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component.go
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component.go
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package multiaddr
import (
"bytes"
"encoding/binary"
"fmt"
"strings"
)
// Component is a single multiaddr Component.
type Component struct {
bytes []byte
protocol Protocol
offset int
}
func (c *Component) Bytes() []byte {
return c.bytes
}
func (c *Component) Equal(o Multiaddr) bool {
return bytes.Equal(c.bytes, o.Bytes())
}
func (c *Component) Protocols() []Protocol {
return []Protocol{c.protocol}
}
func (c *Component) Decapsulate(o Multiaddr) Multiaddr {
if c.Equal(o) {
return nil
}
return c
}
func (c *Component) Encapsulate(o Multiaddr) Multiaddr {
m := multiaddr{bytes: c.bytes}
return m.Encapsulate(o)
}
func (c *Component) ValueForProtocol(code int) (string, error) {
if c.protocol.Code != code {
return "", ErrProtocolNotFound
}
return c.Value(), nil
}
func (c *Component) Protocol() Protocol {
return c.protocol
}
func (c *Component) RawValue() []byte {
return c.bytes[c.offset:]
}
func (c *Component) Value() string {
if c.protocol.Transcoder == nil {
return ""
}
value, err := c.protocol.Transcoder.BytesToString(c.bytes[c.offset:])
if err != nil {
// This Component must have been checked.
panic(err)
}
return value
}
func (c *Component) String() string {
var b strings.Builder
c.writeTo(&b)
return b.String()
}
// writeTo is an efficient, private function for string-formatting a multiaddr.
// Trust me, we tend to allocate a lot when doing this.
func (c *Component) writeTo(b *strings.Builder) {
b.WriteByte('/')
b.WriteString(c.protocol.Name)
value := c.Value()
if len(value) == 0 {
return
}
if !(c.protocol.Path && value[0] == '/') {
b.WriteByte('/')
}
b.WriteString(value)
}
// NewComponent constructs a new multiaddr component
func NewComponent(protocol, value string) (*Component, error) {
p := ProtocolWithName(protocol)
if p.Code == 0 {
return nil, fmt.Errorf("unsupported protocol: %s", protocol)
}
if p.Transcoder != nil {
bts, err := p.Transcoder.StringToBytes(value)
if err != nil {
return nil, err
}
return newComponent(p, bts), nil
} else if value != "" {
return nil, fmt.Errorf("protocol %s doesn't take a value", p.Name)
}
return newComponent(p, nil), nil
// TODO: handle path /?
}
func newComponent(protocol Protocol, bvalue []byte) *Component {
size := len(bvalue)
size += len(protocol.VCode)
if protocol.Size < 0 {
size += VarintSize(len(bvalue))
}
maddr := make([]byte, size)
var offset int
offset += copy(maddr[offset:], protocol.VCode)
if protocol.Size < 0 {
offset += binary.PutUvarint(maddr[offset:], uint64(len(bvalue)))
}
copy(maddr[offset:], bvalue)
// For debugging
if len(maddr) != offset+len(bvalue) {
panic("incorrect length")
}
return &Component{
bytes: maddr,
protocol: protocol,
offset: offset,
}
}