85 lines
1.7 KiB
V
85 lines
1.7 KiB
V
// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module builtin
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/*
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This is work in progress.
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A very early test version of the hashmap with a fixed size.
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Only works with string keys and int values for now.
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I added this to improve performance of the V compiler,
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which uses lots of O(log n) map get's. Turned out with N < 10 000
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the performance gains are basically non-existent.
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*/
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import math
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struct hashmap {
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cap int
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keys []string
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table []hashmapentry
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elm_size int
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pub:
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nr_collisions int
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}
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struct hashmapentry {
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key string
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val int
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next &hashmapentry // linked list for collisions
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}
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const (
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min_cap = 2 << 10
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max_cap = 2 << 20
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)
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fn new_hashmap(planned_nr_items int) hashmap {
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mut cap := planned_nr_items * 3
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if cap < min_cap {
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cap = min_cap
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}
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if cap > max_cap {
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cap = max_cap
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}
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return hashmap{
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cap: cap
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elm_size: 4
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table: _make(cap, cap, sizeof(hashmapentry))
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}
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}
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fn (m mut hashmap) set(key string, val int) {
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hash := int(math.abs(key.hash()))
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idx := hash % m.cap
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if m.table[idx].key.len != 0 {
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//println('\nset() idx=$idx key="$key" hash="$hash" val=$val')
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m.nr_collisions++
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//println('collision:' + m.table[idx].key)
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mut e := &m.table[idx]
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for e.next != 0 {
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e = e.next
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}
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e.next = &hashmapentry{key, val, 0}
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} else {
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m.table[idx] = hashmapentry{key, val, 0}
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}
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}
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fn (m mut hashmap) get(key string) int {
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hash := int(math.abs(key.hash()))
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idx := hash % m.cap
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mut e := &m.table[idx]
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for e.next != 0 { // todo unsafe {
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if e.key == key {
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return e.val
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}
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e = e.next
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}
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return e.val
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}
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