[common] clipboard: define streamed clipboard ABIs

idd/LGCommon/CClipboardRing.cpp

@@ -0,0 +1,116 @@
+/**
+ * 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
+ */
+
+#include "CClipboardRing.h"
+
+#include "Atomic.h"
+
+#include <string.h>
+
+void CClipboardRing::Initialize(
+  ClipboardMapping& mapping, uint64_t epoch)
+{
+  memset(&mapping, 0, sizeof(mapping));
+  mapping.magic     = LG_CLIPBOARD_MAPPING_MAGIC;
+  mapping.version   = LG_CLIPBOARD_MAPPING_VERSION;
+  mapping.size      = sizeof(mapping);
+  mapping.slotBytes = KVMFR_CLIPBOARD_DATA_BYTES;
+  mapping.slotCount = KVMFR_CLIPBOARD_SLOT_COUNT;
+  mapping.epoch     = epoch;
+}
+
+bool CClipboardRing::Valid(
+  const ClipboardMapping& mapping, uint64_t epoch)
+{
+  if (mapping.magic     != LG_CLIPBOARD_MAPPING_MAGIC   ||
+      mapping.version   != LG_CLIPBOARD_MAPPING_VERSION ||
+      mapping.size      != sizeof(mapping)               ||
+      mapping.slotBytes != KVMFR_CLIPBOARD_DATA_BYTES    ||
+      mapping.slotCount != KVMFR_CLIPBOARD_SLOT_COUNT    ||
+      !mapping.epoch || mapping.epoch != epoch)
+    return false;
+
+  ClipboardRing& helper =
+    const_cast<ClipboardRing&>(mapping.helperToIdd);
+  ClipboardRing& idd =
+    const_cast<ClipboardRing&>(mapping.iddToHelper);
+  const uint32_t helperProduced = Atomic::Load(helper.produced);
+  const uint32_t helperConsumed = Atomic::Load(helper.consumed);
+  const uint32_t iddProduced    = Atomic::Load(idd.produced);
+  const uint32_t iddConsumed    = Atomic::Load(idd.consumed);
+  return helperProduced - helperConsumed <= KVMFR_CLIPBOARD_SLOT_COUNT &&
+    iddProduced - iddConsumed <= KVMFR_CLIPBOARD_SLOT_COUNT;
+}
+
+ClipboardRingSlot * CClipboardRing::BeginWrite(
+  ClipboardRing& ring, uint32_t& ticket)
+{
+  const uint32_t produced = Atomic::Load(ring.produced);
+  const uint32_t consumed = Atomic::Load(ring.consumed);
+  const uint32_t pending = produced - consumed;
+  if (pending >= KVMFR_CLIPBOARD_SLOT_COUNT)
+    return nullptr;
+
+  ticket = produced;
+  return &ring.slots[produced % KVMFR_CLIPBOARD_SLOT_COUNT];
+}
+
+bool CClipboardRing::EndWrite(ClipboardRing& ring, uint32_t ticket)
+{
+  if (Atomic::Load(ring.produced) != ticket)
+    return false;
+
+  Atomic::Fence();
+  Atomic::Store(ring.produced, ticket + 1U);
+  return true;
+}
+
+const ClipboardRingSlot * CClipboardRing::BeginRead(
+  ClipboardRing& ring, uint32_t& ticket)
+{
+  const uint32_t consumed = Atomic::Load(ring.consumed);
+  const uint32_t pending = Atomic::Load(ring.produced) - consumed;
+  if (!pending || pending > KVMFR_CLIPBOARD_SLOT_COUNT)
+    return nullptr;
+
+  Atomic::Fence();
+  ticket = consumed;
+  return &ring.slots[consumed % KVMFR_CLIPBOARD_SLOT_COUNT];
+}
+
+bool CClipboardRing::EndRead(ClipboardRing& ring, uint32_t ticket)
+{
+  if (Atomic::Load(ring.consumed) != ticket)
+    return false;
+
+  Atomic::Fence();
+  Atomic::Store(ring.consumed, ticket + 1U);
+  return true;
+}
+
+bool CClipboardRing::Valid(const ClipboardRingSlot& slot)
+{
+  return slot.header.version == KVMFR_CLIPBOARD_VERSION &&
+    slot.header.type >= KVMFR_CLIPBOARD_MESSAGE_CLAIM &&
+    slot.header.type <= KVMFR_CLIPBOARD_MESSAGE_GRANT &&
+    slot.header.length <= KVMFR_CLIPBOARD_DATA_BYTES &&
+    (slot.header.type == KVMFR_CLIPBOARD_MESSAGE_DATA ||
+      !slot.header.length);
+}