1 files changed, 86 insertions, 0 deletions
diff --git a/src/bin/pg_rewind/rewind_source.h b/src/bin/pg_rewind/rewind_source.h
new file mode 100644
index 0000000..1310e86
--- /dev/null
+++ b/src/bin/pg_rewind/rewind_source.h
@@ -0,0 +1,86 @@
+/*-------------------------------------------------------------------------
+ *
+ * rewind_source.h
+ *	  Abstraction for fetching from source server.
+ *
+ * The source server can be either a libpq connection to a live system,
+ * or a local data directory. The 'rewind_source' struct abstracts the
+ * operations to fetch data from the source system, so that the rest of
+ * the code doesn't need to care what kind of a source its dealing with.
+ *
+ * Copyright (c) 2013-2022, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef REWIND_SOURCE_H
+#define REWIND_SOURCE_H
+
+#include "access/xlogdefs.h"
+#include "file_ops.h"
+#include "filemap.h"
+#include "libpq-fe.h"
+
+typedef struct rewind_source
+{
+	/*
+	 * Traverse all files in the source data directory, and call 'callback' on
+	 * each file.
+	 */
+	void		(*traverse_files) (struct rewind_source *,
+								   process_file_callback_t callback);
+
+	/*
+	 * Fetch a single file into a malloc'd buffer. The file size is returned
+	 * in *filesize. The returned buffer is always zero-terminated, which is
+	 * handy for text files.
+	 */
+	char	   *(*fetch_file) (struct rewind_source *, const char *path,
+							   size_t *filesize);
+
+	/*
+	 * Request to fetch (part of) a file in the source system, specified by an
+	 * offset and length, and write it to the same offset in the corresponding
+	 * target file. The source implementation may queue up the request and
+	 * execute it later when convenient. Call finish_fetch() to flush the
+	 * queue and execute all requests.
+	 */
+	void		(*queue_fetch_range) (struct rewind_source *, const char *path,
+									  off_t offset, size_t len);
+
+	/*
+	 * Like queue_fetch_range(), but requests replacing the whole local file
+	 * from the source system. 'len' is the expected length of the file,
+	 * although when the source is a live server, the file may change
+	 * concurrently. The implementation is not obliged to copy more than 'len'
+	 * bytes, even if the file is larger. However, to avoid copying a
+	 * truncated version of the file, which can cause trouble if e.g. a
+	 * configuration file is modified concurrently, the implementation should
+	 * try to copy the whole file, even if it's larger than expected.
+	 */
+	void		(*queue_fetch_file) (struct rewind_source *, const char *path,
+									 size_t len);
+
+	/*
+	 * Execute all requests queued up with queue_fetch_range().
+	 */
+	void		(*finish_fetch) (struct rewind_source *);
+
+	/*
+	 * Get the current WAL insert position in the source system.
+	 */
+	XLogRecPtr	(*get_current_wal_insert_lsn) (struct rewind_source *);
+
+	/*
+	 * Free this rewind_source object.
+	 */
+	void		(*destroy) (struct rewind_source *);
+
+} rewind_source;
+
+/* in libpq_source.c */
+extern rewind_source *init_libpq_source(PGconn *conn);
+
+/* in local_source.c */
+extern rewind_source *init_local_source(const char *datadir);
+
+#endif							/* FETCH_H */