+++ /dev/null
-// Copyright 2019 The Go 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 label
-
-import (
- "fmt"
- "io"
- "reflect"
- "unsafe"
-)
-
-// Key is used as the identity of a Label.
-// Keys are intended to be compared by pointer only, the name should be unique
-// for communicating with external systems, but it is not required or enforced.
-type Key interface {
- // Name returns the key name.
- Name() string
- // Description returns a string that can be used to describe the value.
- Description() string
-
- // Format is used in formatting to append the value of the label to the
- // supplied buffer.
- // The formatter may use the supplied buf as a scratch area to avoid
- // allocations.
- Format(w io.Writer, buf []byte, l Label)
-}
-
-// Label holds a key and value pair.
-// It is normally used when passing around lists of labels.
-type Label struct {
- key Key
- packed uint64
- untyped interface{}
-}
-
-// Map is the interface to a collection of Labels indexed by key.
-type Map interface {
- // Find returns the label that matches the supplied key.
- Find(key Key) Label
-}
-
-// List is the interface to something that provides an iterable
-// list of labels.
-// Iteration should start from 0 and continue until Valid returns false.
-type List interface {
- // Valid returns true if the index is within range for the list.
- // It does not imply the label at that index will itself be valid.
- Valid(index int) bool
- // Label returns the label at the given index.
- Label(index int) Label
-}
-
-// list implements LabelList for a list of Labels.
-type list struct {
- labels []Label
-}
-
-// filter wraps a LabelList filtering out specific labels.
-type filter struct {
- keys []Key
- underlying List
-}
-
-// listMap implements LabelMap for a simple list of labels.
-type listMap struct {
- labels []Label
-}
-
-// mapChain implements LabelMap for a list of underlying LabelMap.
-type mapChain struct {
- maps []Map
-}
-
-// OfValue creates a new label from the key and value.
-// This method is for implementing new key types, label creation should
-// normally be done with the Of method of the key.
-func OfValue(k Key, value interface{}) Label { return Label{key: k, untyped: value} }
-
-// UnpackValue assumes the label was built using LabelOfValue and returns the value
-// that was passed to that constructor.
-// This method is for implementing new key types, for type safety normal
-// access should be done with the From method of the key.
-func (t Label) UnpackValue() interface{} { return t.untyped }
-
-// Of64 creates a new label from a key and a uint64. This is often
-// used for non uint64 values that can be packed into a uint64.
-// This method is for implementing new key types, label creation should
-// normally be done with the Of method of the key.
-func Of64(k Key, v uint64) Label { return Label{key: k, packed: v} }
-
-// Unpack64 assumes the label was built using LabelOf64 and returns the value that
-// was passed to that constructor.
-// This method is for implementing new key types, for type safety normal
-// access should be done with the From method of the key.
-func (t Label) Unpack64() uint64 { return t.packed }
-
-// OfString creates a new label from a key and a string.
-// This method is for implementing new key types, label creation should
-// normally be done with the Of method of the key.
-func OfString(k Key, v string) Label {
- hdr := (*reflect.StringHeader)(unsafe.Pointer(&v))
- return Label{
- key: k,
- packed: uint64(hdr.Len),
- untyped: unsafe.Pointer(hdr.Data),
- }
-}
-
-// UnpackString assumes the label was built using LabelOfString and returns the
-// value that was passed to that constructor.
-// This method is for implementing new key types, for type safety normal
-// access should be done with the From method of the key.
-func (t Label) UnpackString() string {
- var v string
- hdr := (*reflect.StringHeader)(unsafe.Pointer(&v))
- hdr.Data = uintptr(t.untyped.(unsafe.Pointer))
- hdr.Len = int(t.packed)
- return *(*string)(unsafe.Pointer(hdr))
-}
-
-// Valid returns true if the Label is a valid one (it has a key).
-func (t Label) Valid() bool { return t.key != nil }
-
-// Key returns the key of this Label.
-func (t Label) Key() Key { return t.key }
-
-// Format is used for debug printing of labels.
-func (t Label) Format(f fmt.State, r rune) {
- if !t.Valid() {
- io.WriteString(f, `nil`)
- return
- }
- io.WriteString(f, t.Key().Name())
- io.WriteString(f, "=")
- var buf [128]byte
- t.Key().Format(f, buf[:0], t)
-}
-
-func (l *list) Valid(index int) bool {
- return index >= 0 && index < len(l.labels)
-}
-
-func (l *list) Label(index int) Label {
- return l.labels[index]
-}
-
-func (f *filter) Valid(index int) bool {
- return f.underlying.Valid(index)
-}
-
-func (f *filter) Label(index int) Label {
- l := f.underlying.Label(index)
- for _, f := range f.keys {
- if l.Key() == f {
- return Label{}
- }
- }
- return l
-}
-
-func (lm listMap) Find(key Key) Label {
- for _, l := range lm.labels {
- if l.Key() == key {
- return l
- }
- }
- return Label{}
-}
-
-func (c mapChain) Find(key Key) Label {
- for _, src := range c.maps {
- l := src.Find(key)
- if l.Valid() {
- return l
- }
- }
- return Label{}
-}
-
-var emptyList = &list{}
-
-func NewList(labels ...Label) List {
- if len(labels) == 0 {
- return emptyList
- }
- return &list{labels: labels}
-}
-
-func Filter(l List, keys ...Key) List {
- if len(keys) == 0 {
- return l
- }
- return &filter{keys: keys, underlying: l}
-}
-
-func NewMap(labels ...Label) Map {
- return listMap{labels: labels}
-}
-
-func MergeMaps(srcs ...Map) Map {
- var nonNil []Map
- for _, src := range srcs {
- if src != nil {
- nonNil = append(nonNil, src)
- }
- }
- if len(nonNil) == 1 {
- return nonNil[0]
- }
- return mapChain{maps: nonNil}
-}
projects / dotfiles / .git / blobdiff