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/********************************************************************* |
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* * |
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* Copyright (c) 1997,1998, 1999 * |
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* Multimedia DB Group and DEIS - CSITE-CNR, * |
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* University of Bologna, Bologna, ITALY. * |
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* * |
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* All Rights Reserved. * |
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* * |
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* Permission to use, copy, and distribute this software and its * |
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* documentation for NON-COMMERCIAL purposes and without fee is * |
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* hereby granted provided that this copyright notice appears in * |
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* all copies. * |
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* * |
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* THE AUTHORS MAKE NO REPRESENTATIONS OR WARRANTIES ABOUT THE * |
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* SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING * |
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* BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, * |
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* FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHOR * |
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* SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A * |
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* RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS * |
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* DERIVATIVES. * |
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* * |
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*********************************************************************/ |
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|
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#include <sys/stat.h> |
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#include <fcntl.h> |
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#include <string.h> |
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#ifdef UNIX |
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#include <unistd.h> |
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#else |
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#include <io.h> |
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#endif |
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|
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#ifdef UNIX |
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#define O_BINARY 0 |
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#endif |
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|
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#include "MTfile.h" |
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|
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extern int IOread, IOwrite; |
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|
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// The first page in the file has these "magic words" |
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// and the head of the deleted page list. |
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static char magic[]="GiST data file"; |
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|
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void |
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MTfile::Create(const char *filename) |
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{ |
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if(IsOpen()) return; |
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/*#d##D# |
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fileHandle=open(filename, O_RDWR|O_BINARY); |
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if(fileHandle>=0) { |
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close(fileHandle); |
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return; |
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} |
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*/ |
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fileHandle=open(filename, O_BINARY|O_RDWR|O_CREAT|O_TRUNC, S_IREAD|S_IWRITE); |
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if(fileHandle<0) return; |
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SetOpen(1); |
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|
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/* Reserve page 0 */ |
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char *page=new char[PageSize()]; |
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|
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memset(page, 0, PageSize()); |
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memcpy(page, magic, sizeof magic); |
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write(fileHandle, page, PageSize()); |
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delete page; |
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} |
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|
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void |
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MTfile::Open(const char *filename) |
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{ |
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char *page; |
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|
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if(IsOpen()) return; |
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fileHandle=open(filename, O_RDWR|O_BINARY); |
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if(fileHandle<0) return; |
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// Verify that the magic words are there |
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page=new char[PageSize()]; |
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read(fileHandle, page, PageSize()); |
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if(memcmp(page, magic, sizeof(magic))) { |
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close(fileHandle); |
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delete page; |
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return; |
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} |
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delete page; |
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SetOpen(1); |
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} |
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|
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void |
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MTfile::Close() |
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{ |
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if(!IsOpen()) return; |
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close(fileHandle); |
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SetOpen(0); |
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} |
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|
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void |
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MTfile::Read(GiSTpage page, char *buf) |
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{ |
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if(IsOpen()) { |
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lseek(fileHandle, page*PageSize(), SEEK_SET); |
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read(fileHandle, buf, PageSize()); |
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IOread++; |
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} |
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} |
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|
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void |
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MTfile::Write(GiSTpage page, const char *buf) |
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{ |
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if(IsOpen()) { |
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lseek(fileHandle, page*PageSize(), SEEK_SET); |
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write(fileHandle, buf, PageSize()); |
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IOwrite++; |
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} |
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} |
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|
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GiSTpage |
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MTfile::Allocate() |
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{ |
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GiSTpage page; |
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char *buf; |
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|
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if(!IsOpen()) return (0); |
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// See if there's a deleted page |
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buf=new char[PageSize()]; |
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Read(0, buf); |
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memcpy(&page, buf+sizeof(magic), sizeof(GiSTpage)); |
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if(page) { |
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// Reclaim this page |
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Read(page, buf); |
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Write(0, buf); |
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} |
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else { |
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page=lseek(fileHandle, 0, SEEK_END)/PageSize(); |
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memset(buf, 0, PageSize()); |
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write(fileHandle, buf, PageSize()); |
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} |
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delete buf; |
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return page; |
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} |
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|
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void |
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MTfile::Deallocate(GiSTpage page) |
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{ |
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char *buf; |
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GiSTpage temp; |
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|
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if(!IsOpen()) return; |
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// Get the old head of the list |
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buf=new char[PageSize()]; |
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Read(0, buf); |
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memcpy(&temp, buf+sizeof(magic), sizeof(GiSTpage)); |
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// Write the new head of the list |
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memcpy(buf+sizeof(magic), &page, sizeof(GiSTpage)); |
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Write(0, buf); |
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// In our new head, put link to old head |
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memcpy(buf+sizeof(magic), &temp, sizeof(GiSTpage)); |
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Write(page, buf); |
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delete buf; |
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} |
