From a01cea572daf71b08624824941b561723967bf80 Mon Sep 17 00:00:00 2001
From: DTB <trinity@trinity.moe>
Date: Fri, 19 Jul 2024 18:26:59 -0600
Subject: [PATCH] dj(1): replace do/while on hard seeking

---
 src/dj.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/src/dj.c b/src/dj.c
index 22772cb..4af59ff 100644
--- a/src/dj.c
+++ b/src/dj.c
@@ -259,28 +259,27 @@ int main(int argc, char *argv[]) {
 		}
 	}
 
-	/* hard seeking */
-	if (io[1].seek > 0) {
-		size_t t;
+	assert(io[1].bufuse == 0); /* requirement for hard seeking */
 
-		do {
-			memset(
-				io[1].buf, '\0',
-				(t = io[1].bufuse = MIN(io[1].bs, io[1].seek))
-			);
+	/* hard seeking; t is io[1].bufuse, before Io_write subtracts from it */
+	for(size_t t; io[1].seek > 0; io[1].seek -= (t - io[1].bufuse)) {
+		memset(
+			io[1].buf, '\0', /* set buf to all nulls */
+			(t = io[1].bufuse = MIN(io[1].bs, io[1].seek)) /* saturate block */
+		);
 
-			if (Io_write(&io[1])->bufuse == t && !noerror && io[1].error == 0) {
-				Io_write(&io[1]); /* second chance */
-			}
-			if (io[1].error != 0) {
-				return oserr(io[1].fn, io[1].error);
-			}
-		} while ((io[1].seek -= (t - io[1].bufuse)) > 0 && io[1].bufuse != t);
+		if (Io_write(&io[1])->bufuse == t && !noerror && io[1].error == 0) {
+			Io_write(&io[1]); /* second chance */
+		}
 
-		io[1].bufuse = 0;
+		if (io[1].error != 0) { return oserr(io[1].fn, io[1].error); }
+
+		if (io[1].bufuse == t) { break; } /* all writes failed! */
 	}
 
-	if (io[1].seek > 0) {
+	io[1].bufuse = 0;
+
+	if (io[1].seek > 0) { /* hard seeking failed */
 		fprintio(stderr, fmt, io);
 		return oserr(io[1].fn, errno);
 	}