vendor!

vendor/github.com/jmoiron/sqlx/reflectx/README.md

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+# reflectx
+
+The sqlx package has special reflect needs.  In particular, it needs to:
+
+* be able to map a name to a field
+* understand embedded structs
+* understand mapping names to fields by a particular tag
+* user specified name -> field mapping functions
+
+These behaviors mimic the behaviors by the standard library marshallers and also the
+behavior of standard Go accessors.
+
+The first two are amply taken care of by `Reflect.Value.FieldByName`, and the third is
+addressed by `Reflect.Value.FieldByNameFunc`, but these don't quite understand struct
+tags in the ways that are vital to most marshallers, and they are slow.
+
+This reflectx package extends reflect to achieve these goals.

vendor/github.com/jmoiron/sqlx/reflectx/reflect.go

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+// Package reflectx implements extensions to the standard reflect lib suitable
+// for implementing marshalling and unmarshalling packages.  The main Mapper type
+// allows for Go-compatible named attribute access, including accessing embedded
+// struct attributes and the ability to use  functions and struct tags to
+// customize field names.
+//
+package reflectx
+
+import (
+	"reflect"
+	"runtime"
+	"strings"
+	"sync"
+)
+
+// A FieldInfo is metadata for a struct field.
+type FieldInfo struct {
+	Index    []int
+	Path     string
+	Field    reflect.StructField
+	Zero     reflect.Value
+	Name     string
+	Options  map[string]string
+	Embedded bool
+	Children []*FieldInfo
+	Parent   *FieldInfo
+}
+
+// A StructMap is an index of field metadata for a struct.
+type StructMap struct {
+	Tree  *FieldInfo
+	Index []*FieldInfo
+	Paths map[string]*FieldInfo
+	Names map[string]*FieldInfo
+}
+
+// GetByPath returns a *FieldInfo for a given string path.
+func (f StructMap) GetByPath(path string) *FieldInfo {
+	return f.Paths[path]
+}
+
+// GetByTraversal returns a *FieldInfo for a given integer path.  It is
+// analogous to reflect.FieldByIndex, but using the cached traversal
+// rather than re-executing the reflect machinery each time.
+func (f StructMap) GetByTraversal(index []int) *FieldInfo {
+	if len(index) == 0 {
+		return nil
+	}
+
+	tree := f.Tree
+	for _, i := range index {
+		if i >= len(tree.Children) || tree.Children[i] == nil {
+			return nil
+		}
+		tree = tree.Children[i]
+	}
+	return tree
+}
+
+// Mapper is a general purpose mapper of names to struct fields.  A Mapper
+// behaves like most marshallers in the standard library, obeying a field tag
+// for name mapping but also providing a basic transform function.
+type Mapper struct {
+	cache      map[reflect.Type]*StructMap
+	tagName    string
+	tagMapFunc func(string) string
+	mapFunc    func(string) string
+	mutex      sync.Mutex
+}
+
+// NewMapper returns a new mapper using the tagName as its struct field tag.
+// If tagName is the empty string, it is ignored.
+func NewMapper(tagName string) *Mapper {
+	return &Mapper{
+		cache:   make(map[reflect.Type]*StructMap),
+		tagName: tagName,
+	}
+}
+
+// NewMapperTagFunc returns a new mapper which contains a mapper for field names
+// AND a mapper for tag values.  This is useful for tags like json which can
+// have values like "name,omitempty".
+func NewMapperTagFunc(tagName string, mapFunc, tagMapFunc func(string) string) *Mapper {
+	return &Mapper{
+		cache:      make(map[reflect.Type]*StructMap),
+		tagName:    tagName,
+		mapFunc:    mapFunc,
+		tagMapFunc: tagMapFunc,
+	}
+}
+
+// NewMapperFunc returns a new mapper which optionally obeys a field tag and
+// a struct field name mapper func given by f.  Tags will take precedence, but
+// for any other field, the mapped name will be f(field.Name)
+func NewMapperFunc(tagName string, f func(string) string) *Mapper {
+	return &Mapper{
+		cache:   make(map[reflect.Type]*StructMap),
+		tagName: tagName,
+		mapFunc: f,
+	}
+}
+
+// TypeMap returns a mapping of field strings to int slices representing
+// the traversal down the struct to reach the field.
+func (m *Mapper) TypeMap(t reflect.Type) *StructMap {
+	m.mutex.Lock()
+	mapping, ok := m.cache[t]
+	if !ok {
+		mapping = getMapping(t, m.tagName, m.mapFunc, m.tagMapFunc)
+		m.cache[t] = mapping
+	}
+	m.mutex.Unlock()
+	return mapping
+}
+
+// FieldMap returns the mapper's mapping of field names to reflect values.  Panics
+// if v's Kind is not Struct, or v is not Indirectable to a struct kind.
+func (m *Mapper) FieldMap(v reflect.Value) map[string]reflect.Value {
+	v = reflect.Indirect(v)
+	mustBe(v, reflect.Struct)
+
+	r := map[string]reflect.Value{}
+	tm := m.TypeMap(v.Type())
+	for tagName, fi := range tm.Names {
+		r[tagName] = FieldByIndexes(v, fi.Index)
+	}
+	return r
+}
+
+// FieldByName returns a field by the its mapped name as a reflect.Value.
+// Panics if v's Kind is not Struct or v is not Indirectable to a struct Kind.
+// Returns zero Value if the name is not found.
+func (m *Mapper) FieldByName(v reflect.Value, name string) reflect.Value {
+	v = reflect.Indirect(v)
+	mustBe(v, reflect.Struct)
+
+	tm := m.TypeMap(v.Type())
+	fi, ok := tm.Names[name]
+	if !ok {
+		return v
+	}
+	return FieldByIndexes(v, fi.Index)
+}
+
+// FieldsByName returns a slice of values corresponding to the slice of names
+// for the value.  Panics if v's Kind is not Struct or v is not Indirectable
+// to a struct Kind.  Returns zero Value for each name not found.
+func (m *Mapper) FieldsByName(v reflect.Value, names []string) []reflect.Value {
+	v = reflect.Indirect(v)
+	mustBe(v, reflect.Struct)
+
+	tm := m.TypeMap(v.Type())
+	vals := make([]reflect.Value, 0, len(names))
+	for _, name := range names {
+		fi, ok := tm.Names[name]
+		if !ok {
+			vals = append(vals, *new(reflect.Value))
+		} else {
+			vals = append(vals, FieldByIndexes(v, fi.Index))
+		}
+	}
+	return vals
+}
+
+// TraversalsByName returns a slice of int slices which represent the struct
+// traversals for each mapped name.  Panics if t is not a struct or Indirectable
+// to a struct.  Returns empty int slice for each name not found.
+func (m *Mapper) TraversalsByName(t reflect.Type, names []string) [][]int {
+	t = Deref(t)
+	mustBe(t, reflect.Struct)
+	tm := m.TypeMap(t)
+
+	r := make([][]int, 0, len(names))
+	for _, name := range names {
+		fi, ok := tm.Names[name]
+		if !ok {
+			r = append(r, []int{})
+		} else {
+			r = append(r, fi.Index)
+		}
+	}
+	return r
+}
+
+// FieldByIndexes returns a value for the field given by the struct traversal
+// for the given value.
+func FieldByIndexes(v reflect.Value, indexes []int) reflect.Value {
+	for _, i := range indexes {
+		v = reflect.Indirect(v).Field(i)
+		// if this is a pointer and it's nil, allocate a new value and set it
+		if v.Kind() == reflect.Ptr && v.IsNil() {
+			alloc := reflect.New(Deref(v.Type()))
+			v.Set(alloc)
+		}
+		if v.Kind() == reflect.Map && v.IsNil() {
+			v.Set(reflect.MakeMap(v.Type()))
+		}
+	}
+	return v
+}
+
+// FieldByIndexesReadOnly returns a value for a particular struct traversal,
+// but is not concerned with allocating nil pointers because the value is
+// going to be used for reading and not setting.
+func FieldByIndexesReadOnly(v reflect.Value, indexes []int) reflect.Value {
+	for _, i := range indexes {
+		v = reflect.Indirect(v).Field(i)
+	}
+	return v
+}
+
+// Deref is Indirect for reflect.Types
+func Deref(t reflect.Type) reflect.Type {
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	return t
+}
+
+// -- helpers & utilities --
+
+type kinder interface {
+	Kind() reflect.Kind
+}
+
+// mustBe checks a value against a kind, panicing with a reflect.ValueError
+// if the kind isn't that which is required.
+func mustBe(v kinder, expected reflect.Kind) {
+	if k := v.Kind(); k != expected {
+		panic(&reflect.ValueError{Method: methodName(), Kind: k})
+	}
+}
+
+// methodName returns the caller of the function calling methodName
+func methodName() string {
+	pc, _, _, _ := runtime.Caller(2)
+	f := runtime.FuncForPC(pc)
+	if f == nil {
+		return "unknown method"
+	}
+	return f.Name()
+}
+
+type typeQueue struct {
+	t  reflect.Type
+	fi *FieldInfo
+	pp string // Parent path
+}
+
+// A copying append that creates a new slice each time.
+func apnd(is []int, i int) []int {
+	x := make([]int, len(is)+1)
+	for p, n := range is {
+		x[p] = n
+	}
+	x[len(x)-1] = i
+	return x
+}
+
+type mapf func(string) string
+
+// parseName parses the tag and the target name for the given field using
+// the tagName (eg 'json' for `json:"foo"` tags), mapFunc for mapping the
+// field's name to a target name, and tagMapFunc for mapping the tag to
+// a target name.
+func parseName(field reflect.StructField, tagName string, mapFunc, tagMapFunc mapf) (tag, fieldName string) {
+	// first, set the fieldName to the field's name
+	fieldName = field.Name
+	// if a mapFunc is set, use that to override the fieldName
+	if mapFunc != nil {
+		fieldName = mapFunc(fieldName)
+	}
+
+	// if there's no tag to look for, return the field name
+	if tagName == "" {
+		return "", fieldName
+	}
+
+	// if this tag is not set using the normal convention in the tag,
+	// then return the fieldname..  this check is done because according
+	// to the reflect documentation:
+	//    If the tag does not have the conventional format,
+	//    the value returned by Get is unspecified.
+	// which doesn't sound great.
+	if !strings.Contains(string(field.Tag), tagName+":") {
+		return "", fieldName
+	}
+
+	// at this point we're fairly sure that we have a tag, so lets pull it out
+	tag = field.Tag.Get(tagName)
+
+	// if we have a mapper function, call it on the whole tag
+	// XXX: this is a change from the old version, which pulled out the name
+	// before the tagMapFunc could be run, but I think this is the right way
+	if tagMapFunc != nil {
+		tag = tagMapFunc(tag)
+	}
+
+	// finally, split the options from the name
+	parts := strings.Split(tag, ",")
+	fieldName = parts[0]
+
+	return tag, fieldName
+}
+
+// parseOptions parses options out of a tag string, skipping the name
+func parseOptions(tag string) map[string]string {
+	parts := strings.Split(tag, ",")
+	options := make(map[string]string, len(parts))
+	if len(parts) > 1 {
+		for _, opt := range parts[1:] {
+			// short circuit potentially expensive split op
+			if strings.Contains(opt, "=") {
+				kv := strings.Split(opt, "=")
+				options[kv[0]] = kv[1]
+				continue
+			}
+			options[opt] = ""
+		}
+	}
+	return options
+}
+
+// getMapping returns a mapping for the t type, using the tagName, mapFunc and
+// tagMapFunc to determine the canonical names of fields.
+func getMapping(t reflect.Type, tagName string, mapFunc, tagMapFunc mapf) *StructMap {
+	m := []*FieldInfo{}
+
+	root := &FieldInfo{}
+	queue := []typeQueue{}
+	queue = append(queue, typeQueue{Deref(t), root, ""})
+
+QueueLoop:
+	for len(queue) != 0 {
+		// pop the first item off of the queue
+		tq := queue[0]
+		queue = queue[1:]
+
+		// ignore recursive field
+		for p := tq.fi.Parent; p != nil; p = p.Parent {
+			if tq.fi.Field.Type == p.Field.Type {
+				continue QueueLoop
+			}
+		}
+
+		nChildren := 0
+		if tq.t.Kind() == reflect.Struct {
+			nChildren = tq.t.NumField()
+		}
+		tq.fi.Children = make([]*FieldInfo, nChildren)
+
+		// iterate through all of its fields
+		for fieldPos := 0; fieldPos < nChildren; fieldPos++ {
+
+			f := tq.t.Field(fieldPos)
+
+			// parse the tag and the target name using the mapping options for this field
+			tag, name := parseName(f, tagName, mapFunc, tagMapFunc)
+
+			// if the name is "-", disabled via a tag, skip it
+			if name == "-" {
+				continue
+			}
+
+			fi := FieldInfo{
+				Field:   f,
+				Name:    name,
+				Zero:    reflect.New(f.Type).Elem(),
+				Options: parseOptions(tag),
+			}
+
+			// if the path is empty this path is just the name
+			if tq.pp == "" {
+				fi.Path = fi.Name
+			} else {
+				fi.Path = tq.pp + "." + fi.Name
+			}
+
+			// skip unexported fields
+			if len(f.PkgPath) != 0 && !f.Anonymous {
+				continue
+			}
+
+			// bfs search of anonymous embedded structs
+			if f.Anonymous {
+				pp := tq.pp
+				if tag != "" {
+					pp = fi.Path
+				}
+
+				fi.Embedded = true
+				fi.Index = apnd(tq.fi.Index, fieldPos)
+				nChildren := 0
+				ft := Deref(f.Type)
+				if ft.Kind() == reflect.Struct {
+					nChildren = ft.NumField()
+				}
+				fi.Children = make([]*FieldInfo, nChildren)
+				queue = append(queue, typeQueue{Deref(f.Type), &fi, pp})
+			} else if fi.Zero.Kind() == reflect.Struct || (fi.Zero.Kind() == reflect.Ptr && fi.Zero.Type().Elem().Kind() == reflect.Struct) {
+				fi.Index = apnd(tq.fi.Index, fieldPos)
+				fi.Children = make([]*FieldInfo, Deref(f.Type).NumField())
+				queue = append(queue, typeQueue{Deref(f.Type), &fi, fi.Path})
+			}
+
+			fi.Index = apnd(tq.fi.Index, fieldPos)
+			fi.Parent = tq.fi
+			tq.fi.Children[fieldPos] = &fi
+			m = append(m, &fi)
+		}
+	}
+
+	flds := &StructMap{Index: m, Tree: root, Paths: map[string]*FieldInfo{}, Names: map[string]*FieldInfo{}}
+	for _, fi := range flds.Index {
+		flds.Paths[fi.Path] = fi
+		if fi.Name != "" && !fi.Embedded {
+			flds.Names[fi.Path] = fi
+		}
+	}
+
+	return flds
+}