From 4b76652eff2b6f7d23c800dbc48c509792c726b3 Mon Sep 17 00:00:00 2001
From: Michael Forney <mforney@mforney.org>
Date: Wed, 28 Apr 2021 01:41:26 -0700
Subject: [PATCH] dd: Always move excess to beginning of buffer after
 read/write loops

Otherwise, while we may have enough room for at least one input
block, we may not have enough room for an output block.
---
 dd.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/dd.c b/dd.c
index 5522db5..6061048 100644
--- a/dd.c
+++ b/dd.c
@@ -222,11 +222,10 @@ main(int argc, char *argv[])
 				ofull++;
 			opos += ret;
 		} while ((eof && ipos < opos) || (!eof && ipos - opos >= obs));
-		if (len - ipos < ibs) {
+		if (opos < ipos)
 			memmove(buf, buf + opos, ipos - opos);
-			ipos -= opos;
-			opos = 0;
-		}
+		ipos -= opos;
+		opos = 0;
 	}
 	summary();