* Copyright (c) 2019 Apple Inc. All rights reserved.
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
* This is for functions that operate on the calling process alone.
* @function os_proc_available_memory
* Return the number of bytes remaining, at the time of the call, before the
* current process will hit its current dirty memory limit.
* Developers can query this value efficiently whenever it is needed. The return
* value is only a snapshot at the time of the call. Caching the result is not
* advised. The result may be instantaneously invalidated by actions taken in
* another thread or another framework.
* Memory limits can change during the app life cycle. Make sure to check accordingly.
* The size returned is not representative of the total memory of the device, it
* is the current dirty memory limit minus the dirty memory footprint used at the
* time of the query.
* This interface allows an app to efficiently consume all available memory resources.
* Significant memory use, even under the current memory limit, may still cause
* system-wide performance including the termination of other apps and system
* processes. Take care to use the minimum amount of memory needed to satisfy the
* user’s need.
* If you need more information than just the available memory, you can use task_info().
* The information returned is equivalent to the task_vm_info.limit_bytes_remaining
* field. task_info() is a more expensive call, and will return information such
* as your phys_footprint, which is used to calculate the return of this function.
* Dirty memory contains data that must be kept in RAM (or the equivalent) even
* when unused. It is memory that has been modified.
* @param none
* The remaining bytes. 0 is returned if the calling process is not an app, or
* the calling process exceeds its memory limit.
API_UNAVAILABLE(macos) API_AVAILABLE(ios(13.0), tvos(13.0), watchos(6.0), bridgeos(4.0))