<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content="text/html; charset=us-ascii" http-equiv=Content-Type> <META name=GENERATOR content="MSHTML 8.00.7600.16671"></HEAD> <BODY> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>For very big serializable dictionaries with small keys but memory consuming values, one might think of a dictionary that holds its values in a direct accessible file on disk. Within RAM, the dictionary can map the keys to their values by means of intermediate file-pointers. Does such type of dictionary already exists? If not and some people are interested, I am very well willing and prepared to make such a dictionary.</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>I am thinking of the following:</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>Call the dictionary a "da" and its file a "da-file".</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>Opening a da-file opens it for both input and output and reads the mutable top-da containing an index that maps keys onto file-positions.</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>Closing a da-file stores the mutated top-da, then stores the pointer to the new top-da in a manner as atomic as possible.</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>A da-file may contain sub-das.</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>When a program/system crashes without closing a da-file, the logical content of the file will be consistent. In this case new or updated data may be physically present, but will not exists in logical sense. Opening the da-file after a crash shows the same dictionary as when last opened. When a program/system crashes while storing the pointer to the top-da, we may have a problem. However, it will be possible to reconstruct the most recent consistent da-file.</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>The dictionary will contain history info such as to allow going back to a previous state of the da-file. This can be acheived by storing all new data at the end of the file and storing the pointer to the current top-da in the first block of the file. Each da will have a pointer to its predecessor.</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>A cleanup-procedure will be present such as to prepare a new da-file whose physical content corresponds to the logical content according to its current top-da.</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>Procedures:</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>open-da-file -> da</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>close-da-file -> da</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>make-da -> da (for new sub-das)</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>da-ref</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>da-set!</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>da-remove!</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>da-revert! -> da (go back in history for top or sub-da)</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>copy-da-file (cleaning up)</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>da-repair (repairs da-file which is inconsistent because of a failure while storing the pointer to the top-da while closing the da-file)</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>May be closing das and da-files can be made optional by means of a guard, but I do not yet fully understand how to do this.</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010>Jos</SPAN></FONT></DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV> <DIV><FONT size=2 face=Arial><SPAN class=651382310-03112010></SPAN></FONT> </DIV></BODY></HTML>