Replace deprecated io/ioutil functions

[Juneezee]

The io/ioutil package has been deprecated as of Go 1.16 ¹. This commit replaces the existing io/ioutil functions with their new definitions in io and os packages.

Footnotes

1. https://golang.org/doc/go1.16#ioutil ↩

[Juneezee]

I replaced ioutil.ReadDir with os.Open ¹ + Readdirnames ² because we are only making use of the file names here.

I wrote a small benchmark, and the results show that it is slightly faster and more efficient to use Readdirnames.

// Before running the benchmark, create 1000 .txt files in /tmp
// for i in {1..1000}; do touch "/tmp/file_$i.txt"; done

func IoutilReadDir(dirname string, extension string) ([]string, error) {
	dslStrings := make([]string, 0)

	entries, err := ioutil.ReadDir(dirname)
	if err != nil {
		return nil, err
	}

	for i := range entries {
		entry := &entries[i]
		name := (*entry).Name()
		if !strings.HasSuffix(name, extension) {
			continue
		}

		path := dirname + "/" + name
		dslString, err := LoadStringFromFile(path)
		if err != nil {
			return nil, err
		}

		dslStrings = append(dslStrings, dslString)
	}

	return dslStrings, nil
}

func OsReadDir(dirname string, extension string) ([]string, error) {
	dslStrings := make([]string, 0)

	entries, err := os.ReadDir(dirname)
	if err != nil {
		return nil, err
	}

	for i := range entries {
		entry := &entries[i]
		name := (*entry).Name()
		if !strings.HasSuffix(name, extension) {
			continue
		}

		path := dirname + "/" + name
		dslString, err := LoadStringFromFile(path)
		if err != nil {
			return nil, err
		}

		dslStrings = append(dslStrings, dslString)
	}

	return dslStrings, nil
}

func OsReaddirnames(dirname string, extension string) ([]string, error) {
	f, err := os.Open(dirname)
	if err != nil {
		return nil, err
	}

	entries, err := f.Readdirnames(-1)
	if err != nil {
		return nil, err
	}

	dslStrings := make([]string, 0, len(entries))

	for _, name := range entries {
		if !strings.HasSuffix(name, extension) {
			continue
		}

		path := dirname + "/" + name
		dslString, err := LoadStringFromFile(path)
		if err != nil {
			return nil, err
		}

		dslStrings = append(dslStrings, dslString)
	}

	return dslStrings, nil
}

func BenchmarkIoutilReadDir(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_, err := IoutilReadDir("/tmp", ".txt")
		if err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkOsReadDir(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_, err := OsReadDir("/tmp", ".txt")
		if err != nil {
			b.Fatal(err)
		}
	}
}

func BenchmarkOsReaddirnames(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_, err := OsReaddirnames("/tmp", ".txt")
		if err != nil {
			b.Fatal(err)
		}
	}
}

goos: linux
goarch: amd64
pkg: github.com/johnkerl/miller/pkg/lib
cpu: AMD Ryzen 7 PRO 4750U with Radeon Graphics
BenchmarkIoutilReadDir-16     	     126	   9289861 ns/op	 1237645 B/op	    9122 allocs/op
BenchmarkOsReadDir-16         	     158	   7633255 ns/op	 1056843 B/op	    8091 allocs/op
BenchmarkOsReaddirnames-16    	     218	   5493111 ns/op	  959764 B/op	    7048 allocs/op
PASS
ok  	github.com/johnkerl/miller/pkg/lib	5.852s

Footnotes

1. https://pkg.go.dev/os#Open ↩

2. https://pkg.go.dev/os#File.Readdirnames ↩

[johnkerl]

This is fantastic @Juneezee -- thank you!! :)