whatcanGOwrong

go/pkg/mod/github.com/cilium/ebpf@v0.11.0/asm/metadata.go

@@ -0,0 +1,80 @@
+package asm
+
+// Metadata contains metadata about an instruction.
+type Metadata struct {
+	head *metaElement
+}
+
+type metaElement struct {
+	next       *metaElement
+	key, value interface{}
+}
+
+// Find the element containing key.
+//
+// Returns nil if there is no such element.
+func (m *Metadata) find(key interface{}) *metaElement {
+	for e := m.head; e != nil; e = e.next {
+		if e.key == key {
+			return e
+		}
+	}
+	return nil
+}
+
+// Remove an element from the linked list.
+//
+// Copies as many elements of the list as necessary to remove r, but doesn't
+// perform a full copy.
+func (m *Metadata) remove(r *metaElement) {
+	current := &m.head
+	for e := m.head; e != nil; e = e.next {
+		if e == r {
+			// We've found the element we want to remove.
+			*current = e.next
+
+			// No need to copy the tail.
+			return
+		}
+
+		// There is another element in front of the one we want to remove.
+		// We have to copy it to be able to change metaElement.next.
+		cpy := &metaElement{key: e.key, value: e.value}
+		*current = cpy
+		current = &cpy.next
+	}
+}
+
+// Set a key to a value.
+//
+// If value is nil, the key is removed. Avoids modifying old metadata by
+// copying if necessary.
+func (m *Metadata) Set(key, value interface{}) {
+	if e := m.find(key); e != nil {
+		if e.value == value {
+			// Key is present and the value is the same. Nothing to do.
+			return
+		}
+
+		// Key is present with a different value. Create a copy of the list
+		// which doesn't have the element in it.
+		m.remove(e)
+	}
+
+	// m.head is now a linked list that doesn't contain key.
+	if value == nil {
+		return
+	}
+
+	m.head = &metaElement{key: key, value: value, next: m.head}
+}
+
+// Get the value of a key.
+//
+// Returns nil if no value with the given key is present.
+func (m *Metadata) Get(key interface{}) interface{} {
+	if e := m.find(key); e != nil {
+		return e.value
+	}
+	return nil
+}