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test/hashmap.go: delete
It's in an odd style and it's unclear what true purpose it serves as a test other than to be another Go program. R=gri CC=golang-dev https://golang.org/cl/5674111
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test/hashmap.go
181
test/hashmap.go
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// run
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// Copyright 2009 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 main
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// ----------------------------------------------------------------------------
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// Helper functions
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func ASSERT(p bool) {
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if !p {
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// panic 0
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}
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}
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// ----------------------------------------------------------------------------
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// Implementation of the HashMap
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type KeyType interface {
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Hash() uint32
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Match(other KeyType) bool
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}
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type ValueType interface {
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// empty interface
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}
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type Entry struct {
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key KeyType
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value ValueType
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}
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type Array [1024]Entry
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type HashMap struct {
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map_ *Array
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log2_capacity_ uint32
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occupancy_ uint32
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}
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func (m *HashMap) capacity() uint32 {
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return 1 << m.log2_capacity_
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}
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func (m *HashMap) Clear() {
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// Mark all entries as empty.
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var i uint32 = m.capacity() - 1
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for i > 0 {
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m.map_[i].key = nil
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i = i - 1
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}
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m.occupancy_ = 0
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}
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func (m *HashMap) Initialize (initial_log2_capacity uint32) {
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m.log2_capacity_ = initial_log2_capacity
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m.map_ = new(Array)
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m.Clear()
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}
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func (m *HashMap) Probe (key KeyType) *Entry {
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ASSERT(key != nil)
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var i uint32 = key.Hash() % m.capacity()
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ASSERT(0 <= i && i < m.capacity())
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ASSERT(m.occupancy_ < m.capacity()) // guarantees loop termination
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for m.map_[i].key != nil && !m.map_[i].key.Match(key) {
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i++
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if i >= m.capacity() {
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i = 0
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}
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}
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return &m.map_[i]
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}
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func (m *HashMap) Lookup (key KeyType, insert bool) *Entry {
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// Find a matching entry.
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var p *Entry = m.Probe(key)
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if p.key != nil {
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return p
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}
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// No entry found; insert one if necessary.
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if insert {
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p.key = key
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p.value = nil
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m.occupancy_++
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// Grow the map if we reached >= 80% occupancy.
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if m.occupancy_ + m.occupancy_/4 >= m.capacity() {
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m.Resize()
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p = m.Probe(key)
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}
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return p
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}
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// No entry found and none inserted.
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return nil
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}
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func (m *HashMap) Resize() {
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var hmap *Array = m.map_
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var n uint32 = m.occupancy_
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// Allocate a new map of twice the current size.
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m.Initialize(m.log2_capacity_ << 1)
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// Rehash all current entries.
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var i uint32 = 0
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for n > 0 {
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if hmap[i].key != nil {
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m.Lookup(hmap[i].key, true).value = hmap[i].value
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n = n - 1
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}
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i++
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}
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}
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// ----------------------------------------------------------------------------
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// Test code
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type Number struct {
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x uint32
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}
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func (n *Number) Hash() uint32 {
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return n.x * 23
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}
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func (n *Number) Match(other KeyType) bool {
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// var y *Number = other
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// return n.x == y.x
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return false
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}
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func MakeNumber (x uint32) *Number {
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var n *Number = new(Number)
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n.x = x
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return n
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}
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func main() {
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// func (n int) int { return n + 1; }(1)
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//print "HashMap - gri 2/8/2008\n"
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var hmap *HashMap = new(HashMap)
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hmap.Initialize(0)
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var x1 *Number = MakeNumber(1001)
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var x2 *Number = MakeNumber(2002)
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var x3 *Number = MakeNumber(3003)
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_, _, _ = x1, x2, x3
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// this doesn't work I think...
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//hmap.Lookup(x1, true)
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//hmap.Lookup(x2, true)
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//hmap.Lookup(x3, true)
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//print "done\n"
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}
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