import from go-ipfs

file.go

+package util
+
+import "os"
+
+func FileExists(filename string) bool {
+	fi, err := os.Lstat(filename)
+	if fi != nil || (err != nil && !os.IsNotExist(err)) {
+		return true
+	}
+	return false
+}

file_test.go

+package util
+
+import "testing"
+
+func TestFileDoesNotExist(t *testing.T) {
+	t.Parallel()
+	if FileExists("i would be surprised to discover that this file exists") {
+		t.Fail()
+	}
+}

time.go

+package util
+
+import "time"
+
+var TimeFormatIpfs = time.RFC3339Nano
+
+func ParseRFC3339(s string) (time.Time, error) {
+	t, err := time.Parse(TimeFormatIpfs, s)
+	if err != nil {
+		return time.Time{}, err
+	}
+	return t.UTC(), nil
+}
+
+func FormatRFC3339(t time.Time) string {
+	return t.UTC().Format(TimeFormatIpfs)
+}

time_test.go

+package util
+
+import (
+	"testing"
+	"time"
+)
+
+func TestTimeFormatParseInversion(t *testing.T) {
+	v, err := ParseRFC3339(FormatRFC3339(time.Now()))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if v.Location() != time.UTC {
+		t.Fatal("Time should be UTC")
+	}
+}

util.go

+// Package util implements various utility functions used within ipfs
+// that do not currently have a better place to live.
+package util
+
+import (
+	"errors"
+	"io"
+	"math/rand"
+	"os"
+	"path/filepath"
+	"runtime/debug"
+	"strings"
+	"time"
+
+	b58 "github.com/jbenet/go-base58"
+	mh "github.com/jbenet/go-multihash"
+)
+
+// Debug is a global flag for debugging.
+var Debug bool
+
+// ErrNotImplemented signifies a function has not been implemented yet.
+var ErrNotImplemented = errors.New("Error: not implemented yet.")
+
+// ErrTimeout implies that a timeout has been triggered
+var ErrTimeout = errors.New("Error: Call timed out.")
+
+// ErrSeErrSearchIncomplete implies that a search type operation didnt
+// find the expected node, but did find 'a' node.
+var ErrSearchIncomplete = errors.New("Error: Search Incomplete.")
+
+// ErrCast is returned when a cast fails AND the program should not panic.
+func ErrCast() error {
+	debug.PrintStack()
+	return errCast
+}
+
+var errCast = errors.New("cast error")
+
+// ExpandPathnames takes a set of paths and turns them into absolute paths
+func ExpandPathnames(paths []string) ([]string, error) {
+	var out []string
+	for _, p := range paths {
+		abspath, err := filepath.Abs(p)
+		if err != nil {
+			return nil, err
+		}
+		out = append(out, abspath)
+	}
+	return out, nil
+}
+
+type randGen struct {
+	rand.Rand
+}
+
+func NewTimeSeededRand() io.Reader {
+	src := rand.NewSource(time.Now().UnixNano())
+	return &randGen{
+		Rand: *rand.New(src),
+	}
+}
+
+func NewSeededRand(seed int64) io.Reader {
+	src := rand.NewSource(seed)
+	return &randGen{
+		Rand: *rand.New(src),
+	}
+}
+
+func (r *randGen) Read(p []byte) (n int, err error) {
+	for i := 0; i < len(p); i++ {
+		p[i] = byte(r.Rand.Intn(255))
+	}
+	return len(p), nil
+}
+
+// GetenvBool is the way to check an env var as a boolean
+func GetenvBool(name string) bool {
+	v := strings.ToLower(os.Getenv(name))
+	return v == "true" || v == "t" || v == "1"
+}
+
+// MultiErr is a util to return multiple errors
+type MultiErr []error
+
+func (m MultiErr) Error() string {
+	if len(m) == 0 {
+		return "no errors"
+	}
+
+	s := "Multiple errors: "
+	for i, e := range m {
+		if i != 0 {
+			s += ", "
+		}
+		s += e.Error()
+	}
+	return s
+}
+
+func Partition(subject string, sep string) (string, string, string) {
+	if i := strings.Index(subject, sep); i != -1 {
+		return subject[:i], subject[i : i+len(sep)], subject[i+len(sep):]
+	}
+	return subject, "", ""
+}
+
+func RPartition(subject string, sep string) (string, string, string) {
+	if i := strings.LastIndex(subject, sep); i != -1 {
+		return subject[:i], subject[i : i+len(sep)], subject[i+len(sep):]
+	}
+	return subject, "", ""
+}
+
+// Hash is the global IPFS hash function. uses multihash SHA2_256, 256 bits
+func Hash(data []byte) mh.Multihash {
+	h, err := mh.Sum(data, mh.SHA2_256, -1)
+	if err != nil {
+		// this error can be safely ignored (panic) because multihash only fails
+		// from the selection of hash function. If the fn + length are valid, it
+		// won't error.
+		panic("multihash failed to hash using SHA2_256.")
+	}
+	return h
+}
+
+// IsValidHash checks whether a given hash is valid (b58 decodable, len > 0)
+func IsValidHash(s string) bool {
+	out := b58.Decode(s)
+	if out == nil || len(out) == 0 {
+		return false
+	}
+	_, err := mh.Cast(out)
+	if err != nil {
+		return false
+	}
+	return true
+}
+
+// XOR takes two byte slices, XORs them together, returns the resulting slice.
+func XOR(a, b []byte) []byte {
+	c := make([]byte, len(a))
+	for i := 0; i < len(a); i++ {
+		c[i] = a[i] ^ b[i]
+	}
+	return c
+}

util_test.go

+package util
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestXOR(t *testing.T) {
+	cases := [][3][]byte{
+		{
+			{0xFF, 0xFF, 0xFF},
+			{0xFF, 0xFF, 0xFF},
+			{0x00, 0x00, 0x00},
+		},
+		{
+			{0x00, 0xFF, 0x00},
+			{0xFF, 0xFF, 0xFF},
+			{0xFF, 0x00, 0xFF},
+		},
+		{
+			{0x55, 0x55, 0x55},
+			{0x55, 0xFF, 0xAA},
+			{0x00, 0xAA, 0xFF},
+		},
+	}
+
+	for _, c := range cases {
+		r := XOR(c[0], c[1])
+		if !bytes.Equal(r, c[2]) {
+			t.Error("XOR failed")
+		}
+	}
+}
+
+func BenchmarkHash256K(b *testing.B) {
+	buf := make([]byte, 256*1024)
+	NewTimeSeededRand().Read(buf)
+	b.SetBytes(int64(256 * 1024))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Hash(buf)
+	}
+}
+
+func BenchmarkHash512K(b *testing.B) {
+	buf := make([]byte, 512*1024)
+	NewTimeSeededRand().Read(buf)
+	b.SetBytes(int64(512 * 1024))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Hash(buf)
+	}
+}
+
+func BenchmarkHash1M(b *testing.B) {
+	buf := make([]byte, 1024*1024)
+	NewTimeSeededRand().Read(buf)
+	b.SetBytes(int64(1024 * 1024))
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		Hash(buf)
+	}
+}