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, 84 insertions, 0 deletions

diff --git a/lib/timediff.c b/lib/timediff.c
new file mode 100644
index 000000000..003477c63
--- /dev/null
+++ b/lib/timediff.c
@@ -0,0 +1,84 @@
+/***************************************************************************
+ *                                  _   _ ____  _
+ *  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 "timediff.h"
+
+/*
+ * 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)
+{
+  if(!tv)
+    return NULL;
+
+  if(ms < 0)
+    return NULL;
+
+  if(ms > 0) {
+    timediff_t tv_sec = ms / 1000;
+    timediff_t tv_usec = (ms % 1000) * 1000; /* max=999999 */
+#ifdef HAVE_SUSECONDS_T
+#if TIMEDIFF_T_MAX > TIME_T_MAX
+    /* tv_sec overflow check in case time_t is signed */
+    if(tv_sec > TIME_T_MAX)
+      tv_sec = TIME_T_MAX;
+#endif
+    tv->tv_sec = (time_t)tv_sec;
+    tv->tv_usec = (suseconds_t)tv_usec;
+#elif defined(WIN32) /* maybe also others in the future */
+#if TIMEDIFF_T_MAX > LONG_MAX
+    /* tv_sec overflow check on Windows there we know it is long */
+    if(tv_sec > LONG_MAX)
+      tv_sec = LONG_MAX;
+#endif
+    tv->tv_sec = (long)tv_sec;
+    tv->tv_usec = (long)tv_usec;
+#else
+#if TIMEDIFF_T_MAX > INT_MAX
+    /* tv_sec overflow check in case time_t is signed */
+    if(tv_sec > INT_MAX)
+      tv_sec = INT_MAX;
+#endif
+    tv->tv_sec = (int)tv_sec;
+    tv->tv_usec = (int)tv_usec;
+#endif
+  }
+  else {
+    tv->tv_sec = 0;
+    tv->tv_usec = 0;
+  }
+
+  return tv;
+}
+
+/*
+ * Converts a timeval structure into number of milliseconds.
+ */
+timediff_t curlx_tvtoms(struct timeval *tv)
+{
+  return (tv->tv_sec*1000) + (timediff_t)(((double)tv->tv_usec)/1000.0);
+}