relocating the server's backup manifest code

From a9386c0c1059cbf567005a6606956ecf808e1071 Mon Sep 17 00:00:00 2001
From: Robert Haas <rhaas@postgresql.org>
Date: Sat, 18 Apr 2020 08:28:50 -0400
Subject: [PATCH v1] Move the server's backup manifest code to a separate file.

basebackup.c is already a pretty big and complicated file, so it
makes more sense to keep the backup manifest support routines
in a separate file, for clarity and ease of maintenance.
---
 src/backend/replication/Makefile          |   1 +
 src/backend/replication/backup_manifest.c | 362 ++++++++++++++++++++
 src/backend/replication/basebackup.c      | 391 +---------------------
 src/include/replication/backup_manifest.h |  64 ++++
 4 files changed, 429 insertions(+), 389 deletions(-)
 create mode 100644 src/backend/replication/backup_manifest.c
 create mode 100644 src/include/replication/backup_manifest.h

diff --git a/src/backend/replication/Makefile b/src/backend/replication/Makefile
index fd08f093e1..a0381e52f3 100644
--- a/src/backend/replication/Makefile
+++ b/src/backend/replication/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I. -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
+	backup_manifest.o \
 	basebackup.o \
 	repl_gram.o \
 	slot.o \
diff --git a/src/backend/replication/backup_manifest.c b/src/backend/replication/backup_manifest.c
new file mode 100644
index 0000000000..1f11e91a3f
--- /dev/null
+++ b/src/backend/replication/backup_manifest.c
@@ -0,0 +1,362 @@
+/*-------------------------------------------------------------------------
+ *
+ * backup_manifest.c
+ *	  code for generating and sending a backup manifest
+ *
+ * Portions Copyright (c) 2010-2020, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/backup_manifest.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/timeline.h"
+#include "libpq/libpq.h"
+#include "libpq/pqformat.h"
+#include "mb/pg_wchar.h"
+#include "replication/backup_manifest.h"
+#include "utils/builtins.h"
+#include "utils/json.h"
+
+/*
+ * Convenience macro for appending data to the backup manifest.
+ */
+#define AppendToManifest(manifest, ...) \
+	{ \
+		char *_manifest_s = psprintf(__VA_ARGS__);	\
+		AppendStringToManifest(manifest, _manifest_s);	\
+		pfree(_manifest_s);	\
+	}
+
+/*
+ * Initialize state so that we can construct a backup manifest.
+ *
+ * NB: Although the checksum type for the data files is configurable, the
+ * checksum for the manifest itself always uses SHA-256. See comments in
+ * SendBackupManifest.
+ */
+void
+InitializeManifest(manifest_info *manifest, manifest_option want_manifest,
+				   pg_checksum_type manifest_checksum_type)
+{
+	if (want_manifest == MANIFEST_OPTION_NO)
+		manifest->buffile = NULL;
+	else
+		manifest->buffile = BufFileCreateTemp(false);
+	manifest->checksum_type = manifest_checksum_type;
+	pg_sha256_init(&manifest->manifest_ctx);
+	manifest->manifest_size = UINT64CONST(0);
+	manifest->force_encode = (want_manifest == MANIFEST_OPTION_FORCE_ENCODE);
+	manifest->first_file = true;
+	manifest->still_checksumming = true;
+
+	if (want_manifest != MANIFEST_OPTION_NO)
+		AppendToManifest(manifest,
+						 "{ \"PostgreSQL-Backup-Manifest-Version\": 1,\n"
+						 "\"Files\": [");
+}
+
+/*
+ * Append a cstring to the manifest.
+ */
+void
+AppendStringToManifest(manifest_info *manifest, char *s)
+{
+	int			len = strlen(s);
+	size_t		written;
+
+	Assert(manifest != NULL);
+	if (manifest->still_checksumming)
+		pg_sha256_update(&manifest->manifest_ctx, (uint8 *) s, len);
+	written = BufFileWrite(manifest->buffile, s, len);
+	if (written != len)
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not write to temporary file: %m")));
+	manifest->manifest_size += len;
+}
+
+/*
+ * Add an entry to the backup manifest for a file.
+ */
+void
+AddFileToManifest(manifest_info *manifest, const char *spcoid,
+				  const char *pathname, size_t size, pg_time_t mtime,
+				  pg_checksum_context *checksum_ctx)
+{
+	char		pathbuf[MAXPGPATH];
+	int			pathlen;
+	StringInfoData buf;
+
+	if (!IsManifestEnabled(manifest))
+		return;
+
+	/*
+	 * If this file is part of a tablespace, the pathname passed to this
+	 * function will be relative to the tar file that contains it. We want the
+	 * pathname relative to the data directory (ignoring the intermediate
+	 * symlink traversal).
+	 */
+	if (spcoid != NULL)
+	{
+		snprintf(pathbuf, sizeof(pathbuf), "pg_tblspc/%s/%s", spcoid,
+				 pathname);
+		pathname = pathbuf;
+	}
+
+	/*
+	 * Each file's entry needs to be separated from any entry that follows by a
+	 * comma, but there's no comma before the first one or after the last one.
+	 * To make that work, adding a file to the manifest starts by terminating
+	 * the most recently added line, with a comma if appropriate, but does not
+	 * terminate the line inserted for this file.
+	 */
+	initStringInfo(&buf);
+	if (manifest->first_file)
+	{
+		appendStringInfoString(&buf, "\n");
+		manifest->first_file = false;
+	}
+	else
+		appendStringInfoString(&buf, ",\n");
+
+	/*
+	 * Write the relative pathname to this file out to the manifest. The
+	 * manifest is always stored in UTF-8, so we have to encode paths that are
+	 * not valid in that encoding.
+	 */
+	pathlen = strlen(pathname);
+	if (!manifest->force_encode &&
+		pg_verify_mbstr(PG_UTF8, pathname, pathlen, true))
+	{
+		appendStringInfoString(&buf, "{ \"Path\": ");
+		escape_json(&buf, pathname);
+		appendStringInfoString(&buf, ", ");
+	}
+	else
+	{
+		appendStringInfoString(&buf, "{ \"Encoded-Path\": \"");
+		enlargeStringInfo(&buf, 2 * pathlen);
+		buf.len += hex_encode((char *) pathname, pathlen,
+							  &buf.data[buf.len]);
+		appendStringInfoString(&buf, "\", ");
+	}
+
+	appendStringInfo(&buf, "\"Size\": %zu, ", size);
+
+	/*
+	 * Convert last modification time to a string and append it to the
+	 * manifest. Since it's not clear what time zone to use and since time
+	 * zone definitions can change, possibly causing confusion, use GMT
+	 * always.
+	 */
+	appendStringInfoString(&buf, "\"Last-Modified\": \"");
+	enlargeStringInfo(&buf, 128);
+	buf.len += pg_strftime(&buf.data[buf.len], 128, "%Y-%m-%d %H:%M:%S %Z",
+						   pg_gmtime(&mtime));
+	appendStringInfoString(&buf, "\"");
+
+	/* Add checksum information. */
+	if (checksum_ctx->type != CHECKSUM_TYPE_NONE)
+	{
+		uint8		checksumbuf[PG_CHECKSUM_MAX_LENGTH];
+		int			checksumlen;
+
+		checksumlen = pg_checksum_final(checksum_ctx, checksumbuf);
+
+		appendStringInfo(&buf,
+						 ", \"Checksum-Algorithm\": \"%s\", \"Checksum\": \"",
+						 pg_checksum_type_name(checksum_ctx->type));
+		enlargeStringInfo(&buf, 2 * checksumlen);
+		buf.len += hex_encode((char *) checksumbuf, checksumlen,
+							  &buf.data[buf.len]);
+		appendStringInfoString(&buf, "\"");
+	}
+
+	/* Close out the object. */
+	appendStringInfoString(&buf, " }");
+
+	/* OK, add it to the manifest. */
+	AppendStringToManifest(manifest, buf.data);
+
+	/* Avoid leaking memory. */
+	pfree(buf.data);
+}
+
+/*
+ * Add information about the WAL that will need to be replayed when restoring
+ * this backup to the manifest.
+ */
+void
+AddWALInfoToManifest(manifest_info *manifest, XLogRecPtr startptr,
+					 TimeLineID starttli, XLogRecPtr endptr, TimeLineID endtli)
+{
+	List	   *timelines;
+	ListCell   *lc;
+	bool		first_wal_range = true;
+	bool		found_start_timeline = false;
+
+	if (!IsManifestEnabled(manifest))
+		return;
+
+	/* Terminate the list of files. */
+	AppendStringToManifest(manifest, "\n],\n");
+
+	/* Read the timeline history for the ending timeline. */
+	timelines = readTimeLineHistory(endtli);
+
+	/* Start a list of LSN ranges. */
+	AppendStringToManifest(manifest, "\"WAL-Ranges\": [\n");
+
+	foreach(lc, timelines)
+	{
+		TimeLineHistoryEntry *entry = lfirst(lc);
+		XLogRecPtr	tl_beginptr;
+
+		/*
+		 * We only care about timelines that were active during the backup.
+		 * Skip any that ended before the backup started. (Note that if
+		 * entry->end is InvalidXLogRecPtr, it means that the timeline has not
+		 * yet ended.)
+		 */
+		if (!XLogRecPtrIsInvalid(entry->end) && entry->end < startptr)
+			continue;
+
+		/*
+		 * Because the timeline history file lists newer timelines before
+		 * older ones, the first timeline we encounter that is new enough to
+		 * matter ought to match the ending timeline of the backup.
+		 */
+		if (first_wal_range && endtli != entry->tli)
+			ereport(ERROR,
+					errmsg("expected end timeline %u but found timeline %u",
+						   starttli, entry->tli));
+
+		if (!XLogRecPtrIsInvalid(entry->begin))
+			tl_beginptr = entry->begin;
+		else
+		{
+			tl_beginptr = startptr;
+
+			/*
+			 * If we reach a TLI that has no valid beginning LSN, there can't
+			 * be any more timelines in the history after this point, so we'd
+			 * better have arrived at the expected starting TLI. If not,
+			 * something's gone horribly wrong.
+			 */
+			if (starttli != entry->tli)
+				ereport(ERROR,
+						errmsg("expected start timeline %u but found timeline %u",
+							   starttli, entry->tli));
+		}
+
+		AppendToManifest(manifest,
+						 "%s{ \"Timeline\": %u, \"Start-LSN\": \"%X/%X\", \"End-LSN\": \"%X/%X\" }",
+						 first_wal_range ? "" : ",\n",
+						 entry->tli,
+						 (uint32) (tl_beginptr >> 32), (uint32) tl_beginptr,
+						 (uint32) (endptr >> 32), (uint32) endptr);
+
+		if (starttli == entry->tli)
+		{
+			found_start_timeline = true;
+			break;
+		}
+
+		endptr = entry->begin;
+		first_wal_range = false;
+	}
+
+	/*
+	 * The last entry in the timeline history for the ending timeline should
+	 * be the ending timeline itself. Verify that this is what we observed.
+	 */
+	if (!found_start_timeline)
+		ereport(ERROR,
+				errmsg("start timeline %u not found history of timeline %u",
+					   starttli, endtli));
+
+	/* Terminate the list of WAL ranges. */
+	AppendStringToManifest(manifest, "\n],\n");
+}
+
+/*
+ * Finalize the backup manifest, and send it to the client.
+ */
+void
+SendBackupManifest(manifest_info *manifest)
+{
+	StringInfoData protobuf;
+	uint8		checksumbuf[PG_SHA256_DIGEST_LENGTH];
+	char		checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH];
+	size_t		manifest_bytes_done = 0;
+
+	if (!IsManifestEnabled(manifest))
+		return;
+
+	/*
+	 * Append manifest checksum, so that the problems with the manifest itself
+	 * can be detected.
+	 *
+	 * We always use SHA-256 for this, regardless of what algorithm is chosen
+	 * for checksumming the files.  If we ever want to make the checksum
+	 * algorithm used for the manifest file variable, the client will need a
+	 * way to figure out which algorithm to use as close to the beginning of
+	 * the manifest file as possible, to avoid having to read the whole thing
+	 * twice.
+	 */
+	manifest->still_checksumming = false;
+	pg_sha256_final(&manifest->manifest_ctx, checksumbuf);
+	AppendStringToManifest(manifest, "\"Manifest-Checksum\": \"");
+	hex_encode((char *) checksumbuf, sizeof checksumbuf, checksumstringbuf);
+	checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH - 1] = '\0';
+	AppendStringToManifest(manifest, checksumstringbuf);
+	AppendStringToManifest(manifest, "\"}\n");
+
+	/*
+	 * We've written all the data to the manifest file.  Rewind the file so
+	 * that we can read it all back.
+	 */
+	if (BufFileSeek(manifest->buffile, 0, 0L, SEEK_SET))
+		ereport(ERROR,
+				(errcode_for_file_access(),
+				 errmsg("could not rewind temporary file: %m")));
+
+	/* Send CopyOutResponse message */
+	pq_beginmessage(&protobuf, 'H');
+	pq_sendbyte(&protobuf, 0);	/* overall format */
+	pq_sendint16(&protobuf, 0); /* natts */
+	pq_endmessage(&protobuf);
+
+	/*
+	 * Send CopyData messages.
+	 *
+	 * We choose to read back the data from the temporary file in chunks of
+	 * size BLCKSZ; this isn't necessary, but buffile.c uses that as the I/O
+	 * size, so it seems to make sense to match that value here.
+	 */
+	while (manifest_bytes_done < manifest->manifest_size)
+	{
+		char		manifestbuf[BLCKSZ];
+		size_t		bytes_to_read;
+		size_t		rc;
+
+		bytes_to_read = Min(sizeof(manifestbuf),
+							manifest->manifest_size - manifest_bytes_done);
+		rc = BufFileRead(manifest->buffile, manifestbuf, bytes_to_read);
+		if (rc != bytes_to_read)
+			ereport(ERROR,
+					(errcode_for_file_access(),
+					 errmsg("could not read from temporary file: %m")));
+		pq_putmessage('d', manifestbuf, bytes_to_read);
+		manifest_bytes_done += bytes_to_read;
+	}
+
+	/* No more data, so send CopyDone message */
+	pq_putemptymessage('c');
+
+	/* Release resources */
+	BufFileClose(manifest->buffile);
+}
diff --git a/src/backend/replication/basebackup.c b/src/backend/replication/basebackup.c
index f5b2411d54..f3fb5716a4 100644
--- a/src/backend/replication/basebackup.c
+++ b/src/backend/replication/basebackup.c
@@ -16,10 +16,8 @@
 #include <unistd.h>
 #include <time.h>
 
-#include "access/timeline.h"
 #include "access/xlog_internal.h"	/* for pg_start/stop_backup */
 #include "catalog/pg_type.h"
-#include "common/checksum_helper.h"
 #include "common/file_perm.h"
 #include "commands/progress.h"
 #include "lib/stringinfo.h"
@@ -32,9 +30,9 @@
 #include "port.h"
 #include "postmaster/syslogger.h"
 #include "replication/basebackup.h"
+#include "replication/backup_manifest.h"
 #include "replication/walsender.h"
 #include "replication/walsender_private.h"
-#include "storage/buffile.h"
 #include "storage/bufpage.h"
 #include "storage/checksum.h"
 #include "storage/dsm_impl.h"
@@ -42,19 +40,11 @@
 #include "storage/ipc.h"
 #include "storage/reinit.h"
 #include "utils/builtins.h"
-#include "utils/json.h"
 #include "utils/ps_status.h"
 #include "utils/relcache.h"
 #include "utils/resowner.h"
 #include "utils/timestamp.h"
 
-typedef enum manifest_option
-{
-	MANIFEST_OPTION_YES,
-	MANIFEST_OPTION_NO,
-	MANIFEST_OPTION_FORCE_ENCODE
-} manifest_option;
-
 typedef struct
 {
 	const char *label;
@@ -68,18 +58,6 @@ typedef struct
 	pg_checksum_type manifest_checksum_type;
 } basebackup_options;
 
-struct manifest_info
-{
-	BufFile    *buffile;
-	pg_checksum_type checksum_type;
-	pg_sha256_ctx manifest_ctx;
-	uint64		manifest_size;
-	bool		force_encode;
-	bool		first_file;
-	bool		still_checksumming;
-};
-
-
 static int64 sendDir(const char *path, int basepathlen, bool sizeonly,
 					 List *tablespaces, bool sendtblspclinks,
 					 manifest_info *manifest, const char *spcoid);
@@ -94,18 +72,6 @@ static int64 _tarWriteDir(const char *pathbuf, int basepathlen, struct stat *sta
 						  bool sizeonly);
 static void send_int8_string(StringInfoData *buf, int64 intval);
 static void SendBackupHeader(List *tablespaces);
-static bool IsManifestEnabled(manifest_info *manifest);
-static void InitializeManifest(manifest_info *manifest,
-							   basebackup_options *opt);
-static void AppendStringToManifest(manifest_info *manifest, char *s);
-static void AddFileToManifest(manifest_info *manifest, const char *spcoid,
-							  const char *pathname, size_t size,
-							  pg_time_t mtime,
-							  pg_checksum_context *checksum_ctx);
-static void AddWALInfoToManifest(manifest_info *manifest, XLogRecPtr startptr,
-								 TimeLineID starttli, XLogRecPtr endptr,
-								 TimeLineID endtli);
-static void SendBackupManifest(manifest_info *manifest);
 static void perform_base_backup(basebackup_options *opt);
 static void parse_basebackup_options(List *options, basebackup_options *opt);
 static void SendXlogRecPtrResult(XLogRecPtr ptr, TimeLineID tli);
@@ -142,16 +108,6 @@ do { \
 				(errmsg("could not read from file \"%s\"", filename))); \
 } while (0)
 
-/*
- * Convenience macro for appending data to the backup manifest.
- */
-#define AppendToManifest(manifest, ...) \
-	{ \
-		char *_manifest_s = psprintf(__VA_ARGS__);	\
-		AppendStringToManifest(manifest, _manifest_s);	\
-		pfree(_manifest_s);	\
-	}
-
 /* The actual number of bytes, transfer of which may cause sleep. */
 static uint64 throttling_sample;
 
@@ -342,7 +298,7 @@ perform_base_backup(basebackup_options *opt)
 
 	labelfile = makeStringInfo();
 	tblspc_map_file = makeStringInfo();
-	InitializeManifest(&manifest, opt);
+	InitializeManifest(&manifest, opt->manifest, opt->manifest_checksum_type);
 
 	total_checksum_failures = 0;
 
@@ -1068,349 +1024,6 @@ SendBackupHeader(List *tablespaces)
 	pq_puttextmessage('C', "SELECT");
 }
 
-/*
- * Does the user want a backup manifest?
- *
- * It's simplest to always have a manifest_info object, so that we don't need
- * checks for NULL pointers in too many places. However, if the user doesn't
- * want a manifest, we set manifest->buffile to NULL.
- */
-static bool
-IsManifestEnabled(manifest_info *manifest)
-{
-	return (manifest->buffile != NULL);
-}
-
-/*
- * Initialize state so that we can construct a backup manifest.
- *
- * NB: Although the checksum type for the data files is configurable, the
- * checksum for the manifest itself always uses SHA-256. See comments in
- * SendBackupManifest.
- */
-static void
-InitializeManifest(manifest_info *manifest, basebackup_options *opt)
-{
-	if (opt->manifest == MANIFEST_OPTION_NO)
-		manifest->buffile = NULL;
-	else
-		manifest->buffile = BufFileCreateTemp(false);
-	manifest->checksum_type = opt->manifest_checksum_type;
-	pg_sha256_init(&manifest->manifest_ctx);
-	manifest->manifest_size = UINT64CONST(0);
-	manifest->force_encode = (opt->manifest == MANIFEST_OPTION_FORCE_ENCODE);
-	manifest->first_file = true;
-	manifest->still_checksumming = true;
-
-	if (opt->manifest != MANIFEST_OPTION_NO)
-		AppendToManifest(manifest,
-						 "{ \"PostgreSQL-Backup-Manifest-Version\": 1,\n"
-						 "\"Files\": [");
-}
-
-/*
- * Append a cstring to the manifest.
- */
-static void
-AppendStringToManifest(manifest_info *manifest, char *s)
-{
-	int			len = strlen(s);
-	size_t		written;
-
-	Assert(manifest != NULL);
-	if (manifest->still_checksumming)
-		pg_sha256_update(&manifest->manifest_ctx, (uint8 *) s, len);
-	written = BufFileWrite(manifest->buffile, s, len);
-	if (written != len)
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not write to temporary file: %m")));
-	manifest->manifest_size += len;
-}
-
-/*
- * Add an entry to the backup manifest for a file.
- */
-static void
-AddFileToManifest(manifest_info *manifest, const char *spcoid,
-				  const char *pathname, size_t size, pg_time_t mtime,
-				  pg_checksum_context *checksum_ctx)
-{
-	char		pathbuf[MAXPGPATH];
-	int			pathlen;
-	StringInfoData buf;
-
-	if (!IsManifestEnabled(manifest))
-		return;
-
-	/*
-	 * If this file is part of a tablespace, the pathname passed to this
-	 * function will be relative to the tar file that contains it. We want the
-	 * pathname relative to the data directory (ignoring the intermediate
-	 * symlink traversal).
-	 */
-	if (spcoid != NULL)
-	{
-		snprintf(pathbuf, sizeof(pathbuf), "pg_tblspc/%s/%s", spcoid,
-				 pathname);
-		pathname = pathbuf;
-	}
-
-	/*
-	 * Each file's entry needs to be separated from any entry that follows by a
-	 * comma, but there's no comma before the first one or after the last one.
-	 * To make that work, adding a file to the manifest starts by terminating
-	 * the most recently added line, with a comma if appropriate, but does not
-	 * terminate the line inserted for this file.
-	 */
-	initStringInfo(&buf);
-	if (manifest->first_file)
-	{
-		appendStringInfoString(&buf, "\n");
-		manifest->first_file = false;
-	}
-	else
-		appendStringInfoString(&buf, ",\n");
-
-	/*
-	 * Write the relative pathname to this file out to the manifest. The
-	 * manifest is always stored in UTF-8, so we have to encode paths that are
-	 * not valid in that encoding.
-	 */
-	pathlen = strlen(pathname);
-	if (!manifest->force_encode &&
-		pg_verify_mbstr(PG_UTF8, pathname, pathlen, true))
-	{
-		appendStringInfoString(&buf, "{ \"Path\": ");
-		escape_json(&buf, pathname);
-		appendStringInfoString(&buf, ", ");
-	}
-	else
-	{
-		appendStringInfoString(&buf, "{ \"Encoded-Path\": \"");
-		enlargeStringInfo(&buf, 2 * pathlen);
-		buf.len += hex_encode((char *) pathname, pathlen,
-							  &buf.data[buf.len]);
-		appendStringInfoString(&buf, "\", ");
-	}
-
-	appendStringInfo(&buf, "\"Size\": %zu, ", size);
-
-	/*
-	 * Convert last modification time to a string and append it to the
-	 * manifest. Since it's not clear what time zone to use and since time
-	 * zone definitions can change, possibly causing confusion, use GMT
-	 * always.
-	 */
-	appendStringInfoString(&buf, "\"Last-Modified\": \"");
-	enlargeStringInfo(&buf, 128);
-	buf.len += pg_strftime(&buf.data[buf.len], 128, "%Y-%m-%d %H:%M:%S %Z",
-						   pg_gmtime(&mtime));
-	appendStringInfoString(&buf, "\"");
-
-	/* Add checksum information. */
-	if (checksum_ctx->type != CHECKSUM_TYPE_NONE)
-	{
-		uint8		checksumbuf[PG_CHECKSUM_MAX_LENGTH];
-		int			checksumlen;
-
-		checksumlen = pg_checksum_final(checksum_ctx, checksumbuf);
-
-		appendStringInfo(&buf,
-						 ", \"Checksum-Algorithm\": \"%s\", \"Checksum\": \"",
-						 pg_checksum_type_name(checksum_ctx->type));
-		enlargeStringInfo(&buf, 2 * checksumlen);
-		buf.len += hex_encode((char *) checksumbuf, checksumlen,
-							  &buf.data[buf.len]);
-		appendStringInfoString(&buf, "\"");
-	}
-
-	/* Close out the object. */
-	appendStringInfoString(&buf, " }");
-
-	/* OK, add it to the manifest. */
-	AppendStringToManifest(manifest, buf.data);
-
-	/* Avoid leaking memory. */
-	pfree(buf.data);
-}
-
-/*
- * Add information about the WAL that will need to be replayed when restoring
- * this backup to the manifest.
- */
-static void
-AddWALInfoToManifest(manifest_info *manifest, XLogRecPtr startptr,
-					 TimeLineID starttli, XLogRecPtr endptr, TimeLineID endtli)
-{
-	List	   *timelines;
-	ListCell   *lc;
-	bool		first_wal_range = true;
-	bool		found_start_timeline = false;
-
-	if (!IsManifestEnabled(manifest))
-		return;
-
-	/* Terminate the list of files. */
-	AppendStringToManifest(manifest, "\n],\n");
-
-	/* Read the timeline history for the ending timeline. */
-	timelines = readTimeLineHistory(endtli);
-
-	/* Start a list of LSN ranges. */
-	AppendStringToManifest(manifest, "\"WAL-Ranges\": [\n");
-
-	foreach(lc, timelines)
-	{
-		TimeLineHistoryEntry *entry = lfirst(lc);
-		XLogRecPtr	tl_beginptr;
-
-		/*
-		 * We only care about timelines that were active during the backup.
-		 * Skip any that ended before the backup started. (Note that if
-		 * entry->end is InvalidXLogRecPtr, it means that the timeline has not
-		 * yet ended.)
-		 */
-		if (!XLogRecPtrIsInvalid(entry->end) && entry->end < startptr)
-			continue;
-
-		/*
-		 * Because the timeline history file lists newer timelines before
-		 * older ones, the first timeline we encounter that is new enough to
-		 * matter ought to match the ending timeline of the backup.
-		 */
-		if (first_wal_range && endtli != entry->tli)
-			ereport(ERROR,
-					errmsg("expected end timeline %u but found timeline %u",
-						   starttli, entry->tli));
-
-		if (!XLogRecPtrIsInvalid(entry->begin))
-			tl_beginptr = entry->begin;
-		else
-		{
-			tl_beginptr = startptr;
-
-			/*
-			 * If we reach a TLI that has no valid beginning LSN, there can't
-			 * be any more timelines in the history after this point, so we'd
-			 * better have arrived at the expected starting TLI. If not,
-			 * something's gone horribly wrong.
-			 */
-			if (starttli != entry->tli)
-				ereport(ERROR,
-						errmsg("expected start timeline %u but found timeline %u",
-							   starttli, entry->tli));
-		}
-
-		AppendToManifest(manifest,
-						 "%s{ \"Timeline\": %u, \"Start-LSN\": \"%X/%X\", \"End-LSN\": \"%X/%X\" }",
-						 first_wal_range ? "" : ",\n",
-						 entry->tli,
-						 (uint32) (tl_beginptr >> 32), (uint32) tl_beginptr,
-						 (uint32) (endptr >> 32), (uint32) endptr);
-
-		if (starttli == entry->tli)
-		{
-			found_start_timeline = true;
-			break;
-		}
-
-		endptr = entry->begin;
-		first_wal_range = false;
-	}
-
-	/*
-	 * The last entry in the timeline history for the ending timeline should
-	 * be the ending timeline itself. Verify that this is what we observed.
-	 */
-	if (!found_start_timeline)
-		ereport(ERROR,
-				errmsg("start timeline %u not found history of timeline %u",
-					   starttli, endtli));
-
-	/* Terminate the list of WAL ranges. */
-	AppendStringToManifest(manifest, "\n],\n");
-}
-
-/*
- * Finalize the backup manifest, and send it to the client.
- */
-static void
-SendBackupManifest(manifest_info *manifest)
-{
-	StringInfoData protobuf;
-	uint8		checksumbuf[PG_SHA256_DIGEST_LENGTH];
-	char		checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH];
-	size_t		manifest_bytes_done = 0;
-
-	if (!IsManifestEnabled(manifest))
-		return;
-
-	/*
-	 * Append manifest checksum, so that the problems with the manifest itself
-	 * can be detected.
-	 *
-	 * We always use SHA-256 for this, regardless of what algorithm is chosen
-	 * for checksumming the files.  If we ever want to make the checksum
-	 * algorithm used for the manifest file variable, the client will need a
-	 * way to figure out which algorithm to use as close to the beginning of
-	 * the manifest file as possible, to avoid having to read the whole thing
-	 * twice.
-	 */
-	manifest->still_checksumming = false;
-	pg_sha256_final(&manifest->manifest_ctx, checksumbuf);
-	AppendStringToManifest(manifest, "\"Manifest-Checksum\": \"");
-	hex_encode((char *) checksumbuf, sizeof checksumbuf, checksumstringbuf);
-	checksumstringbuf[PG_SHA256_DIGEST_STRING_LENGTH - 1] = '\0';
-	AppendStringToManifest(manifest, checksumstringbuf);
-	AppendStringToManifest(manifest, "\"}\n");
-
-	/*
-	 * We've written all the data to the manifest file.  Rewind the file so
-	 * that we can read it all back.
-	 */
-	if (BufFileSeek(manifest->buffile, 0, 0L, SEEK_SET))
-		ereport(ERROR,
-				(errcode_for_file_access(),
-				 errmsg("could not rewind temporary file: %m")));
-
-	/* Send CopyOutResponse message */
-	pq_beginmessage(&protobuf, 'H');
-	pq_sendbyte(&protobuf, 0);	/* overall format */
-	pq_sendint16(&protobuf, 0); /* natts */
-	pq_endmessage(&protobuf);
-
-	/*
-	 * Send CopyData messages.
-	 *
-	 * We choose to read back the data from the temporary file in chunks of
-	 * size BLCKSZ; this isn't necessary, but buffile.c uses that as the I/O
-	 * size, so it seems to make sense to match that value here.
-	 */
-	while (manifest_bytes_done < manifest->manifest_size)
-	{
-		char		manifestbuf[BLCKSZ];
-		size_t		bytes_to_read;
-		size_t		rc;
-
-		bytes_to_read = Min(sizeof(manifestbuf),
-							manifest->manifest_size - manifest_bytes_done);
-		rc = BufFileRead(manifest->buffile, manifestbuf, bytes_to_read);
-		if (rc != bytes_to_read)
-			ereport(ERROR,
-					(errcode_for_file_access(),
-					 errmsg("could not read from temporary file: %m")));
-		pq_putmessage('d', manifestbuf, bytes_to_read);
-		manifest_bytes_done += bytes_to_read;
-	}
-
-	/* No more data, so send CopyDone message */
-	pq_putemptymessage('c');
-
-	/* Release resources */
-	BufFileClose(manifest->buffile);
-}
-
 /*
  * Send a single resultset containing just a single
  * XLogRecPtr record (in text format)
diff --git a/src/include/replication/backup_manifest.h b/src/include/replication/backup_manifest.h
new file mode 100644
index 0000000000..4f7ee82dd6
--- /dev/null
+++ b/src/include/replication/backup_manifest.h
@@ -0,0 +1,64 @@
+/*-------------------------------------------------------------------------
+ *
+ * backup_manifest.h
+ *	  Routines for generating a backup manifest.
+ *
+ * Portions Copyright (c) 2010-2020, PostgreSQL Global Development Group
+ *
+ * src/include/replication/backup_manifest.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef BACKUP_MANIFEST_H
+#define BACKUP_MANIFEST_H
+
+#include "access/xlogdefs.h"
+#include "common/checksum_helper.h"
+#include "pgtime.h"
+#include "storage/buffile.h"
+
+typedef enum manifest_option
+{
+	MANIFEST_OPTION_YES,
+	MANIFEST_OPTION_NO,
+	MANIFEST_OPTION_FORCE_ENCODE
+} manifest_option;
+
+typedef struct manifest_info
+{
+	BufFile    *buffile;
+	pg_checksum_type checksum_type;
+	pg_sha256_ctx manifest_ctx;
+	uint64		manifest_size;
+	bool		force_encode;
+	bool		first_file;
+	bool		still_checksumming;
+} manifest_info;
+
+/*
+ * Does the user want a backup manifest?
+ *
+ * It's simplest to always have a manifest_info object, so that we don't need
+ * checks for NULL pointers in too many places. However, if the user doesn't
+ * want a manifest, we set manifest->buffile to NULL.
+ */
+static inline bool
+IsManifestEnabled(manifest_info *manifest)
+{
+	return (manifest->buffile != NULL);
+}
+
+extern void InitializeManifest(manifest_info *manifest,
+							   manifest_option want_manifest,
+							   pg_checksum_type manifest_checksum_type);
+extern void AppendStringToManifest(manifest_info *manifest, char *s);
+extern void AddFileToManifest(manifest_info *manifest, const char *spcoid,
+							  const char *pathname, size_t size,
+							  pg_time_t mtime,
+							  pg_checksum_context *checksum_ctx);
+extern void AddWALInfoToManifest(manifest_info *manifest, XLogRecPtr startptr,
+								 TimeLineID starttli, XLogRecPtr endptr,
+								 TimeLineID endtli);
+extern void SendBackupManifest(manifest_info *manifest);
+
+#endif
-- 
2.17.2 (Apple Git-113)