2008-03-12 22:10:10 +00:00
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// $G $F.go && $L $F.$A && ./$A.out
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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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2009-01-20 22:40:40 +00:00
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func ASSERT(p bool) {
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2008-08-29 20:21:00 +00:00
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if !p {
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// panic 0;
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}
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2008-03-12 22:10:10 +00:00
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}
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// ----------------------------------------------------------------------------
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// Implementation of the HashMap
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2009-01-20 22:40:40 +00:00
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type KeyType interface {
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2008-08-29 20:21:00 +00:00
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Hash() uint32;
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Match(other *KeyType) bool
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2008-03-12 22:10:10 +00:00
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}
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2009-01-20 22:40:40 +00:00
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type ValueType interface {
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2008-08-29 20:21:00 +00:00
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// empty interface
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2008-03-12 22:10:10 +00:00
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}
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2009-01-20 22:40:40 +00:00
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type Entry struct {
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key *KeyType;
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value *ValueType;
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2008-03-12 22:10:10 +00:00
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}
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// Using the Array type below doesn't seem to work
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//type Array array [1024] Entry;
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2009-01-20 22:40:40 +00:00
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type HashMap struct {
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2008-08-29 20:21:00 +00:00
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map_ *[1024] Entry;
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log2_capacity_ uint32;
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occupancy_ uint32;
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2008-03-12 22:10:10 +00:00
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}
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func (m *HashMap) capacity() uint32 {
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2008-08-29 20:33:34 +00:00
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return 1 << m.log2_capacity_;
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2008-03-12 22:10:10 +00:00
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}
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func (m *HashMap) Clear() {
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2008-08-29 20:21:00 +00:00
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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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2008-03-12 22:10:10 +00:00
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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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2009-01-06 23:19:02 +00:00
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m.map_ = new([1024] Entry);
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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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2008-12-19 11:05:37 +00:00
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2008-08-29 20:21:00 +00:00
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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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2008-12-19 11:05:37 +00:00
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2008-08-29 20:21:00 +00:00
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return &m.map_[i];
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2008-03-12 22:10:10 +00:00
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}
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func (m *HashMap) Lookup (key *KeyType, insert bool) *Entry {
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2008-08-29 20:21:00 +00:00
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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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2008-08-29 20:21:00 +00:00
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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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2008-12-19 11:05:37 +00:00
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2008-08-29 20:21:00 +00:00
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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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2008-03-12 22:10:10 +00:00
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}
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func (m *HashMap) Resize() {
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2008-08-29 20:21:00 +00:00
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var hmap *[1024] Entry = m.map_;
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var n uint32 = m.occupancy_;
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2008-12-19 11:05:37 +00:00
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2008-08-29 20:21:00 +00:00
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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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2008-12-19 11:05:37 +00:00
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2008-08-29 20:21:00 +00:00
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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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2008-03-12 22:10:10 +00:00
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}
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// ----------------------------------------------------------------------------
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// Test code
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2009-01-20 22:40:40 +00:00
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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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2008-03-12 22:10:10 +00:00
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}
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2009-01-20 22:40:40 +00:00
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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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2008-03-12 22:10:10 +00:00
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}
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func main() {
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2008-08-29 20:21:00 +00:00
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//f unc (n int) int { return n + 1; }(1);
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//print "HashMap - gri 2/8/2008\n";
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2009-01-06 23:19:02 +00:00
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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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2008-08-29 20:21:00 +00:00
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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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