Implement temporary streams.

A temporary stream functions as a memory stream until its size reaches
a preconfigured threshold value.  Once it is reached, the stream storage
is automatically converted to a temporary file, and all data written so far
are transferred to the new storage.  If the temporary file cannot be
created, the stream continues to operate in memory-based mode.

This stream type is intended to decrease the number of used file
descriptors.

* include/mailutils/sys/Makefile.am: Add temp_stream.h
* include/mailutils/sys/temp_stream.h: New file.
* include/mailutils/stream.h (mu_temp_file_threshold_size): New extern.
(mu_temp_stream_create): New proto.
* libmailutils/stream/Makefile.am: Add temp_stream.c.
* libmailutils/stream/temp_stream.c: New file.
* libmailutils/string/Makefile.am: Add strtosize.c

* libmailutils/tests/.gitignore: Update.
* libmailutils/tests/Makefile.am
* libmailutils/tests/strtoc.c: Add tests for mu_c_hsize.
* libmailutils/tests/temp_stream.c: New test program.
* libmailutils/tests/testsuite.at: Test the temp_stream functionality.
* testsuite/testsuite.inc (MU_CHECK): New macro.

* libmailutils/mailbox/body.c (body_get_transport): Use mu_temp_stream_create.

3 files changed, 40 insertions, 1 deletions

diff --git a/include/mailutils/stream.h b/include/mailutils/stream.h
index a91f168de..dc3bb12ad 100644
--- a/include/mailutils/stream.h
+++ b/include/mailutils/stream.h
@@ -474,7 +474,10 @@ int mu_nullstream_create (mu_stream_t *pref, int flags);
 
 int mu_wordwrap_stream_create (mu_stream_t *pstream, mu_stream_t transport,
 			       size_t left_margin, size_t right_margin);
-  
+
+extern size_t mu_temp_file_threshold_size;
+int mu_temp_stream_create (mu_stream_t *pstream, size_t threshold);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/include/mailutils/sys/Makefile.am b/include/mailutils/sys/Makefile.am
index 31225ef81..435792aa0 100644
--- a/include/mailutils/sys/Makefile.am
+++ b/include/mailutils/sys/Makefile.am
@@ -59,6 +59,7 @@ sysinclude_HEADERS = \
  stream.h\
  syslogstream.h\
  temp_file_stream.h\
+ temp_stream.h\
  tls-stream.h\
  url.h\
  xscript-stream.h\
diff --git a/include/mailutils/sys/temp_stream.h b/include/mailutils/sys/temp_stream.h
new file mode 100644
index 000000000..9061aef7e
--- /dev/null
+++ b/include/mailutils/sys/temp_stream.h
@@ -0,0 +1,35 @@
+/* GNU Mailutils -- a suite of utilities for electronic mail
+   Copyright (C) 2020 Free Software Foundation, Inc.
+
+   This library is free software; you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   This library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with GNU Mailutils.  If not, see <http://www.gnu.org/licenses/>. */
+
+#ifndef _MAILUTILS_SYS_TEMP_STREAM_H
+#define _MAILUTILS_SYS_TEMP_STREAM_H
+
+#include <mailutils/sys/stream.h>
+#include <mailutils/sys/memory_stream.h>
+#include <mailutils/sys/temp_file_stream.h>
+
+struct _mu_temp_stream
+{
+  union
+  {
+    struct _mu_stream stream;
+    struct _mu_memory_stream mem;
+    struct _mu_temp_file_stream file;
+  } s;
+  size_t max_size;
+  int (*saved_write) (struct _mu_stream *, const char *, size_t, size_t *);
+};
+#endif