zdtm: Add write_value/read_value helpers into zdtm library

Add write_value/read_value helpers to write/read buffer to/from files into zdmt
library.

Signed-off-by: Bui Quang Minh <minhquangbui99@gmail.com>

test/zdtm/lib/Makefile

@@ -4,7 +4,7 @@ CFLAGS	+= $(USERCFLAGS)
 
 LIB	:= libzdtmtst.a
 
-LIBSRC	:= datagen.c msg.c parseargs.c test.c streamutil.c lock.c ns.c tcp.c unix.c fs.c sysctl.c mem.c
+LIBSRC	:= datagen.c msg.c parseargs.c test.c streamutil.c lock.c ns.c tcp.c unix.c fs.c sysctl.c mem.c file.c
 
 PKG_CONFIG ?= pkg-config
 pkg-config-check = $(shell sh -c '$(PKG_CONFIG) $(1) && echo y')

test/zdtm/lib/file.c

@@ -0,0 +1,46 @@
+#include <fcntl.h>
+#include <unistd.h>
+#include "zdtmtst.h"
+
+int write_value(const char *path, const char *value)
+{
+	int fd, l;
+
+	fd = open(path, O_WRONLY);
+	if (fd < 0) {
+		pr_perror("open %s", path);
+		return -1;
+	}
+
+	l = write(fd, value, strlen(value));
+	if (l < 0) {
+		pr_perror("failed to write %s to %s", value, path);
+		close(fd);
+		return -1;
+	}
+
+	close(fd);
+	return 0;
+}
+
+int read_value(const char *path, char *value, int size)
+{
+	int fd, ret;
+
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		pr_perror("open %s", path);
+		return -1;
+	}
+
+	ret = read(fd, (void *)value, size);
+	if (ret < 0) {
+		pr_perror("read %s", path);
+		close(fd);
+		return -1;
+	}
+
+	value[ret] = '\0';
+	close(fd);
+	return 0;
+}

test/zdtm/lib/zdtmtst.h

@@ -216,4 +216,7 @@ static inline void cleanup_closep(void *p)
 		TEMP_FAILURE_RETRY(close(*pp));
 }
 
+extern int write_value(const char *path, const char *value);
+extern int read_value(const char *path, char *value, int size);
+
 #endif /* _VIMITESU_H_ */

test/zdtm/static/cgroup04.c

@@ -19,26 +19,6 @@ char *dirname;
 TEST_OPTION(dirname, string, "cgroup directory name", 1);
 static const char *cgname = "zdtmtst";
 
-int write_value(const char *path, const char *value)
-{
-	int fd, l;
-
-	fd = open(path, O_WRONLY);
-	if (fd < 0) {
-		pr_perror("open %s", path);
-		return -1;
-	}
-
-	l = write(fd, value, strlen(value));
-	close(fd);
-	if (l < 0) {
-		pr_perror("failed to write %s to %s", value, path);
-		return -1;
-	}
-
-	return 0;
-}
-
 int mount_and_add(const char *controller, const char *path, const char *prop, const char *value)
 {
 	char aux[1024], paux[1024], subdir[1024];