快速的C数组内存释放 [英] C array memory deallocation from swift

问题描述

var cpuInfo: processor_info_array_t = nil
var numCpuInfo: mach_msg_type_number_t = 0
var coresTotalUsage: Float = 0.0
var numCPUsU: natural_t = 0
let err = host_processor_info(mach_host_self(), PROCESSOR_CPU_LOAD_INFO, &numCPUsU, &cpuInfo, &numCpuInfo);
assert(err == KERN_SUCCESS, "Failed call to host_processor_info")

我正在调用上面的C API host_processor_info来从swift快速获取进程负载信息，那里没有问题. cpuInfo是一个inout参数(指针)，返回时将指向包含该API分配的CPU信息的结构. 调用方负责分配内存；我可以很容易地从目标C做到这一点，但是没有任何运气.我知道我可以将该调用包装到目标C扩展中，但是我正在尝试快速学习，并且在可能的情况下，希望避免使用obj-c解决方案.

Hi, I am calling the above C API host_processor_info to get process load informations from swift, no problem there. cpuInfo is a inout parameter (pointer) that, on return, will point to a structure containing the CPU information allocated by that API. The caller is reponsible for deallocating the memory; I can do that easily from objective C but haven't had any luck in swift. I know I could wrap that call into an objective C extension but I'm trying to learn swift and would like, if possible, avoid the obj-c solution.

在obj-c中，我将使用:

in obj-c I would deallocate with:

size_t cpuInfoSize = sizeof(integer_t) * numCpuInfo;
vm_deallocate(mach_task_self(), (vm_address_t) cpuInfo, cpuInfoSize)

swift中的cpuInfo是一个UnsafeMutablePointer，不能转换为vm_address_t.

cpuInfo in swift is an UnsafeMutablePointer not convertible into a vm_address_t.

任何帮助表示感谢，谢谢.

Any help appreciated, thanks.

推荐答案

processor_info_array_t是指针类型，而vm_address_t是整数类型 (最终是UInt的别名). (从<i386/vm_types.h>中的评论来看 这可能是出于历史原因.) 在Swift中将指针转换为整数(大小相同)的唯一方法是unsafeBitCast.

processor_info_array_t is a pointer type, and vm_address_t is an integer type (ultimately an alias for UInt). (Judging from the comments in <i386/vm_types.h> this might to be for historical reasons.) The only way to convert a pointer to an integer (of the same size) in Swift is unsafeBitCast.

mach_init.h定义

extern mach_port_t      mach_task_self_;
#define mach_task_self() mach_task_self_

只有extern变量在Swift中可见，在宏中不可见.

Only the extern variable is visible in Swift, not the macro.

这给出了:

let cpuInfoSize = vm_size_t(sizeof(integer_t)) * vm_size_t(numCpuInfo)
vm_deallocate(mach_task_self_, unsafeBitCast(cpuInfo, vm_address_t.self), cpuInfoSize)

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