t.go

package main

import (
	"bufio"
	"log"
	"os"
	"path/filepath"
	"runtime/pprof"
)

// FilePackageTuple is a tuple consisting of a file name and a package name
// containing the file.
type FilePackageTuple struct {
	File    string
	Package string
}

func process(list string) []FilePackageTuple {
	result := make([]FilePackageTuple, 0, 16)
	file, _ := os.Open(list)

	reader := bufio.NewReader(file)
	for {
		line, err := reader.ReadString('\n')
		if err != nil {
			break
		}

		result = append(result, FilePackageTuple{File: line, Package: list})
	}

	file.Close()

	return result
}

func processChan(list string, out chan []FilePackageTuple) {
	out <- process(list)
}

// NewFileToPackageMap reads a map file -> [pkg] from dpkg
func NewFileToPackageMap() map[string][]string {
	match, err := filepath.Glob("/var/lib/dpkg/info/*.list")
	if err != nil {
		log.Fatalf("%s", err)
	}

	fileToPkg := make(map[string][]string, 1024*16)

	// Process this bastard in parallel
	out := make(chan []FilePackageTuple)
	for _, list := range match {
		go processChan(list, out)
	}
	for _ = range match {
		res := <-out
		for _, t := range res {
			fileToPkg[t.File] = append(fileToPkg[t.File], t.Package)
		}
	}
	close(out)
	return fileToPkg
}

func main() {

	f, err := os.Create("cpu")
	if err != nil {
		log.Fatal(err)
	}
	pprof.StartCPUProfile(f)
	defer pprof.StopCPUProfile()

	_ = NewFileToPackageMap()
	/*for file, pkgs := range fileToPkg {
		fmt.Printf("%s => %v\n", file, pkgs)
	}*/

}