Gabriel Ivăncescu : jscript: Convert filetime to date properly using unsigned division.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 0c875dfa5fc34619777c5d9782e84cd9f82bbdc4
URL:    https://gitlab.winehq.org/wine/wine/-/commit/0c875dfa5fc34619777c5d9782e84cd...

Author: Gabriel Ivăncescu 
Date:   Tue Nov  8 20:50:35 2022 +0200

jscript: Convert filetime to date properly using unsigned division.

Also, the result has to be signed type before converting to double, since
it can be negative then (e.g. if system clock is set before 1970).

Signed-off-by: Gabriel Ivăncescu

---

dlls/jscript/date.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/dlls/jscript/date.c b/dlls/jscript/date.c
index bc09f05d4b9..f90a3eb052f 100644
--- a/dlls/jscript/date.c
+++ b/dlls/jscript/date.c
@@ -28,9 +28,6 @@

WINE_DEFAULT_DEBUG_CHANNEL(jscript);

-/* 1601 to 1970 is 369 years plus 89 leap days */
-#define TIME_EPOCH  ((ULONGLONG)(369 * 365 + 89) * 86400 * 1000)
-
 typedef struct {
     jsdisp_t dispex;

@@ -55,6 +52,16 @@ static inline DateInstance *date_this(jsval_t vthis)
     return (jsdisp && is_class(jsdisp, JSCLASS_DATE)) ? date_from_jsdisp(jsdisp) : NULL;
 }

+static inline double file_time_to_date_time(const FILETIME *ftime)
+{
+    /* 1601 to 1970 is 369 years plus 89 leap days */
+    const LONGLONG time_epoch = (LONGLONG)(369 * 365 + 89) * 86400 * 1000;
+
+    LONGLONG time = (((ULONGLONG)ftime->dwHighDateTime << 32) | ftime->dwLowDateTime) / 10000;
+
+    return time - time_epoch;
+}
+
 /*ECMA-262 3rd Edition    15.9.1.2 */
 #define MS_PER_DAY 86400000
 #define MS_PER_HOUR 3600000
@@ -406,12 +413,9 @@ static inline DOUBLE time_clip(DOUBLE time)
 static double date_now(void)
 {
     FILETIME ftime;
-    LONGLONG time;

GetSystemTimeAsFileTime(&ftime);
-    time = ((LONGLONG)ftime.dwHighDateTime << 32) + ftime.dwLowDateTime;
-
-    return time/10000 - TIME_EPOCH;
+    return file_time_to_date_time(&ftime);
 }

static SYSTEMTIME create_systemtime(DOUBLE time)
@@ -2410,14 +2414,11 @@ static HRESULT DateConstr_value(script_ctx_t *ctx, jsval_t vthis, WORD flags, un

case INVOKE_FUNC: {
         FILETIME system_time, local_time;
-        LONGLONG lltime;

GetSystemTimeAsFileTime(&system_time);
         FileTimeToLocalFileTime(&system_time, &local_time);
-        lltime = ((LONGLONG)local_time.dwHighDateTime<<32)
-            + local_time.dwLowDateTime;

-        return date_to_string(lltime/10000-TIME_EPOCH, FALSE, 0, r);
+        return date_to_string(file_time_to_date_time(&local_time), FALSE, 0, r);
     }

default: