feat: add threadpool and started pooling executors

include/threadpool.h

@@ -0,0 +1,42 @@
+#ifndef SCI_THREADPOOL_H
+#define SCI_THREADPOOL_H
+#include <stdbool.h>
+#include <stddef.h>
+#include <pthread.h>
+// Very inspired by: https://nachtimwald.com/2019/04/12/thread-pool-in-c/
+
+// a work function
+typedef void (*thread_func)(void *arg);
+
+// linked list for work functions
+typedef struct threadpool_work {
+    thread_func func;
+    void* arg;
+    struct threadpool_work* next;
+} threadpool_work;
+
+// thread pool object
+typedef struct {
+    threadpool_work* work_first;
+    threadpool_work* work_last;
+    pthread_mutex_t work_mutex;
+    pthread_cond_t work_cond;
+    pthread_cond_t working_cond;
+    size_t working_count;
+    size_t thread_count;
+    bool stop;
+} threadpool;
+
+// create a new threadpool instance with `num` amount of worker threads
+threadpool* threadpool_create(size_t num);
+
+// destroy a threadpool instance
+void threadpool_destroy(threadpool* pool);
+
+// add work to the threadpool
+bool threadpool_add_work(threadpool* pool, thread_func func, void* arg);
+
+// wait for the remaining work in the threadpool to complete
+void threadpool_wait(threadpool* pool);
+
+#endif