--- a/src/lib/istream-data.c	Mon Jul 25 10:24:44 2016 +0300
+++ b/src/lib/istream-data.c	Fri Aug 12 01:24:16 2016 +0200
@@ -36,3 +36,27 @@
 	i_stream_set_name(&stream->istream, "(buffer)");
 	return &stream->istream;
 }
+
+static void i_stream_copied_data_free(void *data)
+{
+	i_free(data);
+}
+struct istream *
+i_stream_create_copy_from_data(const void *data, size_t size)
+{
+	struct istream *stream;
+	void *buffer;
+
+	if (size == 0) {
+		buffer = "";
+	} else {
+		buffer = i_malloc(size);
+		memcpy(buffer, data, size);
+	}
+	stream = i_stream_create_from_data(buffer, size);
+	if (size > 0) {
+		i_stream_add_destroy_callback
+			(stream, i_stream_copied_data_free, buffer);
+	}
+	return stream;
+}

--- a/src/lib/istream.h	Mon Jul 25 10:24:44 2016 +0300
+++ b/src/lib/istream.h	Fri Aug 12 01:24:16 2016 +0200
@@ -43,11 +43,22 @@
 struct istream *i_stream_create_mmap(int fd, size_t block_size,
 				     uoff_t start_offset, uoff_t v_size,
 				     bool autoclose_fd);
+/* Create an input stream using the provided data block. That data block must
+remain allocated during the full lifetime of the stream. */
 struct istream *i_stream_create_from_data(const void *data, size_t size);
 #define i_stream_create_from_buffer(buf) \
 	i_stream_create_from_data((buf)->data, (buf)->used)
 #define i_stream_create_from_string(str) \
 	i_stream_create_from_data(str_data(str), str_len(str))
+/* Create an input stream using a copy of the provided data block. The
+   provided data block may be freed at any time. The copy is freed when the
+   stream is destroyed. */
+struct istream *
+i_stream_create_copy_from_data(const void *data, size_t size);
+#define i_stream_create_copy_from_buffer(buf) \
+	i_stream_create_copy_from_data((buf)->data, (buf)->used)
+#define i_stream_create_copy_from_string(str) \
+	i_stream_create_copy_from_data(str_data(str), str_len(str))
 struct istream *i_stream_create_limit(struct istream *input, uoff_t v_size);
 struct istream *i_stream_create_range(struct istream *input,
 				      uoff_t v_offset, uoff_t v_size);