From 74780131bd84759c1de6ec24fd896d78b6f7a9db Mon Sep 17 00:00:00 2001
From: Max Kellermann <max.kellermann@gmail.com>
Date: Mon, 4 Jul 2022 10:05:17 +0200
Subject: [PATCH] lib/zlib/GzipOutputStream: add SyncFlush()

---
 src/lib/zlib/GzipOutputStream.cxx | 25 ++++++++++++++++++++++++-
 src/lib/zlib/GzipOutputStream.hxx |  7 ++++++-
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/src/lib/zlib/GzipOutputStream.cxx b/src/lib/zlib/GzipOutputStream.cxx
index a72811ed7..48e0b8435 100644
--- a/src/lib/zlib/GzipOutputStream.cxx
+++ b/src/lib/zlib/GzipOutputStream.cxx
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2014-2018 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2014-2021 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -54,6 +54,29 @@ GzipOutputStream::~GzipOutputStream()
 	deflateEnd(&z);
 }
 
+void
+GzipOutputStream::SyncFlush()
+{
+	/* no more input */
+	z.next_in = nullptr;
+	z.avail_in = 0;
+
+	do {
+		Bytef output[16384];
+		z.next_out = output;
+		z.avail_out = sizeof(output);
+
+		int result = deflate(&z, Z_SYNC_FLUSH);
+		if (result != Z_OK)
+			throw ZlibError(result);
+
+		if (z.next_out == output)
+			break;
+
+		next.Write(output, z.next_out - output);
+	} while (z.avail_out == 0);
+}
+
 void
 GzipOutputStream::Finish()
 {
diff --git a/src/lib/zlib/GzipOutputStream.hxx b/src/lib/zlib/GzipOutputStream.hxx
index 88b465c95..3c91daf0e 100644
--- a/src/lib/zlib/GzipOutputStream.hxx
+++ b/src/lib/zlib/GzipOutputStream.hxx
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2014-2018 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2014-2021 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -54,6 +54,11 @@ public:
 	explicit GzipOutputStream(OutputStream &_next);
 	~GzipOutputStream();
 
+	/**
+	 * Throws on error.
+	 */
+	void SyncFlush();
+
 	/**
 	 * Finish the file and write all data remaining in zlib's
 	 * output buffer.