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.Decapsulate by Components #239

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Mar 28, 2024
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49 changes: 34 additions & 15 deletions multiaddr.go
Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,6 @@ import (
"encoding/json"
"fmt"
"log"
"strings"

"golang.org/x/exp/slices"
)
Expand Down Expand Up @@ -150,26 +149,46 @@ func (m *multiaddr) Encapsulate(o Multiaddr) Multiaddr {
}

// Decapsulate unwraps Multiaddr up until the given Multiaddr is found.
func (m *multiaddr) Decapsulate(o Multiaddr) Multiaddr {
s1 := m.String()
s2 := o.String()
i := strings.LastIndex(s1, s2)
if i < 0 {
// if multiaddr not contained, returns a copy.
cpy := make([]byte, len(m.bytes))
copy(cpy, m.bytes)
return &multiaddr{bytes: cpy}
func (m *multiaddr) Decapsulate(right Multiaddr) Multiaddr {
if right == nil {
return m
}

if i == 0 {
leftParts := Split(m)
rightParts := Split(right)

lastIndex := -1
for i := range leftParts {
foundMatch := false
for j, rightC := range rightParts {
if len(leftParts) <= i+j {
foundMatch = false
break
}

foundMatch = rightC.Equal(leftParts[i+j])
if !foundMatch {
break
}
}

if foundMatch {
lastIndex = i
}
}

if lastIndex == 0 {
return nil
}

ma, err := NewMultiaddr(s1[:i])
if err != nil {
panic("Multiaddr.Decapsulate incorrect byte boundaries.")
if lastIndex < 0 {
// if multiaddr not contained, returns a copy.
cpy := make([]byte, len(m.bytes))
copy(cpy, m.bytes)
return &multiaddr{bytes: cpy}
}
return ma

return Join(leftParts[:lastIndex]...)
}

var ErrProtocolNotFound = fmt.Errorf("protocol not found in multiaddr")
Expand Down
41 changes: 41 additions & 0 deletions multiaddr_test.go
Original file line number Diff line number Diff line change
Expand Up @@ -454,6 +454,47 @@ func TestDecapsulateComment(t *testing.T) {
require.Nil(t, rest, "expected a nil multiaddr if we decapsulate everything")
}

func TestDecapsulate(t *testing.T) {
t.Run("right is nil", func(t *testing.T) {
left := StringCast("/ip4/1.2.3.4/tcp/1")
var right Multiaddr
left.Decapsulate(right)
})

testcases := []struct {
left, right, expected string
}{
{"/ip4/1.2.3.4/tcp/1234", "/ip4/1.2.3.4", ""},
{"/ip4/1.2.3.4", "/ip4/1.2.3.4/tcp/1234", "/ip4/1.2.3.4"},
{"/ip4/1.2.3.5/tcp/1234", "/ip4/5.3.2.1", "/ip4/1.2.3.5/tcp/1234"},
{"/ip4/1.2.3.5/udp/1234/quic-v1", "/udp/1234", "/ip4/1.2.3.5"},
{"/ip4/1.2.3.6/udp/1234/quic-v1", "/udp/1234/quic-v1", "/ip4/1.2.3.6"},
{"/ip4/1.2.3.7/tcp/1234", "/ws", "/ip4/1.2.3.7/tcp/1234"},
{"/dnsaddr/wss.com/tcp/4001", "/ws", "/dnsaddr/wss.com/tcp/4001"},
{"/dnsaddr/wss.com/tcp/4001/ws", "/wss", "/dnsaddr/wss.com/tcp/4001/ws"},
{"/dnsaddr/wss.com/ws", "/wss", "/dnsaddr/wss.com/ws"},
{"/dnsaddr/wss.com/ws", "/dnsaddr/wss.com", ""},
{"/dnsaddr/wss.com/tcp/4001/wss", "/wss", "/dnsaddr/wss.com/tcp/4001"},
}

for _, tc := range testcases {
t.Run(tc.left, func(t *testing.T) {
left := StringCast(tc.left)
right := StringCast(tc.right)
actualMa := left.Decapsulate(right)

if tc.expected == "" {
require.Nil(t, actualMa, "expected nil")
return
}

actual := actualMa.String()
expected := StringCast(tc.expected).String()
require.Equal(t, expected, actual)
})
}
}

func assertValueForProto(t *testing.T, a Multiaddr, p int, exp string) {
t.Logf("checking for %s in %s", ProtocolWithCode(p).Name, a)
fv, err := a.ValueForProtocol(p)
Expand Down
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