v/vlib/builtin/hashmap/hashmap.v

233 lines
5.3 KiB
V

// Copyright (c) 2019 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module hashmap
const (
initial_size = 2 << 4
initial_cap = initial_size - 1
probe_offset = u16(256)
load_factor = 0.8
)
// hash-function should not be in this file
const (
fnv64_prime = 1099511628211
fnv64_offset_basis = 14695981039346656037
fnv32_offset_basis = u32(2166136261)
fnv32_prime = u32(16777619)
)
[inline]
fn fnv1a64(data string) u64 {
mut hash := fnv64_offset_basis
for i := 0; i < data.len; i++ {
hash = (hash ^ u64(data[i])) * fnv64_prime
}
return hash
}
pub struct Hashmap {
mut:
info &u16
key_values &KeyValue
cap int
pub mut:
load_factor f32
size int
}
struct KeyValue {
key string
mut:
value int
}
pub fn new_hashmap() Hashmap {
return Hashmap{
info: &u16(calloc(sizeof(u16) * initial_size))
key_values: &KeyValue(calloc(sizeof(KeyValue) * initial_size))
cap: initial_cap
load_factor: 0.8
size: 0
}
}
pub fn (h mut Hashmap) set(key string, value int) {
// The load factor is 0.5.
// It will be adjustable in the future and with
// a higher default settings to lower memory usage.
if (f32(h.size) / f32(h.cap)) > h.load_factor {
h.rehash()
}
// Hash-function will be swapped for wyhash
hash := fnv1a64(key)
mut info := u16((hash >> 56) | probe_offset)
mut index := hash & h.cap
// While probe count is less
for info < h.info[index] {
index = (index + 1) & h.cap
info += probe_offset
}
// While we might have a match
for info == h.info[index] {
if key == h.key_values[index].key {
h.key_values[index].value = value
return
}
index = (index + 1) & h.cap
info += probe_offset
}
// Match is not possible anymore.
// Probe until an empty index is found.
// Swap when probe count is higher/richer (Robin Hood).
mut current_kv := KeyValue{key, value}
for h.info[index] != 0 {
if info > h.info[index] {
// Swap info word
tmp_info := h.info[index]
h.info[index] = info
info = tmp_info
// Swap KeyValue
tmp_kv := h.key_values[index]
h.key_values[index] = current_kv
current_kv = tmp_kv
}
index = (index + 1) & h.cap
info += probe_offset
}
// Should almost never happen
if (info & 0xFF00) == 0xFF00 {
h.rehash()
h.set(current_kv.key, current_kv.value)
return
}
h.info[index] = info
h.key_values[index] = current_kv
h.size++
}
fn (h mut Hashmap) rehash() {
old_cap := h.cap
h.cap = ((h.cap + 1) << 1) - 1
mut new_key_values := &KeyValue(calloc(sizeof(KeyValue) * (h.cap + 1)))
mut new_info := &u16(calloc(sizeof(u16) * (h.cap + 1)))
for i in 0 .. (old_cap + 1) {
if h.info[i] != 0 {
mut kv := h.key_values[i]
hash := fnv1a64(kv.key)
mut info := u16((hash >> 56) | probe_offset)
mut index := hash & h.cap
// While probe count is less
for info < new_info[index] {
index = (index + 1) & h.cap
info += probe_offset
}
// Probe until an empty index is found.
// Swap when probe count is higher/richer (Robin Hood).
for new_info[index] != 0 {
if info > new_info[index] {
// Swap info word
tmp_info := new_info[index]
new_info[index] = info
info = tmp_info
// Swap KeyValue
tmp_kv := new_key_values[index]
new_key_values[index] = kv
kv = tmp_kv
}
index = (index + 1) & h.cap
info += probe_offset
}
// Should almost never happen
if (info & 0xFF00) == 0xFF00 {
h.rehash()
h.set(kv.key, kv.value)
return
}
new_info[index] = info
new_key_values[index] = kv
}
}
h.key_values = new_key_values
h.info = new_info
}
pub fn (h mut Hashmap) delete(key string) {
hash := fnv1a64(key)
mut index := hash & h.cap
mut info := u16((hash >> 56) | probe_offset)
for info < h.info[index] {
index = (index + 1) & h.cap
info += probe_offset
}
// Perform backwards shifting
for info == h.info[index] {
if key == h.key_values[index].key {
mut old_index := index
index = (index + 1) & h.cap
mut current_info := h.info[index]
for (current_info >> 8) > 1 {
h.info[old_index] = current_info - probe_offset
h.key_values[old_index] = h.key_values[index]
old_index = index
index = (index + 1) & h.cap
current_info = h.info[index]
}
h.info[old_index] = 0
h.size--
return
}
index = (index + 1) & h.cap
info += probe_offset
}
}
pub fn (h Hashmap) get(key string) int {
hash := fnv1a64(key)
mut index := hash & h.cap
mut info := u16((hash >> 56) | probe_offset)
for info < h.info[index] {
index = (index + 1) & h.cap
info += probe_offset
}
for info == h.info[index] {
if key == h.key_values[index].key {
return h.key_values[index].value
}
index = (index + 1) & h.cap
info += probe_offset
}
return 0
}
pub fn (h Hashmap) exists(key string) bool {
hash := fnv1a64(key)
mut index := hash & h.cap
mut info := u16((hash >> 56) | probe_offset)
for info < h.info[index] {
index = (index + 1) & h.cap
info += probe_offset
}
for info == h.info[index] {
if key == h.key_values[index].key {
return true
}
index = (index + 1) & h.cap
info += probe_offset
}
return false
}
pub fn (h Hashmap) keys() []string {
mut keys := [''].repeat(h.size)
mut j := 0
for i in 0 .. (h.cap + 1) {
if h.info[i] != 0 {
keys[j] = h.key_values[i].key
j++
}
}
return keys
}