copyright notices, coroutines

1 files changed, 72 insertions, 0 deletions

diff --git a/coroutine.h b/coroutine.h
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+/* coroutine.h - Simple coroutine and request/response implementation
+ *
+ * Copyright (C) 2024  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-Licence-Identifier: AGPL-3.0-or-later
+ */
+
+#ifndef _COROUTINE_H_
+#define _COROUTINE_H_
+
+#include <stddef.h>  /* for size_t */
+#include <stdbool.h> /* for bool, true, false */
+
+/* typedefs *******************************************************************/
+typedef size_t cid_t; /* 0=none; otherwise 1-indexed */
+typedef void (*cr_fn_t)(void *stack);
+typedef struct {
+	cr_fn_t fn;
+	void *stack;
+	unsigned int state;
+	bool blocked;
+} _cr_entry_t;
+
+/* globals ********************************************************************/
+extern _cr_entry_t *_coroutine_table;
+extern cid_t        _cur_cid;
+
+/* bona-fide functions ********************************************************/
+void coroutine_init(void);
+cid_t coroutine_add(cr_fn_t fn, void *stack);
+void coroutine_task(void);
+
+/* core macros for use in a cr_fn_t() *****************************************/
+#define cr_begin()        switch(_coroutine_table[_cur_cid].state) { case 0:
+#define cr_exit()         do { _coroutine_table[_cur_cid] = (cr_entry_t){0}; return; } while (0)
+#define cr_yield()        _cr_yield(__COUNTER__)
+#define _cr_yield(_state) do { _coroutine_table[_cur_cid].state = _state; return; case _state:; } while (0)
+#define cr_end()          }
+
+/* request/response channels **************************************************/
+#define cr_chan_t(req_t, resp_t) struct { \
+		cid_t requester;          \
+		cid_t responder;          \
+		req_t  req;               \
+		resp_t resp;              \
+	}
+#define cr_chan_req(ch, _resp_p, _req) do {                                \
+		(ch)->requester = _cur_cid;                                \
+		(ch)->req = (_req);                                        \
+		if ((ch)->responder != 0)                                  \
+			_coroutine_table[(ch)->responder].blocked = false; \
+		_coroutine_table[_cur_cid].blocked = true;                 \
+		cr_yield();                                                \
+		if ((typeof(&(ch)->resp))(_resp_p))                        \
+			*((typeof(&(ch)->resp))(_resp_p)) = (ch)->resp;    \
+	} while (0)
+#define cr_chan_have_req(ch) ((ch)->requester != 0)
+#define cr_chan_recv_req(ch, _req_p) do {                          \
+		(ch)->responder = _cur_cid;                        \
+		if ((ch)->requester == 0) {                        \
+			_coroutine_table[_cur_cid].blocked = true; \
+			cr_yield();                                \
+		}                                                  \
+		*(_req_p) = (ch)->req;                             \
+	} while (0)
+#define cr_chan_send_resp(ch, _resp) do {                          \
+		(ch)->responder = 0;                               \
+		(ch)->requester = 0;                               \
+		(ch)->resp = (_resp);                              \
+		_coroutine_table[(ch)->requester].blocked = false; \
+	} while (0)
+
+#endif /* _COROUTINE_H_ */