user/fs: create a shared library for handling directory reads

2 files changed, 51 insertions, 0 deletions

diff --git a/src/user/lib/fs/dir.c b/src/user/lib/fs/dir.c
new file mode 100644
index 0000000..25ae606
--- /dev/null
+++ b/src/user/lib/fs/dir.c
@@ -0,0 +1,37 @@
+#include <errno.h>
+#include <string.h>
+#include <user/lib/fs/dir.h>
+
+void dir_start(struct dirbuild *db, long offset, char *buf, size_t buflen) {
+	db->offset = offset;
+	db->buf = buf;
+	db->bpos = 0;
+	db->blen = buflen;
+	db->error = 0;
+
+	if (offset < 0)
+		db->error = -ENOSYS; // TODO
+}
+
+bool dir_append(struct dirbuild *db, const char *name) {
+	if (db->error) return true;
+
+	long len = strlen(name) + 1;
+
+	if (db->offset < len) {
+		name += db->offset;
+		len  -= db->offset;
+		db->offset = 0;
+
+		// TODO no buffer overrun check
+		memcpy(db->buf + db->bpos, name, len);
+		db->bpos += len;
+	} else {
+		db->offset -= len;
+	}
+	return false;
+}
+
+long dir_finish(struct dirbuild *db) {
+	return db->error ? db->error : db->bpos;
+}
diff --git a/src/user/lib/fs/dir.h b/src/user/lib/fs/dir.h
new file mode 100644
index 0000000..1a8c7f5
--- /dev/null
+++ b/src/user/lib/fs/dir.h
@@ -0,0 +1,14 @@
+#pragma once
+#include <stdbool.h>
+#include <stddef.h>
+
+struct dirbuild {
+	long offset;
+	char *buf;
+	long bpos, blen;
+	long error;
+};
+
+void dir_start(struct dirbuild *db, long offset, char *buf, size_t buflen);
+bool dir_append(struct dirbuild *db, const char *name);
+long dir_finish(struct dirbuild *db);