[Windows] increase precision of boot_time() and proc create_time() (#1693)

5 files changed, 60 insertions, 64 deletions

diff --git a/HISTORY.rst b/HISTORY.rst
index 44d887e3..539c6fd4 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -19,6 +19,8 @@ XXXX-XX-XX
 - 1679_: [Windows] net_connections() and Process.connections() are 10% faster.
 - 1681_: [Linux] disk_partitions() now also shows swap partitions.
 - 1686_: [Windows] added support for PyPy on Windows.
+- 1693_: [Windows] boot_time() and Process.create_time() now have the precision
+  of a micro second (before the precision was of a second).
 
 **Bug fixes**
 
diff --git a/psutil/_psutil_common.c b/psutil/_psutil_common.c
index 028e48e0..07578eda 100644
--- a/psutil/_psutil_common.c
+++ b/psutil/_psutil_common.c
@@ -352,6 +352,7 @@ psutil_set_winver() {
     return 0;
 }
 
+
 int
 psutil_load_globals() {
     if (psutil_loadlibs() != 0)
@@ -362,4 +363,41 @@ psutil_load_globals() {
     InitializeCriticalSection(&PSUTIL_CRITICAL_SECTION);
     return 0;
 }
+
+
+/*
+ * Convert the hi and lo parts of a FILETIME structure or a LARGE_INTEGER
+ * to a UNIX time.
+ * A FILETIME contains a 64-bit value representing the number of
+ * 100-nanosecond intervals since January 1, 1601 (UTC).
+ * A UNIX time is the number of seconds that have elapsed since the
+ * UNIX epoch, that is the time 00:00:00 UTC on 1 January 1970.
+ */
+static double
+_to_unix_time(ULONGLONG hiPart, ULONGLONG loPart) {
+    ULONGLONG ret;
+
+    // 100 nanosecond intervals since January 1, 1601.
+    ret = hiPart << 32;
+    ret += loPart;
+    // Change starting time to the Epoch (00:00:00 UTC, January 1, 1970).
+    ret -= 116444736000000000ull;
+    // Convert nano secs to secs.
+    return (double) ret / 10000000ull;
+}
+
+
+double
+psutil_FiletimeToUnixTime(FILETIME ft) {
+    return _to_unix_time((ULONGLONG)ft.dwHighDateTime,
+                         (ULONGLONG)ft.dwLowDateTime);
+
+}
+
+
+double
+psutil_LargeIntegerToUnixTime(LARGE_INTEGER li) {
+    return _to_unix_time((ULONGLONG)li.HighPart,
+                         (ULONGLONG)li.LowPart);
+}
 #endif  // PSUTIL_WINDOWS
diff --git a/psutil/_psutil_common.h b/psutil/_psutil_common.h
index 97543206..34c428c0 100644
--- a/psutil/_psutil_common.h
+++ b/psutil/_psutil_common.h
@@ -134,4 +134,6 @@ int psutil_setup(void);
     PVOID psutil_GetProcAddress(LPCSTR libname, LPCSTR procname);
     PVOID psutil_GetProcAddressFromLib(LPCSTR libname, LPCSTR procname);
     PVOID psutil_SetFromNTStatusErr(NTSTATUS Status, const char *syscall);
+    double psutil_FiletimeToUnixTime(FILETIME ft);
+    double psutil_LargeIntegerToUnixTime(LARGE_INTEGER li);
 #endif
diff --git a/psutil/_psutil_windows.c b/psutil/_psutil_windows.c
index f9405707..64592103 100644
--- a/psutil/_psutil_windows.c
+++ b/psutil/_psutil_windows.c
@@ -79,30 +79,13 @@ psutil_get_num_cpus(int fail_on_err) {
  */
 static PyObject *
 psutil_boot_time(PyObject *self, PyObject *args) {
-    ULONGLONG uptime;
-    time_t pt;
+    ULONGLONG upTime;
     FILETIME fileTime;
-    ULONGLONG ll;
 
     GetSystemTimeAsFileTime(&fileTime);
-    /*
-    HUGE thanks to:
-    http://johnstewien.spaces.live.com/blog/cns!E6885DB5CEBABBC8!831.entry
-
-    This function converts the FILETIME structure to the 32 bit
-    Unix time structure.
-    The time_t is a 32-bit value for the number of seconds since
-    January 1, 1970. A FILETIME is a 64-bit for the number of
-    100-nanosecond periods since January 1, 1601. Convert by
-    subtracting the number of 100-nanosecond period between 01-01-1970
-    and 01-01-1601, from time_t the divide by 1e+7 to get to the same
-    base granularity.
-    */
-    ll = (((ULONGLONG)
-        (fileTime.dwHighDateTime)) << 32) + fileTime.dwLowDateTime;
-    pt = (time_t)((ll - 116444736000000000ull) / 10000000ull);
-    uptime = GetTickCount64() / 1000ull;
-    return Py_BuildValue("K", pt - uptime);
+    // Number of milliseconds that have elapsed since the system was started.
+    upTime = GetTickCount64() / 1000ull;
+    return Py_BuildValue("d", psutil_FiletimeToUnixTime(fileTime) - upTime);
 }
 
 
@@ -320,10 +303,10 @@ psutil_proc_cpu_times(PyObject *self, PyObject *args) {
      */
     return Py_BuildValue(
        "(dd)",
-       (double)(ftUser.dwHighDateTime * 429.4967296 + \
-                ftUser.dwLowDateTime * 1e-7),
-       (double)(ftKernel.dwHighDateTime * 429.4967296 + \
-                ftKernel.dwLowDateTime * 1e-7)
+       (double)(ftUser.dwHighDateTime * HI_T + \
+                ftUser.dwLowDateTime * LO_T),
+       (double)(ftKernel.dwHighDateTime * HI_T + \
+                ftKernel.dwLowDateTime * LO_T)
    );
 }
 
@@ -335,7 +318,6 @@ psutil_proc_cpu_times(PyObject *self, PyObject *args) {
 static PyObject *
 psutil_proc_create_time(PyObject *self, PyObject *args) {
     DWORD       pid;
-    long long   unix_time;
     HANDLE      hProcess;
     FILETIME    ftCreate, ftExit, ftKernel, ftUser;
 
@@ -363,34 +345,7 @@ psutil_proc_create_time(PyObject *self, PyObject *args) {
     }
 
     CloseHandle(hProcess);
-
-    /*
-    // Make sure the process is not gone as OpenProcess alone seems to be
-    // unreliable in doing so (it seems a previous call to p.wait() makes
-    // it unreliable).
-    // This check is important as creation time is used to make sure the
-    // process is still running.
-    ret = GetExitCodeProcess(hProcess, &exitCode);
-    CloseHandle(hProcess);
-    if (ret != 0) {
-        if (exitCode != STILL_ACTIVE)
-            return NoSuchProcess("GetExitCodeProcess");
-    }
-    else {
-        // Ignore access denied as it means the process is still alive.
-        // For all other errors, we want an exception.
-        if (GetLastError() != ERROR_ACCESS_DENIED)
-            return PyErr_SetFromWindowsErr(0);
-    }
-    */
-
-    // Convert the FILETIME structure to a Unix time.
-    // It's the best I could find by googling and borrowing code here
-    // and there. The time returned has a precision of 1 second.
-    unix_time = ((LONGLONG)ftCreate.dwHighDateTime) << 32;
-    unix_time += ftCreate.dwLowDateTime - 116444736000000000LL;
-    unix_time /= 10000000;
-    return Py_BuildValue("d", (double)unix_time);
+    return Py_BuildValue("d", psutil_FiletimeToUnixTime(ftCreate));
 }
 
 
@@ -844,10 +799,10 @@ psutil_proc_threads(PyObject *self, PyObject *args) {
             py_tuple = Py_BuildValue(
                 "kdd",
                 te32.th32ThreadID,
-                (double)(ftUser.dwHighDateTime * 429.4967296 + \
-                         ftUser.dwLowDateTime * 1e-7),
-                (double)(ftKernel.dwHighDateTime * 429.4967296 + \
-                         ftKernel.dwLowDateTime * 1e-7));
+                (double)(ftUser.dwHighDateTime * HI_T + \
+                         ftUser.dwLowDateTime * LO_T),
+                (double)(ftKernel.dwHighDateTime * HI_T + \
+                         ftKernel.dwLowDateTime * LO_T));
             if (!py_tuple)
                 goto error;
             if (PyList_Append(py_retlist, py_tuple))
diff --git a/psutil/arch/windows/process_info.c b/psutil/arch/windows/process_info.c
index d8104c81..73a69912 100644
--- a/psutil/arch/windows/process_info.c
+++ b/psutil/arch/windows/process_info.c
@@ -578,7 +578,8 @@ out:
  * fills the structure with various process information in one shot
  * by using NtQuerySystemInformation.
  * We use this as a fallback when faster functions fail with access
- * denied. This is slower because it iterates over all processes.
+ * denied. This is slower because it iterates over all processes
+ * but it doesn't require any privilege (also work for PID 0).
  * On success return 1, else 0 with Python exception already set.
  */
 int
@@ -669,7 +670,7 @@ psutil_proc_info(PyObject *self, PyObject *args) {
     ULONG ctx_switches = 0;
     double user_time;
     double kernel_time;
-    long long create_time;
+    double create_time;
     PyObject *py_retlist;
 
     if (! PyArg_ParseTuple(args, _Py_PARSE_PID, &pid))
@@ -692,9 +693,7 @@ psutil_proc_info(PyObject *self, PyObject *args) {
         create_time = 0;
     }
     else {
-        create_time = ((LONGLONG)process->CreateTime.HighPart) << 32;
-        create_time += process->CreateTime.LowPart - 116444736000000000LL;
-        create_time /= 10000000;
+        create_time = psutil_LargeIntegerToUnixTime(process->CreateTime);
     }
 
     py_retlist = Py_BuildValue(
@@ -707,7 +706,7 @@ psutil_proc_info(PyObject *self, PyObject *args) {
         ctx_switches,                           // num ctx switches
         user_time,                              // cpu user time
         kernel_time,                            // cpu kernel time
-        (double)create_time,                    // create time
+        create_time,                            // create time
         (int)process->NumberOfThreads,          // num threads
         // IO counters
         process->ReadOperationCount.QuadPart,   // io rcount