syncthing/vendor/github.com/d4l3k/messagediff/messagediff.go
2016-09-13 22:20:22 +02:00

235 lines
5.6 KiB
Go

package messagediff
import (
"fmt"
"reflect"
"sort"
"strings"
"unsafe"
)
// PrettyDiff does a deep comparison and returns the nicely formated results.
func PrettyDiff(a, b interface{}) (string, bool) {
d, equal := DeepDiff(a, b)
var dstr []string
for path, added := range d.Added {
dstr = append(dstr, fmt.Sprintf("added: %s = %#v\n", path.String(), added))
}
for path, removed := range d.Removed {
dstr = append(dstr, fmt.Sprintf("removed: %s = %#v\n", path.String(), removed))
}
for path, modified := range d.Modified {
dstr = append(dstr, fmt.Sprintf("modified: %s = %#v\n", path.String(), modified))
}
sort.Strings(dstr)
return strings.Join(dstr, ""), equal
}
// DeepDiff does a deep comparison and returns the results.
func DeepDiff(a, b interface{}) (*Diff, bool) {
d := newDiff()
return d, d.diff(reflect.ValueOf(a), reflect.ValueOf(b), nil)
}
func newDiff() *Diff {
return &Diff{
Added: make(map[*Path]interface{}),
Removed: make(map[*Path]interface{}),
Modified: make(map[*Path]interface{}),
visited: make(map[visit]bool),
}
}
func (d *Diff) diff(aVal, bVal reflect.Value, path Path) bool {
// Validity checks. Should only trigger if nil is one of the original arguments.
if !aVal.IsValid() && !bVal.IsValid() {
return true
}
if !bVal.IsValid() {
d.Modified[&path] = nil
return false
} else if !aVal.IsValid() {
d.Modified[&path] = bVal.Interface()
return false
}
if aVal.Type() != bVal.Type() {
d.Modified[&path] = bVal.Interface()
return false
}
kind := aVal.Kind()
// Borrowed from the reflect package to handle recursive data structures.
hard := func(k reflect.Kind) bool {
switch k {
case reflect.Array, reflect.Map, reflect.Slice, reflect.Struct:
return true
}
return false
}
if aVal.CanAddr() && bVal.CanAddr() && hard(kind) {
addr1 := unsafe.Pointer(aVal.UnsafeAddr())
addr2 := unsafe.Pointer(bVal.UnsafeAddr())
if uintptr(addr1) > uintptr(addr2) {
// Canonicalize order to reduce number of entries in visited.
// Assumes non-moving garbage collector.
addr1, addr2 = addr2, addr1
}
// Short circuit if references are already seen.
typ := aVal.Type()
v := visit{addr1, addr2, typ}
if d.visited[v] {
return true
}
// Remember for later.
d.visited[v] = true
}
// End of borrowed code.
equal := true
switch kind {
case reflect.Map, reflect.Ptr, reflect.Func, reflect.Chan, reflect.Slice:
if aVal.IsNil() && bVal.IsNil() {
return true
}
if aVal.IsNil() || bVal.IsNil() {
d.Modified[&path] = bVal.Interface()
return false
}
}
switch kind {
case reflect.Array, reflect.Slice:
aLen := aVal.Len()
bLen := bVal.Len()
for i := 0; i < min(aLen, bLen); i++ {
localPath := append(path, SliceIndex(i))
if eq := d.diff(aVal.Index(i), bVal.Index(i), localPath); !eq {
equal = false
}
}
if aLen > bLen {
for i := bLen; i < aLen; i++ {
localPath := append(path, SliceIndex(i))
d.Removed[&localPath] = aVal.Index(i).Interface()
equal = false
}
} else if aLen < bLen {
for i := aLen; i < bLen; i++ {
localPath := append(path, SliceIndex(i))
d.Added[&localPath] = bVal.Index(i).Interface()
equal = false
}
}
case reflect.Map:
for _, key := range aVal.MapKeys() {
aI := aVal.MapIndex(key)
bI := bVal.MapIndex(key)
localPath := append(path, MapKey{key.Interface()})
if !bI.IsValid() {
d.Removed[&localPath] = aI.Interface()
equal = false
} else if eq := d.diff(aI, bI, localPath); !eq {
equal = false
}
}
for _, key := range bVal.MapKeys() {
aI := aVal.MapIndex(key)
if !aI.IsValid() {
bI := bVal.MapIndex(key)
localPath := append(path, MapKey{key.Interface()})
d.Added[&localPath] = bI.Interface()
equal = false
}
}
case reflect.Struct:
typ := aVal.Type()
for i := 0; i < typ.NumField(); i++ {
index := []int{i}
field := typ.FieldByIndex(index)
localPath := append(path, StructField(field.Name))
aI := unsafeReflectValue(aVal.FieldByIndex(index))
bI := unsafeReflectValue(bVal.FieldByIndex(index))
if eq := d.diff(aI, bI, localPath); !eq {
equal = false
}
}
case reflect.Ptr:
equal = d.diff(aVal.Elem(), bVal.Elem(), path)
default:
if reflect.DeepEqual(aVal.Interface(), bVal.Interface()) {
equal = true
} else {
d.Modified[&path] = bVal.Interface()
equal = false
}
}
return equal
}
func min(a, b int) int {
if a < b {
return a
}
return b
}
// During deepValueEqual, must keep track of checks that are
// in progress. The comparison algorithm assumes that all
// checks in progress are true when it reencounters them.
// Visited comparisons are stored in a map indexed by visit.
// This is borrowed from the reflect package.
type visit struct {
a1 unsafe.Pointer
a2 unsafe.Pointer
typ reflect.Type
}
// Diff represents a change in a struct.
type Diff struct {
Added, Removed, Modified map[*Path]interface{}
visited map[visit]bool
}
// Path represents a path to a changed datum.
type Path []PathNode
func (p Path) String() string {
var out string
for _, n := range p {
out += n.String()
}
return out
}
// PathNode represents one step in the path.
type PathNode interface {
String() string
}
// StructField is a path element representing a field of a struct.
type StructField string
func (n StructField) String() string {
return fmt.Sprintf(".%s", string(n))
}
// MapKey is a path element representing a key of a map.
type MapKey struct {
Key interface{}
}
func (n MapKey) String() string {
return fmt.Sprintf("[%#v]", n.Key)
}
// SliceIndex is a path element representing a index of a slice.
type SliceIndex int
func (n SliceIndex) String() string {
return fmt.Sprintf("[%d]", n)
}