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decode.go
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decode.go
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// Copyright 2021 CUE Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package cue
import (
"bytes"
"encoding"
"encoding/json"
"reflect"
"sort"
"strconv"
"strings"
"sync"
"unicode"
"unicode/utf8"
"github.com/wylswz/cue-se/cue/errors"
"github.com/wylswz/cue-se/internal/core/adt"
)
// Decode initializes the value pointed to by x with Value v.
// An error is returned if x is nil or not a pointer.
//
// If x is a struct, Decode will validate the constraints specified in the field tags.
func (v Value) Decode(x interface{}) error {
var d decoder
w := reflect.ValueOf(x)
if w.Kind() != reflect.Pointer || w.IsNil() {
d.addErr(errors.Newf(v.Pos(), "cannot decode into unsettable value"))
return d.errs
}
d.decode(w.Elem(), v, false)
return d.errs
}
type decoder struct {
errs errors.Error
}
func (d *decoder) addErr(err error) {
if err != nil {
d.errs = errors.Append(d.errs, errors.Promote(err, ""))
}
}
func incompleteError(v Value) errors.Error {
return &valueError{
v: v,
err: &adt.Bottom{
Code: adt.IncompleteError,
Err: errors.Newf(v.Pos(),
"cannot convert non-concrete value %v", v)},
}
}
func (d *decoder) clear(x reflect.Value) {
if x.CanSet() {
x.SetZero()
}
}
func (d *decoder) decode(x reflect.Value, v Value, isPtr bool) {
if !x.IsValid() {
d.addErr(errors.Newf(v.Pos(), "cannot decode into invalid value"))
return
}
v, _ = v.Default()
if v.v == nil {
d.clear(x)
return
}
if err := v.Err(); err != nil {
d.addErr(err)
return
}
switch x.Kind() {
case reflect.Ptr, reflect.Map, reflect.Slice, reflect.Interface:
// nullable types
if v.Null() == nil || !v.IsConcrete() {
d.clear(x)
return
}
default:
// TODO: allow incomplete values.
if !v.IsConcrete() {
d.addErr(incompleteError(v))
return
}
}
ij, it, x := indirect(x, v.Null() == nil)
if ij != nil {
b, err := v.marshalJSON()
d.addErr(err)
d.addErr(ij.UnmarshalJSON(b))
return
}
if it != nil {
b, err := v.Bytes()
if err != nil {
err = errors.Wrapf(err, v.Pos(), "Decode")
d.addErr(err)
return
}
d.addErr(it.UnmarshalText(b))
return
}
kind := x.Kind()
if kind == reflect.Interface {
value := d.interfaceValue(v)
x.Set(reflect.ValueOf(value))
return
}
switch kind {
case reflect.Ptr:
d.decode(x.Elem(), v, true)
case reflect.Bool:
b, err := v.Bool()
d.addErr(err)
x.SetBool(b)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
i, err := v.Int64()
d.addErr(err)
if x.OverflowInt(i) {
d.addErr(errors.Newf(v.Pos(), "integer %d overflows %s", i, kind))
break
}
x.SetInt(i)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
i, err := v.Uint64()
d.addErr(err)
if x.OverflowUint(i) {
d.addErr(errors.Newf(v.Pos(), "integer %d overflows %s", i, kind))
break
}
x.SetUint(i)
case reflect.Float32, reflect.Float64:
f, err := v.Float64()
d.addErr(err)
if x.OverflowFloat(f) {
d.addErr(errors.Newf(v.Pos(), "float %g overflows %s", f, kind))
break
}
x.SetFloat(f)
case reflect.String:
s, err := v.String()
d.addErr(err)
x.SetString(s)
case reflect.Array:
d.clear(x)
t := x.Type()
n := x.Len()
if t.Elem().Kind() == reflect.Uint8 && v.Kind() == BytesKind {
b, err := v.Bytes()
d.addErr(err)
for i, c := range b {
if i >= n {
break
}
x.Index(i).SetUint(uint64(c))
}
break
}
var a []Value
list, err := v.List()
d.addErr(err)
for list.Next() {
a = append(a, list.Value())
}
for i, v := range a {
if i >= n {
break
}
d.decode(x.Index(i), v, false)
}
case reflect.Slice:
t := x.Type()
if t.Elem().Kind() == reflect.Uint8 && v.Kind() == BytesKind {
b, err := v.Bytes()
d.addErr(err)
x.SetBytes(b)
break
}
var a []Value
list, err := v.List()
d.addErr(err)
for list.Next() {
a = append(a, list.Value())
}
switch cap := x.Cap(); {
case cap == 0, // force a non-nil list
cap < len(a):
x.Set(reflect.MakeSlice(t, len(a), len(a)))
default:
x.SetLen(len(a))
}
for i, v := range a {
d.decode(x.Index(i), v, false)
}
case reflect.Struct:
d.convertStruct(x, v)
case reflect.Map:
d.convertMap(x, v)
default:
d.clear(x)
}
}
func (d *decoder) interfaceValue(v Value) (x interface{}) {
var err error
v, _ = v.Default()
switch v.Kind() {
case NullKind:
return nil
case BoolKind:
x, err = v.Bool()
case IntKind:
if i, err := v.Int64(); err == nil {
return int(i)
}
x, err = v.Int(nil)
case FloatKind:
x, err = v.Float64() // or big int or
case StringKind:
x, err = v.String()
case BytesKind:
x, err = v.Bytes()
case ListKind:
var a []interface{}
list, err := v.List()
d.addErr(err)
for list.Next() {
a = append(a, d.interfaceValue(list.Value()))
}
if a == nil {
a = []interface{}{}
}
x = a
case StructKind:
m := map[string]interface{}{}
iter, err := v.Fields()
d.addErr(err)
for iter.Next() {
m[iter.Label()] = d.interfaceValue(iter.Value())
}
x = m
default:
err = incompleteError(v)
}
d.addErr(err)
return x
}
var textUnmarshalerType = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
// convertMap keeps an existing map and overwrites any entry found in v,
// keeping other preexisting entries.
func (d *decoder) convertMap(x reflect.Value, v Value) {
// Delete existing elements
t := x.Type()
// Map key must either have string kind, have an integer kind,
// or be an encoding.TextUnmarshaler.
switch t.Key().Kind() {
case reflect.String,
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
default:
if !reflect.PointerTo(t.Key()).Implements(textUnmarshalerType) {
d.addErr(errors.Newf(v.Pos(), "unsupported key type %v", t.Key()))
return
}
}
if x.IsNil() {
x.Set(reflect.MakeMap(t))
}
var mapElem reflect.Value
iter, err := v.Fields()
d.addErr(err)
for iter.Next() {
key := iter.Label()
var kv reflect.Value
kt := t.Key()
if reflect.PointerTo(kt).Implements(textUnmarshalerType) {
kv = reflect.New(kt)
err := kv.Interface().(encoding.TextUnmarshaler).UnmarshalText([]byte(key))
d.addErr(err)
kv = kv.Elem()
} else {
switch kt.Kind() {
case reflect.String:
kv = reflect.ValueOf(key).Convert(kt)
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
n, err := strconv.ParseInt(key, 10, 64)
d.addErr(err)
if reflect.Zero(kt).OverflowInt(n) {
d.addErr(errors.Newf(v.Pos(), "key integer %d overflows %s", n, kt))
break
}
kv = reflect.ValueOf(n).Convert(kt)
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
n, err := strconv.ParseUint(key, 10, 64)
d.addErr(err)
if reflect.Zero(kt).OverflowUint(n) {
d.addErr(errors.Newf(v.Pos(), "key integer %d overflows %s", n, kt))
break
}
kv = reflect.ValueOf(n).Convert(kt)
default:
panic("json: Unexpected key type") // should never occur
}
}
if !mapElem.IsValid() {
mapElem = reflect.New(t.Elem()).Elem()
} else {
mapElem.SetZero()
}
d.decode(mapElem, iter.Value(), false)
if kv.IsValid() {
x.SetMapIndex(kv, mapElem)
}
}
}
func (d *decoder) convertStruct(x reflect.Value, v Value) {
t := x.Type()
fields := cachedTypeFields(t)
iter, err := v.Fields()
d.addErr(err)
for iter.Next() {
var f *goField
key := iter.Label()
if i, ok := fields.nameIndex[key]; ok {
// Found an exact name match.
f = &fields.list[i]
} else {
// Fall back to the expensive case-insensitive
// linear search.
key := []byte(key)
for i := range fields.list {
ff := &fields.list[i]
if ff.equalFold(ff.nameBytes, key) {
f = ff
break
}
}
}
if f == nil {
continue
}
// Figure out field corresponding to key.
subv := x
for _, i := range f.index {
if subv.Kind() == reflect.Ptr {
if subv.IsNil() {
// If a struct embeds a pointer to an unexported type,
// it is not possible to set a newly allocated value
// since the field is unexported.
//
// See https://golang.org/issue/21357
if !subv.CanSet() {
d.addErr(errors.Newf(v.Pos(),
"cannot set embedded pointer to unexported struct: %v",
subv.Type().Elem()))
subv = reflect.Value{}
break
}
subv.Set(reflect.New(subv.Type().Elem()))
}
subv = subv.Elem()
}
subv = subv.Field(i)
}
// TODO: make this an option
// else if d.disallowUnknownFields {
// d.saveError(fmt.Errorf("json: unknown field %q", key))
// }
d.decode(subv, iter.Value(), false)
}
}
type structFields struct {
list []goField
nameIndex map[string]int
}
func isValidTag(s string) bool {
if s == "" {
return false
}
for _, c := range s {
switch {
case strings.ContainsRune("!#$%&()*+-./:;<=>?@[]^_{|}~ ", c):
// Backslash and quote chars are reserved, but
// otherwise any punctuation chars are allowed
// in a tag name.
case !unicode.IsLetter(c) && !unicode.IsDigit(c):
return false
}
}
return true
}
// A field represents a single Go field found in a struct.
type goField struct {
name string
nameBytes []byte // []byte(name)
equalFold func(s, t []byte) bool // bytes.EqualFold or equivalent
nameNonEsc string // `"` + name + `":`
nameEscHTML string // `"` + HTMLEscape(name) + `":`
tag bool
index []int
typ reflect.Type
omitEmpty bool
}
// byIndex sorts goField by index sequence.
type byIndex []goField
func (x byIndex) Less(i, j int) bool {
for k, xik := range x[i].index {
if k >= len(x[j].index) {
return false
}
if xik != x[j].index[k] {
return xik < x[j].index[k]
}
}
return len(x[i].index) < len(x[j].index)
}
// typeFields returns a list of fields that JSON should recognize for the given type.
// The algorithm is breadth-first search over the set of structs to include - the top struct
// and then any reachable anonymous structs.
func typeFields(t reflect.Type) structFields {
// Anonymous fields to explore at the current level and the next.
current := []goField{}
next := []goField{{typ: t}}
// Count of queued names for current level and the next.
var count, nextCount map[reflect.Type]int
// Types already visited at an earlier level.
visited := map[reflect.Type]bool{}
// Fields found.
var fields []goField
// Buffer to run HTMLEscape on field names.
var nameEscBuf bytes.Buffer
for len(next) > 0 {
current, next = next, current[:0]
count, nextCount = nextCount, map[reflect.Type]int{}
for _, f := range current {
if visited[f.typ] {
continue
}
visited[f.typ] = true
// Scan f.typ for fields to include.
for i := 0; i < f.typ.NumField(); i++ {
sf := f.typ.Field(i)
isUnexported := sf.PkgPath != ""
if sf.Anonymous {
t := sf.Type
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
if isUnexported && t.Kind() != reflect.Struct {
// Ignore embedded fields of unexported non-struct types.
continue
}
// Do not ignore embedded fields of unexported struct types
// since they may have exported fields.
} else if isUnexported {
// Ignore unexported non-embedded fields.
continue
}
tag := sf.Tag.Get("json")
if tag == "-" {
continue
}
name, opts := parseTag(tag)
if !isValidTag(name) {
name = ""
}
index := make([]int, len(f.index)+1)
copy(index, f.index)
index[len(f.index)] = i
ft := sf.Type
if ft.Name() == "" && ft.Kind() == reflect.Ptr {
// Follow pointer.
ft = ft.Elem()
}
// Record found field and index sequence.
if name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
tagged := name != ""
if name == "" {
name = sf.Name
}
field := goField{
name: name,
tag: tagged,
index: index,
typ: ft,
omitEmpty: opts.Contains("omitempty"),
}
field.nameBytes = []byte(field.name)
field.equalFold = foldFunc(field.nameBytes)
// Build nameEscHTML and nameNonEsc ahead of time.
nameEscBuf.Reset()
nameEscBuf.WriteString(`"`)
json.HTMLEscape(&nameEscBuf, field.nameBytes)
nameEscBuf.WriteString(`":`)
field.nameEscHTML = nameEscBuf.String()
field.nameNonEsc = `"` + field.name + `":`
fields = append(fields, field)
if count[f.typ] > 1 {
// If there were multiple instances, add a second,
// so that the annihilation code will see a duplicate.
// It only cares about the distinction between 1 or 2,
// so don't bother generating any more copies.
fields = append(fields, fields[len(fields)-1])
}
continue
}
// Record new anonymous struct to explore in next round.
nextCount[ft]++
if nextCount[ft] == 1 {
next = append(next, goField{name: ft.Name(), index: index, typ: ft})
}
}
}
}
sort.Slice(fields, func(i, j int) bool {
x := fields
// sort field by name, breaking ties with depth, then
// breaking ties with "name came from json tag", then
// breaking ties with index sequence.
if x[i].name != x[j].name {
return x[i].name < x[j].name
}
if len(x[i].index) != len(x[j].index) {
return len(x[i].index) < len(x[j].index)
}
if x[i].tag != x[j].tag {
return x[i].tag
}
return byIndex(x).Less(i, j)
})
// Delete all fields that are hidden by the Go rules for embedded fields,
// except that fields with JSON tags are promoted.
// The fields are sorted in primary order of name, secondary order
// of field index length. Loop over names; for each name, delete
// hidden fields by choosing the one dominant field that survives.
out := fields[:0]
for advance, i := 0, 0; i < len(fields); i += advance {
// One iteration per name.
// Find the sequence of fields with the name of this first field.
fi := fields[i]
name := fi.name
for advance = 1; i+advance < len(fields); advance++ {
fj := fields[i+advance]
if fj.name != name {
break
}
}
if advance == 1 { // Only one field with this name
out = append(out, fi)
continue
}
dominant, ok := dominantField(fields[i : i+advance])
if ok {
out = append(out, dominant)
}
}
fields = out
sort.Slice(fields, byIndex(fields).Less)
nameIndex := make(map[string]int, len(fields))
for i, field := range fields {
nameIndex[field.name] = i
}
return structFields{fields, nameIndex}
}
// dominantField looks through the fields, all of which are known to
// have the same name, to find the single field that dominates the
// others using Go's embedding rules, modified by the presence of
// JSON tags. If there are multiple top-level fields, the boolean
// will be false: This condition is an error in Go and we skip all
// the fields.
func dominantField(fields []goField) (goField, bool) {
// The fields are sorted in increasing index-length order, then by presence of tag.
// That means that the first field is the dominant one. We need only check
// for error cases: two fields at top level, either both tagged or neither tagged.
if len(fields) > 1 && len(fields[0].index) == len(fields[1].index) && fields[0].tag == fields[1].tag {
return goField{}, false
}
return fields[0], true
}
var fieldCache sync.Map // map[reflect.Type]structFields
// cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
func cachedTypeFields(t reflect.Type) structFields {
if f, ok := fieldCache.Load(t); ok {
return f.(structFields)
}
f, _ := fieldCache.LoadOrStore(t, typeFields(t))
return f.(structFields)
}
// tagOptions is the string following a comma in a struct field's "json"
// tag, or the empty string. It does not include the leading comma.
type tagOptions string
// parseTag splits a struct field's json tag into its name and
// comma-separated options.
func parseTag(tag string) (string, tagOptions) {
if idx := strings.Index(tag, ","); idx != -1 {
return tag[:idx], tagOptions(tag[idx+1:])
}
return tag, tagOptions("")
}
// Contains reports whether a comma-separated list of options
// contains a particular substr flag. substr must be surrounded by a
// string boundary or commas.
func (o tagOptions) Contains(optionName string) bool {
if len(o) == 0 {
return false
}
s := string(o)
for s != "" {
var next string
i := strings.Index(s, ",")
if i >= 0 {
s, next = s[:i], s[i+1:]
}
if s == optionName {
return true
}
s = next
}
return false
}
// foldFunc returns one of four different case folding equivalence
// functions, from most general (and slow) to fastest:
//
// 1) bytes.EqualFold, if the key s contains any non-ASCII UTF-8
// 2) equalFoldRight, if s contains special folding ASCII ('k', 'K', 's', 'S')
// 3) asciiEqualFold, no special, but includes non-letters (including _)
// 4) simpleLetterEqualFold, no specials, no non-letters.
//
// The letters S and K are special because they map to 3 runes, not just 2:
// - S maps to s and to U+017F 'ſ' Latin small letter long s
// - k maps to K and to U+212A 'K' Kelvin sign
//
// See https://play.golang.org/p/tTxjOc0OGo
//
// The returned function is specialized for matching against s and
// should only be given s. It's not curried for performance reasons.
func foldFunc(s []byte) func(s, t []byte) bool {
nonLetter := false
special := false // special letter
for _, b := range s {
if b >= utf8.RuneSelf {
return bytes.EqualFold
}
upper := b & caseMask
if upper < 'A' || upper > 'Z' {
nonLetter = true
} else if upper == 'K' || upper == 'S' {
// See above for why these letters are special.
special = true
}
}
if special {
return equalFoldRight
}
if nonLetter {
return asciiEqualFold
}
return simpleLetterEqualFold
}
const (
caseMask = ^byte(0x20) // Mask to ignore case in ASCII.
kelvin = '\u212a'
smallLongEss = '\u017f'
)
// equalFoldRight is a specialization of bytes.EqualFold when s is
// known to be all ASCII (including punctuation), but contains an 's',
// 'S', 'k', or 'K', requiring a Unicode fold on the bytes in t.
// See comments on foldFunc.
func equalFoldRight(s, t []byte) bool {
for _, sb := range s {
if len(t) == 0 {
return false
}
tb := t[0]
if tb < utf8.RuneSelf {
if sb != tb {
sbUpper := sb & caseMask
if 'A' <= sbUpper && sbUpper <= 'Z' {
if sbUpper != tb&caseMask {
return false
}
} else {
return false
}
}
t = t[1:]
continue
}
// sb is ASCII and t is not. t must be either kelvin
// sign or long s; sb must be s, S, k, or K.
tr, size := utf8.DecodeRune(t)
switch sb {
case 's', 'S':
if tr != smallLongEss {
return false
}
case 'k', 'K':
if tr != kelvin {
return false
}
default:
return false
}
t = t[size:]
}
return len(t) == 0
}
// asciiEqualFold is a specialization of bytes.EqualFold for use when
// s is all ASCII (but may contain non-letters) and contains no
// special-folding letters.
// See comments on foldFunc.
func asciiEqualFold(s, t []byte) bool {
if len(s) != len(t) {
return false
}
for i, sb := range s {
tb := t[i]
if sb == tb {
continue
}
if ('a' <= sb && sb <= 'z') || ('A' <= sb && sb <= 'Z') {
if sb&caseMask != tb&caseMask {
return false
}
} else {
return false
}
}
return true
}
// simpleLetterEqualFold is a specialization of bytes.EqualFold for
// use when s is all ASCII letters (no underscores, etc) and also
// doesn't contain 'k', 'K', 's', or 'S'.
// See comments on foldFunc.
func simpleLetterEqualFold(s, t []byte) bool {
if len(s) != len(t) {
return false
}
for i, b := range s {
if b&caseMask != t[i]&caseMask {
return false
}
}
return true
}
// indirect walks down v allocating pointers as needed,
// until it gets to a non-pointer.
// If it encounters an Unmarshaler, indirect stops and returns that.
// If decodingNull is true, indirect stops at the first settable pointer so it
// can be set to nil.
func indirect(v reflect.Value, decodingNull bool) (json.Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
// Issue #24153 indicates that it is generally not a guaranteed property
// that you may round-trip a reflect.Value by calling Value.Addr().Elem()
// and expect the value to still be settable for values derived from
// unexported embedded struct fields.
//
// The logic below effectively does this when it first addresses the value
// (to satisfy possible pointer methods) and continues to dereference
// subsequent pointers as necessary.
//
// After the first round-trip, we set v back to the original value to
// preserve the original RW flags contained in reflect.Value.
v0 := v
haveAddr := false
// If v is a named type and is addressable,
// start with its address, so that if the type has pointer methods,
// we find them.
if v.Kind() != reflect.Ptr && v.Type().Name() != "" && v.CanAddr() {
haveAddr = true
v = v.Addr()
}
for {
// Load value from interface, but only if the result will be
// usefully addressable.
if v.Kind() == reflect.Interface && !v.IsNil() {
e := v.Elem()
if e.Kind() == reflect.Ptr && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Ptr) {
haveAddr = false
v = e
continue
}
}
if v.Kind() != reflect.Ptr {
break
}
if decodingNull && v.CanSet() {
break
}
// Prevent infinite loop if v is an interface pointing to its own address:
// var v interface{}
// v = &v
if v.Elem().Kind() == reflect.Interface && v.Elem().Elem() == v {
v = v.Elem()
break
}
if v.IsNil() {
v.Set(reflect.New(v.Type().Elem()))
}
if v.Type().NumMethod() > 0 && v.CanInterface() {
if u, ok := v.Interface().(json.Unmarshaler); ok {
return u, nil, reflect.Value{}
}
if !decodingNull {
if u, ok := v.Interface().(encoding.TextUnmarshaler); ok {
return nil, u, reflect.Value{}
}
}
}
if haveAddr {
v = v0 // restore original value after round-trip Value.Addr().Elem()
haveAddr = false
} else {
v = v.Elem()
}
}
return nil, nil, v
}