Merge pull request #112 from multiformats/fix/deterministic

fix: minimal varint decoding

codec.go

@@ -4,6 +4,8 @@ import (
 	"bytes"
 	"fmt"
 	"strings"
+
+	"github.com/multiformats/go-varint"
 )
 
 func stringToBytes(s string) ([]byte, error) {
@@ -30,7 +32,7 @@ func stringToBytes(s string) ([]byte, error) {
 		if p.Code == 0 {
 			return nil, fmt.Errorf("failed to parse multiaddr %q: unknown protocol %s", s, sp[0])
 		}
-		_, _ = b.Write(CodeToVarint(p.Code))
+		_, _ = b.Write(p.VCode)
 		sp = sp[1:]
 
 		if p.Size == 0 { // no length.
@@ -52,7 +54,7 @@ func stringToBytes(s string) ([]byte, error) {
 			return nil, fmt.Errorf("failed to parse multiaddr %q: invalid value %q for protocol %s: %s", s, sp[0], p.Name, err)
 		}
 		if p.Size < 0 { // varint size.
-			_, _ = b.Write(CodeToVarint(len(a)))
+			_, _ = b.Write(varint.ToUvarint(uint64(len(a))))
 		}
 		b.Write(a)
 		sp = sp[1:]

component.go

@@ -6,6 +6,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"strings"
+
+	"github.com/multiformats/go-varint"
 )
 
 // Component is a single multiaddr Component.
@@ -158,7 +160,7 @@ func newComponent(protocol Protocol, bvalue []byte) *Component {
 	size := len(bvalue)
 	size += len(protocol.VCode)
 	if protocol.Size < 0 {
-		size += VarintSize(len(bvalue))
+		size += varint.UvarintSize(uint64(len(bvalue)))
 	}
 	maddr := make([]byte, size)
 	var offset int

go.mod

 module github.com/multiformats/go-multiaddr
 
-require github.com/multiformats/go-multihash v0.0.8
+require (
+	github.com/multiformats/go-multihash v0.0.8
+	github.com/multiformats/go-varint v0.0.1
+)
 
-go 1.12
+go 1.13

go.sum

@@ -6,6 +6,8 @@ github.com/mr-tron/base58 v1.1.2 h1:ZEw4I2EgPKDJ2iEw0cNmLB3ROrEmkOtXIkaG7wZg+78=
 github.com/mr-tron/base58 v1.1.2/go.mod h1:BinMc/sQntlIE1frQmRFPUoPA1Zkr8VRgBdjWI2mNwc=
 github.com/multiformats/go-multihash v0.0.8 h1:wrYcW5yxSi3dU07n5jnuS5PrNwyHy0zRHGVoUugWvXg=
 github.com/multiformats/go-multihash v0.0.8/go.mod h1:YSLudS+Pi8NHE7o6tb3D8vrpKa63epEDmG8nTduyAew=
+github.com/multiformats/go-varint v0.0.1 h1:TR/0rdQtnNxuN2IhiB639xC3tWM4IUi7DkTBVTdGW/M=
+github.com/multiformats/go-varint v0.0.1/go.mod h1:3Ls8CIEsrijN6+B7PbrXRPxHRPuXSrVKRY101jdMZYE=
 github.com/spaolacci/murmur3 v1.1.0 h1:7c1g84S4BPRrfL5Xrdp6fOJ206sU9y293DDHaoy0bLI=
 github.com/spaolacci/murmur3 v1.1.0/go.mod h1:JwIasOWyU6f++ZhiEuf87xNszmSA2myDM2Kzu9HwQUA=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=

varint.go

 package multiaddr
 
 import (
-	"encoding/binary"
-	"fmt"
-	"math/bits"
-)
+	"math"
 
-// VarintSize returns the size (in bytes) of `num` encoded as a varint.
-func VarintSize(num int) int {
-	bits := bits.Len(uint(num))
-	q, r := bits/7, bits%7
-	size := q
-	if r > 0 || size == 0 {
-		size++
-	}
-	return size
-}
+	"github.com/multiformats/go-varint"
+)
 
 // CodeToVarint converts an integer to a varint-encoded []byte
 func CodeToVarint(num int) []byte {
-	buf := make([]byte, VarintSize(num))
-	n := binary.PutUvarint(buf, uint64(num))
-	return buf[:n]
+	if num < 0 || num > math.MaxInt32 {
+		panic("invalid code")
+	}
+	return varint.ToUvarint(uint64(num))
 }
 
-// VarintToCode converts a varint-encoded []byte to an integer protocol code
-func VarintToCode(buf []byte) int {
-	num, _, err := ReadVarintCode(buf)
+func ReadVarintCode(b []byte) (int, int, error) {
+	code, n, err := varint.FromUvarint(b)
 	if err != nil {
-		panic(err)
+		return 0, 0, err
 	}
-	return num
-}
-
-// ReadVarintCode reads a varint code from the beginning of buf.
-// returns the code, and the number of bytes read.
-func ReadVarintCode(buf []byte) (int, int, error) {
-	num, n := binary.Uvarint(buf)
-	if n < 0 {
-		return 0, 0, fmt.Errorf("varints larger than uint64 not yet supported")
+	if code > math.MaxInt32 {
+		// we only allow 32bit codes.
+		return 0, 0, varint.ErrOverflow
 	}
-	return int(num), n, nil
+	return int(code), n, err
 }

varint_test.go

-package multiaddr
-
-import (
-	"encoding/binary"
-	"testing"
-)
-
-func checkVarint(t *testing.T, x int) {
-	buf := make([]byte, binary.MaxVarintLen64)
-	expected := binary.PutUvarint(buf, uint64(x))
-
-	size := VarintSize(x)
-	if size != expected {
-		t.Fatalf("expected varintsize of %d to be %d, got %d", x, expected, size)
-	}
-}
-
-func TestVarintSize(t *testing.T) {
-	max := 1 << 16
-	for x := 0; x < max; x++ {
-		checkVarint(t, x)
-	}
-}