-- DBLog.mesa
-- created by Donahue, November 12, 1982 1:55 pm
-- last edited by Donahue, April 27, 1983 8:22 am

DIRECTORY
  IO USING[ STREAM ],
  Rope USING[ ROPE ];
  
DBLog: DEFINITIONS =  {

   OPEN Rope;

Log: TYPE = REF LogObj;

LogObj: TYPE =
    MONITORED RECORD[ condition: CONDITION, locked: BOOL _ FALSE,
                              name: ROPE, stream: IO.STREAM _ NIL ];

Initialize: PROC[fileName: ROPE] RETURNS[log: Log];

Flush: PROC[log: Log, reOpen: BOOL _ TRUE];

Length: PROC[log: Log] RETURNS[INT];

LogOp: PROC[log: Log, op: ROPE];

LogText: PROC[log: Log, prefix: ROPE, text: IO.STREAM] RETURNS[start: INT];

-- writes an entry in the log with the given text

Replay: PROC[ log: Log, from: INT,
                   opProc: PROC[op: ROPE],
                   textProc: PROC[prefix: ROPE, text: IO.STREAM] ];
  -- perform all the log actions from this specified point
  -- by calling the appropriate procedure for each entry
  
Copy: PROC[ oldLog: Log, newLog: Log, from: INT,
                 filterText: PROC[prefix: ROPE, text: IO.STREAM, pos: INT] RETURNS[copy: BOOLEAN],
                 filterOps: PROC[ op: ROPE] RETURNS[copy: BOOLEAN] ]
  -- copy all of the text entries from the old log to the new log (beginning at from)
  -- the filter procedures are applied to each entry
  -- (pos gives the potential position of the prefix in the new log for text entries)
  -- if the filter returns FALSE then the entry is not copied
 }.