This represents a difference of two WordNumbers, the length of an online log file, etc.

Must be called before any of the procs below.

The total space available for the log.

The space actually used by the log at the time of the call.

Reads the log file determined by EstablishLogFile. Returns the WordNumber of a record near the start of the log.

The intended use of this proc is in recovery from the loss of the restart file. This proc takes a long time, but is seldom used.

RETURNS [notStartOfRecord: BOOL, currentRecord: RecordID];

! InvalidPage

Creates a stream using physical log addressing. RecordIDs returned by Advance will be

based on the assumption that the RecordID of record found at firstWord is firstWord.

checkpointWord: WordNumber, checkpointRecord, firstRecord: RecordID]

RETURNS [notStartOfRecord: BOOL, currentRecord: RecordID];

! InvalidPage

Creates a stream using logical log addressing. The logical-physical correspondence is

defined by checkpointWord and checkpointRecord. firstRecord must be less

than checkpointRecord.

OpenRecordStreamFromXXX was pointed to a page with random garbage in it.

After this error, the caller should CloseRecordStream[] immediately.

! YggLog.Error{ invalidRecordID, invalidRecord }

This proc may be called before calling GetCurrentRecord, in order to detect errors

that would otherwise be raised by the GetCurrentRecord call.

RETURNS [status: YggLog.ReadProcStatus, wordsRead: CARDINAL];

This proc has the same type as Get below.

This call does not change the state of the stream.

RETURNS [PageNumber, YggLogRep.PageVersion];

! (none)

A somewhat peculiar operation, provided for purposes of recovery.

RETURNS [endOfLog, truncatedRecord: BOOL, currentRecord: RecordID];

! (none)

Positions to next log record, returns its ID.

If endOfLog, then "currentRecord" is past the end of log.

If truncatedRecord, then the record before "currentRecord" was incomplete.

There is no guarantee that "currentRecord" exists in its entirety, only that some prefix

exists.

Shuts down the stream. Must be called before opening the stream again.

nextRecord: RecordID];

Sets up the output stream for writing to file page nextPage, naming the first record that it writes there nextRecord. Uses YggLog.wordsPerPage (which must be initialized before calling this procedure).

If normalOperation, then perform more stringent checking for log full.

RETURNS [thisRecord, followingRecord: RecordID];

! YggLog.Error {writeID, totalLen, logFull}

Caller need not ensure that all pages of "from" are in main store; Put will touch each

page before entering the log tail monitor.

If writeID and a log record ID won't fit in the first block, Error[writeID].

If total lenth of write request is not IN [minBlockLen .. maxBlockLen], Error[totalLen].

Error[logFull] is a server crash; it does not release the log tail monitor or log core monitor.

! YggLog.Error {recordNonexistent, recordNotOnline} (thisRecord is not valid.)

If thisRecord is represented in the online log, returns its location.

Intended for use by the proc that writes checkpointComplete records.

! (none)

Force all records prior to (not including) followingRecord to be recorded

stably in the online log.

! (none)

Returns the RecordID that would have been assigned if this call had been a Put.

! (none)

Flushes all log buffers to disk, and returns log writing component to initial state.

This many pages past end of log do not have well-defined values. On restart, these

pages need to be reinitialized.

! YggLog.Error {recordNonexistent, recordNotOnline} (beforeRecord is not valid to release.)

The caller certifies that all records prior to (not including) beforeRecord may

be purged from the online log.

RETURNS [status: YggLog.ReadProcStatus, wordsRead: CARDINAL];

Extracts all or part of the contents of a log record. wordsRead is the number of

words of log record touched by the Get call (bounded above by the total length

of the block "to").

RETURN ConstArith.Compare[a, b] };