MachMessageDeadline WIP

util/mach/mach_message.h

+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_MACH_MACH_MESSAGE_H_
+#define CRASHPAD_UTIL_MACH_MACH_MESSAGE_H_
+
+#include <mach/mach.h>
+#include <stdint.h>
+
+#include <limits>
+
+namespace crashpad {
+
+//! \brief The time before which a MachMessageWithDeadline() call should
+//!     complete.
+//!
+//! A value of this type may be one of the special constants
+//! #kMachMessageNonblocking or #kMachMessageWaitIndefinitely. Any other values
+//! should be produced by calling MachMessageDeadlineFromTimeout().
+//!
+//! Internally, these are currently specified on the same time base as
+//! ClockMonotonicNanoseconds(), although this is an implementation detail.
+using MachMessageDeadline = uint64_t;
+
+//! \brief Special constants used as \ref MachMessageDeadline values.
+enum : MachMessageDeadline {
+  //! \brief MachMessageWithDeadline() should not block at all in its operation.
+  kMachMessageNonblocking = 0,
+
+  //! \brief MachMessageWithDeadline() should wait indefinitely for the
+  //!     requested operation to complete.
+  kMachMessageWaitIndefinitely =
+      std::numeric_limits<MachMessageDeadline>::max(),
+};
+
+//! \brief Computes the deadline for a specified timeout value.
+//!
+//! While deadlines exist on an absolute time scale, timeouts are relative. This
+//! function calculates the deadline as \a timeout_ms milliseconds after it
+//! executes.
+//!
+//! If \a timeout_ms is `0`, this function will return #kMachMessageNonblocking.
+MachMessageDeadline MachMessageDeadlineFromTimeout(
+    mach_msg_timeout_t timeout_ms);
+
+//! \brief Runs `mach_msg()` with a deadline, as opposed to a timeout.
+//!
+//! This function is similar to `mach_msg()`, with the following differences:
+//!  - The `timeout` parameter has been replaced by \a deadline. The deadline
+//!    applies uniformly to a call that is requested to both send and receive
+//!    a message.
+//!  - The `MACH_SEND_TIMEOUT` and `MACH_RCV_TIMEOUT` bits in \a options are
+//!    not used. Timeouts are specified by the \a deadline argument.
+//!  - The `send_size` parameter has been removed. Its value is implied by
+//!    \a message when \a options contains `MACH_SEND_MSG`.
+//!  - The \a run_even_if_expired parameter has been added.
+//!
+//! Like the `mach_msg()` wrapper in `libsyscall`, this function will retry
+//! operations when experiencing `MACH_SEND_INTERRUPTED` and
+//! `MACH_RCV_INTERRUPTED`, unless \a options contains `MACH_SEND_INTERRUPT` or
+//! `MACH_RCV_INTERRUPT`. Unlike `mach_msg()`, which restarts the call with the
+//! full timeout when this occurs, this function continues enforcing the
+//! user-specified \a deadline.
+//!
+//! Except as noted, the parameters and return value are identical to those of
+//! `mach_msg()`.
+//!
+//! \param[in] deadline The time by which this call should complete. If the
+//!     deadline is exceeded, this call will return `MACH_SEND_TIMED_OUT` or
+//!     `MACH_RCV_TIMED_OUT`.
+//! \param[in] run_even_if_expired If `true`, a deadline that is expired when
+//!     this function is called will be treated as though a deadline of
+//!     #kMachMessageNonblocking had been specified. When `false`, an expired
+//!     deadline will result in a `MACH_SEND_TIMED_OUT` or `MACH_RCV_TIMED_OUT`
+//!     return value, even if the deadline is already expired when the function
+//!     is called.
+mach_msg_return_t MachMessageWithDeadline(mach_msg_header_t* message,
+                                          mach_msg_option_t options,
+                                          mach_msg_size_t receive_size,
+                                          mach_port_name_t receive_port,
+                                          MachMessageDeadline deadline,
+                                          mach_port_name_t notify_port,
+                                          bool run_even_if_expired);
+
+//! \brief Initializes a reply message for a MIG server routine based on its
+//!     corresponding request.
+//!
+//! If a request is handled by a server routine, it may be necessary to revise
+//! some of the fields set by this function, such as `msgh_size` and any fields
+//! defined in a routine’s reply structure type.
+//!
+//! \param[in] in_header The request message to base the reply on.
+//! \param[out] out_header The reply message to initialize. \a out_header will
+//!     be treated as a `mig_reply_error_t*` and all of its fields will be set
+//!     except for `RetCode`, which must be set by SetMIGReplyError(). This
+//!     argument is accepted as a `mach_msg_header_t*` instead of a
+//!     `mig_reply_error_t*` because that is the type that callers are expected
+//!     to possess in the C API.
+void PrepareMIGReplyFromRequest(const mach_msg_header_t* in_header,
+                                mach_msg_header_t* out_header);
+
+//! \brief Sets the error code in a reply message for a MIG server routine.
+//!
+//! \param[inout] out_header The reply message to operate on. \a out_header will
+//!     be treated as a `mig_reply_error_t*` and its `RetCode` field will be
+//!     set. This argument is accepted as a `mach_msg_header_t*` instead of a
+//!     `mig_reply_error_t*` because that is the type that callers are expected
+//!     to possess in the C API.
+//! \param[in] error The error code to store in \a out_header.
+//!
+//! \sa PrepareMIGReplyFromRequest()
+void SetMIGReplyError(mach_msg_header_t* out_header, kern_return_t error);
+
+//! \brief Returns a Mach message trailer for a message that has been received.
+//!
+//! This function must only be called on Mach messages that have been received
+//! via the Mach messaging interface, such as `mach_msg()`. Messages constructed
+//! for sending do not contain trailers.
+//!
+//! \param[in] header A pointer to a received Mach message.
+//!
+//! \return A pointer to the trailer following the received Mach message’s body.
+//!     The contents of the trailer depend on the options provided to
+//!     `mach_msg()` or a similar function when the message was received.
+const mach_msg_trailer_t* MachMessageTrailerFromHeader(
+    const mach_msg_header_t* header);
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_MACH_MACH_MESSAGE_H_