[pacman-dev] [PATCH v3] cache terminal column width and handle SIGWINCH

[Simon Gomizelj]

Instead of doing ioctl each time, cache the result. Handle SIGWINCH to
we know the size of the terminal has changed (clear the cache).
---
Whitespace problems.

God damn it, sorry for the spam, its been a while since I've done this.
I'll take more care in the future.

 src/pacman/pacman.c | 10 ++++++++++
 src/pacman/util.c   | 24 +++++++++++++++++++-----
 src/pacman/util.h   |  1 +
 3 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/src/pacman/pacman.c b/src/pacman/pacman.c
index df73bcf..1643a63 100644
--- a/src/pacman/pacman.c
+++ b/src/pacman/pacman.c
@@ -1044,6 +1044,16 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	new_action.sa_handler = columns_reset;
+	sigemptyset(&new_action.sa_mask);
+	new_action.sa_flags = 0;
+
+	sigaction(SIGWINCH, NULL, &old_action);
+	if(old_action.sa_handler != SIG_IGN) {
+		sigaction(SIGWINCH, &new_action, NULL);
+	}
+
+
 	/* i18n init */
 #if defined(ENABLE_NLS)
 	localize();
diff --git a/src/pacman/util.c b/src/pacman/util.c
index 23eea98..b08ad43 100644
--- a/src/pacman/util.c
+++ b/src/pacman/util.c
@@ -46,6 +46,7 @@
 #include "conf.h"
 #include "callback.h"
 
+static volatile unsigned cached_columns = 0;
 
 struct table_cell_t {
 	char *label;
@@ -155,29 +156,42 @@ static int flush_term_input(int fd)
 	return 0;
 }
 
+/* intended to be used as a SIGWINCH handler */
+void columns_reset(int signum)
+{
+	cached_columns = 0;
+}
+
 /* gets the current screen column width */
 unsigned short getcols(int fd)
 {
 	const unsigned short default_tty = 80;
 	const unsigned short default_notty = 0;
-	unsigned short termwidth = 0;
+	unsigned short columns = 0;
+
+	if(cached_columns > 0) {
+		return cached_columns;
+	}
 
 	if(!isatty(fd)) {
-		return default_notty;
+		cached_columns = default_notty;
+		return cached_columns;
 	}
 
 #if defined(TIOCGSIZE)
 	struct ttysize win;
 	if(ioctl(fd, TIOCGSIZE, &win) == 0) {
-		termwidth = win.ts_cols;
+		columns = win.ts_cols;
 	}
 #elif defined(TIOCGWINSZ)
 	struct winsize win;
 	if(ioctl(fd, TIOCGWINSZ, &win) == 0) {
-		termwidth = win.ws_col;
+		columns = win.ws_col;
 	}
 #endif
-	return termwidth == 0 ? default_tty : termwidth;
+
+	cached_columns = columns == 0 ? default_tty : columns;
+	return cached_columns;
 }
 
 /* does the same thing as 'rm -rf' */
diff --git a/src/pacman/util.h b/src/pacman/util.h
index e2297f8..d7f7b3c 100644
--- a/src/pacman/util.h
+++ b/src/pacman/util.h
@@ -49,6 +49,7 @@ int trans_init(alpm_transflag_t flags, int check_valid);
 int trans_release(void);
 int needs_root(void);
 int check_syncdbs(size_t need_repos, int check_valid);
+void columns_reset(int signum);
 unsigned short getcols(int fd);
 int rmrf(const char *path);
 void indentprint(const char *str, unsigned short indent, unsigned short cols);
-- 
1.8.4.2