compat/timer-resolution: don't include windows.h in header

2 files changed, 76 insertions, 24 deletions

diff --git a/compat/timer-resolution.cpp b/compat/timer-resolution.cpp
index 597ee91e..d59c250d 100644
--- a/compat/timer-resolution.cpp
+++ b/compat/timer-resolution.cpp
@@ -8,12 +8,11 @@
 #include "timer-resolution.hpp"
 
 #if defined _WIN32
-#   include <windows.h>
-
 #   include <QLibrary>
 #   include <QDebug>
 
-typedef LONG (__stdcall *funptr_NtSetTimerResolution) (ULONG, BOOLEAN, PULONG);
+using namespace timer_impl;
+
 static funptr_NtSetTimerResolution init_timer_resolution_funptr();
 static funptr_NtSetTimerResolution get_funptr();
 
@@ -41,62 +40,72 @@ static funptr_NtSetTimerResolution init_timer_resolution_funptr()
 
 static funptr_NtSetTimerResolution get_funptr()
 {
+    // starting with C++11 static initializers are fully
+    // thread-safe and run the first time function is called
+
+    // cf. http://stackoverflow.com/questions/8102125/is-local-static-variable-initialization-thread-safe-in-c11
+
     static auto ret = init_timer_resolution_funptr();
     return ret;
 }
 
-timer_resolution::timer_resolution(int msecs) : old_value(-1)
+timer_resolution::timer_resolution(int msecs) : old_value(fail_())
 {
-    if (msecs <= 0 || msecs > 30)
+    if (msecs <= 0 || msecs > 100)
     {
         qDebug() << "can't set timer resolution to" << msecs << "ms";
         return;
     }
 
-    funptr_NtSetTimerResolution f = get_funptr();
-    if (f == nullptr)
+    funptr_NtSetTimerResolution set_timer_res = get_funptr();
+    if (set_timer_res == nullptr)
         return;
 
     // hundredth of a nanosecond
-    const ULONG value = msecs * ULONG(10000);
-    NTSTATUS error = f(value, TRUE, &old_value);
-    ULONG old_value_ = -1;
+    const ulong_ value = msecs * ulong_(10000);
+    ntstatus_ res;
 
-    if (error != 0)
+    res = set_timer_res(value, true_(), &old_value);
+
+    if (res < 0)
     {
-        old_value = -1;
-        qDebug() << "NtSetTimerResolution erred with" << error;
+        old_value = fail_();
+        qDebug() << "NtSetTimerResolution erred with" << res;
         return;
     }
 
     // see if it stuck
 
-    error = f(value, TRUE, &old_value_);
-    if (error != 0)
+    ulong_ old_value_ = fail_();
+
+    res = set_timer_res(value, true_(), &old_value_);
+    if (res < 0)
     {
-        old_value = -1;
-        qDebug() << "NtSetTimerResolution check erred with" << error;
+        old_value = fail_();
+        qDebug() << "NtSetTimerResolution check erred with" << res;
         return;
     }
 
     if (old_value_ != old_value)
     {
+        using t = long long;
+
         qDebug() << "NtSetTimerResolution:"
                  << "old value didn't stick"
-                 << "current resolution" << old_value_
-                 << "* 100 ns";
-        old_value = -1;
+                 << "current resolution" << (t(old_value_) * t(100))
+                 << "ns";
+        old_value = fail_();
         return;
     }
 }
 
 timer_resolution::~timer_resolution()
 {
-    if (old_value != ULONG(-1))
+    if (old_value != fail_())
     {
         funptr_NtSetTimerResolution f = get_funptr();
-        ULONG fuzz = -1;
-        (void) f(old_value, TRUE, &fuzz);
+        ulong_ fuzz = fail_();
+        (void) f(old_value, true_(), &fuzz);
     }
 }
 
diff --git a/compat/timer-resolution.hpp b/compat/timer-resolution.hpp
index 5db877c0..8c18a600 100644
--- a/compat/timer-resolution.hpp
+++ b/compat/timer-resolution.hpp
@@ -3,14 +3,57 @@
 #if defined _WIN32
 #   include "export.hpp"
 
+#include <type_traits>
+
+namespace timer_impl
+{
+
+// cf. https://msdn.microsoft.com/en-us/library/windows/desktop/aa383751%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396
+// for NTSTATUS, see http://stackoverflow.com/questions/3378622/how-to-understand-the-ntstatus-nt-success-typedef-in-windows-ddk
+
+using ulong_ = unsigned long;
+using long_ = long;
+using byte_ = unsigned char;
+using boolean_ = byte_;
+
+using true_ = std::integral_constant<int, 1>;
+
+using fail_ = std::integral_constant<byte_, byte_(-1)>;
+
+// cf. http://stackoverflow.com/questions/3378622/how-to-understand-the-ntstatus-nt-success-typedef-in-windows-ddk
+
+// typedef __success(return >= 0) LONG NTSTATUS;
+
+// __success(expr) T f() :  indicates whether function f succeeded or
+// not. If is true at exit, all the function's guarantees (as given
+// by other annotations) must hold. If is false at exit, the caller
+// should not expect any of the function's guarantees to hold. If not used,
+// the function must always satisfy its guarantees. Added automatically to
+// functions that indicate success in standard ways, such as by returning an
+// HRESULT.
+
+using ntstatus_ = long_;
+
+// finally what we want
+// this is equivalent to typedef syntax
+
+using funptr_NtSetTimerResolution = ntstatus_ (__stdcall *)(ulong_, boolean_, ulong_*);
+
+// RAII wrapper
+
 class OTR_COMPAT_EXPORT timer_resolution final
 {
-    unsigned long old_value;
+    ulong_ old_value;
 
 public:
     timer_resolution(int msecs);
     ~timer_resolution();
 };
+
+}
+
+using timer_impl::timer_resolution;
+
 #else
 struct timer_resolution final
 {