-- Transport Mechanism: support for B-Tree package -- [Juniper]<DMS>MS>BTreeSupport.mesa -- Randy Gobbel 19-May-81 21:20:17 -- Andrew Birrell 2-Sep-80 14:38:22 DIRECTORY BTreeSupportDefs USING [FileHandle, PageHandle, PageNumber], Storage USING [Free, Node], VMDefs USING [ GetFileLength, Mark, PageAddress, pageSize, ReadPage, Release, RemapPage, SetFileLength, UsePage]; BTreeSupport: PROGRAM IMPORTS Storage, VMDefs EXPORTS BTreeSupportDefs = BEGIN ReadPage: PUBLIC PROCEDURE [ fileH: BTreeSupportDefs.FileHandle, pageN: BTreeSupportDefs.PageNumber] RETURNS [pageH: BTreeSupportDefs.PageHandle] = BEGIN addr: VMDefs.PageAddress = [file: LOOPHOLE[fileH], page: pageN]; RETURN[LOOPHOLE[VMDefs.ReadPage[addr, 0 --lookAhead-- ]]] END; UsePage: PUBLIC PROCEDURE [ fileH: BTreeSupportDefs.FileHandle, pageN: BTreeSupportDefs.PageNumber] RETURNS [pageH: BTreeSupportDefs.PageHandle] = BEGIN addr: VMDefs.PageAddress = [file: LOOPHOLE[fileH], page: pageN]; pageH ← LOOPHOLE[VMDefs.UsePage[addr]]; IF addr.page = VMDefs.GetFileLength[addr.file].page THEN VMDefs.SetFileLength[addr.file, [page: addr.page + 1, byte: 0]]; END; WritePage: PUBLIC PROCEDURE [ fileH: BTreeSupportDefs.FileHandle, pageN: BTreeSupportDefs.PageNumber, pageH: BTreeSupportDefs.PageHandle] = BEGIN addr: VMDefs.PageAddress = [file: LOOPHOLE[fileH], page: pageN]; VMDefs.RemapPage[LOOPHOLE[pageH], addr]; VMDefs.Mark[LOOPHOLE[pageH]]; VMDefs.Release[LOOPHOLE[pageH]]; END; ReleasePage: PUBLIC PROCEDURE [pageH: BTreeSupportDefs.PageHandle] = BEGIN VMDefs.Release[LOOPHOLE[pageH]]; END; SetLength: PUBLIC PROCEDURE [ fileH: BTreeSupportDefs.FileHandle, pageN: BTreeSupportDefs.PageNumber] = BEGIN addr: VMDefs.PageAddress = [file: LOOPHOLE[fileH], page: pageN]; VMDefs.SetFileLength[addr.file, [page: addr.page, byte: 0]]; END; PageSize: PUBLIC PROCEDURE RETURNS [nWords: CARDINAL] = BEGIN RETURN[VMDefs.pageSize] END; AllocateWords: PUBLIC PROCEDURE [nWords: CARDINAL] RETURNS [POINTER] = BEGIN RETURN[Storage.Node[nWords]]; END; FreeWords: PUBLIC PROCEDURE [pntr: POINTER] = BEGIN Storage.Free[pntr]; END; END.