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//! Utility functions.
use std::{
    collections::BTreeMap,
    ffi::CString,
    fs::{self, File},
    io::{self, BufReader},
    str::FromStr,
};

use crate::generated::{TC_H_MAJ_MASK, TC_H_MIN_MASK};

use libc::if_nametoindex;

use io::BufRead;

const ONLINE_CPUS: &str = "/sys/devices/system/cpu/online";
pub(crate) const POSSIBLE_CPUS: &str = "/sys/devices/system/cpu/possible";

/// Returns the numeric IDs of the CPUs currently online.
pub fn online_cpus() -> Result<Vec<u32>, io::Error> {
    let data = fs::read_to_string(ONLINE_CPUS)?;
    parse_cpu_ranges(data.trim()).map_err(|_| {
        io::Error::new(
            io::ErrorKind::Other,
            format!("unexpected {} format", ONLINE_CPUS),
        )
    })
}

/// Get the number of possible cpus.
///
/// See `/sys/devices/system/cpu/possible`.
pub fn nr_cpus() -> Result<usize, io::Error> {
    Ok(possible_cpus()?.len())
}

/// Get the list of possible cpus.
///
/// See `/sys/devices/system/cpu/possible`.
pub(crate) fn possible_cpus() -> Result<Vec<u32>, io::Error> {
    let data = fs::read_to_string(POSSIBLE_CPUS)?;
    parse_cpu_ranges(data.trim()).map_err(|_| {
        io::Error::new(
            io::ErrorKind::Other,
            format!("unexpected {} format", POSSIBLE_CPUS),
        )
    })
}

fn parse_cpu_ranges(data: &str) -> Result<Vec<u32>, ()> {
    let mut cpus = Vec::new();
    for range in data.split(',') {
        cpus.extend({
            match range
                .splitn(2, '-')
                .map(u32::from_str)
                .collect::<Result<Vec<_>, _>>()
                .map_err(|_| ())?
                .as_slice()
            {
                &[] | &[_, _, _, ..] => return Err(()),
                &[start] => start..=start,
                &[start, end] => start..=end,
            }
        })
    }

    Ok(cpus)
}

/// Loads kernel symbols from `/proc/kallsyms`.
///
/// The symbols can be passed to [`StackTrace::resolve`](crate::maps::stack_trace::StackTrace::resolve).
pub fn kernel_symbols() -> Result<BTreeMap<u64, String>, io::Error> {
    let mut reader = BufReader::new(File::open("/proc/kallsyms")?);
    parse_kernel_symbols(&mut reader)
}

fn parse_kernel_symbols(reader: &mut dyn BufRead) -> Result<BTreeMap<u64, String>, io::Error> {
    let mut syms = BTreeMap::new();

    for line in reader.lines() {
        let line = line?;
        let parts = line.splitn(4, ' ').collect::<Vec<_>>();
        let addr = u64::from_str_radix(parts[0], 16)
            .map_err(|_| io::Error::new(io::ErrorKind::InvalidData, line.clone()))?;
        let name = parts[2].to_owned();
        syms.insert(addr, name);
    }

    Ok(syms)
}

pub(crate) fn ifindex_from_ifname(if_name: &str) -> Result<u32, io::Error> {
    let c_str_if_name = CString::new(if_name)?;
    let c_if_name = c_str_if_name.as_ptr();
    // Safety: libc wrapper
    let if_index = unsafe { if_nametoindex(c_if_name) };
    if if_index == 0 {
        return Err(io::Error::last_os_error());
    }
    Ok(if_index)
}

pub(crate) fn tc_handler_make(major: u32, minor: u32) -> u32 {
    (major & TC_H_MAJ_MASK) | (minor & TC_H_MIN_MASK)
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_parse_online_cpus() {
        assert_eq!(parse_cpu_ranges("0").unwrap(), vec![0]);
        assert_eq!(parse_cpu_ranges("0,1").unwrap(), vec![0, 1]);
        assert_eq!(parse_cpu_ranges("0,1,2").unwrap(), vec![0, 1, 2]);
        assert_eq!(
            parse_cpu_ranges("0-7").unwrap(),
            (0..=7).collect::<Vec<_>>()
        );
        assert_eq!(
            parse_cpu_ranges("0-3,4-7").unwrap(),
            (0..=7).collect::<Vec<_>>()
        );
        assert_eq!(
            parse_cpu_ranges("0-5,6,7").unwrap(),
            (0..=7).collect::<Vec<_>>()
        );
        assert!(parse_cpu_ranges("").is_err());
        assert!(parse_cpu_ranges("0-1,2-").is_err());
        assert!(parse_cpu_ranges("foo").is_err());
    }

    #[test]
    fn test_parse_kernel_symbols() {
        let data = "0000000000002000 A irq_stack_backing_store\n\
                          0000000000006000 A cpu_tss_rw [foo bar]\n"
            .as_bytes();
        let syms = parse_kernel_symbols(&mut BufReader::new(data)).unwrap();
        assert_eq!(syms.keys().collect::<Vec<_>>(), vec![&0x2000, &0x6000]);
        assert_eq!(
            syms.get(&0x2000u64).unwrap().as_str(),
            "irq_stack_backing_store"
        );
        assert_eq!(syms.get(&0x6000u64).unwrap().as_str(), "cpu_tss_rw");
    }
}