gotosocial/vendor/codeberg.org/gruf/go-structr/index.go

424 lines
9.3 KiB
Go

package structr
import (
"reflect"
"strings"
"sync"
"unsafe"
"codeberg.org/gruf/go-byteutil"
"github.com/dolthub/swiss"
)
// IndexConfig defines config variables
// for initializing a struct index.
type IndexConfig struct {
// Fields should contain a comma-separated
// list of struct fields used when generating
// keys for this index. Nested fields should
// be specified using periods. An example:
// "Username,Favorites.Color"
//
// Note that nested fields where the nested
// struct field is a ptr are supported, but
// nil ptr values in nesting will result in
// that particular value NOT being indexed.
// e.g. with "Favorites.Color" if *Favorites
// is nil then it will not be indexed.
//
// Field types supported include any of those
// supported by the `go-mangler` library.
Fields string
// Multiple indicates whether to accept multiple
// possible values for any single index key. The
// default behaviour is to only accept one value
// and overwrite existing on any write operation.
Multiple bool
// AllowZero indicates whether to accept zero
// value fields in index keys. i.e. whether to
// index structs for this set of field values
// IF any one of those field values is the zero
// value for that type. The default behaviour
// is to skip indexing structs for this lookup
// when any of the indexing fields are zero.
AllowZero bool
}
// Index is an exposed Cache internal model, used to
// extract struct keys, generate hash checksums for them
// and store struct results by the init defined config.
// This model is exposed to provide faster lookups in the
// case that you would like to manually provide the used
// index via the Cache.___By() series of functions, or
// access the underlying index key generator.
type Index struct {
// ptr is a pointer to
// the source Cache/Queue
// index is attached to.
ptr unsafe.Pointer
// name is the actual name of this
// index, which is the unparsed
// string value of contained fields.
name string
// backing data store of the index, containing
// the cached results contained within wrapping
// index_entry{} which also contains the exact
// key each result is stored under. the hash map
// only keys by the xxh3 hash checksum for speed.
data *swiss.Map[string, *list]
// struct fields encompassed by
// keys (+ hashes) of this index.
fields []struct_field
// index flags:
// - 1 << 0 = unique
// - 1 << 1 = allow zero
flags uint8
}
// Name returns the receiving Index name.
func (i *Index) Name() string {
return i.name
}
// Key generates Key{} from given parts for
// the type of lookup this Index uses in cache.
// NOTE: panics on incorrect no. parts / types given.
func (i *Index) Key(parts ...any) Key {
buf := new_buffer()
key := i.key(buf, parts)
free_buffer(buf)
return Key{
raw: parts,
key: key,
}
}
// Keys generates []Key{} from given (multiple) parts
// for the type of lookup this Index uses in the cache.
// NOTE: panics on incorrect no. parts / types given.
func (i *Index) Keys(parts ...[]any) []Key {
keys := make([]Key, 0, len(parts))
buf := new_buffer()
for _, parts := range parts {
key := i.key(buf, parts)
if key == "" {
continue
}
keys = append(keys, Key{
raw: parts,
key: key,
})
}
free_buffer(buf)
return keys
}
// init will initialize the cache with given type, config and capacity.
func (i *Index) init(t reflect.Type, cfg IndexConfig, cap int) {
switch {
// The only 2 types we support are
// structs, and ptrs to a struct.
case t.Kind() == reflect.Struct:
case t.Kind() == reflect.Pointer &&
t.Elem().Kind() == reflect.Struct:
default:
panic("index only support struct{} and *struct{}")
}
// Set name from the raw
// struct fields string.
i.name = cfg.Fields
// Set struct flags.
if cfg.AllowZero {
set_allow_zero(&i.flags)
}
if !cfg.Multiple {
set_is_unique(&i.flags)
}
// Split to get containing struct fields.
fields := strings.Split(cfg.Fields, ",")
// Preallocate expected struct field slice.
i.fields = make([]struct_field, len(fields))
for x, name := range fields {
// Split name to account for nesting.
names := strings.Split(name, ".")
// Look for usable struct field.
i.fields[x] = find_field(t, names)
}
// Initialize index_entry list store.
i.data = swiss.NewMap[string, *list](uint32(cap))
}
// get_one will fetch one indexed item under key.
func (i *Index) get_one(key Key) *indexed_item {
// Get list at hash.
l, _ := i.data.Get(key.key)
if l == nil {
return nil
}
// Extract entry from first list elem.
entry := (*index_entry)(l.head.data)
return entry.item
}
// get will fetch all indexed items under key, passing each to hook.
func (i *Index) get(key string, hook func(*indexed_item)) {
if hook == nil {
panic("nil hook")
}
// Get list at hash.
l, _ := i.data.Get(key)
if l == nil {
return
}
// Iterate all entries in list.
l.rangefn(func(elem *list_elem) {
// Extract element entry + item.
entry := (*index_entry)(elem.data)
item := entry.item
// Pass to hook.
hook(item)
})
}
// key uses hasher to generate Key{} from given raw parts.
func (i *Index) key(buf *byteutil.Buffer, parts []any) string {
if len(parts) != len(i.fields) {
panicf("incorrect number key parts: want=%d received=%d",
len(i.fields),
len(parts),
)
}
buf.B = buf.B[:0]
if !allow_zero(i.flags) {
for x, field := range i.fields {
before := len(buf.B)
buf.B = field.mangle(buf.B, parts[x])
if string(buf.B[before:]) == field.zerostr {
return ""
}
buf.B = append(buf.B, '.')
}
} else {
for x, field := range i.fields {
buf.B = field.mangle(buf.B, parts[x])
buf.B = append(buf.B, '.')
}
}
return string(buf.B)
}
// append will append the given index entry to appropriate
// doubly-linked-list in index hashmap. this handles case
// of key collisions and overwriting 'unique' entries.
func (i *Index) append(key string, item *indexed_item) {
// Look for existing.
l, _ := i.data.Get(key)
if l == nil {
// Allocate new.
l = new_list()
i.data.Put(key, l)
} else if is_unique(i.flags) {
// Remove head.
elem := l.head
l.remove(elem)
// Drop index from inner item.
e := (*index_entry)(elem.data)
e.item.drop_index(e)
// Free unused entry.
free_index_entry(e)
}
// Prepare new index entry.
entry := new_index_entry()
entry.item = item
entry.key = key
entry.index = i
// Add ourselves to item's index tracker.
item.indexed = append(item.indexed, entry)
// Add entry to index list.
l.push_front(&entry.elem)
}
// delete will remove all indexed items under key, passing each to hook.
func (i *Index) delete(key string, hook func(*indexed_item)) {
if hook == nil {
panic("nil hook")
}
// Get list at hash.
l, _ := i.data.Get(key)
if l == nil {
return
}
// Delete at hash.
i.data.Delete(key)
// Iterate entries in list.
for x := 0; x < l.len; x++ {
// Pop list head.
elem := l.head
l.remove(elem)
// Extract element entry + item.
entry := (*index_entry)(elem.data)
item := entry.item
// Drop index from item.
item.drop_index(entry)
// Free now-unused entry.
free_index_entry(entry)
// Pass to hook.
hook(item)
}
// Release list.
free_list(l)
}
// delete_entry deletes the given index entry.
func (i *Index) delete_entry(entry *index_entry) {
// Get list at hash sum.
l, _ := i.data.Get(entry.key)
if l == nil {
return
}
// Remove list entry.
l.remove(&entry.elem)
if l.len == 0 {
// Remove entry from map.
i.data.Delete(entry.key)
// Release list.
free_list(l)
}
// Drop this index from item.
entry.item.drop_index(entry)
}
// compact will reduce the size of underlying
// index map if the cap vastly exceeds len.
func (i *Index) compact() {
// Maximum load factor before
// 'swiss' allocates new hmap:
// maxLoad = 7 / 8
//
// So we apply the inverse/2, once
// $maxLoad/2 % of hmap is empty we
// compact the map to drop buckets.
len := i.data.Count()
cap := i.data.Capacity()
if cap-len > (cap*7)/(8*2) {
// Create a new map only as big as required.
data := swiss.NewMap[string, *list](uint32(len))
i.data.Iter(func(k string, v *list) (stop bool) {
data.Put(k, v)
return false
})
// Set new map.
i.data = data
}
}
// index_entry represents a single entry
// in an Index{}, where it will be accessible
// by Key{} pointing to a containing list{}.
type index_entry struct {
// list elem that entry is stored
// within, under containing index.
// elem.data is ptr to index_entry.
elem list_elem
// raw cache key
// for this entry.
key string
// index this is stored in.
index *Index
// underlying indexed item.
item *indexed_item
}
var index_entry_pool sync.Pool
// new_index_entry returns a new prepared index_entry.
func new_index_entry() *index_entry {
v := index_entry_pool.Get()
if v == nil {
v = new(index_entry)
}
entry := v.(*index_entry)
ptr := unsafe.Pointer(entry)
entry.elem.data = ptr
return entry
}
// free_index_entry releases the index_entry.
func free_index_entry(entry *index_entry) {
entry.elem.data = nil
entry.key = ""
entry.index = nil
entry.item = nil
index_entry_pool.Put(entry)
}
func is_unique(f uint8) bool {
const mask = uint8(1) << 0
return f&mask != 0
}
func set_is_unique(f *uint8) {
const mask = uint8(1) << 0
(*f) |= mask
}
func allow_zero(f uint8) bool {
const mask = uint8(1) << 1
return f&mask != 0
}
func set_allow_zero(f *uint8) {
const mask = uint8(1) << 1
(*f) |= mask
}