DominicBreuker/pspy

package psscanner

import (
    "fmt"
    "io"
    "os"
    "strconv"
)

type procList map[int]struct{}

type pidProcessor interface {
    processNewPid(pid int)
}

func (pl procList) refresh(p pidProcessor) error {
    pids, err := getPIDs()
    if err != nil {
        return err
    }

    for i := len(pids) - 1; i >= 0; i-- {
        pid := pids[i]
        _, ok := pl[pid]
        if !ok {
            p.processNewPid(pid)
            pl[pid] = struct{}{}
        }
    }

    return nil
}

func getPIDs() ([]int, error) {
    f, err := dirOpen("/proc")
    if err != nil {
        return nil, fmt.Errorf("opening proc dir: %v", err)
    }
    defer f.Close()

    names, err := f.Readdirnames(-1)
    if err != nil {
        return nil, fmt.Errorf("reading proc dir: %v", err)
    }

    pids := make([]int, 0)
    for _, f := range names {
        pid, err := strconv.Atoi(f)
        if err != nil || pid <= 0 {
            continue
        }
        pids = append(pids, pid)
    }
    return pids, nil
}

type readDirNamesCloser interface {
    Readdirnames(n int) (names []string, err error)
    io.Closer
}

var dirOpen func(string) (readDirNamesCloser, error) = func(s string) (readDirNamesCloser, error) {
    return os.Open(s)
}