bar: Use atsigexit() to reset the bar

1 files changed, 47 insertions, 132 deletions

diff --git a/src/bar.c b/src/bar.c
index 6eba78f..b928373 100644
--- a/src/bar.c
+++ b/src/bar.c
@@ -3,11 +3,12 @@
 
 #include "prelude.h"
 #include "bar.h"
+#include "alloc.h"
 #include "atomic.h"
 #include "bfstd.h"
 #include "bit.h"
-#include "diag.h"
 #include "dstring.h"
+#include "sighook.h"
 #include <errno.h>
 #include <fcntl.h>
 #include <signal.h>
@@ -16,82 +17,26 @@
 #include <string.h>
 #include <sys/ioctl.h>
 
-/**
- * Sentinel values for bfs_bar::refcount.
- */
-enum {
-	/** The bar is currently uninitialized. */
-	BFS_BAR_UNINIT = 0,
-	/** The bar is being initialized/destroyed. */
-	BFS_BAR_BUSY   = 1,
-	/** Values >= this are valid refcounts. */
-	BFS_BAR_READY  = 2,
-};
-
 struct bfs_bar {
-	/**
-	 * A file descriptor to the TTY.  Must be atomic because signal handlers
-	 * can race with bfs_bar_hide().
-	 */
-	atomic int fd;
-	/** A reference count protecting `fd`. */
-	atomic unsigned int refcount;
-
-	/** The width of the TTY. */
+	int fd;
 	atomic unsigned int width;
-	/** The height of the TTY. */
 	atomic unsigned int height;
-};
 
-/** The global status bar instance. */
-static struct bfs_bar the_bar = {
-	.fd = -1,
+	struct sighook *exit_hook;
+	struct sighook *winch_hook;
 };
 
-/** Try to acquire a reference to bar->fd. */
-static int bfs_bar_getfd(struct bfs_bar *bar) {
-	unsigned int refs = load(&bar->refcount, relaxed);
-	do {
-		if (refs < BFS_BAR_READY) {
-			errno = EAGAIN;
-			return -1;
-		}
-	} while (!compare_exchange_weak(&bar->refcount, &refs, refs + 1, acquire, relaxed));
-
-	return load(&bar->fd, relaxed);
-}
-
-/** Release a reference to bar->fd. */
-static void bfs_bar_putfd(struct bfs_bar *bar) {
-	int fd = load(&bar->fd, relaxed);
-
-	unsigned int refs = fetch_sub(&bar->refcount, 1, release);
-	bfs_assert(refs >= BFS_BAR_READY);
-
-	if (refs == 2) {
-		close_quietly(fd);
-		store(&bar->fd, -1, relaxed);
-		store(&bar->refcount, BFS_BAR_UNINIT, release);
-	}
-}
-
 /** Get the terminal size, if possible. */
 static int bfs_bar_getsize(struct bfs_bar *bar) {
 #ifdef TIOCGWINSZ
-	int fd = bfs_bar_getfd(bar);
-	if (fd < 0) {
-		return -1;
-	}
-
 	struct winsize ws;
-	int ret = ioctl(fd, TIOCGWINSZ, &ws);
-	if (ret == 0) {
-		store(&bar->width, ws.ws_col, relaxed);
-		store(&bar->height, ws.ws_row, relaxed);
+	if (ioctl(bar->fd, TIOCGWINSZ, &ws) != 0) {
+		return -1;
 	}
 
-	bfs_bar_putfd(bar);
-	return ret;
+	store(&bar->width, ws.ws_col, relaxed);
+	store(&bar->height, ws.ws_row, relaxed);
+	return 0;
 #else
 	errno = ENOTSUP;
 	return -1;
@@ -100,14 +45,7 @@ static int bfs_bar_getsize(struct bfs_bar *bar) {
 
 /** Write a string to the status bar (async-signal-safe). */
 static int bfs_bar_write(struct bfs_bar *bar, const char *str, size_t len) {
-	int fd = bfs_bar_getfd(bar);
-	if (fd < 0) {
-		return -1;
-	}
-
-	int ret = xwrite(fd, str, len) == len ? 0 : -1;
-	bfs_bar_putfd(bar);
-	return ret;
+	return xwrite(bar->fd, str, len) == len ? 0 : -1;
 }
 
 /** Write a string to the status bar (async-signal-safe). */
@@ -160,13 +98,10 @@ static int bfs_bar_resize(struct bfs_bar *bar) {
 
 #ifdef SIGWINCH
 /** SIGWINCH handler. */
-static void sighand_winch(int sig) {
-	int error = errno;
-
-	bfs_bar_getsize(&the_bar);
-	bfs_bar_resize(&the_bar);
-
-	errno = error;
+static void bfs_bar_sigwinch(int sig, siginfo_t *info, void *arg) {
+	struct bfs_bar *bar = arg;
+	bfs_bar_getsize(bar);
+	bfs_bar_resize(bar);
 }
 #endif
 
@@ -181,19 +116,9 @@ static int bfs_bar_reset(struct bfs_bar *bar) {
 }
 
 /** Signal handler for process-terminating signals. */
-static void sighand_reset(int sig) {
-	bfs_bar_reset(&the_bar);
-	raise(sig);
-}
-
-/** Register sighand_reset() for a signal. */
-static void reset_before_death_by(int sig) {
-	struct sigaction sa = {
-		.sa_handler = sighand_reset,
-		.sa_flags = SA_RESETHAND,
-	};
-	sigemptyset(&sa.sa_mask);
-	sigaction(sig, &sa, NULL);
+static void bfs_bar_sigexit(int sig, siginfo_t *info, void *arg) {
+	struct bfs_bar *bar = arg;
+	bfs_bar_reset(bar);
 }
 
 /** printf() to the status bar with a single write(). */
@@ -214,54 +139,48 @@ static int bfs_bar_printf(struct bfs_bar *bar, const char *format, ...) {
 }
 
 struct bfs_bar *bfs_bar_show(void) {
-	unsigned int refs = BFS_BAR_UNINIT;
-	if (!compare_exchange_strong(&the_bar.refcount, &refs, BFS_BAR_BUSY, acq_rel, relaxed)) {
-		errno = EBUSY;
-		goto fail;
+	struct bfs_bar *bar = ALLOC(struct bfs_bar);
+	if (!bar) {
+		return NULL;
 	}
 
 	char term[L_ctermid];
 	ctermid(term);
 	if (strlen(term) == 0) {
 		errno = ENOTTY;
-		goto unref;
+		goto fail;
 	}
 
-	int fd = open(term, O_RDWR | O_CLOEXEC);
-	if (fd < 0) {
-		goto unref;
+	bar->fd = open(term, O_RDWR | O_CLOEXEC);
+	if (bar->fd < 0) {
+		goto fail;
 	}
-	store(&the_bar.fd, fd, relaxed);
-	store(&the_bar.refcount, BFS_BAR_READY, release);
 
-	if (bfs_bar_getsize(&the_bar) != 0) {
-		goto put;
+	if (bfs_bar_getsize(bar) != 0) {
+		goto fail_close;
 	}
 
-	reset_before_death_by(SIGABRT);
-	reset_before_death_by(SIGINT);
-	reset_before_death_by(SIGPIPE);
-	reset_before_death_by(SIGQUIT);
-	reset_before_death_by(SIGTERM);
+	bar->exit_hook = atsigexit(bfs_bar_sigexit, bar);
+	if (!bar->exit_hook) {
+		goto fail_close;
+	}
 
 #ifdef SIGWINCH
-	struct sigaction sa = {
-		.sa_handler = sighand_winch,
-		.sa_flags = SA_RESTART,
-	};
-	sigemptyset(&sa.sa_mask);
-	sigaction(SIGWINCH, &sa, NULL);
+	bar->winch_hook = sighook(SIGWINCH, bfs_bar_sigwinch, bar, 0);
+	if (!bar->winch_hook) {
+		goto fail_hook;
+	}
 #endif
 
-	bfs_bar_resize(&the_bar);
-	return &the_bar;
+	bfs_bar_resize(bar);
+	return bar;
 
-put:
-	bfs_bar_putfd(&the_bar);
-	return NULL;
-unref:
-	store(&the_bar.refcount, 0, release);
+fail_hook:
+	sigunhook(bar->exit_hook);
+fail_close:
+	close_quietly(bar->fd);
 fail:
+	free(bar);
 	return NULL;
 }
 
@@ -289,15 +208,11 @@ void bfs_bar_hide(struct bfs_bar *bar) {
 		return;
 	}
 
-	signal(SIGABRT, SIG_DFL);
-	signal(SIGINT, SIG_DFL);
-	signal(SIGPIPE, SIG_DFL);
-	signal(SIGQUIT, SIG_DFL);
-	signal(SIGTERM, SIG_DFL);
-#ifdef SIGWINCH
-	signal(SIGWINCH, SIG_DFL);
-#endif
+	sigunhook(bar->winch_hook);
+	sigunhook(bar->exit_hook);
 
 	bfs_bar_reset(bar);
-	bfs_bar_putfd(bar);
+
+	xclose(bar->fd);
+	free(bar);
 }