501 lines
12 KiB
Go
501 lines
12 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package yaml
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import (
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"bytes"
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"encoding"
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"encoding/json"
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"reflect"
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"sort"
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"strings"
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"sync"
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"unicode"
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"unicode/utf8"
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)
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// indirect walks down v allocating pointers as needed,
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// until it gets to a non-pointer.
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// if it encounters an Unmarshaler, indirect stops and returns that.
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// if decodingNull is true, indirect stops at the last pointer so it can be set to nil.
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func indirect(v reflect.Value, decodingNull bool) (json.Unmarshaler, encoding.TextUnmarshaler, reflect.Value) {
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// If v is a named type and is addressable,
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// start with its address, so that if the type has pointer methods,
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// we find them.
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if v.Kind() != reflect.Ptr && v.Type().Name() != "" && v.CanAddr() {
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v = v.Addr()
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}
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for {
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// Load value from interface, but only if the result will be
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// usefully addressable.
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if v.Kind() == reflect.Interface && !v.IsNil() {
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e := v.Elem()
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if e.Kind() == reflect.Ptr && !e.IsNil() && (!decodingNull || e.Elem().Kind() == reflect.Ptr) {
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v = e
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continue
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}
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}
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if v.Kind() != reflect.Ptr {
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break
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}
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if v.Elem().Kind() != reflect.Ptr && decodingNull && v.CanSet() {
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break
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}
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if v.IsNil() {
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if v.CanSet() {
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v.Set(reflect.New(v.Type().Elem()))
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} else {
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v = reflect.New(v.Type().Elem())
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}
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}
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if v.Type().NumMethod() > 0 {
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if u, ok := v.Interface().(json.Unmarshaler); ok {
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return u, nil, reflect.Value{}
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}
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if u, ok := v.Interface().(encoding.TextUnmarshaler); ok {
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return nil, u, reflect.Value{}
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}
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}
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v = v.Elem()
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}
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return nil, nil, v
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}
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// A field represents a single field found in a struct.
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type field struct {
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name string
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nameBytes []byte // []byte(name)
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equalFold func(s, t []byte) bool // bytes.EqualFold or equivalent
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tag bool
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index []int
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typ reflect.Type
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omitEmpty bool
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quoted bool
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}
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func fillField(f field) field {
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f.nameBytes = []byte(f.name)
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f.equalFold = foldFunc(f.nameBytes)
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return f
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}
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// byName sorts field by name, breaking ties with depth,
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// then breaking ties with "name came from json tag", then
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// breaking ties with index sequence.
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type byName []field
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func (x byName) Len() int { return len(x) }
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func (x byName) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
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func (x byName) Less(i, j int) bool {
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if x[i].name != x[j].name {
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return x[i].name < x[j].name
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}
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if len(x[i].index) != len(x[j].index) {
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return len(x[i].index) < len(x[j].index)
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}
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if x[i].tag != x[j].tag {
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return x[i].tag
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}
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return byIndex(x).Less(i, j)
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}
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// byIndex sorts field by index sequence.
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type byIndex []field
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func (x byIndex) Len() int { return len(x) }
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func (x byIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
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func (x byIndex) Less(i, j int) bool {
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for k, xik := range x[i].index {
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if k >= len(x[j].index) {
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return false
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}
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if xik != x[j].index[k] {
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return xik < x[j].index[k]
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}
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}
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return len(x[i].index) < len(x[j].index)
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}
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// typeFields returns a list of fields that JSON should recognize for the given type.
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// The algorithm is breadth-first search over the set of structs to include - the top struct
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// and then any reachable anonymous structs.
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func typeFields(t reflect.Type) []field {
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// Anonymous fields to explore at the current level and the next.
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current := []field{}
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next := []field{{typ: t}}
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// Count of queued names for current level and the next.
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count := map[reflect.Type]int{}
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nextCount := map[reflect.Type]int{}
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// Types already visited at an earlier level.
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visited := map[reflect.Type]bool{}
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// Fields found.
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var fields []field
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for len(next) > 0 {
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current, next = next, current[:0]
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count, nextCount = nextCount, map[reflect.Type]int{}
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for _, f := range current {
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if visited[f.typ] {
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continue
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}
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visited[f.typ] = true
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// Scan f.typ for fields to include.
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for i := 0; i < f.typ.NumField(); i++ {
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sf := f.typ.Field(i)
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if sf.PkgPath != "" { // unexported
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continue
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}
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tag := sf.Tag.Get("json")
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if tag == "-" {
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continue
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}
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name, opts := parseTag(tag)
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if !isValidTag(name) {
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name = ""
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}
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index := make([]int, len(f.index)+1)
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copy(index, f.index)
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index[len(f.index)] = i
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ft := sf.Type
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if ft.Name() == "" && ft.Kind() == reflect.Ptr {
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// Follow pointer.
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ft = ft.Elem()
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}
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// Record found field and index sequence.
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if name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
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tagged := name != ""
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if name == "" {
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name = sf.Name
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}
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fields = append(fields, fillField(field{
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name: name,
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tag: tagged,
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index: index,
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typ: ft,
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omitEmpty: opts.Contains("omitempty"),
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quoted: opts.Contains("string"),
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}))
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if count[f.typ] > 1 {
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// If there were multiple instances, add a second,
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// so that the annihilation code will see a duplicate.
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// It only cares about the distinction between 1 or 2,
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// so don't bother generating any more copies.
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fields = append(fields, fields[len(fields)-1])
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}
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continue
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}
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// Record new anonymous struct to explore in next round.
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nextCount[ft]++
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if nextCount[ft] == 1 {
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next = append(next, fillField(field{name: ft.Name(), index: index, typ: ft}))
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}
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}
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}
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}
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sort.Sort(byName(fields))
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// Delete all fields that are hidden by the Go rules for embedded fields,
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// except that fields with JSON tags are promoted.
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// The fields are sorted in primary order of name, secondary order
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// of field index length. Loop over names; for each name, delete
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// hidden fields by choosing the one dominant field that survives.
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out := fields[:0]
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for advance, i := 0, 0; i < len(fields); i += advance {
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// One iteration per name.
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// Find the sequence of fields with the name of this first field.
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fi := fields[i]
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name := fi.name
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for advance = 1; i+advance < len(fields); advance++ {
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fj := fields[i+advance]
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if fj.name != name {
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break
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}
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}
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if advance == 1 { // Only one field with this name
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out = append(out, fi)
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continue
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}
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dominant, ok := dominantField(fields[i : i+advance])
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if ok {
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out = append(out, dominant)
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}
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}
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fields = out
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sort.Sort(byIndex(fields))
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return fields
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}
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// dominantField looks through the fields, all of which are known to
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// have the same name, to find the single field that dominates the
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// others using Go's embedding rules, modified by the presence of
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// JSON tags. If there are multiple top-level fields, the boolean
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// will be false: This condition is an error in Go and we skip all
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// the fields.
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func dominantField(fields []field) (field, bool) {
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// The fields are sorted in increasing index-length order. The winner
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// must therefore be one with the shortest index length. Drop all
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// longer entries, which is easy: just truncate the slice.
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length := len(fields[0].index)
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tagged := -1 // Index of first tagged field.
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for i, f := range fields {
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if len(f.index) > length {
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fields = fields[:i]
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break
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}
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if f.tag {
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if tagged >= 0 {
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// Multiple tagged fields at the same level: conflict.
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// Return no field.
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return field{}, false
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}
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tagged = i
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}
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}
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if tagged >= 0 {
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return fields[tagged], true
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}
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// All remaining fields have the same length. If there's more than one,
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// we have a conflict (two fields named "X" at the same level) and we
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// return no field.
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if len(fields) > 1 {
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return field{}, false
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}
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return fields[0], true
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}
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var fieldCache struct {
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sync.RWMutex
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m map[reflect.Type][]field
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}
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// cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
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func cachedTypeFields(t reflect.Type) []field {
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fieldCache.RLock()
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f := fieldCache.m[t]
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fieldCache.RUnlock()
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if f != nil {
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return f
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}
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// Compute fields without lock.
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// Might duplicate effort but won't hold other computations back.
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f = typeFields(t)
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if f == nil {
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f = []field{}
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}
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fieldCache.Lock()
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if fieldCache.m == nil {
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fieldCache.m = map[reflect.Type][]field{}
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}
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fieldCache.m[t] = f
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fieldCache.Unlock()
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return f
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}
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func isValidTag(s string) bool {
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if s == "" {
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return false
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}
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for _, c := range s {
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switch {
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case strings.ContainsRune("!#$%&()*+-./:<=>?@[]^_{|}~ ", c):
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// Backslash and quote chars are reserved, but
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// otherwise any punctuation chars are allowed
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// in a tag name.
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default:
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if !unicode.IsLetter(c) && !unicode.IsDigit(c) {
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return false
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}
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}
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}
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return true
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}
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const (
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caseMask = ^byte(0x20) // Mask to ignore case in ASCII.
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kelvin = '\u212a'
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smallLongEss = '\u017f'
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)
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// foldFunc returns one of four different case folding equivalence
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// functions, from most general (and slow) to fastest:
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//
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// 1) bytes.EqualFold, if the key s contains any non-ASCII UTF-8
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// 2) equalFoldRight, if s contains special folding ASCII ('k', 'K', 's', 'S')
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// 3) asciiEqualFold, no special, but includes non-letters (including _)
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// 4) simpleLetterEqualFold, no specials, no non-letters.
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//
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// The letters S and K are special because they map to 3 runes, not just 2:
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// * S maps to s and to U+017F 'ſ' Latin small letter long s
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// * k maps to K and to U+212A 'K' Kelvin sign
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// See http://play.golang.org/p/tTxjOc0OGo
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//
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// The returned function is specialized for matching against s and
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// should only be given s. It's not curried for performance reasons.
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func foldFunc(s []byte) func(s, t []byte) bool {
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nonLetter := false
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special := false // special letter
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for _, b := range s {
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if b >= utf8.RuneSelf {
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return bytes.EqualFold
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}
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upper := b & caseMask
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if upper < 'A' || upper > 'Z' {
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nonLetter = true
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} else if upper == 'K' || upper == 'S' {
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// See above for why these letters are special.
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special = true
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}
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}
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if special {
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return equalFoldRight
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}
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if nonLetter {
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return asciiEqualFold
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}
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return simpleLetterEqualFold
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}
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// equalFoldRight is a specialization of bytes.EqualFold when s is
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// known to be all ASCII (including punctuation), but contains an 's',
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// 'S', 'k', or 'K', requiring a Unicode fold on the bytes in t.
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// See comments on foldFunc.
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func equalFoldRight(s, t []byte) bool {
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for _, sb := range s {
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if len(t) == 0 {
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return false
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}
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tb := t[0]
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if tb < utf8.RuneSelf {
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if sb != tb {
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sbUpper := sb & caseMask
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if 'A' <= sbUpper && sbUpper <= 'Z' {
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if sbUpper != tb&caseMask {
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return false
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}
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} else {
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return false
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}
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}
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t = t[1:]
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continue
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}
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// sb is ASCII and t is not. t must be either kelvin
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// sign or long s; sb must be s, S, k, or K.
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tr, size := utf8.DecodeRune(t)
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switch sb {
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case 's', 'S':
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if tr != smallLongEss {
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return false
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}
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case 'k', 'K':
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if tr != kelvin {
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return false
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}
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default:
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return false
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}
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t = t[size:]
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}
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if len(t) > 0 {
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return false
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}
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return true
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}
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// asciiEqualFold is a specialization of bytes.EqualFold for use when
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// s is all ASCII (but may contain non-letters) and contains no
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// special-folding letters.
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// See comments on foldFunc.
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func asciiEqualFold(s, t []byte) bool {
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if len(s) != len(t) {
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return false
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}
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for i, sb := range s {
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tb := t[i]
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if sb == tb {
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continue
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}
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if ('a' <= sb && sb <= 'z') || ('A' <= sb && sb <= 'Z') {
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if sb&caseMask != tb&caseMask {
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return false
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}
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} else {
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return false
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}
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}
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return true
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}
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// simpleLetterEqualFold is a specialization of bytes.EqualFold for
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// use when s is all ASCII letters (no underscores, etc) and also
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// doesn't contain 'k', 'K', 's', or 'S'.
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// See comments on foldFunc.
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func simpleLetterEqualFold(s, t []byte) bool {
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if len(s) != len(t) {
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return false
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}
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for i, b := range s {
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if b&caseMask != t[i]&caseMask {
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return false
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}
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}
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return true
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}
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// tagOptions is the string following a comma in a struct field's "json"
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// tag, or the empty string. It does not include the leading comma.
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type tagOptions string
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// parseTag splits a struct field's json tag into its name and
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// comma-separated options.
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func parseTag(tag string) (string, tagOptions) {
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if idx := strings.Index(tag, ","); idx != -1 {
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return tag[:idx], tagOptions(tag[idx+1:])
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}
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return tag, tagOptions("")
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}
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// Contains reports whether a comma-separated list of options
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// contains a particular substr flag. substr must be surrounded by a
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// string boundary or commas.
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func (o tagOptions) Contains(optionName string) bool {
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if len(o) == 0 {
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return false
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}
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s := string(o)
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for s != "" {
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var next string
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i := strings.Index(s, ",")
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if i >= 0 {
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s, next = s[:i], s[i+1:]
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}
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if s == optionName {
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return true
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}
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s = next
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}
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return false
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}
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