Move mojo::{Wait,WaitMany}() to (the newly-added) mojo/public/cpp/system/wait.h.

mojo/public/cpp/system/wait.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MOJO_PUBLIC_CPP_SYSTEM_WAIT_H_
+#define MOJO_PUBLIC_CPP_SYSTEM_WAIT_H_
+
+#include <stdint.h>
+
+#include <cstddef>
+
+#include "mojo/public/c/system/handle.h"
+#include "mojo/public/c/system/result.h"
+#include "mojo/public/c/system/time.h"
+#include "mojo/public/c/system/wait.h"
+#include "mojo/public/cpp/system/handle.h"
+
+namespace mojo {
+
+inline MojoResult Wait(Handle handle,
+                       MojoHandleSignals signals,
+                       MojoDeadline deadline,
+                       MojoHandleSignalsState* signals_state) {
+  return MojoWait(handle.value(), signals, deadline, signals_state);
+}
+
+const uint32_t kInvalidWaitManyIndexValue = static_cast<uint32_t>(-1);
+
+// Simplify the interpretation of the output from |MojoWaitMany()|.
+struct WaitManyResult {
+  explicit WaitManyResult(MojoResult mojo_wait_many_result)
+      : result(mojo_wait_many_result), index(kInvalidWaitManyIndexValue) {}
+
+  WaitManyResult(MojoResult mojo_wait_many_result, uint32_t result_index)
+      : result(mojo_wait_many_result), index(result_index) {}
+
+  // A valid handle index is always returned if |WaitMany()| succeeds, but may
+  // or may not be returned if |WaitMany()| returns an error. Use this helper
+  // function to check if |index| is a valid index into the handle array.
+  bool IsIndexValid() const { return index != kInvalidWaitManyIndexValue; }
+
+  // The |signals_states| array is always returned by |WaitMany()| on success,
+  // but may or may not be returned if |WaitMany()| returns an error. Use this
+  // helper function to check if |signals_states| holds valid data.
+  bool AreSignalsStatesValid() const {
+    return result != MOJO_RESULT_INVALID_ARGUMENT &&
+           result != MOJO_RESULT_RESOURCE_EXHAUSTED;
+  }
+
+  MojoResult result;
+  uint32_t index;
+};
+
+// |HandleVectorType| and |FlagsVectorType| should be similar enough to
+// |std::vector<Handle>| and |std::vector<MojoHandleSignals>|, respectively:
+//  - They should have a (const) |size()| method that returns an unsigned type.
+//  - They must provide contiguous storage, with access via (const) reference to
+//    that storage provided by a (const) |operator[]()| (by reference).
+template <class HandleVectorType,
+          class FlagsVectorType,
+          class SignalsStateVectorType>
+inline WaitManyResult WaitMany(const HandleVectorType& handles,
+                               const FlagsVectorType& signals,
+                               MojoDeadline deadline,
+                               SignalsStateVectorType* signals_states) {
+  if (signals.size() != handles.size() ||
+      (signals_states && signals_states->size() != signals.size()))
+    return WaitManyResult(MOJO_RESULT_INVALID_ARGUMENT);
+  if (handles.size() >= kInvalidWaitManyIndexValue)
+    return WaitManyResult(MOJO_RESULT_RESOURCE_EXHAUSTED);
+
+  if (handles.size() == 0) {
+    return WaitManyResult(
+        MojoWaitMany(nullptr, nullptr, 0, deadline, nullptr, nullptr));
+  }
+
+  uint32_t result_index = kInvalidWaitManyIndexValue;
+  const Handle& first_handle = handles[0];
+  const MojoHandleSignals& first_signals = signals[0];
+  MojoHandleSignalsState* first_state =
+      signals_states ? &(*signals_states)[0] : nullptr;
+  MojoResult result =
+      MojoWaitMany(reinterpret_cast<const MojoHandle*>(&first_handle),
+                   &first_signals, static_cast<uint32_t>(handles.size()),
+                   deadline, &result_index, first_state);
+  return WaitManyResult(result, result_index);
+}
+
+// C++ 4.10, regarding pointer conversion, says that an integral null pointer
+// constant can be converted to |std::nullptr_t|. The opposite direction is not
+// allowed.
+template <class HandleVectorType, class FlagsVectorType>
+inline WaitManyResult WaitMany(const HandleVectorType& handles,
+                               const FlagsVectorType& signals,
+                               MojoDeadline deadline,
+                               std::nullptr_t signals_states) {
+  if (signals.size() != handles.size())
+    return WaitManyResult(MOJO_RESULT_INVALID_ARGUMENT);
+  if (handles.size() >= kInvalidWaitManyIndexValue)
+    return WaitManyResult(MOJO_RESULT_RESOURCE_EXHAUSTED);
+
+  if (handles.size() == 0) {
+    return WaitManyResult(
+        MojoWaitMany(nullptr, nullptr, 0, deadline, nullptr, nullptr));
+  }
+
+  uint32_t result_index = kInvalidWaitManyIndexValue;
+  const Handle& first_handle = handles[0];
+  const MojoHandleSignals& first_signals = signals[0];
+  MojoResult result = MojoWaitMany(
+      reinterpret_cast<const MojoHandle*>(&first_handle), &first_signals,
+      static_cast<uint32_t>(handles.size()), deadline, &result_index, nullptr);
+  return WaitManyResult(result, result_index);
+}
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_SYSTEM_WAIT_H_