feat: add threadpool and started pooling executors

include/threadlist.h

@@ -0,0 +1,33 @@
+#ifndef SCI_THREADLIST_H
+#define SCI_THREADLIST_H
+#include <pthread.h>
+
+// doubly linked list implementation for managing threads
+typedef struct pthread_list_node {
+    pthread_t thread;
+    struct pthread_list_node* previous;
+    struct pthread_list_node* next;
+} pthread_list_node;
+
+// Create a new root node.
+pthread_list_node* create_thread_node(pthread_t thread);
+
+// Add a new node to the end of the list.
+// Returns the new node.
+pthread_list_node* add_thread(pthread_t thread, pthread_list_node* root);
+
+pthread_list_node* add_thread_node(pthread_list_node* root, pthread_list_node* node);
+
+// Remove a node from the list.
+// This will not call pthread_join, so make sure that the thread is joined before calling.
+void remove_thread_node(pthread_list_node* node);
+
+// Completely clear the thread list.
+// This will call pthread_join on all nodes.
+// The list is completely invalid after this call and should be discarded.
+// Note:
+//  - `root` has already been free'd.
+//  - this function is not thread-safe.
+void clear_thread_list(pthread_list_node* root);
+
+#endif