1 files changed, 92 insertions, 0 deletions
diff --git a/src/port/pgcheckdir.c b/src/port/pgcheckdir.c
new file mode 100644
index 0000000..6c09cf2
--- /dev/null
+++ b/src/port/pgcheckdir.c
@@ -0,0 +1,92 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgcheckdir.c
+ *
+ * A simple subroutine to check whether a directory exists and is empty or not.
+ * Useful in both initdb and the backend.
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *		src/port/pgcheckdir.c
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+#include <dirent.h>
+
+
+/*
+ * Test to see if a directory exists and is empty or not.
+ *
+ * Returns:
+ *		0 if nonexistent
+ *		1 if exists and empty
+ *		2 if exists and contains _only_ dot files
+ *		3 if exists and contains a mount point
+ *		4 if exists and not empty
+ *		-1 if trouble accessing directory (errno reflects the error)
+ */
+int
+pg_check_dir(const char *dir)
+{
+	int			result = 1;
+	DIR		   *chkdir;
+	struct dirent *file;
+	bool		dot_found = false;
+	bool		mount_found = false;
+	int			readdir_errno;
+
+	chkdir = opendir(dir);
+	if (chkdir == NULL)
+		return (errno == ENOENT) ? 0 : -1;
+
+	while (errno = 0, (file = readdir(chkdir)) != NULL)
+	{
+		if (strcmp(".", file->d_name) == 0 ||
+			strcmp("..", file->d_name) == 0)
+		{
+			/* skip this and parent directory */
+			continue;
+		}
+#ifndef WIN32
+		/* file starts with "." */
+		else if (file->d_name[0] == '.')
+		{
+			dot_found = true;
+		}
+		/* lost+found directory */
+		else if (strcmp("lost+found", file->d_name) == 0)
+		{
+			mount_found = true;
+		}
+#endif
+		else
+		{
+			result = 4;			/* not empty */
+			break;
+		}
+	}
+
+	if (errno)
+		result = -1;			/* some kind of I/O error? */
+
+	/* Close chkdir and avoid overwriting the readdir errno on success */
+	readdir_errno = errno;
+	if (closedir(chkdir))
+		result = -1;			/* error executing closedir */
+	else
+		errno = readdir_errno;
+
+	/* We report on mount point if we find a lost+found directory */
+	if (result == 1 && mount_found)
+		result = 3;
+
+	/* We report on dot-files if we _only_ find dot files */
+	if (result == 1 && dot_found)
+		result = 2;
+
+	return result;
+}