co 2023 DTB. License AGPLv3+: GNU AGPL version 3 or later
 .\"
 .SH SEE ALSO
 .BR dd (1p)
+.BR lseek (3p)

src/dj.c

@@ -56,7 +56,6 @@ static char *fmt_human = "%d+%d > %d+%d; %d > %d\n";
 static char *stdin_name = "<stdin>";
 static char *stdout_name = "<stdout>";
 
-
 static int creat_mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH
 	| S_IWOTH; /* Consistent with touch(1p). */
 static int read_flags = O_RDONLY; /* Consistent with Busybox dd(1). */
@@ -69,15 +68,19 @@ static int write_flags = O_WRONLY | O_CREAT;
 
 static struct Io *
 Io_read(struct Io *io){
+	int t;
 
 	assert(io->bs > 0);
+	assert(io->bufuse < io->bs);
 
-	io->bytes += (io->bufuse = read(io->fd, io->buf, io->bs));
+	io->bufuse += (t = read(io->fd, &(io->buf)[io->bufuse],
+		io->bs - io->bufuse));
 
 	assert(io->bufuse <= io->bs);
 
-	io->prec += (0 < io->bufuse && io->bufuse < io->bs);
-	io->rec  += (io->bufuse == io->bs);
+	io->bytes += t;
+	io->prec  += (0 < io->bufuse && io->bufuse < io->bs);
+	io->rec   += (io->bufuse == io->bs);
 
 	return io;
 }
@@ -90,11 +93,11 @@ Io_write(struct Io *io){
 	assert(io->bufuse <= io->bs);
 
 	if((t = write(io->fd, io->buf, io->bufuse)) > 0)
-		memmove(io->buf, io->buf + t, (io->bufuse -= t));
+		memmove(io->buf, &(io->buf)[t], (io->bufuse -= t));
 
 	io->bytes += t;
-	io->prec  += (t > 0 && io->bufuse > 0);
-	io->rec   += (t > 0 && io->bufuse == 0);
+	io->prec  += (0 < io->bufuse && 0 < t);
+	io->rec   += (io->bufuse == 0 && 0 < t);
 
 	return io;
 }
@@ -233,58 +236,58 @@ int main(int argc, char *argv[]){
 			io[i].seek = 0;
 	}
 
-	/* hard skipping */
-	if(io[0].seek > 0){
-		do{
-			if((io[0].bufuse = read(
-						io[0].fd, io[0].buf, MIN(io[0].bs, io[0].seek)))
-					== 0)
-				/* second chance */
-				io->bufuse = read(
-					io[0].fd, io[0].buf, MIN(io[0].bs, io[0].seek));
-		}while((io[0].seek -= io[0].bufuse) > 0 && io[0].bufuse != 0);
-		io[0].bufuse = 0;
-	}
-
 	/* hard seeking */
 	if(io[1].seek > 0){
-		memset(io[1].buf, '\0', io[1].bs);
-		/* We're going to cheat and use bufuse as the retval for write(2),
-		 * which is fine because it'll be zeroed as this function returns
-		 * anyway. */
+		size_t t;
 		do{
-			if((io[1].bufuse = write(
-						io[1].fd, io[1].buf, MIN(io[1].bs, io[1].seek)))
-					== 0)
-				/* second chance */
-				io[1].bufuse = write(
-					io[1].fd, io[1].buf, MIN(io[1].bs, io[1].seek));
-		}while((io[1].seek -= io[1].bufuse) > 0 && io[1].bufuse != 0);
+			memset(io[1].buf, '\0',
+				(t = io[1].bufuse = MIN(io[1].bs, io[1].seek)));
+			if(Io_write(&io[1])->bufuse == t && !noerror)
+				Io_write(&io[1]); /* second chance */
+		}while((io[1].seek -= (t - io[1].bufuse)) > 0 && io[1].bufuse != t);
 		io[1].bufuse = 0;
 	}
 
-	/* Sought bytes aren't counted in the statistics because successful seeking
-	 * is guaranteed here. */
-	for(i = 0; i < 2; ++i)
-		if(io[i].seek > 0)
-			return oserr(io[i].fn);
+	if(io[1].seek > 0){
+		fprintio(stderr, fmt, io);
+		return oserr(io[1].fn);
+	}
 
-	do{	/* read */
-		if(Io_read(&io[0])->bufuse == 0 && !noerror)
-			Io_read(&io[0]); /* second chance */
-		if(io[0].bufuse == 0) /* that's all she wrote */
-			break;
+	do{
+		assert(io[0].bufuse == 0);
 
-		if(io[0].bufuse < io[0].bs){
-			fprintf(stderr, "%s: Partial read:\n\t", program_name);
-			fprintio(stderr, fmt, io);
-			if(!noerror)
-				count = 1;
-			if(align >= 0){
-				/* fill the rest of the ibuf with padding */
-				memset(io[0].buf + io[0].bufuse, align,
-					io[0].bs - io[0].bufuse);
-				io->bufuse = io->bs;
+		{ /* read */
+			char skipping;
+			int t;
+
+			if((skipping = (io[0].seek > 0)) && io[0].seek < io[0].bs)
+				io[0].bufuse = io[0].bs - io[0].seek;
+
+			t = io[0].bufuse;
+			if(Io_read(&io[0])->bufuse == t && !noerror)
+				Io_read(&io[0]); /* second chance */
+			if(io[0].bufuse == t) /* that's all she wrote */
+				break;
+
+			if(/* t < io[0].bufuse && */ io[0].bufuse < io[0].bs){
+				assert(!skipping);
+
+				fprintf(stderr, "%s: Partial read:\n\t", program_name);
+				fprintio(stderr, fmt, io);
+				if(!noerror)
+					count = 1;
+				if(align >= 0){
+					/* fill the rest of the ibuf with padding */
+					memset(&(io[0].buf)[io[0].bufuse], align,
+						io[0].bs - io[0].bufuse);
+					io->bufuse = io->bs;
+				}
+			}
+
+			if(skipping){
+				io[0].bufuse = 0;
+				count += (count != 0);
+				continue;
 			}
 		}
 
@@ -299,16 +302,16 @@ int main(int argc, char *argv[]){
 				memcpy(io[1].buf, io[0].buf,
 				       (io[1].bufuse = (n = MIN(io[0].bufuse, io[1].bs))));
 				/* permute the copied units out of ibuf */
-				memmove(io[0].buf, io[0].buf + n, (io[0].bufuse -= n));
+				memmove(io[0].buf, &(io[0].buf)[n], (io[0].bufuse -= n));
 			}else /* if(io[0].bs < io[1].bs) */ {
 				int n;
 
 				/* drain what we can from ibuf */
-				memcpy(io[1].buf + io[1].bufuse, io[0].buf,
+				memcpy(&(io[1].buf)[io[1].bufuse], io[0].buf,
 				       (n = MIN(io[0].bufuse, io[1].bs - io[1].bufuse)));
 				io[1].bufuse += n;
 				/* permute out the copied units */
-				memmove(io[0].buf, io[0].buf + n, io[0].bs - n);
+				memmove(io[0].buf, &(io[0].buf)[n], io[0].bs - n);
 				io[0].bufuse -= n;
 
 				if(io[0].bs + io[1].bufuse <= io[1].bs && count != 1)
@@ -323,7 +326,7 @@ int main(int argc, char *argv[]){
 				break;
 			}
 
-			if(0 < io[1].bufuse && io[1].bufuse < t){
+			if(0 < io[1].bufuse /* && io[1].bufuse < t */){
 				fprintf(stderr, "%s: Partial write:\n\t", program_name);
 				fprintio(stderr, fmt, io);
 				if(!noerror)