create appmanifest package (#192)

create appmanifest package for managing AppManifests

appmanifest/appmanifest.go

@@ -0,0 +1,126 @@
+// package appmanifest provides utilities for managing app manifest files
+// used by MDM InstallApplication commands.
+package appmanifest
+
+import (
+	"crypto/md5"
+	"fmt"
+	"io"
+
+	"github.com/pkg/errors"
+)
+
+// DefaultMD5Size is the default size of each file chunk that needs to be hashed
+const DefaultMD5Size = 10 << 20 // 10MB
+
+// http://help.apple.com/deployment/osx/#/ior5df10f73a
+type Manifest struct {
+	ManifestItems []Item `plist:"items"`
+}
+
+type Item struct {
+	Assets []Asset `plist:"assets"`
+	// Apple claims the metadata struct is required,
+	// but testing shows otherwise.
+	Metadata *Metadata `plist:"metadata,omitempty"`
+}
+
+type Asset struct {
+	Kind    string   `plist:"kind"`
+	MD5Size int64    `plist:"md5-size"`
+	MD5s    []string `plist:"md5s"`
+	URL     string   `plist:"url"`
+}
+
+type Metadata struct {
+	BundleInfo
+	Items    []BundleInfo `plist:"items,omitempty"`
+	Kind     string       `plist:"kind"`
+	Subtitle string       `plist:"subtitle"`
+	Title    string       `plist:"title"`
+}
+
+type BundleInfo struct {
+	BundleIdentifier string `plist:"bundle-identifier"`
+	BundleVersion    string `plist:"bundle-version"`
+}
+
+// File is an io.Reader which knows its size.
+type File interface {
+	io.Reader
+	Size() int64
+}
+
+type Option func(*config)
+
+// WithMD5Size overrides the DefaultMD5Size when creating an AppManifest.
+func WithMD5Size(md5Size int64) Option {
+	return func(c *config) {
+		c.md5Size = md5Size
+	}
+}
+
+type config struct {
+	md5Size int64
+}
+
+// Create an AppManifest and write it to an io.Writer.
+func Create(file File, url string, opts ...Option) (*Manifest, error) {
+	c := config{
+		md5Size: DefaultMD5Size,
+	}
+
+	for _, opt := range opts {
+		opt(&c)
+	}
+
+	fSize := file.Size()
+	if c.md5Size > fSize {
+		c.md5Size = fSize
+	}
+
+	// create a list of md5s
+	md5s, err := calculateMD5s(file, c.md5Size)
+	if err != nil {
+		return nil, errors.Wrap(err, "calculate appmanifest md5s")
+	}
+
+	// create an asset
+	ast := Asset{
+		Kind:    "software-package",
+		MD5Size: c.md5Size,
+		MD5s:    md5s,
+		URL:     url,
+	}
+
+	// make a manifest
+	m := Manifest{
+		ManifestItems: []Item{
+			Item{
+				Assets: []Asset{ast},
+			},
+		},
+	}
+
+	return &m, nil
+}
+
+// reads a file and returns a slice of hashes, one for each
+// 10mb chunk
+func calculateMD5s(f io.Reader, s int64) ([]string, error) {
+	h := md5.New()
+	var md5s []string
+	for {
+		n, err := io.CopyN(h, f, s)
+		if n > 0 {
+			md5s = append(md5s, fmt.Sprintf("%x", h.Sum(nil)))
+			h.Reset()
+		}
+		if err != nil {
+			if err == io.EOF {
+				err = nil
+			}
+			return md5s, err
+		}
+	}
+}

appmanifest/appmanifest_test.go

@@ -0,0 +1,56 @@
+package appmanifest
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestCalucalteMD5s(t *testing.T) {
+	ok := []string{
+		"f1c9645dbc14efddc7d8a322685f26eb",
+		"f1c9645dbc14efddc7d8a322685f26eb",
+		"f1c9645dbc14efddc7d8a322685f26eb",
+		"93b885adfe0da089cdf634904fd59f71",
+	}
+	buf := make([]byte, DefaultMD5Size*3+1)
+	r := bytes.NewReader(buf)
+	md5s, err := calculateMD5s(r, DefaultMD5Size)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(md5s) != len(ok) {
+		t.Fatal("expected", len(ok), "got", len(md5s))
+	}
+	for i, h := range md5s {
+		if ok[i] != h {
+			t.Fatal("expected", ok[i], "got", h)
+		}
+	}
+}
+
+/*
+Benchmark10MB-8  	  500000	      3297 ns/op	   32896 B/op	       3 allocs/op
+Benchmark100MB-8 	  300000	      3528 ns/op	   32897 B/op	       3 allocs/op
+Benchmark1000MB-8	       1	1967685209 ns/op	 3334064 B/op	     829 allocs/op
+*/
+
+func benchmarkSize(b *testing.B, size int) {
+	var buf = make([]byte, size)
+	r := bytes.NewReader(buf)
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		calculateMD5s(r, DefaultMD5Size)
+	}
+}
+
+func Benchmark10MB(b *testing.B) {
+	benchmarkSize(b, DefaultMD5Size)
+}
+
+func Benchmark100MB(b *testing.B) {
+	benchmarkSize(b, DefaultMD5Size*10)
+}
+
+func Benchmark1000MB(b *testing.B) {
+	benchmarkSize(b, DefaultMD5Size*100)
+}