add an example to the tests to play around with the feature

cid.go

@@ -14,6 +14,21 @@ import (
 
 const UnsupportedVersionString = "<unsupported cid version>"
 
+var (
+	// ErrVarintBuffSmall means that a buffer passed to the cid parser was not
+	// long enough, or did not contain an invalid cid
+	ErrVarintBuffSmall = errors.New("reading varint: buffer too small")
+
+	// ErrVarintTooBig means that the varint in the given cid was above the
+	// limit of 2^64
+	ErrVarintTooBig = errors.New("reading varint: varint bigger than 64bits" +
+		" and not supported")
+
+	// ErrCidTooShort means that the cid passed to decode was not long
+	// enough to be a valid Cid
+	ErrCidTooShort = errors.New("cid too short")
+)
+
 const (
 	Raw = 0x55
 
@@ -70,7 +85,7 @@ func Parse(v interface{}) (*Cid, error) {
 
 func Decode(v string) (*Cid, error) {
 	if len(v) < 2 {
-		return nil, fmt.Errorf("cid too short")
+		return nil, ErrCidTooShort
 	}
 
 	if len(v) == 46 && v[:2] == "Qm" {
@@ -90,12 +105,6 @@ func Decode(v string) (*Cid, error) {
 	return Cast(data)
 }
 
-var (
-	ErrVarintBuffSmall = errors.New("reading varint: buffer to small")
-	ErrVarintTooBig    = errors.New("reading varint: varint bigger than 64bits" +
-		" and not supported")
-)
-
 func uvError(read int) error {
 	switch {
 	case read == 0:

cid_test.go

@@ -202,6 +202,18 @@ func TestHexDecode(t *testing.T) {
 	}
 }
 
+func ExampleDecode() {
+	encoded := "zb2rhhFAEMepUBbGyP1k8tGfz7BSciKXP6GHuUeUsJBaK6cqG"
+	c, err := Decode(encoded)
+	if err != nil {
+		fmt.Printf("Error: %s", err)
+		return
+	}
+
+	fmt.Println(c)
+	// Output: zb2rhhFAEMepUBbGyP1k8tGfz7BSciKXP6GHuUeUsJBaK6cqG
+}
+
 func TestFromJson(t *testing.T) {
 	cval := "zb2rhhFAEMepUBbGyP1k8tGfz7BSciKXP6GHuUeUsJBaK6cqG"
 	jsoncid := []byte(`{"/":"` + cval + `"}`)

set.go

@@ -27,7 +27,7 @@ func (s *Set) Len() int {
 
 func (s *Set) Keys() []*Cid {
 	out := make([]*Cid, 0, len(s.set))
-	for k, _ := range s.set {
+	for k := range s.set {
 		c, _ := Cast([]byte(k))
 		out = append(out, c)
 	}
@@ -44,7 +44,7 @@ func (s *Set) Visit(c *Cid) bool {
 }
 
 func (s *Set) ForEach(f func(c *Cid) error) error {
-	for cs, _ := range s.set {
+	for cs := range s.set {
 		c, _ := Cast([]byte(cs))
 		err := f(c)
 		if err != nil {