1 files changed, 116 insertions, 0 deletions
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
new file mode 100644
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+++ b/src/include/access/xlogreader.h
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+/*-------------------------------------------------------------------------
+ *
+ * xlogreader.h
+ *		Definitions for the generic XLog reading facility
+ *
+ * Portions Copyright (c) 2013, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		src/include/access/xlogreader.h
+ *
+ * NOTES
+ *		See the definition of the XLogReaderState struct for instructions on
+ *		how to use the XLogReader infrastructure.
+ *
+ *		The basic idea is to allocate an XLogReaderState via
+ *		XLogReaderAllocate(), and call XLogReadRecord() until it returns NULL.
+ *-------------------------------------------------------------------------
+ */
+#ifndef XLOGREADER_H
+#define XLOGREADER_H
+
+#include "access/xlog_internal.h"
+
+typedef struct XLogReaderState XLogReaderState;
+
+/* Function type definition for the read_page callback */
+typedef int (*XLogPageReadCB) (XLogReaderState *xlogreader,
+										   XLogRecPtr targetPagePtr,
+										   int reqLen,
+										   char *readBuf,
+										   TimeLineID *pageTLI);
+
+struct XLogReaderState
+{
+	/* ----------------------------------------
+	 * Public parameters
+	 * ----------------------------------------
+	 */
+
+	/*
+	 * Data input callback (mandatory).
+	 *
+	 * This callback shall read at least reqLen valid bytes of the xlog page
+	 * starting at targetPagePtr, and store them in readBuf.  The callback
+	 * shall return the number of bytes read (never more than XLOG_BLCKSZ), or
+	 * -1 on failure.  The callback shall sleep, if necessary, to wait for the
+	 * requested bytes to become available.  The callback will not be invoked
+	 * again for the same page unless more than the returned number of bytes
+	 * are necessary.
+	 *
+	 * *pageTLI should be set to the TLI of the file the page was read from.
+	 * It is currently used only for error reporting purposes, to reconstruct
+	 * the name of the WAL file where an error occurred.
+	 */
+	XLogPageReadCB read_page;
+
+	/*
+	 * System identifier of the xlog files we're about to read.  Set to zero
+	 * (the default value) if unknown or unimportant.
+	 */
+	uint64		system_identifier;
+
+	/*
+	 * Opaque data for callbacks to use.  Not used by XLogReader.
+	 */
+	void	   *private_data;
+
+	/*
+	 * Start and end point of last record read.  EndRecPtr is also used as the
+	 * position to read next, if XLogReadRecord receives an invalid recptr.
+	 */
+	XLogRecPtr	ReadRecPtr;		/* start of last record read */
+	XLogRecPtr	EndRecPtr;		/* end+1 of last record read */
+
+	/* ----------------------------------------
+	 * private/internal state
+	 * ----------------------------------------
+	 */
+
+	/* Buffer for currently read page (XLOG_BLCKSZ bytes) */
+	char	   *readBuf;
+
+	/* last read segment, segment offset, read length, TLI */
+	XLogSegNo	readSegNo;
+	uint32		readOff;
+	uint32		readLen;
+	TimeLineID	readPageTLI;
+
+	/* beginning of last page read, and its TLI  */
+	XLogRecPtr	latestPagePtr;
+	TimeLineID	latestPageTLI;
+
+	/* Buffer for current ReadRecord result (expandable) */
+	char	   *readRecordBuf;
+	uint32		readRecordBufSize;
+
+	/* Buffer to hold error message */
+	char	   *errormsg_buf;
+};
+
+/* Get a new XLogReader */
+extern XLogReaderState *XLogReaderAllocate(XLogPageReadCB pagereadfunc,
+				   void *private_data);
+
+/* Free an XLogReader */
+extern void XLogReaderFree(XLogReaderState *state);
+
+/* Read the next XLog record. Returns NULL on end-of-WAL or failure */
+extern struct XLogRecord *XLogReadRecord(XLogReaderState *state,
+			   XLogRecPtr recptr, char **errormsg);
+
+#ifdef FRONTEND
+extern XLogRecPtr XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr);
+#endif   /* FRONTEND */
+
+#endif   /* XLOGREADER_H */