unistd/file: fix __safe_read/write return value

JIRA: RTOS-882

unistd/file-internal.h

@@ -20,7 +20,7 @@
 #include <sys/types.h>
 
 
-size_t __safe_write(int fd, const void *buff, size_t size);
+ssize_t __safe_write(int fd, const void *buff, size_t size);
 
 
 ssize_t __safe_read(int fd, void *buf, size_t size);

unistd/file.c

@@ -48,18 +48,17 @@ WRAP_ERRNO_DEF(int, dup2, (int fildes, int fildes2), (fildes, fildes2))
 WRAP_ERRNO_DEF(int, fsync, (int fildes), (fildes))
 
 
-size_t __safe_write(int fd, const void *buff, size_t size)
+ssize_t __safe_write(int fd, const void *buff, size_t size)
 {
 	size_t todo = size;
-	ssize_t wlen;
+	ssize_t wlen = 0;
 	const char *ptr = buff;
 
 	while (todo != 0) {
 		wlen = write(fd, ptr, todo);
 		if (wlen > 0) {
 			todo -= wlen;
 			ptr += wlen;
-			continue;
 		}
 		else if (wlen < 0) {
 			if ((errno == EINTR) || (errno == EAGAIN)) {
@@ -74,6 +73,10 @@ size_t __safe_write(int fd, const void *buff, size_t size)
 		}
 	}
 
+	if (wlen < 0) {
+		return -1;
+	}
+
 	return size - todo;
 }
 
@@ -102,6 +105,10 @@ ssize_t __safe_read(int fd, void *buf, size_t size)
 		}
 	}
 
+	if ((size != 0) && (size == todo)) {
+		return -1;
+	}
+
 	return size - todo;
 }