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

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package structr
import (
"reflect"
"sync"
"unsafe"
)
// QueueConfig defines config vars
// for initializing a struct queue.
type QueueConfig[StructType any] struct {
// Indices defines indices to create
// in the Queue for the receiving
// generic struct parameter type.
Indices []IndexConfig
// Pop is called when queue values
// are popped, during calls to any
// of the Pop___() series of fns.
Pop func(StructType)
}
// Queue provides a structure model queue with
// automated indexing and popping by any init
// defined lookups of field combinations.
type Queue[StructType any] struct {
// indices used in storing passed struct
// types by user defined sets of fields.
indices []Index
// main underlying
// struct item queue.
queue list
// hook functions.
copy func(StructType) StructType
pop func(StructType)
// protective mutex, guards:
// - Queue{}.queue
// - Index{}.data
// - Queue{} hook fns
mutex sync.Mutex
}
// Init initializes the queue with given configuration
// including struct fields to index, and necessary fns.
func (q *Queue[T]) Init(config QueueConfig[T]) {
t := reflect.TypeOf((*T)(nil)).Elem()
if len(config.Indices) == 0 {
panic("no indices provided")
}
// Safely copy over
// provided config.
q.mutex.Lock()
q.indices = make([]Index, len(config.Indices))
for i, cfg := range config.Indices {
q.indices[i].ptr = unsafe.Pointer(q)
q.indices[i].init(t, cfg, 0)
}
q.pop = config.Pop
q.mutex.Unlock()
}
// Index selects index with given name from queue, else panics.
func (q *Queue[T]) Index(name string) *Index {
for i := range q.indices {
if q.indices[i].name == name {
return &q.indices[i]
}
}
panic("unknown index: " + name)
}
// PopFront pops the current value at front of the queue.
func (q *Queue[T]) PopFront() (T, bool) {
t := q.PopFrontN(1)
if len(t) == 0 {
var t T
return t, false
}
return t[0], true
}
// PopBack pops the current value at back of the queue.
func (q *Queue[T]) PopBack() (T, bool) {
t := q.PopBackN(1)
if len(t) == 0 {
var t T
return t, false
}
return t[0], true
}
// PopFrontN attempts to pop n values from front of the queue.
func (q *Queue[T]) PopFrontN(n int) []T {
return q.pop_n(n, func() *list_elem {
return q.queue.head
})
}
// PopBackN attempts to pop n values from back of the queue.
func (q *Queue[T]) PopBackN(n int) []T {
return q.pop_n(n, func() *list_elem {
return q.queue.tail
})
}
// Pop attempts to pop values from queue indexed under any of keys.
func (q *Queue[T]) Pop(index *Index, keys ...Key) []T {
if index == nil {
panic("no index given")
} else if index.ptr != unsafe.Pointer(q) {
panic("invalid index for queue")
}
// Acquire lock.
q.mutex.Lock()
// Preallocate expected ret slice.
values := make([]T, 0, len(keys))
for i := range keys {
// Delete all items under key from index, collecting
// value items and dropping them from all their indices.
index.delete(keys[i], func(item *indexed_item) {
// Append deleted to values.
value := item.data.(T)
values = append(values, value)
// Delete queued.
q.delete(item)
})
}
// Get func ptrs.
pop := q.pop
// Done with lock.
q.mutex.Unlock()
if pop != nil {
// Pass all popped values
// to given user hook (if set).
for _, value := range values {
pop(value)
}
}
return values
}
// PushFront pushes values to front of queue.
func (q *Queue[T]) PushFront(values ...T) {
q.mutex.Lock()
for i := range values {
item := q.index(values[i])
q.queue.push_front(&item.elem)
}
q.mutex.Unlock()
}
// PushBack pushes values to back of queue.
func (q *Queue[T]) PushBack(values ...T) {
q.mutex.Lock()
for i := range values {
item := q.index(values[i])
q.queue.push_back(&item.elem)
}
q.mutex.Unlock()
}
// MoveFront attempts to move values indexed under any of keys to the front of the queue.
func (q *Queue[T]) MoveFront(index *Index, keys ...Key) {
q.mutex.Lock()
for i := range keys {
index.get(keys[i], func(item *indexed_item) {
q.queue.move_front(&item.elem)
})
}
q.mutex.Unlock()
}
// MoveBack attempts to move values indexed under any of keys to the back of the queue.
func (q *Queue[T]) MoveBack(index *Index, keys ...Key) {
q.mutex.Lock()
for i := range keys {
index.get(keys[i], func(item *indexed_item) {
q.queue.move_back(&item.elem)
})
}
q.mutex.Unlock()
}
// Len returns the current length of queue.
func (q *Queue[T]) Len() int {
q.mutex.Lock()
l := q.queue.len
q.mutex.Unlock()
return l
}
func (q *Queue[T]) pop_n(n int, next func() *list_elem) []T {
if next == nil {
panic("nil fn")
}
// Acquire lock.
q.mutex.Lock()
// Preallocate ret slice.
values := make([]T, 0, n)
// Iterate over 'n' items.
for i := 0; i < n; i++ {
// Get next elem.
next := next()
if next == nil {
// reached
// end.
break
}
// Cast the indexed item from elem.
item := (*indexed_item)(next.data)
// Append deleted to values.
value := item.data.(T)
values = append(values, value)
// Delete queued.
q.delete(item)
}
// Get func ptrs.
pop := q.pop
// Done with lock.
q.mutex.Unlock()
if pop != nil {
// Pass all popped values
// to given user hook (if set).
for _, value := range values {
pop(value)
}
}
return values
}
func (q *Queue[T]) index(value T) *indexed_item {
item := new_indexed_item()
// Set item value.
item.data = value
// Get ptr to value data.
ptr := unsafe.Pointer(&value)
// Acquire key buf.
buf := new_buffer()
for i := range q.indices {
// Get current index ptr.
idx := &(q.indices[i])
// Extract fields comprising index key.
parts := extract_fields(ptr, idx.fields)
if parts == nil {
continue
}
// Calculate index key.
key := idx.key(buf, parts)
if key.Zero() {
continue
}
// Append item to index.
idx.append(key, item)
}
// Done with buf.
free_buffer(buf)
return item
}
func (q *Queue[T]) delete(item *indexed_item) {
for len(item.indexed) != 0 {
// Pop last indexed entry from list.
entry := item.indexed[len(item.indexed)-1]
item.indexed = item.indexed[:len(item.indexed)-1]
// Drop index_entry from index.
entry.index.delete_entry(entry)
}
// Drop entry from queue list.
q.queue.remove(&item.elem)
// Free now-unused item.
free_indexed_item(item)
}