sighook: New utilities for hooking signals

This allows multiple hooks to be installed for a single signal.

1 files changed, 73 insertions, 0 deletions

diff --git a/src/sighook.h b/src/sighook.h
new file mode 100644
index 0000000..74d18c0
--- /dev/null
+++ b/src/sighook.h
@@ -0,0 +1,73 @@
+// Copyright © Tavian Barnes <tavianator@tavianator.com>
+// SPDX-License-Identifier: 0BSD
+
+/**
+ * Signal hooks.
+ */
+
+#ifndef BFS_SIGHOOK_H
+#define BFS_SIGHOOK_H
+
+#include <signal.h>
+
+/**
+ * A dynamic signal hook.
+ */
+struct sighook;
+
+/**
+ * Signal hook flags.
+ */
+enum sigflags {
+	/** Suppress the default action for this signal. */
+	SH_CONTINUE = 1 << 0,
+};
+
+/**
+ * A signal hook callback.  Hooks are executed from a signal handler, so must
+ * only call async-signal-safe functions.
+ *
+ * @param sig
+ *         The signal number.
+ * @param info
+ *         Additional information about the signal.
+ * @param arg
+ *         An arbitrary pointer passed to the hook.
+ */
+typedef void sighook_fn(int sig, siginfo_t *info, void *arg);
+
+/**
+ * Install a hook for a signal.
+ *
+ * @param sig
+ *         The signal to hook.
+ * @param fn
+ *         The function to call.
+ * @param arg
+ *         An argument passed to the function.
+ * @param flags
+ *         Flags for the new hook.
+ * @return
+ *         The installed hook, or NULL on failure.
+ */
+struct sighook *sighook(int sig, sighook_fn *fn, void *arg, enum sigflags flags);
+
+/**
+ * On a best-effort basis, invoke the given hook just before the program is
+ * abnormally terminated by a signal.
+ *
+ * @param fn
+ *         The function to call.
+ * @param arg
+ *         An argument passed to the function.
+ * @return
+ *         The installed hook, or NULL on failure.
+ */
+struct sighook *atsigexit(sighook_fn *fn, void *arg);
+
+/**
+ * Remove a signal hook.
+ */
+void sigunhook(struct sighook *hook);
+
+#endif // BFS_SIGHOOK_H