From 463f6ea04af934a68facaca0ff089bc306de3f98 Mon Sep 17 00:00:00 2001
From: Timo Sirainen <timo.sirainen@dovecot.fi>
Date: Wed, 10 Feb 2016 22:02:15 +0200
Subject: [PATCH] lib: Added i_stream_set_persistent_buffers()

---
 src/lib/istream-private.h |  1 +
 src/lib/istream.c         | 14 ++++++++++++++
 src/lib/istream.h         |  4 ++++
 3 files changed, 19 insertions(+)

diff --git a/src/lib/istream-private.h b/src/lib/istream-private.h
index 54a91d83af..c6b69d5754 100644
--- a/src/lib/istream-private.h
+++ b/src/lib/istream-private.h
@@ -52,6 +52,7 @@ struct istream_private {
 	unsigned int line_crlf:1;
 	unsigned int return_nolf_line:1;
 	unsigned int stream_size_passthrough:1; /* stream is parent's size */
+	unsigned int nonpersistent_buffers:1;
 };
 
 struct istream * ATTR_NOWARN_UNUSED_RESULT
diff --git a/src/lib/istream.c b/src/lib/istream.c
index 4f2988936b..2d70a230db 100644
--- a/src/lib/istream.c
+++ b/src/lib/istream.c
@@ -122,6 +122,14 @@ void i_stream_set_return_partial_line(struct istream *stream, bool set)
 	stream->real_stream->return_nolf_line = set;
 }
 
+void i_stream_set_persistent_buffers(struct istream *stream, bool set)
+{
+	do {
+		stream->real_stream->nonpersistent_buffers = !set;
+		stream = stream->real_stream->parent;
+	} while (stream != NULL);
+}
+
 static void i_stream_update(struct istream_private *stream)
 {
 	if (stream->parent == NULL)
@@ -238,6 +246,12 @@ void i_stream_skip(struct istream *stream, uoff_t count)
 		/* within buffer */
 		stream->v_offset += count;
 		_stream->skip += count;
+		if (_stream->nonpersistent_buffers &&
+		    _stream->skip == _stream->pos) {
+			_stream->skip = _stream->pos = 0;
+			_stream->buffer_size = 0;
+			i_free_and_null(_stream->w_buffer);
+		}
 		return;
 	}
 
diff --git a/src/lib/istream.h b/src/lib/istream.h
index d47d36bdb9..0c96e98967 100644
--- a/src/lib/istream.h
+++ b/src/lib/istream.h
@@ -97,6 +97,10 @@ size_t i_stream_get_max_buffer_size(struct istream *stream);
 /* Enable/disable i_stream[_read]_next_line() returning the last line if it
    doesn't end with LF. */
 void i_stream_set_return_partial_line(struct istream *stream, bool set);
+/* Change whether buffers are allocated persistently (default=TRUE). When not,
+   the memory usage is minimized by freeing the stream's buffers whenever they
+   become empty. */
+void i_stream_set_persistent_buffers(struct istream *stream, bool set);
 
 /* Returns number of bytes read if read was ok, -1 if EOF or error, -2 if the
    input buffer is full. */
-- 
2.47.3