From ba29ae2cd257765615aaadd37feea3e6ef8425a0 Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@openldap.org>
Date: Thu, 7 Jan 2016 18:28:29 +0000
Subject: [PATCH] mdbx: backport - Add MDB_PREV_MULTIPLE.

Logical counterpart to GET_MULTIPLE, NEXT_MULTIPLE

Change-Id: I3f42cb1599997e79dbdc76bcf23b78314ededfc9
---
 lmdb.h |  4 +++-
 mdb.c  | 22 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/lmdb.h b/lmdb.h
index 67a43b6c..8b137d57 100644
--- a/lmdb.h
+++ b/lmdb.h
@@ -384,7 +384,9 @@ typedef enum MDB_cursor_op {
 	MDB_PREV_NODUP,			/**< Position at last data item of previous key */
 	MDB_SET,				/**< Position at specified key */
 	MDB_SET_KEY,			/**< Position at specified key, return key + data */
-	MDB_SET_RANGE			/**< Position at first key greater than or equal to specified key. */
+	MDB_SET_RANGE,			/**< Position at first key greater than or equal to specified key. */
+	MDB_PREV_MULTIPLE		/**< Position at previous page and return key and up to
+								a page of duplicate data items. Only for #MDB_DUPFIXED */
 } MDB_cursor_op;
 
 /** @defgroup  errors	Return Codes
diff --git a/mdb.c b/mdb.c
index 4f599dcb..8ad6ef35 100644
--- a/mdb.c
+++ b/mdb.c
@@ -6327,6 +6327,28 @@ fetchm:
 			}
 		}
 		break;
+	case MDB_PREV_MULTIPLE:
+		if (data == NULL) {
+			rc = EINVAL;
+			break;
+		}
+		if (!(mc->mc_db->md_flags & MDB_DUPFIXED)) {
+			rc = MDB_INCOMPATIBLE;
+			break;
+		}
+		if (!(mc->mc_flags & C_INITIALIZED))
+			rc = mdb_cursor_first(mc, key, data);
+		else {
+			MDB_cursor *mx = &mc->mc_xcursor->mx_cursor;
+			if (mx->mc_flags & C_INITIALIZED) {
+				rc = mdb_cursor_sibling(mx, 0);
+				if (rc == MDB_SUCCESS)
+					goto fetchm;
+			} else {
+				rc = MDB_NOTFOUND;
+			}
+		}
+		break;
 	case MDB_NEXT:
 	case MDB_NEXT_DUP:
 	case MDB_NEXT_NODUP: