libsyscall/os/proc.h

   1 /*
   2  * Copyright (c) 2019 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
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   6  * This file contains Original Code and/or Modifications of Original Code
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   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
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  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
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  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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  23  * Please see the License for the specific language governing rights and
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  27  */
  28
  29 #ifndef __OS_PROC__
  30 #define __OS_PROC__
  31
  32 #include <stddef.h>
  33 #include <sys/cdefs.h>
  34 #include <os/availability.h>
  35
  36 /*!
  37  * @header
  38  *
  39  * @preprocinfo
  40  * This is for functions that operate on the calling process alone.
  41  */
  42
  43 __BEGIN_DECLS
  44
  45 /*!
  46  * @function os_proc_available_memory
  47  *
  48  * @abstract
  49  * Return the number of bytes remaining, at the time of the call, before the
  50  * current process will hit its current dirty memory limit.
  51  *
  52  * @discussion
  53  * Developers can query this value efficiently whenever it is needed. The return
  54  * value is only a snapshot at the time of the call. Caching the result is not
  55  * advised. The result may be instantaneously invalidated by actions taken in
  56  * another thread or another framework.
  57  *
  58  * Memory limits can change during the app life cycle. Make sure to check accordingly.
  59  *
  60  * The size returned is not representative of the total memory of the device, it
  61  * is the current dirty memory limit minus the dirty memory footprint used at the
  62  * time of the query.
  63  *
  64  * This interface allows an app to efficiently consume all available memory resources.
  65  * Significant memory use, even under the current memory limit, may still cause
  66  * system-wide performance including the termination of other apps and system
  67  * processes. Take care to use the minimum amount of memory needed to satisfy the
  68  * user’s need.
  69  *
  70  * If you need more information than just the available memory, you can use task_info().
  71  * The information returned is equivalent to the task_vm_info.limit_bytes_remaining
  72  * field. task_info() is a more expensive call, and will return information such
  73  * as your phys_footprint, which is used to calculate the return of this function.
  74  *
  75  * Dirty memory contains data that must be kept in RAM (or the equivalent) even
  76  * when unused. It is memory that has been modified.
  77  *
  78  * @param none
  79  *
  80  * @result
  81  * The remaining bytes. 0 is returned if the calling process is not an app, or
  82  * the calling process exceeds its memory limit.
  83  */
  84
  85     API_UNAVAILABLE(macos) API_AVAILABLE(ios(13.0), tvos(13.0), watchos(6.0), bridgeos(4.0))
  86 extern
  87 size_t os_proc_available_memory(void);
  88
  89 __END_DECLS
  90
  91 #endif