From ba76d67585f88677af9f48b48e7bdc3bb7687def Mon Sep 17 00:00:00 2001
From: Lasse Collin <lasse.collin@tukaani.org>
Date: Sun, 26 Jan 2020 20:53:25 +0200
Subject: [PATCH] xz: Set the --flush-timeout deadline when the first input
 byte arrives.

xz --flush-timeout=2000, old version:

  1. xz is started. The next flush will happen after two seconds.
  2. No input for one second.
  3. A burst of a few kilobytes of input.
  4. No input for one second.
  5. Two seconds have passed and flushing starts.

The first second counted towards the flush-timeout even though
there was no pending data. This can cause flushing to occur more
often than needed.

xz --flush-timeout=2000, after this commit:

  1. xz is started.
  2. No input for one second.
  3. A burst of a few kilobytes of input. The next flush will
     happen after two seconds counted from the time when the
     first bytes of the burst were read.
  4. No input for one second.
  5. No input for another second.
  6. Two seconds have passed and flushing starts.
---
 src/xz/coder.c   | 6 +-----
 src/xz/file_io.c | 6 +++++-
 src/xz/mytime.c  | 1 -
 3 files changed, 6 insertions(+), 7 deletions(-)

diff --git a/src/xz/coder.c b/src/xz/coder.c
index 8bad038e..85f95439 100644
--- a/src/xz/coder.c
+++ b/src/xz/coder.c
@@ -733,9 +733,6 @@ coder_normal(file_pair *pair)
 				if (coder_write_output(pair))
 					break;
 
-				// Set the time of the most recent flushing.
-				mytime_set_flush_time();
-
 				// Mark that we haven't seen any new input
 				// since the previous flush.
 				pair->src_has_seen_input = false;
@@ -906,8 +903,7 @@ coder_run(const char *filename)
 			// is used.
 			if (opt_mode == MODE_TEST || !io_open_dest(pair)) {
 				// Remember the current time. It is needed
-				// for progress indicator and for timed
-				// flushing.
+				// for progress indicator.
 				mytime_set_start_time();
 
 				// Initialize the progress indicator.
diff --git a/src/xz/file_io.c b/src/xz/file_io.c
index 98918034..511aa60f 100644
--- a/src/xz/file_io.c
+++ b/src/xz/file_io.c
@@ -1167,7 +1167,11 @@ io_read(file_pair *pair, io_buf *buf, size_t size)
 		}
 
 		pos += (size_t)(amount);
-		pair->src_has_seen_input = true;
+
+		if (!pair->src_has_seen_input) {
+			pair->src_has_seen_input = true;
+			mytime_set_flush_time();
+		}
 	}
 
 	return pos;
diff --git a/src/xz/mytime.c b/src/xz/mytime.c
index 573b97de..70444001 100644
--- a/src/xz/mytime.c
+++ b/src/xz/mytime.c
@@ -51,7 +51,6 @@ extern void
 mytime_set_start_time(void)
 {
 	start_time = mytime_now();
-	next_flush = start_time + opt_flush_timeout;
 	return;
 }