Implement esnprintf() and make formatted calls more efficient

Within the components, snprintf() was unchecked and had inefficient
calls in some places.
We implement esnprintf() that does all the dirty laundry for us
and use it exclusively now.

components/battery.c

@@ -14,9 +14,16 @@
 		int perc;
 		char path[PATH_MAX];
 
-		snprintf(path, sizeof(path), "%s%s%s", "/sys/class/power_supply/",
-		         bat, "/capacity");
-		return (pscanf(path, "%d", &perc) == 1) ? bprintf("%d", perc) : NULL;
+		if (esnprintf(path, sizeof(path),
+		              "/sys/class/power_supply/%s/capacity",
+		              bat) < 0) {
+			return NULL;
+		}
+		if (pscanf(path, "%d", &perc) != 1) {
+			return NULL;
+		}
+
+		return bprintf("%d", perc);
 	}
 
 	const char *
@@ -32,8 +39,11 @@
 		size_t i;
 		char path[PATH_MAX], state[12];
 
-		snprintf(path, sizeof(path), "%s%s%s", "/sys/class/power_supply/",
-		         bat, "/status");
+		if (esnprintf(path, sizeof(path),
+		              "/sys/class/power_supply/%s/status",
+		              bat) < 0) {
+			return NULL;
+		}
 		if (pscanf(path, "%12s", state) != 1) {
 			return NULL;
 		}
@@ -53,20 +63,29 @@
 		float timeleft;
 		char path[PATH_MAX], state[12];
 
-		snprintf(path, sizeof(path), "%s%s%s", "/sys/class/power_supply/",
-		         bat, "/status");
+		if (esnprintf(path, sizeof(path),
+		              "/sys/class/power_supply/%s/status",
+		              bat) < 0) {
+			return NULL;
+		}
 		if (pscanf(path, "%12s", state) != 1) {
 			return NULL;
 		}
 
 		if (!strcmp(state, "Discharging")) {
-			snprintf(path, sizeof(path), "%s%s%s", "/sys/class/power_supply/",
-					 bat, "/charge_now");
+			if (esnprintf(path, sizeof(path),
+                                      "/sys/class/power_supply/%s/charge_now",
+			              bat) < 0) {
+				return NULL;
+			}
 			if (pscanf(path, "%d", &charge_now) != 1) {
 				return NULL;
 			}
-			snprintf(path, sizeof(path), "%s%s%s", "/sys/class/power_supply/",
-					 bat, "/current_now");
+			if (esnprintf(path, sizeof(path),
+			              "/sys/class/power_supply/%s/current_now",
+			              bat) < 0) {
+				return NULL;
+			}
 			if (pscanf(path, "%d", &current_now) != 1) {
 				return NULL;
 			}

components/netspeeds.c

@@ -17,8 +17,11 @@
 
 		oldrxbytes = rxbytes;
 
-		snprintf(path, sizeof(path),
-		         "/sys/class/net/%s/statistics/rx_bytes", interface);
+		if (esnprintf(path, sizeof(path),
+		              "/sys/class/net/%s/statistics/rx_bytes",
+		              interface) < 0) {
+			return NULL;
+		}
 		if (pscanf(path, "%llu", &rxbytes) != 1) {
 			return NULL;
 		}
@@ -37,8 +40,11 @@
 
 		oldtxbytes = txbytes;
 
-		snprintf(path, sizeof(path),
-		         "/sys/class/net/%s/statistics/tx_bytes", interface);
+		if (esnprintf(path, sizeof(path),
+		              "/sys/class/net/%s/statistics/tx_bytes",
+		              interface) < 0) {
+			return NULL;
+		}
 		if (pscanf(path, "%llu", &txbytes) != 1) {
 			return NULL;
 		}

components/wifi.c

@@ -23,8 +23,11 @@
 		char status[5];
 		FILE *fp;
 
-		snprintf(path, sizeof(path), "%s%s%s", "/sys/class/net/", iface,
-		         "/operstate");
+		if (esnprintf(path, sizeof(path),
+		              "/sys/class/net/%s/operstate",
+		              iface) < 0) {
+			return NULL;
+		}
 		if (!(fp = fopen(path, "r"))) {
 			warn("fopen '%s':", path);
 			return NULL;
@@ -69,7 +72,10 @@
 
 		memset(&wreq, 0, sizeof(struct iwreq));
 		wreq.u.essid.length = IW_ESSID_MAX_SIZE+1;
-		snprintf(wreq.ifr_name, sizeof(wreq.ifr_name), "%s", iface);
+		if (esnprintf(wreq.ifr_name, sizeof(wreq.ifr_name),
+		              "%s", iface) < 0) {
+			return NULL;
+		}
 
 		if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0) {
 			warn("socket 'AF_INET':");

slstatus.c

@@ -91,12 +91,8 @@ main(int argc, char *argv[])
 			if (!(res = args[i].func(args[i].args))) {
 				res = unknown_str;
 			}
-			if ((ret = snprintf(status + len, sizeof(status) - len,
+			if ((ret = esnprintf(status + len, sizeof(status) - len,
 			                    args[i].fmt, res)) < 0) {
-				warn("snprintf:");
-				break;
-			} else if ((size_t)ret >= sizeof(status) - len) {
-				warn("snprintf: Output truncated");
 				break;
 			}
 			len += ret;

util.c

@@ -48,6 +48,27 @@ die(const char *fmt, ...)
 	exit(1);
 }
 
+int
+esnprintf(char *str, size_t size, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, fmt);
+	ret = vsnprintf(str, size, fmt, ap);
+	va_end(ap);
+
+	if (ret < 0) {
+		warn("snprintf:");
+		return -1;
+	} else if ((size_t)ret >= size) {
+		warn("snprintf: Output truncated");
+		return -1;
+	}
+
+	return ret;
+}
+
 const char *
 bprintf(const char *fmt, ...)
 {

util.h

@@ -8,6 +8,7 @@ extern char *argv0;
 void warn(const char *, ...);
 void die(const char *, ...);
 
+int esnprintf(char *str, size_t size, const char *fmt, ...);
 const char *bprintf(const char *fmt, ...);
 const char *fmt_scaled(size_t);
 int pscanf(const char *path, const char *fmt, ...);