Revert of Mojo: Armed Watchers

mojo/public/c/system/watcher.h

Index: mojo/public/c/system/watcher.h
diff --git a/mojo/public/c/system/watcher.h b/mojo/public/c/system/watcher.h
deleted file mode 100644
index f152c50a11cf91578d08a1bcd6649f8d0769410b..0000000000000000000000000000000000000000
--- a/mojo/public/c/system/watcher.h
+++ /dev/null
@@ -1,183 +0,0 @@
-// Copyright 2017 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_C_SYSTEM_WATCHER_H_
-#define MOJO_PUBLIC_C_SYSTEM_WATCHER_H_
-
-#include <stdint.h>
-
-#include "mojo/public/c/system/system_export.h"
-#include "mojo/public/c/system/types.h"
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-// A callback used to notify watchers about events on their watched handles.
-//
-// See documentation for |MojoWatcherNotificationFlags| for details regarding
-// the possible values of |flags|.
-//
-// See documentation for |MojoWatch()| for details regarding the other arguments
-// this callback receives when called.
-typedef void (*MojoWatcherCallback)(uintptr_t context,
-                                    MojoResult result,
-                                    struct MojoHandleSignalsState signals_state,
-                                    MojoWatcherNotificationFlags flags);
-
-// Creates a new watcher.
-//
-// Watchers are used to trigger arbitrary code execution when one or more
-// handles change state to meet certain conditions.
-//
-// A newly registered watcher is initially disarmed and may be armed using
-// |MojoArmWatcher()|. A watcher is also always disarmed immediately before any
-// invocation of one or more notification callbacks in response to a single
-// handle's state changing in some relevant way.
-//
-// Parameters:
-//   |callback|: The |MojoWatcherCallback| to invoke any time the watcher is
-//       notified of an event. See |MojoWatch()| for details regarding arguments
-//       passed to the callback. Note that this may be called from any arbitrary
-//       thread.
-//   |watcher_handle|: The address at which to store the MojoHandle
-//       corresponding to the new watcher if successfully created.
-//
-// Returns:
-//   |MOJO_RESULT_OK| if the watcher has been successfully created.
-//   |MOJO_RESULT_RESOURCE_EXHAUSTED| if a handle could not be allocated for
-//       this watcher.
-MOJO_SYSTEM_EXPORT MojoResult MojoCreateWatcher(MojoWatcherCallback callback,
-                                                MojoHandle* watcher_handle);
-
-// Adds a watch to a watcher. This allows the watcher to fire notifications
-// regarding state changes on the handle corresponding to the arguments given.
-//
-// Note that notifications for a given watch context are guaranteed to be
-// mutually exclusive in execution: the callback will never be entered for a
-// given context while another invocation of the callback is still executing for
-// the same context. As a result it is generally a good idea to ensure that
-// callbacks do as little work as necessary in order to process the
-// notification.
-//
-// Parameters:
-//   |watcher_handle|: The watcher to which |handle| is to be added.
-//   |handle|: The handle to add to the watcher.
-//   |signals|: The signals to watch for on |handle|.
-//   |context|: An arbitrary context value given to any invocation of the
-//       watcher's callback when invoked as a result of some state change
-//       relevant to this combination of |handle| and |signals|. Must be
-//       unique within any given watcher.
-//
-// Callback parameters (see |MojoWatcherNotificationCallback| above):
-//   When the watcher invokes its callback as a result of some notification
-//   relevant to this watch operation, |context| receives the value given here
-//   and |signals_state| receives the last known signals state of this handle.
-//
-//   |result| is one of the following:
-//     |MOJO_RESULT_OK| if at least one of the watched signals is satisfied. The
-//         watcher must be armed for this notification to fire.
-//     |MOJO_RESULT_FAILED_PRECONDITION| if all of the watched signals are
-//         permanently unsatisfiable. The watcher must be armed for this
-//         notification to fire.
-//     |MOJO_RESULT_CANCELLED| if the watch has been cancelled. The may occur if
-//         the watcher has been closed, the watched handle has been closed, or
-//         the watch for |context| has been explicitly cancelled. This is always
-//         the last result received for any given context, and it is guaranteed
-//         to be received exactly once per watch, regardless of how the watch
-//         was cancelled.
-//
-// Returns:
-//   |MOJO_RESULT_OK| if the handle is now being watched by the watcher.
-//   |MOJO_RESULT_INVALID_ARGUMENT| if |watcher_handle| is not a watcher handle,
-//       |handle| is not a valid message pipe or data pipe handle.
-//   |MOJO_RESULT_ALREADY_EXISTS| if the watcher already has a watch registered
-//       for the given value of |context| or for the given |handle|.
-MOJO_SYSTEM_EXPORT MojoResult MojoWatch(MojoHandle watcher_handle,
-                                        MojoHandle handle,
-                                        MojoHandleSignals signals,
-                                        uintptr_t context);
-
-// Removes a watch from a watcher.
-//
-// This ensures that the watch is cancelled as soon as possible. Cancellation
-// may be deferred (or may even block) an aritrarily long time if the watch is
-// already dispatching one or more notifications.
-//
-// When cancellation is complete, the watcher's callback is invoked one final
-// time for |context|, with the result |MOJO_RESULT_CANCELLED|.
-//
-// The same behavior can be elicted by either closing the watched handle
-// associated with this context, or by closing |watcher_handle| itself. In the
-// lastter case, all registered contexts on the watcher are implicitly cancelled
-// in a similar fashion.
-//
-// Parameters:
-//   |watcher_handle|: The handle of the watcher from which to remove a watch.
-//   |context|: The context of the watch to be removed.
-//
-// Returns:
-//   |MOJO_RESULT_OK| if the watch has been cancelled.
-//   |MOJO_RESULT_INVALID_ARGUMENT| if |watcher_handle| is not a watcher handle.
-//   |MOJO_RESULT_NOT_FOUND| if there is no watch registered on this watcher for
-//       the given value of |context|.
-MOJO_SYSTEM_EXPORT MojoResult MojoCancelWatch(MojoHandle watcher_handle,
-                                              uintptr_t context);
-
-// Arms a watcher, enabling a single future event on one of the watched handles
-// to trigger a single notification for each relevant watch context associated
-// with that handle.
-//
-// Parameters:
-//   |watcher_handle|: The handle of the watcher.
-//   |num_ready_contexts|: An address pointing to the number of elements
-//       available for storage in the remaining output buffers. Optional and
-//       only used on failure. See |MOJO_RESULT_FAILED_PRECONDITION| below for
-//       more details.
-//   |ready_contexts|: An output buffer for contexts corresponding to the
-//       watches which would have notified if the watcher were armed. Optional
-//       and only uesd on failure. See |MOJO_RESULT_FAILED_PRECONDITION| below
-//       for more details.
-//   |ready_results|: An output buffer for MojoResult values corresponding to
-//       each context in |ready_contexts|. Optional and only used on failure.
-//       See |MOJO_RESULT_FAILED_PRECONDITION| below for more details.
-//   |ready_signals_states|: An output buffer for |MojoHandleSignalsState|
-//       structures corresponding to each context in |ready_contexts|. Optional
-//       and only used on failure. See |MOJO_RESULT_FAILED_PRECONDITION| below
-//       for more details.
-//
-// Returns:
-//   |MOJO_RESULT_OK| if the watcher has been successfully armed. All arguments
-//       other than |watcher_handle| are ignored in this case.
-//   |MOJO_RESULT_NOT_FOUND| if the watcher does not have any registered watch
-//       contexts. All arguments other than |watcher_handle| are ignored in this
-//       case.
-//   |MOJO_RESULT_INVALID_ARGUMENT| if |watcher_handle| is not a valid watcher
-//       handle, or if |num_ready_contexts| is non-null but any of the output
-//       buffer paramters is null.
-//   |MOJO_RESULT_FAILED_PRECONDITION| if one or more watches would have
-//       notified immediately upon arming the watcher. If |num_handles| is
-//       non-null, this assumes there is enough space for |*num_handles| entries
-//       in each of the subsequent output buffer arguments.
-//
-//       At most that many entries are placed in the output buffers,
-//       corresponding to the watches which would have signalled if the watcher
-//       had been armed successfully. The actual number of entries placed in the
-//       output buffers is written to |*num_ready_contexts| before returning.
-//
-//       If more than (input) |*num_ready_contexts| watch contexts were ready to
-//       notify, the subset presented in output buffers is arbitrary and
-//       implementation-defined.
-MOJO_SYSTEM_EXPORT MojoResult
-MojoArmWatcher(MojoHandle watcher_handle,
-               uint32_t* num_ready_contexts,
-               uintptr_t* ready_contexts,
-               MojoResult* ready_results,
-               struct MojoHandleSignalsState* ready_signals_states);
-
-#ifdef __cplusplus
-}  // extern "C"
-#endif
-
-#endif  // MOJO_PUBLIC_C_SYSTEM_WATCHER_H_