Question

是否有定义iPhone OS中应用程序可用内存量的函数或常量？

我正在寻找一种独立于设备的方式（iPod touch，iPhone，iPad）来了解应用程序剩余的内存量。

Answer 1

此函数将以字节为单位返回可用内存：

#import <mach/mach.h> 
#import <mach/mach_host.h>

natural_t  freeMemory(void) {
    mach_port_t           host_port = mach_host_self();
    mach_msg_type_number_t   host_size = sizeof(vm_statistics_data_t) / sizeof(integer_t);
    vm_size_t               pagesize;
    vm_statistics_data_t     vm_stat;

    host_page_size(host_port, &pagesize);

    if (host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size) != KERN_SUCCESS) NSLog(@"Failed to fetch vm statistics");

    natural_t   mem_used = (vm_stat.active_count + vm_stat.inactive_count + vm_stat.wire_count) * pagesize;
    natural_t   mem_free = vm_stat.free_count * pagesize;
    natural_t   mem_total = mem_used + mem_free;

    return mem_free;
}

Answer 2

iPhone应用程序无法定义最大内存量。您的应用程序是否因内存不足而终止取决于操作系统使用的算法以及其他应用程序同时使用内存（safari，mail等）。

Answer 3

以下 swift 函数将以字节为单位返回系统可用内存（ram）。它会在失败时返回零。

func systemFreeMemorySize() -> UInt?
{
    let HOST_VM_INFO_COUNT: mach_msg_type_number_t = mach_msg_type_number_t(sizeof(vm_statistics_data_t) / sizeof(integer_t))

    let host: host_t = mach_host_self()

    var pageSize: vm_size_t = vm_size_t()
    let hostPageSizeKernStatus: kern_return_t = host_page_size(host, &pageSize)
    guard hostPageSizeKernStatus == KERN_SUCCESS else {
        NSLog("Error with host_page_size(): " + (String.fromCString(mach_error_string(hostPageSizeKernStatus)) ?? "unknown error"))
        return nil
    }

    var stats: vm_statistics_data_t = vm_statistics_data_t()
    var count: mach_msg_type_number_t = HOST_VM_INFO_COUNT

    let kernStatus: kern_return_t = withUnsafeMutablePointer(&stats) {
        return host_statistics(host, HOST_VM_INFO, host_info_t($0), &count)
    }

    guard kernStatus == KERN_SUCCESS else {
        NSLog("Error with host_statistics(): " + (String.fromCString(mach_error_string(kernStatus)) ?? "unknown error"))
        return nil
    }

    return UInt(stats.free_count) * UInt(pageSize)
}

适用于iPhone OS应用的可用内存

3 个答案: