Get CPU usage IOS Swift - ios

Question

I am trying to get overall CPU usage not of a single app. I found some of the resources but they are either written in C or outdated swift. Can anyone help me with this problem? I am trying to conver this https://github.com/beltex/SystemKit/blob/master/SystemKit/System.swift#L12
to swift.
Till now I am able to convert this much
fileprivate func hostCPULoadInfo() -> host_cpu_load_info{
let HOST_CPU_LOAD_INFO_COUNT = MemoryLayout<host_cpu_load_info>.stride / MemoryLayout<integer_t>.stride;
var size = mach_msg_type_number_t(HOST_CPU_LOAD_INFO_COUNT);
var hostInfo = host_cpu_load_info_t.allocate(capacity: 1);
let result = withUnsafeMutablePointer(to: &hostInfo) {$0.withMemoryRebound(to: integer_t.self, capacity: Int(size)){
host_info(mach_host_self(), Int32(HOST_BASIC_INFO), $0, &size)
}
}
let data = hostInfo.move()
hostInfo.deallocate(capacity: 1)
#if DEBUG
if result != KERN_SUCCESS{
print("Error - \(#file): \(#function) - kern_result_t = \(result)");
}
#endif
return data;
}
public func cpuUsage() -> (system: Double, user: Double, idle : Double, nice: Double){
let load = hostCPULoadInfo();
let usrDiff: Double = Double(load.cpu_ticks.0 - loadPrevious.cpu_ticks.0);
let systDiff = Double(load.cpu_ticks.1 - loadPrevious.cpu_ticks.1);
let idleDiff = Double(load.cpu_ticks.2 - loadPrevious.cpu_ticks.2);
let niceDiff = Double(load.cpu_ticks.3 - loadPrevious.cpu_ticks.3);
let totalTicks = usrDiff + systDiff + idleDiff + niceDiff
print("Total ticks is ", totalTicks);
let sys = systDiff / totalTicks * 100.0
let usr = usrDiff / totalTicks * 100.0
let idle = idleDiff / totalTicks * 100.0
let nice = niceDiff / totalTicks * 100.0
return (sys, usr, idle, nice);
}
But the thing is I am getting an error like this
Error - /Users/administrator/Downloads/Documents/Swift/SystemInfo/RAMInformation.swift: hostCPULoadInfo() - kern_result_t = 5
Does anybody knows what's wrong in the above code? I thing I am doing wrong on conversion of host_statistics.
Can anybody help me?

Answer 1

There are three errors in your code:
The CPU statistics is obtained by calling host_statistics(), not
host_info().
The "flavor" argument must be HOST_CPU_LOAD_INFO, not HOST_BASIC_INFO.
hostInfo contains the pointer to the allocated structure,
so that value must be rebound, not the address of the variable.
Putting it all together:
func hostCPULoadInfo() -> host_cpu_load_info? {
let HOST_CPU_LOAD_INFO_COUNT = MemoryLayout<host_cpu_load_info>.stride / MemoryLayout<integer_t>.stride
var size = mach_msg_type_number_t(HOST_CPU_LOAD_INFO_COUNT)
let hostInfo = host_cpu_load_info_t.allocate(capacity: 1)
let result = hostInfo.withMemoryRebound(to: integer_t.self, capacity: HOST_CPU_LOAD_INFO_COUNT) {
host_statistics(mach_host_self(), HOST_CPU_LOAD_INFO, $0, &size)
}
if result != KERN_SUCCESS{
print("Error - \(#file): \(#function) - kern_result_t = \(result)")
return nil
}
let data = hostInfo.move()
hostInfo.deallocate(capacity: 1)
return data
}
(I changed the return type to an optional so that nil can be returned
in the error case).
Alternatively, use a local variable instead of allocating and releasing
the host_cpu_load_info structure:
func hostCPULoadInfo() -> host_cpu_load_info? {
let HOST_CPU_LOAD_INFO_COUNT = MemoryLayout<host_cpu_load_info>.stride/MemoryLayout<integer_t>.stride
var size = mach_msg_type_number_t(HOST_CPU_LOAD_INFO_COUNT)
var cpuLoadInfo = host_cpu_load_info()
let result = withUnsafeMutablePointer(to: &cpuLoadInfo) {
$0.withMemoryRebound(to: integer_t.self, capacity: HOST_CPU_LOAD_INFO_COUNT) {
host_statistics(mach_host_self(), HOST_CPU_LOAD_INFO, $0, &size)
}
}
if result != KERN_SUCCESS{
print("Error - \(#file): \(#function) - kern_result_t = \(result)")
return nil
}
return cpuLoadInfo
}