使用Go中的libproc.h处理OS X的CPU使用情况

Question

I known that excellent replies exist on the subject for questions like:

• How to determine CPU and memory consumption from inside a process?
• Determine Process Info Programmatically in Darwin/OSX
• Get CPU percent usage

The problem is that I'm trying to use libproc.h that defines a proc_threadinfo structure (among others) but the field pth_cpu_usage is always 0 (see trheadInfoHandler() func here to see how I'm using the struct from Go).

Looking at a snippet of Chromium source here (that doesn't use libproc.h), I was wondering if using fields from both proc_threadinfo and proc_taskinfo it could be possible calculate cpu percent usage.

proc_threadinfo.pth_user_time; /* user run time */
proc_threadinfo.pth_system_time; /* system run time */

proc_taskinfo.pti_total_user; /* total time */
proc_taskinfo.pti_total_system;

Edit

Some pseudo code illustrating the right algorithm or a suggestion to put me on the right path will be very appreciated.

Using /proc filesystem I think I was able to calculate CPU % usage in Linux:

func cpuUsageOf(pid int, waitHandler func()) float32 {
    stat1 := procFsStatOf(pid)
    utime1 := stat1.utime // /proc/[pid]/stat field index 13
    stime1 := stat1.stime // /proc/[pid]/stat field index 14
    cputime1 := procFsCpuTimeTotal() // /proc/stat -> sum of cpu values

    waitHandler() // here I wait 1 second

    stat2 := procFsStatOf(pid)
    utime2 := stat2.utime // /proc/[pid]/stat field index 13
    stime2 := stat2.stime // /proc/[pid]/stat field index 14
    cputime2 := procFsCpuTimeTotal() // /proc/stat -> sum of cpu values

    return float32(cpuCount() * ((utime2 + stime2) - (utime1 + stime1)) * 100) / float32(cputime2 - cputime1)
}

For OS X, do I've to use values from proc_threadinfo or proc_taskinfo? And where I can find the same values that in Linux I read from /proc/stat with (procFsCpuTimeTotal())?

Full code here (as in commit 9e34d3c72bf853ff49ef3970ad6a6c9688e9ba23); fast link to OS X code here.