[idd] common: centralize nonzero sequences

idd/LGCommon/LGCommon.vcxproj

@@ -77,6 +77,7 @@
     <ClInclude Include="InputPipeProtocol.h" />
     <ClInclude Include="PipeMsg.h" />
     <ClInclude Include="RefreshRate.h" />
+    <ClInclude Include="Seq.h" />
   </ItemGroup>
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets" />

idd/LGCommon/LGCommon.vcxproj.filters

@@ -44,5 +44,8 @@
     <ClInclude Include="RefreshRate.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="Seq.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
 </Project>

idd/LGCommon/Seq.h

@@ -0,0 +1,54 @@
+/**
+ * Looking Glass
+ * Copyright © 2017-2026 The Looking Glass Authors
+ * https://looking-glass.io
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#pragma once
+
+#include <type_traits>
+
+namespace Seq
+{
+  template<typename T>
+  T Next(T value)
+  {
+    static_assert(std::is_integral<T>::value &&
+      std::is_unsigned<T>::value && !std::is_same<T, bool>::value,
+      "sequence type must be an unsigned integer");
+
+    const T next = value + static_cast<T>(1);
+    return next ? next : static_cast<T>(1);
+  }
+
+  template<typename T>
+  T Inc(T& value)
+  {
+    value = Next(value);
+    return value;
+  }
+
+  template<typename T>
+  T Take(T& value)
+  {
+    if (!value)
+      value = static_cast<T>(1);
+    const T result = value;
+    value = Next(value);
+    return result;
+  }
+}

idd/LGIdd/capture/CFrameScheduler.cpp

@@ -21,6 +21,7 @@
 #include "capture/CFrameScheduler.h"
 
 #include "CDebug.h"
+#include "Seq.h"
 
 #include <string.h>
 
@@ -210,8 +211,7 @@ bool CFrameScheduler::ElectOwner(uint64_t now, uint32_t resetClientID)
   {
     if (m_scheduling)
     {
-      if (!++m_epoch)
+      Seq::Inc(m_epoch);
-        ++m_epoch;
       m_schedule.epoch = m_epoch;
     }
     m_nextDeadline  = m_scheduling ? fastest->nextDelivery : 0;
@@ -517,8 +517,7 @@ void CFrameScheduler::AdvanceDeadlineSerial(uint64_t count)
     return;
 
   for (; epochAdvances; --epochAdvances)
-    if (!++m_epoch)
+    Seq::Inc(m_epoch);
-      ++m_epoch;
   m_schedule.epoch = m_epoch;
 
   Client * client = FindClient(m_schedule.clientID);

idd/LGIdd/transport/CControlHub.cpp

@@ -21,6 +21,7 @@
 #include "transport/CControlHub.h"
 
 #include "CDebug.h"
+#include "Seq.h"
 
 #include <algorithm>
 #include <cstring>
@@ -105,12 +106,6 @@ DWORD WINAPI CControlHub::WorkerProc(void * opaque)
   return 0;
 }
 
-uint64_t CControlHub::NextRevision(uint64_t revision)
-{
-  ++revision;
-  return revision ? revision : 1;
-}
-
 bool CControlHub::TokenMatches(
   const Sink& sink, const ControlToken& token)
 {
@@ -160,8 +155,8 @@ bool CControlHub::Add(
     selected->deliveredTransform = 0;
     memset(selected->retryAt, 0, sizeof(selected->retryAt));
     selected->nextWork       = 0;
-    selected->bindingSerial = NextRevision(selected->bindingSerial);
+    selected->bindingSerial  = Seq::Next(selected->bindingSerial);
-    selected->replaySerial  = NextRevision(selected->replaySerial);
+    selected->replaySerial   = Seq::Next(selected->replaySerial);
     selected->calling        = false;
     selected->active         = false;
     selected->failed         = false;
@@ -174,7 +169,7 @@ bool CControlHub::Add(
     if (selected->target == &control && selected->backend == backend &&
         selected->epoch == epoch && selected->reserved && !selected->failed)
     {
-      selected->replaySerial = NextRevision(selected->replaySerial);
+      selected->replaySerial = Seq::Next(selected->replaySerial);
       selected->active       = true;
       selected->reserved     = false;
       attached               = true;
@@ -285,7 +280,7 @@ void CControlHub::OnControlReplay(const ControlToken& token)
     sink.deliveredPosition  = 0;
     sink.deliveredShape     = 0;
     sink.deliveredTransform = 0;
-    sink.replaySerial = NextRevision(sink.replaySerial);
+    sink.replaySerial       = Seq::Next(sink.replaySerial);
     memset(sink.retryAt, 0, sizeof(sink.retryAt));
     SetEvent(sink.wake);
     return;
@@ -529,14 +524,14 @@ void CControlHub::SendCursor(const IDARG_OUT_QUERY_HWCURSOR& info,
     m_state.cursor.X               = info.X;
     m_state.cursor.Y               = info.Y;
     m_state.sdrWhiteLevel          = sdrWhiteLevel;
-    m_state.positionRevision = NextRevision(m_state.positionRevision);
+    m_state.positionRevision       = Seq::Next(m_state.positionRevision);
 
     if (shape)
     {
       m_state.cursor.IsCursorShapeUpdated = info.IsCursorShapeUpdated;
       m_state.cursor.CursorShapeInfo      = info.CursorShapeInfo;
       m_state.cursorData                  = std::move(cursorData);
-      m_state.shapeRevision = NextRevision(m_state.shapeRevision);
+      m_state.shapeRevision               = Seq::Next(m_state.shapeRevision);
     }
   }
 
@@ -551,7 +546,7 @@ void CControlHub::SetColorTransform(
   {
     CSRWExclusiveLock lock(m_stateLock);
     m_state.transform         = std::move(transform);
-    m_state.transformRevision = NextRevision(m_state.transformRevision);
+    m_state.transformRevision = Seq::Next(m_state.transformRevision);
   }
   WakeAll(WorkType::TRANSFORM);
 }

idd/LGIdd/transport/CControlHub.h

@@ -104,7 +104,6 @@ private:
   bool             m_valid     = false;
 
   static DWORD WINAPI WorkerProc(void * opaque);
-  static uint64_t NextRevision(uint64_t revision);
   static bool TokenMatches(const Sink& sink, const ControlToken& token);
 
   bool BeginWork(Sink& sink, Work& work, DWORD& wait);

idd/LGIdd/transport/CInputHub.cpp

@@ -21,6 +21,7 @@
 #include "transport/CInputHub.h"
 
 #include "input/IInputSink.h"
+#include "Seq.h"
 
 static bool SameClient(const SourceKey& left, const SourceKey& right)
 {
@@ -510,9 +511,7 @@ void CInputHub::InvalidateInteraction()
 
 void CInputHub::AdvanceInteractionSerial()
 {
-  ++m_interactionSerial;
+  Seq::Inc(m_interactionSerial);
-  if (!m_interactionSerial)
-    ++m_interactionSerial;
 }
 
 bool CInputHub::CheckState()

idd/LGIdd/transport/CRecoveryHub.cpp

@@ -20,6 +20,8 @@
 
 #include "transport/CRecoveryHub.h"
 
+#include "Seq.h"
+
 #include <Windows.h>
 
 namespace
@@ -99,16 +101,6 @@ bool CRecoveryHub::ActionMatchesLocked(
     action.active == m_operation.action.active;
 }
 
-uint64_t CRecoveryHub::NextNonzero(uint64_t& value)
-{
-  uint64_t result = value++;
-  if (!result)
-    result = value++;
-  if (!value)
-    ++value;
-  return result;
-}
-
 uint32_t CRecoveryHub::NextSerial()
 {
   uint32_t result = m_nextSerial;
@@ -134,7 +126,7 @@ void CRecoveryHub::SetWaitingLocked(Request& request,
   request.source      = source;
   request.session     = session;
   request.operation   = operation;
-  request.sequence    = NextNonzero(m_nextSequence);
+  request.sequence    = Seq::Take(m_nextSequence);
   request.serial      = serial;
   request.active      = active;
   request.state       = SlotState::WAITING;
@@ -265,8 +257,8 @@ RecoveryAdmission CRecoveryHub::Submit(const SourceKey& source,
 
   m_operation = Operation {};
   m_operation.phase           = OperationPhase::IN_FLIGHT;
-  m_operation.id    = NextNonzero(m_nextOperation);
+  m_operation.id              = Seq::Take(m_nextOperation);
-  m_operation.action.route    = NextNonzero(m_nextRoute);
+  m_operation.action.route    = Seq::Take(m_nextRoute);
   m_operation.action.session  = m_session;
   m_operation.action.serial   = NextSerial();
   m_operation.action.active   = active;

idd/LGIdd/transport/CRecoveryHub.h

@@ -106,7 +106,6 @@ private:
   unsigned FindSourceLocked(const SourceKey& source) const;
   unsigned FindFreeLocked() const;
   bool ActionMatchesLocked(const RecoveryAction& action) const;
-  uint64_t NextNonzero(uint64_t& value);
   uint32_t NextSerial();
   void ClearRequestLocked(Request& request);
   void SetWaitingLocked(Request& request, const SourceKey& source,

idd/LGIdd/transport/CTransportManager.cpp

@@ -21,6 +21,7 @@
 #include "transport/CTransportManager.h"
 
 #include "CDebug.h"
+#include "Seq.h"
 
 #include <Windows.h>
 #include <new>
@@ -737,9 +738,7 @@ void CTransportManager::RetryEntry(Entry& entry, uint64_t now,
     entry.inputAbsent   = false;
     entry.frameAbsent   = false;
     entry.serviceRetryAt = 0;
-    ++entry.epoch;
+    Seq::Inc(entry.epoch);
-    if (!entry.epoch)
-      ++entry.epoch;
   }
 
   if (OpenEntry(entry) != OpenResult::SUCCESS)

idd/LGIdd/transport/lgmp/CLGMPInputTransport.cpp

@@ -23,6 +23,7 @@
 #include "transport/lgmp/CLGMPHost.h"
 #include "CDebug.h"
 #include "CSRWLock.h"
+#include "Seq.h"
 
 #include "common/KVMFRInput.h"
 #include "common/LGMPConfig.h"
@@ -136,8 +137,7 @@ void CLGMPInputTransport::UpdateTargetState(
 
   if (state.state != m_targetState.state)
   {
-    if (++m_endpointGeneration == 0)
+    Seq::Inc(m_endpointGeneration);
-      ++m_endpointGeneration;
   }
   m_targetState = state;
   m_statusDirty = true;
@@ -183,9 +183,7 @@ bool CLGMPInputTransport::PublishStatus()
   status.maxButtons = KVMFR_INPUT_MOUSE_BUTTON_COUNT;
   memcpy(lgmpHostMemPtr(memory), &status, sizeof(status));
 
-  uint32_t serial = m_statusSerial + 1;
+  const uint32_t serial = Seq::Next(m_statusSerial);
-  if (!serial)
-    ++serial;
   const LGMP_STATUS result = lgmpHostQueuePost(m_queue, serial, memory);
   if (result == LGMP_OK)
   {
@@ -263,8 +261,7 @@ bool CLGMPInputTransport::Start(IInputTarget& target)
   {
     CSRWExclusiveLock statusLock(m_statusLock);
     m_targetState = target.GetState({});
-    if (++m_endpointGeneration == 0)
+    Seq::Inc(m_endpointGeneration);
-      ++m_endpointGeneration;
     m_statusDirty = true;
   }
   m_statusFailed.store(false, std::memory_order_release);
@@ -505,9 +502,7 @@ bool CLGMPInputTransport::ProcessMessage(
     return true;
   }
 
-  uint32_t expectedSequence = m_ownerSequence + 1;
+  const uint32_t expectedSequence = Seq::Next(m_ownerSequence);
-  if (!expectedSequence)
-    expectedSequence = 1;
   if (message.sequence != expectedSequence)
   {
     ++m_statistics.sequenceErrors;