text: // sorted_data_interface_test_cursor.cpp
  
  /**
   *    Copyright (C) 2014 MongoDB Inc.
   *
   *    This program is free software: you can redistribute it and/or  modify
   *    it under the terms of the GNU Affero General Public License, version 3,
   *    as published by the Free Software Foundation.
   *
   *    This program is distributed in the hope that it will be useful,
   *    but WITHOUT ANY WARRANTY; without even the implied warranty of
   *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   *    GNU Affero General Public License for more details.
   *
   *    You should have received a copy of the GNU Affero General Public License
   *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
   *
   *    As a special exception, the copyright holders give permission to link the
   *    code of portions of this program with the OpenSSL library under certain
   *    conditions as described in each individual source file and distribute
   *    linked combinations including the program with the OpenSSL library. You
   *    must comply with the GNU Affero General Public License in all respects for
   *    all of the code used other than as permitted herein. If you modify file(s)
   *    with this exception, you may extend this exception to your version of the
   *    file(s), but you are not obligated to do so. If you do not wish to do so,
   *    delete this exception statement from your version. If you delete this
   *    exception statement from all source files in the program, then also delete
   *    it in the license file.
   */
  
  #include "mongo/db/storage/sorted_data_interface_test_harness.h"
  
  #include <memory>
  
  #include "mongo/db/storage/sorted_data_interface.h"
  #include "mongo/unittest/unittest.h"
  
  namespace mongo {
  
      // Verify that a forward cursor is positioned at EOF when the index is empty.
      TEST( SortedDataInterface, CursorIsEOFWhenEmpty ) {
          const std::unique_ptr<HarnessHelper> harnessHelper( newHarnessHelper() );
          const std::unique_ptr<SortedDataInterface> sorted( harnessHelper->newSortedDataInterface( false ) );
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              ASSERT( sorted->isEmpty( opCtx.get() ) );
          }
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              const std::unique_ptr<SortedDataInterface::Cursor> cursor( sorted->newCursor(opCtx.get()) );
  
              ASSERT( !cursor->seek(minKey, true) );
  
              // Cursor at EOF should remain at EOF when advanced
              ASSERT( !cursor->next() );
          }
      }
  
      // Verify that a reverse cursor is positioned at EOF when the index is empty.
      TEST( SortedDataInterface, CursorIsEOFWhenEmptyReversed ) {
          const std::unique_ptr<HarnessHelper> harnessHelper( newHarnessHelper() );
          const std::unique_ptr<SortedDataInterface> sorted( harnessHelper->newSortedDataInterface( false ) );
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              ASSERT( sorted->isEmpty( opCtx.get() ) );
          }
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              const std::unique_ptr<SortedDataInterface::Cursor> cursor( sorted->newCursor(opCtx.get(), false) );
  
              ASSERT( !cursor->seek( maxKey, true ) );
  
              // Cursor at EOF should remain at EOF when advanced
              ASSERT( !cursor->next() );
          }
      }
  
      // Call advance() on a forward cursor until it is exhausted.
      // When a cursor positioned at EOF is advanced, it stays at EOF.
      TEST( SortedDataInterface, ExhaustCursor ) {
          const std::unique_ptr<HarnessHelper> harnessHelper( newHarnessHelper() );
          const std::unique_ptr<SortedDataInterface> sorted( harnessHelper->newSortedDataInterface( false ) );
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              ASSERT( sorted->isEmpty( opCtx.get() ) );
          }
  
          int nToInsert = 10;
          for ( int i = 0; i < nToInsert; i++ ) {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              {
                  WriteUnitOfWork uow( opCtx.get() );
                  BSONObj key = BSON( "" << i );
                  RecordId loc( 42, i * 2 );
                  ASSERT_OK( sorted->insert( opCtx.get(), key, loc, true ) );
                  uow.commit();
              }
          }
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              ASSERT_EQUALS( nToInsert, sorted->numEntries( opCtx.get() ) );
          }
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              const std::unique_ptr<SortedDataInterface::Cursor> cursor( sorted->newCursor(opCtx.get()) );
              for ( int i = 0; i < nToInsert; i++ ) {
                  auto entry = i == 0 ? cursor->seek(minKey, true) : cursor->next();
                  ASSERT_EQ(entry, IndexKeyEntry(BSON("" << i), RecordId(42, i * 2)));
              }
              ASSERT( !cursor->next() );
  
              // Cursor at EOF should remain at EOF when advanced
              ASSERT( !cursor->next() );
          }
      }
  
      // Call advance() on a reverse cursor until it is exhausted.
      // When a cursor positioned at EOF is advanced, it stays at EOF.
      TEST( SortedDataInterface, ExhaustCursorReversed ) {
          const std::unique_ptr<HarnessHelper> harnessHelper( newHarnessHelper() );
          const std::unique_ptr<SortedDataInterface> sorted( harnessHelper->newSortedDataInterface( false ) );
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              ASSERT( sorted->isEmpty( opCtx.get() ) );
          }
  
          int nToInsert = 10;
          for ( int i = 0; i < nToInsert; i++ ) {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              {
                  WriteUnitOfWork uow( opCtx.get() );
                  BSONObj key = BSON( "" << i );
                  RecordId loc( 42, i * 2 );
                  ASSERT_OK( sorted->insert( opCtx.get(), key, loc, true ) );
                  uow.commit();
              }
          }
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              ASSERT_EQUALS( nToInsert, sorted->numEntries( opCtx.get() ) );
          }
  
          {
              const std::unique_ptr<OperationContext> opCtx( harnessHelper->newOperationContext() );
              const std::unique_ptr<SortedDataInterface::Cursor> cursor( sorted->newCursor(opCtx.get(), false) );
              for ( int i = nToInsert - 1; i >= 0; i-- ) {
                  auto entry = (i == nToInsert - 1) ? cursor->seek(maxKey, true) : cursor->next();
                  ASSERT_EQ(entry, IndexKeyEntry(BSON("" << i), RecordId(42, i * 2)));
              }
              ASSERT( !cursor->next() );
  
              // Cursor at EOF should remain at EOF when advanced
              ASSERT( !cursor->next() );
          }
      }
  
  } // namespace mongo
  