Add cursor_prev

diff --git a/libraries/libmdb/mdb.c b/libraries/libmdb/mdb.c
index aa7f3d8ea6a959844425aadfb7da1168ba00e00b..d9fbad616b006ca74522717b8198217b0043ef51 100644 (file)
--- a/libraries/libmdb/mdb.c
+++ b/libraries/libmdb/mdb.c
@@ -362,6 +362,8 @@ static int           mdb_set_key(MDB_node *node, MDB_val *key);
 static int              mdb_sibling(MDB_cursor *cursor, int move_right);
 static int              mdb_cursor_next(MDB_cursor *cursor,
                            MDB_val *key, MDB_val *data);
+static int              mdb_cursor_prev(MDB_cursor *cursor,
+                           MDB_val *key, MDB_val *data);
 static int              mdb_cursor_set(MDB_cursor *cursor,
                            MDB_val *key, MDB_val *data, int *exactp);
 static int              mdb_cursor_first(MDB_cursor *cursor,
@@ -1753,6 +1755,46 @@ mdb_cursor_next(MDB_cursor *cursor, MDB_val *key, MDB_val *data)
        return mdb_set_key(leaf, key);
 }
 
+static int
+mdb_cursor_prev(MDB_cursor *cursor, MDB_val *key, MDB_val *data)
+{
+       MDB_ppage       *top;
+       MDB_page        *mp;
+       MDB_node        *leaf;
+
+       assert(cursor->mc_initialized);
+
+       top = CURSOR_TOP(cursor);
+       mp = top->mp_page;
+
+       DPRINTF("cursor_prev: top page is %lu in cursor %p", mp->mp_pgno, (void *) cursor);
+
+       if (top->mp_ki == 0)  {
+               DPRINTF("=====> move to prev sibling page");
+               if (mdb_sibling(cursor, 0) != MDB_SUCCESS) {
+                       return ENOENT;
+               }
+               top = CURSOR_TOP(cursor);
+               mp = top->mp_page;
+               top->mp_ki = NUMKEYS(mp) - 1;
+               DPRINTF("prev page is %lu, key index %u", mp->mp_pgno, top->mp_ki);
+       } else
+               top->mp_ki--;
+
+       cursor->mc_eof = 0;
+
+       DPRINTF("==> cursor points to page %lu with %u keys, key index %u",
+           mp->mp_pgno, NUMKEYS(mp), top->mp_ki);
+
+       assert(IS_LEAF(mp));
+       leaf = NODEPTR(mp, top->mp_ki);
+
+       if (data && mdb_read_data(cursor->mc_txn->mt_env, leaf, data) != MDB_SUCCESS)
+               return MDB_FAIL;
+
+       return mdb_set_key(leaf, key);
+}
+
 static int
 mdb_cursor_set(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
     int *exactp)
@@ -1831,6 +1873,7 @@ static int
 mdb_cursor_last(MDB_cursor *cursor, MDB_val *key, MDB_val *data)
 {
        int              rc;
+       MDB_ppage       *top;
        MDB_pageparent  mpp;
        MDB_node        *leaf;
        MDB_val lkey;
@@ -1845,7 +1888,10 @@ mdb_cursor_last(MDB_cursor *cursor, MDB_val *key, MDB_val *data)
 
        leaf = NODEPTR(mpp.mp_page, NUMKEYS(mpp.mp_page)-1);
        cursor->mc_initialized = 1;
-       cursor->mc_eof = 1;
+       cursor->mc_eof = 0;
+
+       top = CURSOR_TOP(cursor);
+       top->mp_ki = NUMKEYS(top->mp_page) - 1;
 
        if (data && (rc = mdb_read_data(cursor->mc_txn->mt_env, leaf, data)) != MDB_SUCCESS)
                return rc;
@@ -1880,6 +1926,14 @@ mdb_cursor_get(MDB_cursor *cursor, MDB_val *key, MDB_val *data,
                else
                        rc = mdb_cursor_next(cursor, key, data);
                break;
+       case MDB_PREV:
+               if (!cursor->mc_initialized || cursor->mc_eof) {
+                       while (CURSOR_TOP(cursor) != NULL)
+                               cursor_pop_page(cursor);
+                       rc = mdb_cursor_last(cursor, key, data);
+               } else
+                       rc = mdb_cursor_prev(cursor, key, data);
+               break;
        case MDB_FIRST:
                while (CURSOR_TOP(cursor) != NULL)
                        cursor_pop_page(cursor);

diff --git a/libraries/libmdb/mdb.h b/libraries/libmdb/mdb.h
index 566a32cff933ab20f0ac778bc14d60ab4263508b..c7841c434ce748cc34ce4bad69e324e22eed6427 100644 (file)
--- a/libraries/libmdb/mdb.h
+++ b/libraries/libmdb/mdb.h
@@ -58,7 +58,7 @@ typedef enum MDB_cursor_op {          /* cursor operations */
        MDB_FIRST,
        MDB_NEXT,
        MDB_LAST,
-       MDB_PREV,                               /* not implemented */
+       MDB_PREV,
        MDB_GET_BOTH,                   /* position at key/data */
        MDB_GET_BOTH_RANGE              /* position at key, nearest data */
 } MDB_cursor_op;

diff --git a/libraries/libmdb/mtest.c b/libraries/libmdb/mtest.c
index 628446f840e396a19565306bfcf04e6fc6a1a983..c473ca2214850483a8b78ec5a61bd72d9376ba9d 100644 (file)
--- a/libraries/libmdb/mtest.c
+++ b/libraries/libmdb/mtest.c
@@ -91,11 +91,18 @@ int main(int argc,char * argv[])
                rc = mdbenv_stat(env, &mst);
                rc = mdb_txn_begin(env, 1, &txn);
                rc = mdb_cursor_open(txn, dbi, &cursor);
+               printf("Cursor next\n");
                while ((rc = mdb_cursor_get(cursor, &key, &data, MDB_NEXT)) == 0) {
                        printf("key: %.*s, data: %.*s\n",
                                (int) key.mv_size,  (char *) key.mv_data,
                                (int) data.mv_size, (char *) data.mv_data);
                }
+               printf("Cursor prev\n");
+               while ((rc = mdb_cursor_get(cursor, &key, &data, MDB_PREV)) == 0) {
+                       printf("key: %.*s, data: %.*s\n",
+                               (int) key.mv_size,  (char *) key.mv_data,
+                               (int) data.mv_size, (char *) data.mv_data);
+               }
 #if 0
                /* write ops aren't coordinated with cursors,
                 * this stuff all breaks