github.com/nutsdb/nutsdb@v1.0.4/rwmanger_mmap.go (about) 1 // Copyright 2019 The nutsdb Author. All rights reserved. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package nutsdb 16 17 import ( 18 "errors" 19 20 mmap "github.com/xujiajun/mmap-go" 21 ) 22 23 // MMapRWManager represents the RWManager which using mmap. 24 type MMapRWManager struct { 25 path string 26 fdm *fdManager 27 m mmap.MMap 28 segmentSize int64 29 } 30 31 var ( 32 // ErrUnmappedMemory is returned when a function is called on unmapped memory 33 ErrUnmappedMemory = errors.New("unmapped memory") 34 35 // ErrIndexOutOfBound is returned when given offset out of mapped region 36 ErrIndexOutOfBound = errors.New("offset out of mapped region") 37 ) 38 39 // WriteAt copies data to mapped region from the b slice starting at 40 // given off and returns number of bytes copied to the mapped region. 41 func (mm *MMapRWManager) WriteAt(b []byte, off int64) (n int, err error) { 42 if mm.m == nil { 43 return 0, ErrUnmappedMemory 44 } else if off >= int64(len(mm.m)) || off < 0 { 45 return 0, ErrIndexOutOfBound 46 } 47 48 return copy(mm.m[off:], b), nil 49 } 50 51 // ReadAt copies data to b slice from mapped region starting at 52 // given off and returns number of bytes copied to the b slice. 53 func (mm *MMapRWManager) ReadAt(b []byte, off int64) (n int, err error) { 54 if mm.m == nil { 55 return 0, ErrUnmappedMemory 56 } else if off >= int64(len(mm.m)) || off < 0 { 57 return 0, ErrIndexOutOfBound 58 } 59 60 return copy(b, mm.m[off:]), nil 61 } 62 63 // Sync synchronizes the mapping's contents to the file's contents on disk. 64 func (mm *MMapRWManager) Sync() (err error) { 65 return mm.m.Flush() 66 } 67 68 // Release deletes the memory mapped region, flushes any remaining changes 69 func (mm *MMapRWManager) Release() (err error) { 70 mm.fdm.reduceUsing(mm.path) 71 return mm.m.Unmap() 72 } 73 74 func (mm *MMapRWManager) Size() int64 { 75 return mm.segmentSize 76 } 77 78 // Close will remove the cache in the fdm of the specified path, and call the close method of the os of the file 79 func (mm *MMapRWManager) Close() (err error) { 80 return mm.fdm.closeByPath(mm.path) 81 }