timediff: return timediff_t from the time diff functions

... to cater for systems with unsigned time_t variables.

- Renamed the functions to curlx_timediff and Curl_timediff_us.

- Added overflow protection for both of them in either direction for
  both 32 bit and 64 bit time_ts

- Reprefixed the curlx_time functions to use Curl_*

Reported-by: Peter Piekarski
Fixes #2004
Closes #2005

1 files changed, 5 insertions, 4 deletions

diff --git a/lib/transfer.c b/lib/transfer.c
index 8e66d0d80..4bdbd5e18 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -1174,7 +1174,7 @@ CURLcode Curl_readwrite(struct connectdata *conn,
 
       */
 
-      time_t ms = Curl_tvdiff(k->now, k->start100);
+      timediff_t ms = Curl_timediff(k->now, k->start100);
       if(ms >= data->set.expect_100_timeout) {
         /* we've waited long enough, continue anyway */
         k->exp100 = EXP100_SEND_DATA;
@@ -1198,13 +1198,14 @@ CURLcode Curl_readwrite(struct connectdata *conn,
         failf(data, "Operation timed out after %ld milliseconds with %"
               CURL_FORMAT_CURL_OFF_T " out of %"
               CURL_FORMAT_CURL_OFF_T " bytes received",
-              Curl_tvdiff(k->now, data->progress.t_startsingle), k->bytecount,
-              k->size);
+              Curl_timediff(k->now, data->progress.t_startsingle),
+              k->bytecount, k->size);
       }
       else {
         failf(data, "Operation timed out after %ld milliseconds with %"
               CURL_FORMAT_CURL_OFF_T " bytes received",
-              Curl_tvdiff(k->now, data->progress.t_startsingle), k->bytecount);
+              Curl_timediff(k->now, data->progress.t_startsingle),
+              k->bytecount);
       }
       return CURLE_OPERATION_TIMEDOUT;
     }