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// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package deephash hashes a Go value recursively, in a predictable
// order, without looping.
package deephash
import (
"bufio"
"crypto/sha256"
"fmt"
"reflect"
"inet.af/netaddr"
"tailscale.com/tailcfg"
"tailscale.com/types/wgkey"
)
func Hash(v ...interface{}) string {
h := sha256.New()
// 64 matches the chunk size in crypto/sha256/sha256.go
b := bufio.NewWriterSize(h, 64)
Print(b, v)
b.Flush()
return fmt.Sprintf("%x", h.Sum(nil))
}
// UpdateHash sets last to the hash of v and reports whether its value changed.
func UpdateHash(last *string, v ...interface{}) (changed bool) {
sig := Hash(v)
if *last != sig {
*last = sig
return true
}
return false
}
func Print(w *bufio.Writer, v ...interface{}) {
print(w, reflect.ValueOf(v), make(map[uintptr]bool))
}
var (
netaddrIPType = reflect.TypeOf(netaddr.IP{})
netaddrIPPrefix = reflect.TypeOf(netaddr.IPPrefix{})
wgkeyKeyType = reflect.TypeOf(wgkey.Key{})
wgkeyPrivateType = reflect.TypeOf(wgkey.Private{})
tailcfgDiscoKeyType = reflect.TypeOf(tailcfg.DiscoKey{})
)
func print(w *bufio.Writer, v reflect.Value, visited map[uintptr]bool) {
if !v.IsValid() {
return
}
// Special case some common types.
if v.CanInterface() {
switch v.Type() {
case netaddrIPType:
var b []byte
var err error
if v.CanAddr() {
x := v.Addr().Interface().(*netaddr.IP)
b, err = x.MarshalText()
} else {
x := v.Interface().(netaddr.IP)
b, err = x.MarshalText()
}
if err == nil {
w.Write(b)
return
}
case netaddrIPPrefix:
var b []byte
var err error
if v.CanAddr() {
x := v.Addr().Interface().(*netaddr.IPPrefix)
b, err = x.MarshalText()
} else {
x := v.Interface().(netaddr.IPPrefix)
b, err = x.MarshalText()
}
if err == nil {
w.Write(b)
return
}
case wgkeyKeyType:
if v.CanAddr() {
x := v.Addr().Interface().(*wgkey.Key)
w.Write(x[:])
} else {
x := v.Interface().(wgkey.Key)
w.Write(x[:])
}
return
case wgkeyPrivateType:
if v.CanAddr() {
x := v.Addr().Interface().(*wgkey.Private)
w.Write(x[:])
} else {
x := v.Interface().(wgkey.Private)
w.Write(x[:])
}
return
case tailcfgDiscoKeyType:
if v.CanAddr() {
x := v.Addr().Interface().(*tailcfg.DiscoKey)
w.Write(x[:])
} else {
x := v.Interface().(tailcfg.DiscoKey)
w.Write(x[:])
}
return
}
}
// Generic handling.
switch v.Kind() {
default:
panic(fmt.Sprintf("unhandled kind %v for type %v", v.Kind(), v.Type()))
case reflect.Ptr:
ptr := v.Pointer()
if visited[ptr] {
return
}
visited[ptr] = true
print(w, v.Elem(), visited)
return
case reflect.Struct:
w.WriteString("struct{\n")
for i, n := 0, v.NumField(); i < n; i++ {
fmt.Fprintf(w, " [%d]: ", i)
print(w, v.Field(i), visited)
w.WriteString("\n")
}
w.WriteString("}\n")
case reflect.Slice, reflect.Array:
if v.Type().Elem().Kind() == reflect.Uint8 && v.CanInterface() {
fmt.Fprintf(w, "%q", v.Interface())
return
}
fmt.Fprintf(w, "[%d]{\n", v.Len())
for i, ln := 0, v.Len(); i < ln; i++ {
fmt.Fprintf(w, " [%d]: ", i)
print(w, v.Index(i), visited)
w.WriteString("\n")
}
w.WriteString("}\n")
case reflect.Interface:
print(w, v.Elem(), visited)
case reflect.Map:
sm := newSortedMap(v)
fmt.Fprintf(w, "map[%d]{\n", len(sm.Key))
for i, k := range sm.Key {
print(w, k, visited)
w.WriteString(": ")
print(w, sm.Value[i], visited)
w.WriteString("\n")
}
w.WriteString("}\n")
case reflect.String:
w.WriteString(v.String())
case reflect.Bool:
fmt.Fprintf(w, "%v", v.Bool())
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
fmt.Fprintf(w, "%v", v.Int())
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
fmt.Fprintf(w, "%v", v.Uint())
case reflect.Float32, reflect.Float64:
fmt.Fprintf(w, "%v", v.Float())
case reflect.Complex64, reflect.Complex128:
fmt.Fprintf(w, "%v", v.Complex())
}
}
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