[chore] bump go structr cache version -> v0.6.0 (#2773)

* update go-structr library -> v0.6.0, add necessary wrapping types + code changes to support these changes

* update readme with go-structr package changes

* improved wrapping of the SliceCache type

* add code comments for the cache wrapper types

* remove test.out 😇

---------

Co-authored-by: tobi <31960611+tsmethurst@users.noreply.github.com>

vendor/codeberg.org/gruf/go-structr/list.go

@@ -5,8 +5,6 @@ import (
 	"unsafe"
 )
 
-var list_pool sync.Pool
-
 // elem represents an elem
 // in a doubly-linked list.
 type list_elem struct {
@@ -28,28 +26,28 @@ type list struct {
 	len  int
 }
 
-func list_acquire() *list {
-	// Acquire from pool.
+var list_pool sync.Pool
+
+// new_list returns a new prepared list.
+func new_list() *list {
 	v := list_pool.Get()
 	if v == nil {
 		v = new(list)
 	}
-
-	// Cast list value.
-	return v.(*list)
+	list := v.(*list)
+	return list
 }
 
-func list_release(l *list) {
-	// Reset list.
-	l.head = nil
-	l.tail = nil
-	l.len = 0
-
-	// Release to pool.
-	list_pool.Put(l)
+// free_list releases the list.
+func free_list(list *list) {
+	list.head = nil
+	list.tail = nil
+	list.len = 0
+	list_pool.Put(list)
 }
 
-func list_push_front(l *list, elem *list_elem) {
+// push_front will push the given elem to front (head) of list.
+func (l *list) push_front(elem *list_elem) {
 	if l.len == 0 {
 		// Set new tail + head
 		l.head = elem
@@ -77,12 +75,49 @@ func list_push_front(l *list, elem *list_elem) {
 	l.len++
 }
 
-func list_move_front(l *list, elem *list_elem) {
-	list_remove(l, elem)
-	list_push_front(l, elem)
+// push_back will push the given elem to back (tail) of list.
+func (l *list) push_back(elem *list_elem) {
+	if l.len == 0 {
+		// Set new tail + head
+		l.head = elem
+		l.tail = elem
+
+		// Link elem to itself
+		elem.next = elem
+		elem.prev = elem
+	} else {
+		oldTail := l.tail
+
+		// Link to old tail
+		elem.prev = oldTail
+		oldTail.next = elem
+
+		// Link up to head
+		elem.next = l.head
+		l.head.prev = elem
+
+		// Set new tail
+		l.tail = elem
+	}
+
+	// Incr count
+	l.len++
 }
 
-func list_remove(l *list, elem *list_elem) {
+// move_front will move given elem to front (head) of list.
+func (l *list) move_front(elem *list_elem) {
+	l.remove(elem)
+	l.push_front(elem)
+}
+
+// move_back will move given elem to back (tail) of list.
+func (l *list) move_back(elem *list_elem) {
+	l.remove(elem)
+	l.push_back(elem)
+}
+
+// remove will remove given elem from list.
+func (l *list) remove(elem *list_elem) {
 	if l.len <= 1 {
 		// Drop elem's links
 		elem.next = nil
@@ -121,7 +156,8 @@ func list_remove(l *list, elem *list_elem) {
 	l.len--
 }
 
-func list_rangefn(l *list, fn func(*list_elem)) {
+// rangefn will range all elems in list, passing each to fn.
+func (l *list) rangefn(fn func(*list_elem)) {
 	if fn == nil {
 		panic("nil fn")
 	}