1 /* 2 * A pipe paging coordinator, permitting memory sharing pipe endpoints. 3 * 4 * Copyright (C) 2021 Paul Boddie <paul@boddie.org.uk> 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License as 8 * published by the Free Software Foundation; either version 2 of 9 * the License, or (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License 17 * along with this program; if not, write to the Free Software 18 * Foundation, Inc., 51 Franklin Street, Fifth Floor, 19 * Boston, MA 02110-1301, USA 20 */ 21 22 #pragma once 23 24 #include <set> 25 26 #include <fsserver/notification.h> 27 #include <fsserver/page_mapper.h> 28 #include <fsserver/pages.h> 29 #include <fsserver/pipe_accessor.h> 30 31 32 33 /* Pipe paging support, maintaining the sequence of active regions or sections 34 in a pipe. */ 35 36 class PipePaging : public NotificationSupport 37 { 38 protected: 39 Memory *_memory; 40 Pages *_pages; 41 PageQueue *_queue; 42 43 /* Regions acting as files with their own accessors. */ 44 45 PageMapper *_regions[2]; 46 PipeAccessor _accessors[2]; 47 48 /* The first region is initially exposed to both reader and writer. */ 49 50 int _reading = 0, _writing = 0; 51 52 /* Pipe section/region size. */ 53 54 offset_t _size; 55 56 /* Endpoint status. */ 57 58 unsigned int _active_endpoints = 2; 59 60 /* Common functionality. */ 61 62 virtual PageMapper *_add_region(); 63 64 virtual PageMapper *_next_region(); 65 66 virtual void discard_region(unsigned int i); 67 68 public: 69 explicit PipePaging(Memory *memory, offset_t size); 70 71 virtual ~PipePaging(); 72 73 virtual unsigned int detach(); 74 75 virtual offset_t region_size() 76 { return _size; } 77 78 /* Region management. */ 79 80 virtual PageMapper *add_region(); 81 82 virtual PageMapper *current_region(); 83 84 virtual PageMapper *current_region(bool writing); 85 86 virtual PageMapper *next_region(); 87 88 /* Access management. */ 89 90 virtual int closed(); 91 92 /* Special values for various arrays. */ 93 94 enum PipePagingRoles : unsigned int 95 { 96 READER = 0, 97 WRITER = 1, 98 }; 99 }; 100 101 // vim: tabstop=4 expandtab shiftwidth=4