1 files changed, 130 insertions, 0 deletions
diff --git a/src/bin/pg_rewind/timeline.c b/src/bin/pg_rewind/timeline.c
new file mode 100644
index 0000000..6756c5d
--- /dev/null
+++ b/src/bin/pg_rewind/timeline.c
@@ -0,0 +1,130 @@
+/*-------------------------------------------------------------------------
+ *
+ * timeline.c
+ *	  timeline-related functions.
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres_fe.h"
+
+#include "access/timeline.h"
+#include "access/xlog_internal.h"
+#include "pg_rewind.h"
+
+/*
+ * This is copy-pasted from the backend readTimeLineHistory, modified to
+ * return a malloc'd array and to work without backend functions.
+ */
+/*
+ * Try to read a timeline's history file.
+ *
+ * If successful, return the list of component TLIs (the given TLI followed by
+ * its ancestor TLIs).  If we can't find the history file, assume that the
+ * timeline has no parents, and return a list of just the specified timeline
+ * ID.
+ */
+TimeLineHistoryEntry *
+rewind_parseTimeLineHistory(char *buffer, TimeLineID targetTLI, int *nentries)
+{
+	char	   *fline;
+	TimeLineHistoryEntry *entry;
+	TimeLineHistoryEntry *entries = NULL;
+	int			nlines = 0;
+	TimeLineID	lasttli = 0;
+	XLogRecPtr	prevend;
+	char	   *bufptr;
+	bool		lastline = false;
+
+	/*
+	 * Parse the file...
+	 */
+	prevend = InvalidXLogRecPtr;
+	bufptr = buffer;
+	while (!lastline)
+	{
+		char	   *ptr;
+		TimeLineID	tli;
+		uint32		switchpoint_hi;
+		uint32		switchpoint_lo;
+		int			nfields;
+
+		fline = bufptr;
+		while (*bufptr && *bufptr != '\n')
+			bufptr++;
+		if (!(*bufptr))
+			lastline = true;
+		else
+			*bufptr++ = '\0';
+
+		/* skip leading whitespace and check for # comment */
+		for (ptr = fline; *ptr; ptr++)
+		{
+			if (!isspace((unsigned char) *ptr))
+				break;
+		}
+		if (*ptr == '\0' || *ptr == '#')
+			continue;
+
+		nfields = sscanf(fline, "%u\t%X/%X", &tli, &switchpoint_hi, &switchpoint_lo);
+
+		if (nfields < 1)
+		{
+			/* expect a numeric timeline ID as first field of line */
+			pg_log_error("syntax error in history file: %s", fline);
+			pg_log_error("Expected a numeric timeline ID.");
+			exit(1);
+		}
+		if (nfields != 3)
+		{
+			pg_log_error("syntax error in history file: %s", fline);
+			pg_log_error("Expected a write-ahead log switchpoint location.");
+			exit(1);
+		}
+		if (entries && tli <= lasttli)
+		{
+			pg_log_error("invalid data in history file: %s", fline);
+			pg_log_error("Timeline IDs must be in increasing sequence.");
+			exit(1);
+		}
+
+		lasttli = tli;
+
+		nlines++;
+		entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
+
+		entry = &entries[nlines - 1];
+		entry->tli = tli;
+		entry->begin = prevend;
+		entry->end = ((uint64) (switchpoint_hi)) << 32 | (uint64) switchpoint_lo;
+		prevend = entry->end;
+
+		/* we ignore the remainder of each line */
+	}
+
+	if (entries && targetTLI <= lasttli)
+	{
+		pg_log_error("invalid data in history file");
+		pg_log_error("Timeline IDs must be less than child timeline's ID.");
+		exit(1);
+	}
+
+	/*
+	 * Create one more entry for the "tip" of the timeline, which has no entry
+	 * in the history file.
+	 */
+	nlines++;
+	if (entries)
+		entries = pg_realloc(entries, nlines * sizeof(TimeLineHistoryEntry));
+	else
+		entries = pg_malloc(1 * sizeof(TimeLineHistoryEntry));
+
+	entry = &entries[nlines - 1];
+	entry->tli = targetTLI;
+	entry->begin = prevend;
+	entry->end = InvalidXLogRecPtr;
+
+	*nentries = nlines;
+	return entries;
+}