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