1 files changed, 56 insertions, 0 deletions
diff --git a/src/H5FDonion_header.h b/src/H5FDonion_header.h
new file mode 100644
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+++ b/src/H5FDonion_header.h
@@ -0,0 +1,56 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * Copyright by The HDF Group.                                               *
+ * All rights reserved.                                                      *
+ *                                                                           *
+ * This file is part of HDF5.  The full HDF5 copyright notice, including     *
+ * terms governing use, modification, and redistribution, is contained in    *
+ * the COPYING file, which can be found at the root of the source code       *
+ * distribution tree, or in https://support.hdfgroup.org/ftp/HDF5/releases.  *
+ * If you do not have access to either file, you may request a copy from     *
+ * help@hdfgroup.org.                                                        *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Onion Virtual File Driver (VFD)
+ *
+ * Purpose:     Interface for the onion file's header
+ */
+
+#ifndef H5FDonion_header_H
+#define H5FDonion_header_H
+
+/* Number of bytes to encode fixed-size components */
+#define H5FD_ONION_ENCODED_SIZE_HEADER 40
+
+/* Flags must align exactly one per bit, up to 24 bits */
+#define H5FD_ONION_HEADER_FLAG_WRITE_LOCK        0x1
+#define H5FD_ONION_HEADER_FLAG_DIVERGENT_HISTORY 0x2
+#define H5FD_ONION_HEADER_FLAG_PAGE_ALIGNMENT    0x4
+#define H5FD_ONION_HEADER_SIGNATURE              "OHDH"
+#define H5FD_ONION_HEADER_VERSION_CURR           1
+
+/* In-memory representation of the on-store onion history file header.
+ */
+typedef struct H5FD_onion_header_t {
+    uint8_t  version;
+    uint32_t flags; /* At most three bytes used! */
+    uint32_t page_size;
+    uint64_t origin_eof; /* Size of the 'original' canonical file */
+    uint64_t history_addr;
+    uint64_t history_size;
+    uint32_t checksum;
+} H5FD_onion_header_t;
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+H5_DLL herr_t H5FD__onion_ingest_header(H5FD_onion_header_t *hdr_out, H5FD_t *raw_file, haddr_t addr);
+H5_DLL herr_t H5FD__onion_write_header(H5FD_onion_header_t *header, H5FD_t *file);
+H5_DLL size_t H5FD__onion_header_decode(unsigned char *buf, H5FD_onion_header_t *header);
+H5_DLL size_t H5FD__onion_header_encode(H5FD_onion_header_t *header, unsigned char *buf, uint32_t *checksum);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* H5FDonion_header_H */