libcdecl: Punt gnulib tls module.

[cdecl99.git] / src / thread-posix.h

diff --git a/src/thread-posix.h b/src/thread-posix.h
new file mode 100644 (file)
index 0000000..b1cd990
--- /dev/null
+++ b/src/thread-posix.h
@@ -0,0 +1,68 @@
+/*
+ * Copyright © 2024 Nick Bowler
+ *
+ * Helpers for hosts using POSIX threading (pthreads) API.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <pthread.h>
+
+#if USE_POSIX_THREADS_WEAK
+#  pragma weak pthread_key_create
+#  pragma weak pthread_getspecific
+#  pragma weak pthread_setspecific
+#endif
+
+static struct {
+       union {
+               pthread_key_t mt;
+#if USE_POSIX_THREADS_WEAK
+               void *st;
+#endif
+       } u;
+
+#if USE_POSIX_THREADS_WEAK
+       signed char valid;
+#else
+       bool valid;
+#endif
+} tls_key;
+#define tls_key_valid (tls_key.valid != 0)
+
+static void tls_key_init(void)
+{
+       if (pthread_in_use())
+               tls_key.valid = !pthread_key_create(&tls_key.u.mt, free);
+       else
+               tls_key.valid = -1;
+}
+
+static void *tls_get(void)
+{
+#if USE_POSIX_THREADS_WEAK
+       if (tls_key.valid < 0)
+               return tls_key.u.st;
+#endif
+       return pthread_getspecific(tls_key.u.mt);
+}
+
+static int tls_set(void *p)
+{
+#if USE_POSIX_THREADS_WEAK
+       if (tls_key.valid < 0)
+               return (tls_key.u.st = p, 1);
+#endif
+       return !pthread_setspecific(tls_key.u.mt, p);
+}