swift - MACH_TASK_BASIC_INFO 的 Swift 指针问题

Question

我正在尝试将 ObjC stackoverflow 答案转换为 Swift 并失败。看起来我正在通过 a UnsafeMutablePointer<mach_msg_type_number_t>，而我应该通过 an inout mach_msg_type_number_t，但我似乎无法解决我的问题。根据我对 Swift 指针文档的理解（不多），这些应该是可以互换的..？

更多信息如下。

这是目标C：

struct task_basic_info info;
mach_msg_type_number_t size = sizeof(info);
kern_return_t kerr = task_info(mach_task_self(), TASK_BASIC_INFO, (task_info_t)&info, &size);

就我在 Swift 中得到的信息而言（多行以便于类型检查）

let name: task_name_t = mach_task_self_
let flavor: task_flavor_t = task_flavor_t(MACH_TASK_BASIC_INFO)
var info: mach_task_basic_info
var size: mach_msg_type_number_t = UnsignedFixed(sizeof(mach_task_basic_info_t))
let kerr = task_info(name, flavor, info as task_info_t, &size)

task_info签名是：

func task_info(target_task: task_name_t, flavor: task_flavor_t, task_info_out: task_info_t, task_info_outCnt: UnsafeMutablePointer<mach_msg_type_number_t>) -> kern_return_t

最后一行的错误是：

Cannot convert the expression's type '(@!lvalue task_name_t, task_flavor_t, task_info_t, inout mach_msg_type_number_t)' to type 'kern_return_t'

score 40 · Accepted Answer

花了我一点时间来更新 Airspeed Velocity 对最新 swift 语法（Swift 3，beta 6）的回答，但这是我得到的：

func report_memory() {
    var info = mach_task_basic_info()
    let MACH_TASK_BASIC_INFO_COUNT = MemoryLayout<mach_task_basic_info>.stride/MemoryLayout<natural_t>.stride
    var count = mach_msg_type_number_t(MACH_TASK_BASIC_INFO_COUNT)

    let kerr: kern_return_t = withUnsafeMutablePointer(to: &info) {
        $0.withMemoryRebound(to: integer_t.self, capacity: MACH_TASK_BASIC_INFO_COUNT) {
            task_info(mach_task_self_,
                      task_flavor_t(MACH_TASK_BASIC_INFO),
                      $0,
                      &count)
        }
    }

    if kerr == KERN_SUCCESS {
        print("Memory in use (in bytes): \(info.resident_size)")
    }
    else {
        print("Error with task_info(): " +
            (String(cString: mach_error_string(kerr), encoding: String.Encoding.ascii) ?? "unknown error"))
    }
}

希望这会有所帮助。

score 15 · Accepted Answer

与 C 函数交互时，您不能依赖编译器的错误消息 - 逐个参数分解它，单击命令直到您知道自己在使用什么。首先，您遇到的类型是：

task_name_t：UInt32
task_flavor_t：UInt32
task_info_t：UnsafeMutablePointer<Int32>
UnsafeMutablePointer<mach_msg_type_number_t>：UnsafeMutablePointer<UInt32>
kern_return_t-Int32

在这里，您的代码中有一个棘手的 Swift 位以及一个错误。首先，task_info_out参数需要是 a UnsafeMutablePointer<UInt32>，但需要实际指向的实例mach_task_basic_info。我们可以通过创建 aUnsafeMutablePointer<mach_task_basic_info>并在调用时将其包装在另一个 UnsafeMutablePointer中来解决这个问题——编译器将使用类型推断来知道我们希望将包装指针子类型化为UInt32.

其次，当您应该调用时，您正在调用sizeof(mach_task_basic_info_t)（指向的指针），因此您的字节数最终太低而无法容纳数据结构。mach_task_basic_infosizeinfo(mach_task_basic_info)

在进一步的研究中，这变得有点复杂。原来的代码是不正确的，size应该初始化为常量MACH_TASK_BASIC_INFO_COUNT。不幸的是，这是一个宏，而不是一个简单的常量：

#define MACH_TASK_BASIC_INFO_COUNT (sizeof(mach_task_basic_info_data_t) / sizeof(natural_t))

Swift 不导入这些，所以我们需要自己重新定义它。这是所有这些的工作代码：

// constant
let MACH_TASK_BASIC_INFO_COUNT = (sizeof(mach_task_basic_info_data_t) / sizeof(natural_t))

// prepare parameters
let name   = mach_task_self_
let flavor = task_flavor_t(MACH_TASK_BASIC_INFO)
var size   = mach_msg_type_number_t(MACH_TASK_BASIC_INFO_COUNT)

// allocate pointer to mach_task_basic_info
var infoPointer = UnsafeMutablePointer<mach_task_basic_info>.alloc(1)

// call task_info - note extra UnsafeMutablePointer(...) call
let kerr = task_info(name, flavor, UnsafeMutablePointer(infoPointer), &size)

// get mach_task_basic_info struct out of pointer
let info = infoPointer.move()

// deallocate pointer
infoPointer.dealloc(1)

// check return value for success / failure
if kerr == KERN_SUCCESS {
    println("Memory in use (in bytes): \(info.resident_size)")
} else {
    let errorString = String(CString: mach_error_string(kerr), encoding: NSASCIIStringEncoding)
    println(errorString ?? "Error: couldn't parse error string")
}

score 11 · Accepted Answer

Nate 的回答非常好，但是您可以进行一些调整来简化它。

task_basic_info首先，您可以在堆栈上创建结构，然后使用withUnsafeMutablePointer直接获取指向它的指针，而不是分配/释放指针，您可以将其传入。

func report_memory() {
    var info = mach_task_basic_info()
    var count = mach_msg_type_number_t(sizeofValue(info))/4

    let kerr: kern_return_t = withUnsafeMutablePointer(&info) {

        task_info(mach_task_self_,
            task_flavor_t(MACH_TASK_BASIC_INFO),
            task_info_t($0),
            &count)

    }

    if kerr == KERN_SUCCESS {
        println("Memory in use (in bytes): \(info.resident_size)")
    }
    else {
        println("Error with task_info(): " +
            (String.fromCString(mach_error_string(kerr)) ?? "unknown error"))
    }
}

score 10 · Accepted Answer

要在 Swift 5 中快速复制和粘贴解决方案，请使用

func reportMemory() {
    var taskInfo = task_vm_info_data_t()
    var count = mach_msg_type_number_t(MemoryLayout<task_vm_info>.size) / 4
    let result: kern_return_t = withUnsafeMutablePointer(to: &taskInfo) {
        $0.withMemoryRebound(to: integer_t.self, capacity: 1) {
            task_info(mach_task_self_, task_flavor_t(TASK_VM_INFO), $0, &count)
        }
    }
    let usedMb = Float(taskInfo.phys_footprint) / 1048576.0
    let totalMb = Float(ProcessInfo.processInfo.physicalMemory) / 1048576.0
    result != KERN_SUCCESS ? print("Memory used: ? of \(totalMb)") : print("Memory used: \(usedMb) of \(totalMb)")
}

score 4 · Accepted Answer

Airspeed Velocity 在 Swift 3 中的回答...

func GetMemory()
{
    var info = mach_task_basic_info()
    var count = mach_msg_type_number_t(MemoryLayout.size(ofValue: info))/4

    let kerr: kern_return_t = withUnsafeMutablePointer(to: &info)
    {

        task_info(mach_task_self_,
                  task_flavor_t(MACH_TASK_BASIC_INFO),
                  $0.withMemoryRebound(to: Int32.self, capacity: 1) { zeroPtr in
                    task_info_t(zeroPtr)
                  },
                  &count)

    }

    if kerr == KERN_SUCCESS {
        print("Memory in use (in bytes): \(info.resident_size)")
    }
    else {
        print("Error with task_info(): " +
            (String.init(validatingUTF8: mach_error_string(kerr)) ?? "unknown error"))
    }
}

score 4 · Accepted Answer

Swift 5 + Combine，连续内存监控

以 MB 为单位显示确切的内存，如 XCODE

import Foundation
import Combine

 enum MemoryMonitorState {
    case started
    case paused
}


class MemoryUsageCustom {
    
    private var displayLink: CADisplayLink!

    var state = MemoryMonitorState.paused
    
    let subject = PassthroughSubject<String, Never>()

    
    private static var sharedInstance: MemoryUsageCustom!
    
    public class func shared() -> MemoryUsageCustom {
        if self.sharedInstance == nil {
            self.sharedInstance = MemoryUsageCustom()
        }
        return self.sharedInstance
    }
    
    private init() {
        self.configureDisplayLink()

    }
    
    func startMemoryMonitor() {
        
        if self.state == .started {
            return
        }
        
        self.state = .started
        self.start()
    }
    
    func stopMemoryMonitor() {
        self.state = .paused
        self.pause()
    }
    

    //--------------------------------------------------------------------------------
    
    //MARK:- Display Link
    
    //--------------------------------------------------------------------------------

 
    func configureDisplayLink() {
        self.displayLink = CADisplayLink(target: self, selector: #selector(displayLinkAction(displayLink:)))
        self.displayLink.isPaused = true
        self.displayLink?.add(to: .current, forMode: .common)
    }
    
    private func start() {
        self.displayLink?.isPaused = false
    }
    
    /// Pauses performance monitoring.
    private func pause() {
        self.displayLink?.isPaused = true
    }
    
    @objc func displayLinkAction(displayLink: CADisplayLink) {
        let memoryUsage = self.memoryUsage()
        
        let bytesInMegabyte = 1024.0 * 1024.0
        let usedMemory = Double(memoryUsage.used) / bytesInMegabyte
        let totalMemory = Double(memoryUsage.total) / bytesInMegabyte
        let memory = String(format: "%.1f of %.0f MB used", usedMemory, totalMemory)

     //   self.memoryString = memory
        subject.send(memory)
    }
    
    func memoryUsage() -> (used: UInt64, total: UInt64) {
        var taskInfo = task_vm_info_data_t()
        var count = mach_msg_type_number_t(MemoryLayout<task_vm_info>.size) / 4
        let result: kern_return_t = withUnsafeMutablePointer(to: &taskInfo) {
            $0.withMemoryRebound(to: integer_t.self, capacity: 1) {
                task_info(mach_task_self_, task_flavor_t(TASK_VM_INFO), $0, &count)
            }
        }
        
        var used: UInt64 = 0
        if result == KERN_SUCCESS {
            used = UInt64(taskInfo.phys_footprint)
        }
        
        let total = ProcessInfo.processInfo.physicalMemory
        return (used, total)
    }

}

如何使用

   //Start Monitoring 
    MemoryUsageCustom.shared().startMemoryMonitor()

var storage = Set<AnyCancellable>()

    MemoryUsageCustom.shared().subject.sink {[weak self] (string) in
        print(string)

    }.store(in: &storage)

swift - MACH_TASK_BASIC_INFO 的 Swift 指针问题

6 回答 6

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