timediff.[ch]: add curlx helper functions for timeval conversions

Also move timediff_t definitions from timeval.h to timediff.h and
then make timeval.h include the new standalone-capable timediff.h.

Reviewed-by: Jay Satiro
Reviewed-by: Daniel Stenberg

Supersedes #5888
Closes #8595

1 files changed, 50 insertions, 0 deletions

diff --git a/lib/timediff.h b/lib/timediff.h
new file mode 100644
index 000000000..fcd5f0563
--- /dev/null
+++ b/lib/timediff.h
@@ -0,0 +1,50 @@
+#ifndef HEADER_CURL_TIMEDIFF_H
+#define HEADER_CURL_TIMEDIFF_H
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  Project                     ___| | | |  _ \| |
+ *                             / __| | | | |_) | |
+ *                            | (__| |_| |  _ <| |___
+ *                             \___|\___/|_| \_\_____|
+ *
+ * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
+ *
+ * This software is licensed as described in the file COPYING, which
+ * you should have received as part of this distribution. The terms
+ * are also available at https://curl.se/docs/copyright.html.
+ *
+ * You may opt to use, copy, modify, merge, publish, distribute and/or sell
+ * copies of the Software, and permit persons to whom the Software is
+ * furnished to do so, under the terms of the COPYING file.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ***************************************************************************/
+
+#include "curl_setup.h"
+
+/* Use a larger type even for 32 bit time_t systems so that we can keep
+   microsecond accuracy in it */
+typedef curl_off_t timediff_t;
+#define CURL_FORMAT_TIMEDIFF_T CURL_FORMAT_CURL_OFF_T
+
+#define TIMEDIFF_T_MAX CURL_OFF_T_MAX
+#define TIMEDIFF_T_MIN CURL_OFF_T_MIN
+
+/*
+ * Converts number of milliseconds into a timeval structure.
+ *
+ * Return values:
+ *    NULL IF tv is NULL or ms < 0 (eg. no timeout -> blocking select)
+ *    tv with 0 in both fields IF ms == 0 (eg. 0ms timeout -> polling select)
+ *    tv with converted fields IF ms > 0 (eg. >0ms timeout -> waiting select)
+ */
+struct timeval *curlx_mstotv(struct timeval *tv, timediff_t ms);
+
+/*
+ * Converts a timeval structure into number of milliseconds.
+ */
+timediff_t curlx_tvtoms(struct timeval *tv);
+
+#endif /* HEADER_CURL_TIMEDIFF_H */