Question

我正在尝试将以下代码转换为Swift：

{
    // Set up the variables
    double totalUsedMemory = 0.00;
    mach_port_t host_port;
    mach_msg_type_number_t host_size;
    vm_size_t pagesize;

    // Get the variable values
    host_port = mach_host_self();
    host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
    host_page_size(host_port, &pagesize);

    vm_statistics_data_t vm_stat;

    // Check for any system errors
    if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS) {
        // Error, failed to get Virtual memory info
        return -1;
    }

    // Memory statistics in bytes
    natural_t usedMemory = (natural_t)((vm_stat.active_count +
                            vm_stat.inactive_count +
                            vm_stat.wire_count) * pagesize);
    natural_t allMemory = [self totalMemory];


    return usedMemory;
}

我的Swift代码是：

{
    // Set up the variables
    var totalUsedMemory: Double = 0.00
    var host_port: mach_port_t
    var host_size: mach_msg_type_number_t
    var pagesize:vm_size_t

    // Get the variable values
     host_port = mach_host_self()

    host_size = mach_msg_type_number_t(MemoryLayout<vm_statistics_data_t>.stride / MemoryLayout<integer_t>.stride)

    //                host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
    host_page_size(host_port, &pagesize);

    var vm_stat: vm_statistics_data_t ;

    // Check for any system errors
    if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS) {
        // Error, failed to get Virtual memory info
        return -1;
    }
    // Memory statistics in bytes
    var usedMemory: Int64  = (Int64)((vm_stat.active_count + vm_stat.inactive_count + vm_stat.wire_count) * pagesize);

    return usedMemory;
}

我收到了这两个错误：

**二元运算符'＆amp;'不能应用于'（host_info_t）.Type'（又名'UnsafeMutablePointer.Type'）和'vm_statistics_data_t'（又名'vm_statistics'）
类型的操作数

在此声明中 host_statistics（host_port，HOST_VM_INFO，（host_info_t）＆amp; vm_stat，＆amp; host_size）

和

二进制运算符'*'不能应用于'UInt32'和'vm_size_t'类型的操作数（又名'UInt'）**

在此声明中 - var usedMemory：Int64 =（Int64）（（vm_stat.active_count + vm_stat.inactive_count + vm_stat.wire_count）* pagesize）;

Answer 1

对于指针类型，Swift比C更严格，这使得与这样的函数交互成为一种真正的痛苦，这些函数希望你将指针传递给除了你所依据的事物的实际类型以外的类型。试图传递给函数。所以我同意评论者的意见，你可能最好将这个功能留在（Objective-）C中。但是，如果您绝对转换为Swift，那么您可能需要执行以下操作：

// Initialize a blank vm_statistics_data_t
var vm_stat = vm_statistics_data_t()

// Get a raw pointer to vm_stat
let err: kern_return_t = withUnsafeMutableBytes(of: &vm_stat) {
    // Bind the raw buffer to Int32, since that's what host_statistics
    // seems to want a pointer to.
    let boundBuffer = $0.bindMemory(to: Int32.self)

    // Call host_statistics, and return its status out of the closure.
    return host_statistics(host_port, HOST_VM_INFO, boundBuffer.baseAddress, &host_size)
}

// Now take a look at what we got and compare it against KERN_SUCCESS
if err != KERN_SUCCESS {
    // Error, failed to get Virtual memory info
    return -1;
}

快速转换的C代码

1 个答案: