mirror of
https://github.com/golang/go
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![Matthew Dempsky](/assets/img/avatar_default.png)
The next CL will remove the -G flag, effectively hard-coding it to its current default (-G=3). Change-Id: Ib4743b529206928f9f1cca9fdb19989728327831 Reviewed-on: https://go-review.googlesource.com/c/go/+/388534 Reviewed-by: Keith Randall <khr@golang.org> Trust: Matthew Dempsky <mdempsky@google.com> Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
287 lines
7.1 KiB
Go
287 lines
7.1 KiB
Go
// run
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// Copyright 2021 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 orderedmap provides an ordered map, implemented as a binary tree.
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package main
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import (
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"bytes"
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"context"
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"fmt"
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"runtime"
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)
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type Ordered interface {
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~int | ~int8 | ~int16 | ~int32 | ~int64 |
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~uint | ~uint8 | ~uint16 | ~uint32 | ~uint64 | ~uintptr |
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~float32 | ~float64 |
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~string
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}
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// _Map is an ordered map.
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type _Map[K, V any] struct {
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root *node[K, V]
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compare func(K, K) int
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}
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// node is the type of a node in the binary tree.
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type node[K, V any] struct {
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key K
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val V
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left, right *node[K, V]
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}
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// _New returns a new map. It takes a comparison function that compares two
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// keys and returns < 0 if the first is less, == 0 if they are equal,
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// > 0 if the first is greater.
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func _New[K, V any](compare func(K, K) int) *_Map[K, V] {
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return &_Map[K, V]{compare: compare}
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}
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// _NewOrdered returns a new map whose key is an ordered type.
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// This is like _New, but does not require providing a compare function.
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// The map compare function uses the obvious key ordering.
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func _NewOrdered[K Ordered, V any]() *_Map[K, V] {
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return _New[K, V](func(k1, k2 K) int {
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switch {
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case k1 < k2:
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return -1
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case k1 == k2:
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return 0
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default:
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return 1
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}
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})
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}
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// find looks up key in the map, returning either a pointer to the slot of the
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// node holding key, or a pointer to the slot where should a node would go.
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func (m *_Map[K, V]) find(key K) **node[K, V] {
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pn := &m.root
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for *pn != nil {
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switch cmp := m.compare(key, (*pn).key); {
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case cmp < 0:
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pn = &(*pn).left
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case cmp > 0:
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pn = &(*pn).right
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default:
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return pn
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}
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}
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return pn
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}
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// Insert inserts a new key/value into the map.
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// If the key is already present, the value is replaced.
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// Reports whether this is a new key.
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func (m *_Map[K, V]) Insert(key K, val V) bool {
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pn := m.find(key)
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if *pn != nil {
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(*pn).val = val
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return false
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}
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*pn = &node[K, V]{key: key, val: val}
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return true
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}
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// Find returns the value associated with a key, or the zero value
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// if not present. The found result reports whether the key was found.
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func (m *_Map[K, V]) Find(key K) (V, bool) {
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pn := m.find(key)
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if *pn == nil {
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var zero V
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return zero, false
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}
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return (*pn).val, true
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}
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// keyValue is a pair of key and value used while iterating.
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type keyValue[K, V any] struct {
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key K
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val V
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}
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// iterate returns an iterator that traverses the map.
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func (m *_Map[K, V]) Iterate() *_Iterator[K, V] {
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sender, receiver := _Ranger[keyValue[K, V]]()
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var f func(*node[K, V]) bool
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f = func(n *node[K, V]) bool {
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if n == nil {
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return true
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}
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// Stop the traversal if Send fails, which means that
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// nothing is listening to the receiver.
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return f(n.left) &&
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sender.Send(context.Background(), keyValue[K, V]{n.key, n.val}) &&
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f(n.right)
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}
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go func() {
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f(m.root)
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sender.Close()
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}()
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return &_Iterator[K, V]{receiver}
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}
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// _Iterator is used to iterate over the map.
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type _Iterator[K, V any] struct {
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r *_Receiver[keyValue[K, V]]
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}
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// Next returns the next key and value pair, and a boolean that reports
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// whether they are valid. If not valid, we have reached the end of the map.
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func (it *_Iterator[K, V]) Next() (K, V, bool) {
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keyval, ok := it.r.Next(context.Background())
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if !ok {
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var zerok K
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var zerov V
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return zerok, zerov, false
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}
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return keyval.key, keyval.val, true
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}
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func TestMap() {
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m := _New[[]byte, int](bytes.Compare)
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if _, found := m.Find([]byte("a")); found {
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panic(fmt.Sprintf("unexpectedly found %q in empty map", []byte("a")))
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}
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if !m.Insert([]byte("a"), 'a') {
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panic(fmt.Sprintf("key %q unexpectedly already present", []byte("a")))
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}
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if !m.Insert([]byte("c"), 'c') {
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panic(fmt.Sprintf("key %q unexpectedly already present", []byte("c")))
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}
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if !m.Insert([]byte("b"), 'b') {
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panic(fmt.Sprintf("key %q unexpectedly already present", []byte("b")))
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}
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if m.Insert([]byte("c"), 'x') {
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panic(fmt.Sprintf("key %q unexpectedly not present", []byte("c")))
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}
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if v, found := m.Find([]byte("a")); !found {
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panic(fmt.Sprintf("did not find %q", []byte("a")))
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} else if v != 'a' {
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panic(fmt.Sprintf("key %q returned wrong value %c, expected %c", []byte("a"), v, 'a'))
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}
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if v, found := m.Find([]byte("c")); !found {
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panic(fmt.Sprintf("did not find %q", []byte("c")))
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} else if v != 'x' {
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panic(fmt.Sprintf("key %q returned wrong value %c, expected %c", []byte("c"), v, 'x'))
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}
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if _, found := m.Find([]byte("d")); found {
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panic(fmt.Sprintf("unexpectedly found %q", []byte("d")))
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}
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gather := func(it *_Iterator[[]byte, int]) []int {
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var r []int
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for {
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_, v, ok := it.Next()
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if !ok {
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return r
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}
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r = append(r, v)
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}
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}
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got := gather(m.Iterate())
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want := []int{'a', 'b', 'x'}
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if !_SliceEqual(got, want) {
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panic(fmt.Sprintf("Iterate returned %v, want %v", got, want))
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}
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}
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func main() {
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TestMap()
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}
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// _Equal reports whether two slices are equal: the same length and all
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// elements equal. All floating point NaNs are considered equal.
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func _SliceEqual[Elem comparable](s1, s2 []Elem) bool {
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if len(s1) != len(s2) {
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return false
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}
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for i, v1 := range s1 {
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v2 := s2[i]
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if v1 != v2 {
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isNaN := func(f Elem) bool { return f != f }
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if !isNaN(v1) || !isNaN(v2) {
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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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// Ranger returns a Sender and a Receiver. The Receiver provides a
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// Next method to retrieve values. The Sender provides a Send method
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// to send values and a Close method to stop sending values. The Next
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// method indicates when the Sender has been closed, and the Send
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// method indicates when the Receiver has been freed.
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//
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// This is a convenient way to exit a goroutine sending values when
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// the receiver stops reading them.
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func _Ranger[Elem any]() (*_Sender[Elem], *_Receiver[Elem]) {
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c := make(chan Elem)
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d := make(chan struct{})
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s := &_Sender[Elem]{
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values: c,
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done: d,
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}
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r := &_Receiver[Elem]{
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values: c,
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done: d,
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}
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runtime.SetFinalizer(r, (*_Receiver[Elem]).finalize)
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return s, r
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}
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// A _Sender is used to send values to a Receiver.
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type _Sender[Elem any] struct {
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values chan<- Elem
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done <-chan struct{}
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}
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// Send sends a value to the receiver. It reports whether the value was sent.
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// The value will not be sent if the context is closed or the receiver
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// is freed.
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func (s *_Sender[Elem]) Send(ctx context.Context, v Elem) bool {
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select {
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case <-ctx.Done():
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return false
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case s.values <- v:
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return true
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case <-s.done:
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return false
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}
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}
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// Close tells the receiver that no more values will arrive.
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// After Close is called, the _Sender may no longer be used.
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func (s *_Sender[Elem]) Close() {
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close(s.values)
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}
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// A _Receiver receives values from a _Sender.
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type _Receiver[Elem any] struct {
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values <-chan Elem
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done chan<- struct{}
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}
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// Next returns the next value from the channel. The bool result indicates
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// whether the value is valid.
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func (r *_Receiver[Elem]) Next(ctx context.Context) (v Elem, ok bool) {
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select {
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case <-ctx.Done():
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case v, ok = <-r.values:
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}
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return v, ok
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}
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// finalize is a finalizer for the receiver.
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func (r *_Receiver[Elem]) finalize() {
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close(r.done)
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}
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