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- package toml
-
- // Struct field handling is adapted from code in encoding/json:
- //
- // Copyright 2010 The Go Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style
- // license that can be found in the Go distribution.
-
- import (
- "reflect"
- "sort"
- "sync"
- )
-
- // A field represents a single field found in a struct.
- type field struct {
- name string // the name of the field (`toml` tag included)
- tag bool // whether field has a `toml` tag
- index []int // represents the depth of an anonymous field
- typ reflect.Type // the type of the field
- }
-
- // byName sorts field by name, breaking ties with depth,
- // then breaking ties with "name came from toml tag", then
- // breaking ties with index sequence.
- type byName []field
-
- func (x byName) Len() int { return len(x) }
-
- func (x byName) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
-
- func (x byName) Less(i, j int) bool {
- 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)
- }
-
- // byIndex sorts field by index sequence.
- type byIndex []field
-
- func (x byIndex) Len() int { return len(x) }
-
- func (x byIndex) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
-
- 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 TOML 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) []field {
- // Anonymous fields to explore at the current level and the next.
- current := []field{}
- next := []field{{typ: t}}
-
- // Count of queued names for current level and the next.
- count := map[reflect.Type]int{}
- nextCount := map[reflect.Type]int{}
-
- // Types already visited at an earlier level.
- visited := map[reflect.Type]bool{}
-
- // Fields found.
- var fields []field
-
- 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)
- if sf.PkgPath != "" && !sf.Anonymous { // unexported
- continue
- }
- opts := getOptions(sf.Tag)
- if opts.skip {
- continue
- }
- 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 opts.name != "" || !sf.Anonymous || ft.Kind() != reflect.Struct {
- tagged := opts.name != ""
- name := opts.name
- if name == "" {
- name = sf.Name
- }
- fields = append(fields, field{name, tagged, index, ft})
- 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 {
- f := field{name: ft.Name(), index: index, typ: ft}
- next = append(next, f)
- }
- }
- }
- }
-
- sort.Sort(byName(fields))
-
- // Delete all fields that are hidden by the Go rules for embedded fields,
- // except that fields with TOML 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.Sort(byIndex(fields))
-
- return fields
- }
-
- // 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
- // TOML 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 []field) (field, bool) {
- // The fields are sorted in increasing index-length order. The winner
- // must therefore be one with the shortest index length. Drop all
- // longer entries, which is easy: just truncate the slice.
- length := len(fields[0].index)
- tagged := -1 // Index of first tagged field.
- for i, f := range fields {
- if len(f.index) > length {
- fields = fields[:i]
- break
- }
- if f.tag {
- if tagged >= 0 {
- // Multiple tagged fields at the same level: conflict.
- // Return no field.
- return field{}, false
- }
- tagged = i
- }
- }
- if tagged >= 0 {
- return fields[tagged], true
- }
- // All remaining fields have the same length. If there's more than one,
- // we have a conflict (two fields named "X" at the same level) and we
- // return no field.
- if len(fields) > 1 {
- return field{}, false
- }
- return fields[0], true
- }
-
- var fieldCache struct {
- sync.RWMutex
- m map[reflect.Type][]field
- }
-
- // cachedTypeFields is like typeFields but uses a cache to avoid repeated work.
- func cachedTypeFields(t reflect.Type) []field {
- fieldCache.RLock()
- f := fieldCache.m[t]
- fieldCache.RUnlock()
- if f != nil {
- return f
- }
-
- // Compute fields without lock.
- // Might duplicate effort but won't hold other computations back.
- f = typeFields(t)
- if f == nil {
- f = []field{}
- }
-
- fieldCache.Lock()
- if fieldCache.m == nil {
- fieldCache.m = map[reflect.Type][]field{}
- }
- fieldCache.m[t] = f
- fieldCache.Unlock()
- return f
- }
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