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// Copyright 2015 The Chromium 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 render
import (
"bytes"
"fmt"
"reflect"
"sort"
"strconv"
)
var implicitTypeMap = map[reflect.Kind]string{
reflect.Bool: "bool",
reflect.String: "string",
reflect.Int: "int",
reflect.Int8: "int8",
reflect.Int16: "int16",
reflect.Int32: "int32",
reflect.Int64: "int64",
reflect.Uint: "uint",
reflect.Uint8: "uint8",
reflect.Uint16: "uint16",
reflect.Uint32: "uint32",
reflect.Uint64: "uint64",
reflect.Float32: "float32",
reflect.Float64: "float64",
reflect.Complex64: "complex64",
reflect.Complex128: "complex128",
}
// Render converts a structure to a string representation. Unline the "%#v"
// format string, this resolves pointer types' contents in structs, maps, and
// slices/arrays and prints their field values.
func Render(v interface{}) string {
buf := bytes.Buffer{}
s := (*traverseState)(nil)
s.render(&buf, 0, reflect.ValueOf(v))
return buf.String()
}
// renderPointer is called to render a pointer value.
//
// This is overridable so that the test suite can have deterministic pointer
// values in its expectations.
var renderPointer = func(buf *bytes.Buffer, p uintptr) {
fmt.Fprintf(buf, "0x%016x", p)
}
// traverseState is used to note and avoid recursion as struct members are being
// traversed.
//
// traverseState is allowed to be nil. Specifically, the root state is nil.
type traverseState struct {
parent *traverseState
ptr uintptr
}
func (s *traverseState) forkFor(ptr uintptr) *traverseState {
for cur := s; cur != nil; cur = cur.parent {
if ptr == cur.ptr {
return nil
}
}
fs := &traverseState{
parent: s,
ptr: ptr,
}
return fs
}
func (s *traverseState) render(buf *bytes.Buffer, ptrs int, v reflect.Value) {
if v.Kind() == reflect.Invalid {
buf.WriteString("nil")
return
}
vt := v.Type()
// If the type being rendered is a potentially recursive type (a type that
// can contain itself as a member), we need to avoid recursion.
//
// If we've already seen this type before, mark that this is the case and
// write a recursion placeholder instead of actually rendering it.
//
// If we haven't seen it before, fork our `seen` tracking so any higher-up
// renderers will also render it at least once, then mark that we've seen it
// to avoid recursing on lower layers.
pe := uintptr(0)
vk := vt.Kind()
switch vk {
case reflect.Ptr:
// Since structs and arrays aren't pointers, they can't directly be
// recursed, but they can contain pointers to themselves. Record their
// pointer to avoid this.
switch v.Elem().Kind() {
case reflect.Struct, reflect.Array:
pe = v.Pointer()
}
case reflect.Slice, reflect.Map:
pe = v.Pointer()
}
if pe != 0 {
s = s.forkFor(pe)
if s == nil {
buf.WriteString("<REC(")
writeType(buf, ptrs, vt)
buf.WriteString(")>")
return
}
}
switch vk {
case reflect.Struct:
writeType(buf, ptrs, vt)
buf.WriteRune('{')
for i := 0; i < vt.NumField(); i++ {
if i > 0 {
buf.WriteString(", ")
}
buf.WriteString(vt.Field(i).Name)
buf.WriteRune(':')
s.render(buf, 0, v.Field(i))
}
buf.WriteRune('}')
case reflect.Slice:
if v.IsNil() {
writeType(buf, ptrs, vt)
buf.WriteString("(nil)")
return
}
fallthrough
case reflect.Array:
writeType(buf, ptrs, vt)
buf.WriteString("{")
for i := 0; i < v.Len(); i++ {
if i > 0 {
buf.WriteString(", ")
}
s.render(buf, 0, v.Index(i))
}
buf.WriteRune('}')
case reflect.Map:
writeType(buf, ptrs, vt)
if v.IsNil() {
buf.WriteString("(nil)")
} else {
buf.WriteString("{")
mkeys := v.MapKeys()
tryAndSortMapKeys(vt, mkeys)
for i, mk := range mkeys {
if i > 0 {
buf.WriteString(", ")
}
s.render(buf, 0, mk)
buf.WriteString(":")
s.render(buf, 0, v.MapIndex(mk))
}
buf.WriteRune('}')
}
case reflect.Ptr:
ptrs++
fallthrough
case reflect.Interface:
if v.IsNil() {
writeType(buf, ptrs, v.Type())
buf.WriteRune('(')
fmt.Fprint(buf, "nil")
buf.WriteRune(')')
} else {
s.render(buf, ptrs, v.Elem())
}
case reflect.Chan, reflect.Func, reflect.UnsafePointer:
writeType(buf, ptrs, vt)
buf.WriteRune('(')
renderPointer(buf, v.Pointer())
buf.WriteRune(')')
default:
tstr := vt.String()
implicit := ptrs == 0 && implicitTypeMap[vk] == tstr
if !implicit {
writeType(buf, ptrs, vt)
buf.WriteRune('(')
}
switch vk {
case reflect.String:
fmt.Fprintf(buf, "%q", v.String())
case reflect.Bool:
fmt.Fprintf(buf, "%v", v.Bool())
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
fmt.Fprintf(buf, "%d", v.Int())
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
fmt.Fprintf(buf, "%d", v.Uint())
case reflect.Float32, reflect.Float64:
fmt.Fprintf(buf, "%g", v.Float())
case reflect.Complex64, reflect.Complex128:
fmt.Fprintf(buf, "%g", v.Complex())
}
if !implicit {
buf.WriteRune(')')
}
}
}
func writeType(buf *bytes.Buffer, ptrs int, t reflect.Type) {
parens := ptrs > 0
switch t.Kind() {
case reflect.Chan, reflect.Func, reflect.UnsafePointer:
parens = true
}
if parens {
buf.WriteRune('(')
for i := 0; i < ptrs; i++ {
buf.WriteRune('*')
}
}
switch t.Kind() {
case reflect.Ptr:
if ptrs == 0 {
// This pointer was referenced from within writeType (e.g., as part of
// rendering a list), and so hasn't had its pointer asterisk accounted
// for.
buf.WriteRune('*')
}
writeType(buf, 0, t.Elem())
case reflect.Interface:
if n := t.Name(); n != "" {
buf.WriteString(t.String())
} else {
buf.WriteString("interface{}")
}
case reflect.Array:
buf.WriteRune('[')
buf.WriteString(strconv.FormatInt(int64(t.Len()), 10))
buf.WriteRune(']')
writeType(buf, 0, t.Elem())
case reflect.Slice:
if t == reflect.SliceOf(t.Elem()) {
buf.WriteString("[]")
writeType(buf, 0, t.Elem())
} else {
// Custom slice type, use type name.
buf.WriteString(t.String())
}
case reflect.Map:
if t == reflect.MapOf(t.Key(), t.Elem()) {
buf.WriteString("map[")
writeType(buf, 0, t.Key())
buf.WriteRune(']')
writeType(buf, 0, t.Elem())
} else {
// Custom map type, use type name.
buf.WriteString(t.String())
}
default:
buf.WriteString(t.String())
}
if parens {
buf.WriteRune(')')
}
}
type sortableValueSlice struct {
kind reflect.Kind
elements []reflect.Value
}
func (s *sortableValueSlice) Len() int {
return len(s.elements)
}
func (s *sortableValueSlice) Less(i, j int) bool {
switch s.kind {
case reflect.String:
return s.elements[i].String() < s.elements[j].String()
case reflect.Int:
return s.elements[i].Int() < s.elements[j].Int()
default:
panic(fmt.Errorf("unsupported sort kind: %s", s.kind))
}
}
func (s *sortableValueSlice) Swap(i, j int) {
s.elements[i], s.elements[j] = s.elements[j], s.elements[i]
}
func tryAndSortMapKeys(mt reflect.Type, k []reflect.Value) {
// Try our stock sortable values.
switch mt.Key().Kind() {
case reflect.String, reflect.Int:
vs := &sortableValueSlice{
kind: mt.Key().Kind(),
elements: k,
}
sort.Sort(vs)
}
}