New functions: fnread() and fngetint(), companions to fnwrite()

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

src/util.c

@@ -154,6 +154,35 @@ char *str(char *fmt, ...)
 	return buf;
 }
 
+int fnread(char *buf, size_t len, char *fmt, ...)
+{
+	char path[256];
+	va_list ap;
+	FILE *fp;
+
+	va_start(ap, fmt);
+	vsnprintf(path, sizeof(path), fmt, ap);
+	va_end(ap);
+
+	if (!buf || !len) {
+		struct stat st;
+
+		if (stat(path, &st))
+			return -1;
+
+		return (ssize_t)st.st_size;
+	}
+
+	fp = fopen(path, "r");
+	if (!fp)
+		return -1;
+
+	len = fread(buf, sizeof(char), len, fp);
+	fclose(fp);
+
+	return (int)len;
+}
+
 int fnwrite(char *value, char *fmt, ...)
 {
 	char path[256];
@@ -185,6 +214,21 @@ int fnwrite(char *value, char *fmt, ...)
 	return rc;
 }
 
+int fngetint(char *path, int *val)
+{
+	char buf[10];
+
+	if (fnread(buf, sizeof(buf), path) <= 0)
+		return -1;
+
+	errno = 0;
+	*val = strtoul(chomp(buf), NULL, 0);
+	if (errno)
+		return -1;
+
+	return 0;
+}
+
 /*
  * musl libc default to /dev/null/utmp and /dev/null/wtmp, respectively.
  * See https://www.openwall.com/lists/musl/2012/03/04/4 for reasoning.

src/util.h

@@ -50,7 +50,9 @@ extern char *prognm;
 char *progname     (char *arg0);
 
 char *str          (char *fmt, ...);
+int   fnread       (char *buf, size_t len, char *fmt, ...);
 int   fnwrite      (char *value, char *fmt, ...);
+int   fngetint     (char *path, int *val);
 
 int   has_utmp     (void);
 int   strtobytes   (char *arg);