-- File: AltoFilePrivate.mesa
-- Last edited by Levin: 30-Apr-81 14:26:40
DIRECTORY
AltoDefs USING [BytesPerPage, PageNumber],
AltoFile USING [defaultTime, FileTime, FP, Position],
DiskIODefs USING [CompletionStatus, DiskRequest, FID, vDA],
FileDefs USING [FSInstance],
VMDefs USING [FileHandle, OpenOptions, Page, PageNumber];
AltoFilePrivate: DEFINITIONS =
BEGIN OPEN AltoFile, FileDefs, DiskIODefs;
-- (1) File Manipulation --
-- Types and Related Constants --
AltoPageNumber: TYPE = AltoDefs.PageNumber;
LastPageBytes: TYPE = [0..AltoDefs.BytesPerPage);
infinityPage: AltoPageNumber = LAST[AltoPageNumber];
FileObject: TYPE = MONITORED RECORD [
fileID: FID,
leadervDA: vDA,
lengthKnown: BOOLEAN,
lastPage: AltoPageNumber,
bytes: LastPageBytes,
lengthChanged: BOOLEAN,
openCount: [0..63],
link: FileHandle,
seal: FileSeal,
nRuns: [1..maxRuns],
runTableLock: MONITORLOCK,
runTable: POINTER TO RunTable];
FileHandle: TYPE = POINTER TO FileObject;
maxRuns: CARDINAL = 1024;
maxSeals: CARDINAL = 32768/(maxRuns/2);
-- fits in a word with "maxRuns" in a FileObject
-- the horrible declaration is to avoid implicit LONG CARDINALs.
RunIndex: TYPE = [0..maxRuns);
RunCount: TYPE = [0..maxRuns];
FileSeal: TYPE = [0..maxSeals);
openSeal: FileSeal = 63B;
underwaySeal: FileSeal = 52B;
closedSeal: FileSeal = 14B;
VdaRun: TYPE = RECORD [page: AltoPageNumber, vda: vDA];
RunTable: TYPE = RECORD [runs: SEQUENCE runSpace: RunCount OF VdaRun];
initialRuns: RunIndex = 10; -- initial vda runs
percentToIncrease: CARDINAL = 50; -- percent by which vda run table is extended
minUsefulRuns: RunIndex = 3;
-- Procedures for the Operations level --
Open: PROCEDURE [
instance: FSInstance, name: STRING, options: VMDefs.OpenOptions ← oldReadOnly]
RETURNS [FileHandle];
Close: PROCEDURE [FileHandle];
Abandon: PROCEDURE [FileHandle];
Destroy: PROCEDURE [file: FileHandle];
-- if more than one user has 'file' open, an error is raised. Otherwise, the file
-- is closed, then deleted from the disk and directory.
GetLength: PROCEDURE [file: FileHandle] RETURNS [Position];
-- returns the number of bytes in the file; that is, the number of the byte
-- immediately following the last byte in the file.
SetLength: PROCEDURE [file: FileHandle, length: Position];
-- establishes 'length' as the byte number of the byte immediately following the
-- last byte of the file. If 'length' does not exceed the current file length
-- (as determined by GetFileLength), SetFileLength is equivalent to TruncateFile.
-- Otherwise, the file is extended to the specified length and the added bytes have
-- undefined contents.
Extend: PROCEDURE [file: FileHandle, length: Position, buffer: POINTER];
-- 'length' must exceed the present length (as determined by GetFileLength), but
-- must not leave an undefined gap in the file. This implies that either
-- length.page = GetFileLength[file].page or length.page = GetFileLength[file].page+1
-- and length.byte = 0. Thus, ExtendFile writes at most one page of data to the file,
-- taking this data from 'buffer'. In the event that the last file page is partially
-- full, the entire contents of the buffer are written to disk. It is the client's
-- responsibility to ensure that the initial portion of 'buffer' contains correct
-- data. If 'length' does not satisfy the requirements above, an error is raised.
-- These requirements make it possible for ExtendFile to do its work atomically.
-- That is, if a crash occurs during ExtendFile and the Scavenger is run, then the
-- file will either have its old length (before ExtendFile) or it will have its new
-- length and the data from 'buffer' will appear in the extension.
Truncate: PROCEDURE [file: FileHandle, length: Position];
-- shortens the file so that the byte immediately following its last significant
-- byte is 'length'. If 'length' exceeds the present length (as determined by
-- GetFileLength), an error is raised.
GetTimes: PROCEDURE [file: FileHandle] RETURNS [read, write, create: FileTime];
-- returns the indicated file times for the argument file.
SetCreationTime: PROCEDURE [file: FileHandle, create: FileTime ← defaultTime];
-- sets the creation time of the argument file. If defaulted, the time is set to
-- the current time.
-- Other File Manipulation Procedures --
InitializeFileList: PROCEDURE;
-- initializes open file manipulation facilities.
FinalizeFileList: PROCEDURE;
-- finalizes open file manipulation facilities.
InsertFile: PROCEDURE [
fp: FP, openProc: PROCEDURE [FileHandle, BOOLEAN] RETURNS [BOOLEAN]]
RETURNS [FileHandle];
-- maps 'fp' to a FileHandle and returns it. All clients presenting the same fp
-- will receive the same handle. 'openProc' will be called at an appropriate point
-- and is passed the FileHandle and a boolean which is TRUE if the 'fp' was not
-- previously in use. If the openProc returns FALSE, the insertion of the
-- FileHandle is aborted and InvalidFP is raised.
ReleaseFile: PROCEDURE [file: FileHandle, closeProc: PROCEDURE [FileHandle]];
-- The use count on the indicated file is decremented and, if zero, 'closeProc'
-- is called. The FileHandle then becomes invalid. If the use count is still
-- greater than zero, closeProc is not called and the FileHandle remains usable.
PurgeFile: PROCEDURE [
file: FileHandle, destroyProc: PROCEDURE [FileHandle]];
-- The use count on the indicated file must be zero, otherwise an error occurs.
-- 'destroyProc' is called and it is expected to remove all traces of the file.
FindEOF: PROCEDURE [file: FileHandle];
-- fills in the page and byte number of the last byte in the file by reading from
-- the last known page to the physical end.
-- (2) File I/O Support --
DoDiskRequest: PROCEDURE [
req: POINTER TO DiskRequest, file: FileHandle ← NIL, signalError: BOOLEAN ← TRUE]
RETURNS [CompletionStatus, vDA, LastPageBytes];
-- performs a synchronous disk request specified by 'req'. The caller supplies only
-- the firstPage, firstPagevDA, pagesToSkip, xfers, noRestore, and command fields
-- of the request. If 'file' is non-NIL, the vDAs encountered will be entered in
-- the file's vDA table. The return values are: final completion status, vDA of
-- the page following the last one processed, and the number of bytes in the last
-- page seen. If an unrecoverable error occurred and 'signalError' is TRUE,
-- DiskError is raised.
GetvDAForPage: PROCEDURE [file: FileHandle, page: AltoPageNumber] RETURNS [vDA];
-- looks up page in file's runTable and returns the associated address.
EnterPageAndvDA: PROCEDURE [file: FileHandle, page: AltoPageNumber, vda: vDA];
-- enters the pair <page, vda> into the disk address table associated with file.
FindLastKnownPage: PROCEDURE [file: FileHandle] RETURNS [AltoPageNumber, vDA];
-- returns the pair <page, vda> corresponding to the last page in the file for
-- which vda is not fillInvDA.
TruncatevDATable: PROCEDURE [file: FileHandle, page: AltoPageNumber];
-- alters the file's runTable so that 'page' is the last non-fillInvDA entry.
-- (3) Disk Space Management --
InitializeKD: PROCEDURE;
-- initializes the local disk allocation mechanism.
FinalizeKD: PROCEDURE;
-- finalizes the local disk allocation mechanism.
-- (4) Directory Manipulation --
-- Types and Related Constants --
DirHandle: TYPE = POINTER TO DirObject;
DirObject: TYPE = MONITORED RECORD [
file: VMDefs.FileHandle,
length: Position,
buffer: VMDefs.Page,
page: VMDefs.PageNumber,
fp: FP,
spacePos: Position,
spaceNeeded: CARDINAL,
spaceFound: CARDINAL,
link: DirHandle,
useCount: CARDINAL];
-- Procedures --
InitializeDirectory: PROCEDURE;
-- initializes directory manipulation facilities.
FinalizeDirectory: PROCEDURE;
-- finalizes directory manipulation facilities.
FlushDirectoryBuffer: PROCEDURE [dir: DirHandle];
-- eliminates any cached page buffer.
ResetDirectoryLength: PROCEDURE [dir: DirHandle];
-- recomputes and stores the length of directory 'dir'.
sysDir: DirHandle;
-- a handle for the directory "SysDir".
-- Statistics Logging --
loggingEnabled: BOOLEAN;
-- indicates whether statistics logging is enabled.
END.