diff options
| -rw-r--r-- | src/bar.c | 133 |
1 files changed, 102 insertions, 31 deletions
@@ -6,6 +6,7 @@ #include "atomic.h" #include "bfstd.h" #include "bit.h" +#include "diag.h" #include "dstring.h" #include <errno.h> #include <fcntl.h> @@ -15,9 +16,30 @@ #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 { - int fd; + /** + * 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. */ atomic unsigned int width; + /** The height of the TTY. */ atomic unsigned int height; }; @@ -26,27 +48,71 @@ static struct bfs_bar the_bar = { .fd = -1, }; +/** 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 - struct winsize ws; - if (ioctl(bar->fd, TIOCGWINSZ, &ws) != 0) { + int fd = bfs_bar_getfd(bar); + if (fd < 0) { return -1; } - store(&bar->width, ws.ws_col, relaxed); - store(&bar->height, ws.ws_row, relaxed); - return 0; + 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); + } + + bfs_bar_putfd(bar); + return ret; #else errno = ENOTSUP; return -1; #endif } -/** Async Signal Safe puts(). */ -static int ass_puts(int fd, const char *str) { - size_t len = strlen(str); - return xwrite(fd, str, len) == len ? 0 : -1; +/** 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; +} + +/** Write a string to the status bar (async-signal-safe). */ +static int bfs_bar_puts(struct bfs_bar *bar, const char *str) { + return bfs_bar_write(bar, str, strlen(str)); } /** Number of decimal digits needed for terminal sizes. */ @@ -70,22 +136,24 @@ static char *ass_itoa(char *str, unsigned int n) { /** Update the size of the scrollable region. */ static int bfs_bar_resize(struct bfs_bar *bar) { - char esc_seq[12 + ITOA_DIGITS] = - "\0337" // DECSC: Save cursor - "\033[;"; // DECSTBM: Set scrollable region + char esc_seq[12 + ITOA_DIGITS]; + + char *cur = stpcpy(esc_seq, + "\0337" // DECSC: Save cursor + "\033[;" // DECSTBM: Set scrollable region + ); // DECSTBM takes the height as the second argument unsigned int height = load(&bar->height, relaxed); - char *ptr = esc_seq + strlen(esc_seq); - ptr = ass_itoa(ptr, height - 1); + cur = ass_itoa(cur, height - 1); - strcpy(ptr, + cur = stpcpy(cur, "r" // DECSTBM "\0338" // DECRC: Restore the cursor "\033[J" // ED: Erase display from cursor to end ); - return ass_puts(bar->fd, esc_seq); + return bfs_bar_write(bar, esc_seq, cur - esc_seq); } #ifdef SIGWINCH @@ -102,7 +170,7 @@ static void sighand_winch(int sig) { /** Reset the scrollable region and hide the bar. */ static int bfs_bar_reset(struct bfs_bar *bar) { - return ass_puts(bar->fd, + return bfs_bar_puts(bar, "\0337" // DECSC: Save cursor "\033[r" // DECSTBM: Reset scrollable region "\0338" // DECRC: Restore cursor @@ -138,13 +206,14 @@ static int bfs_bar_printf(struct bfs_bar *bar, const char *format, ...) { return -1; } - int ret = ass_puts(bar->fd, str); + int ret = bfs_bar_write(bar, str, dstrlen(str)); dstrfree(str); return ret; } struct bfs_bar *bfs_bar_show(void) { - if (the_bar.fd >= 0) { + unsigned int refs = BFS_BAR_UNINIT; + if (!compare_exchange_strong(&the_bar.refcount, &refs, BFS_BAR_BUSY, acq_rel, relaxed)) { errno = EBUSY; goto fail; } @@ -153,16 +222,18 @@ struct bfs_bar *bfs_bar_show(void) { ctermid(term); if (strlen(term) == 0) { errno = ENOTTY; - goto fail; + goto unref; } - the_bar.fd = open(term, O_RDWR | O_CLOEXEC); - if (the_bar.fd < 0) { - goto fail; + int fd = open(term, O_RDWR | O_CLOEXEC); + if (fd < 0) { + goto unref; } + store(&the_bar.fd, fd, relaxed); + store(&the_bar.refcount, BFS_BAR_READY, release); if (bfs_bar_getsize(&the_bar) != 0) { - goto fail_close; + goto put; } reset_before_death_by(SIGABRT); @@ -192,9 +263,11 @@ struct bfs_bar *bfs_bar_show(void) { return &the_bar; -fail_close: - close_quietly(the_bar.fd); - the_bar.fd = -1; +put: + bfs_bar_putfd(&the_bar); + return NULL; +unref: + store(&the_bar.refcount, 0, release); fail: return NULL; } @@ -233,7 +306,5 @@ void bfs_bar_hide(struct bfs_bar *bar) { #endif bfs_bar_reset(bar); - - xclose(bar->fd); - bar->fd = -1; + bfs_bar_putfd(bar); } |