Intel汇编语言程序设计(第五版)chapt_14.ppt

1、AssemblyLanguageforIntel-BasedComputers,5thEdition,Chapter14:DiskFundamentals,(c)PearsonEducation,2006-2007.Allrightsreserved.Youmaymodifyandcopythisslideshowforyourpersonaluse,orforuseintheclassroom,aslongasthiscopyrightstatement,theauthorsname,andthetitlearenotchanged.,Slideshowpreparedbytheauthor

2、Revisiondate:June4,2006,KipR.Irvine,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,2,ChapterOverview,DiskStorageSystemsFileSystemsDiskDirectoryReadingandWritingDiskSectors(7305h)System-LevelFileFunctions,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,3,DiskStorageSystems,

3、Tracks,Cylinders,andSectorsDiskPartitions(Volumes),Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,4,TracksandSectors,Physicaldiskgeometry-awayofdescribingthedisksstructuretomakeitreadablebythesystemBIOSTrack-concentriccirclecontainingdataSector-partofatrack,Irvine,KipR.AssemblyLanguage

4、forIntel-BasedComputers5/e,2007.,5,CylindersandSeeking,Cylinder-alltracksreadablefromoneheadpositionSeek-moveread/writeheadsbetweentracks,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,6,DiskFormatting,Physicalformattingakalow-levelformattingUsuallydoneatthefactory.Mustbedonebeforelogi

5、calformattingDefinesthetracks,sectors,andcylindersLogicalformattingPermitsdisktobeaccessedusingsequentiallynumberedlogicalsectorsInstallsafilesystem(ex:NTFS)Mayinstallanoperatingsystem,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,7,Fragmentation,Afragmentedfileisonewhosesectorsarenol

6、ongerlocatedincontiguousareasofthedisk.causesread/writeheadstoskipslowerfileaccesspossibleread/writeerrors,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,8,Translation,Translation-conversionofphysicaldiskgeometrytoasequenceoflogicalsectornumbersPerformedbyaharddiskcontroller(firmware)L

7、ogicalsectornumbersarenumberedsequentially,havenodirectmappingtohardware,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,9,DiskPartitions,LogicalunitsthatdivideaphysicalharddiskAlsocalledvolumes,PrimarypartitionUptofourpermittedEachmaybootadifferentOS,ExtendedpartitionMaximumofonepermit

8、tedMaybedividedintomultiplelogicalpartitions,eachwithadifferentdriveletter,PrimaryandExtendedUptothreeprimaryandoneextended,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,10,LogicalPartitions,CreatedfromanextendedpartitionNolimitonthenumberEachhasaseparatedriveletterUsuallycontaindataC

9、anbebootable(ex:Linux),Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,11,DiskPartitionTable,LocatedinthedisksMasterBootRecord(MBR),followingablockofexecutablecodeFourentries,oneforeachpossiblepartitionEachentrycontainsthefollowingfields:state(non-active,bootable)typeofpartition(BigDOS,

10、Extended,.)beginninghead,cylinder,startingsectornumbernumSectorsWORD1;numberofsectorsbufferOfsWORDbuffer;bufferoffsetbufferSegWORDDATA;buffersegmentDISKIOENDS,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,43,Example,.databufferBYTE512DUP(?)diskStructDISKIO.codemovax,7305h;absoluteRead

11、/Writemovcx,0FFFFh;alwaysthisvaluemovdl,3;driveCmovbx,OFFSETdiskStructmovsi,0;readsectorint21h,Example:ReadoneormoresectorsfromdriveC:,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,44,SectorDisplayProgram,Pseudocode:Askforstartingsectornumberanddrivenumberdowhile(keystrokeESC)Displayh

12、eadingReadonesectorIfMS-DOSerrorthenexitDisplayonesectorWaitforkeystrokeIncrementsectornumberenddo,Viewthesourcecode,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,45,WhatsNext,DiskStorageSystemsFileSystemsDiskDirectoryReadingandWritingDiskSectors(7305h)System-LevelFileFunctions,Irvine

13、,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,46,System-LevelFileFunctions,CommonDisk-RelatedFunctionsGetDiskFreeSpaceCreateSubdirectoryRemoveSubdirecrorySetCurrentDirectoryGetCurrentDirectory,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,47,CommonDisk-RelatedFunctions,Irvine

14、,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,48,ExtGetDskFreSpcStrucStructure(1of2),StructSize:AreturnvaluethatrepresentsthesizeoftheExtGetDskFreSpcStrucstructure,inbytes.Level:Always0.SectorsPerCluster:Thenumberofsectorsinsideeachcluster.BytesPerSector:Thenumberofbytesineachsector.Availab

15、leClusters:Thenumberofavailableclusters.TotalClusters:Thetotalnumberofclustersinthevolume.,StructuredatareturnedbyFucntion7303h:,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,49,ExtGetDskFreSpcStruc(2of2),AvailablePhysSectors:Thenumberofphysicalsectorsavailableinthevolume,withoutadjus

16、tmentforcompression.TotalPhysSectors:Thetotalnumberofphysicalsectorsinthevolume,withoutadjustmentforcompression.AvailableAllocationUnits:Thenumberofavailableallocationunitsinthevolume,withoutadjustmentforcompression.TotalAllocationUnits:Thetotalnumberofallocationunitsinthevolume,withoutadjustmentfor

17、compression.Rsvd:Reservedmember.,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,50,Function7303hGetDiskFreeSpace,AX=7303hES:DIpointstoaExtGetDskFreSpcStrucCX=sizeoftheExtGetDskFreSpcStrucvariableDS:DXpointstoanull-terminatedstringcontainingthedrivename,ViewtheDiskSpc.asmprogram,Irvine,

18、KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,51,CreateSubdirectory,.datapathnameBYTEASM,0.codemovah,39h;createsubdirectorymovdx,OFFSETpathnameint21hjcDisplayError.DisplayError:,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,52,RemoveSubdirecrory,.datapathnameBYTEC:ASM,0.codemo

19、vah,3Ah;removesubdirectorymovdx,OFFSETpathnameint21hjcDisplayError.DisplayError:,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,53,SetCurrentDirectory,.datapathnameBYTEC:ASMPROGS,0.codemovah,3Bh;setcurrentdirectorymovdx,OFFSETpathnameint21hjcDisplayError.DisplayError:,Irvine,KipR.Assem

20、blyLanguageforIntel-BasedComputers5/e,2007.,54,GetCurrentDirectory,.datapathnameBYTE64dup(0);pathstoredherebyMS-DOS.codemovah,47h;getcurrentdirectorypathmovdl,0;ondefaultdrivemovsi,OFFSETpathnameint21hjcDisplayError.DisplayError:,Irvine,KipR.AssemblyLanguageforIntel-BasedComputers5/e,2007.,55,Yourturn.