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// -*- Mode: C++ -*- |
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// GiSTfile.cpp |
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// |
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// Copyright (c) 1996, Regents of the University of California |
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// $Header: /usr/local/devel/GiST/libGiST/libGiST/GiSTfile.cpp,v 1.1.1.1 1996/08/06 23:47:21 jmh Exp $ |
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#include <stdio.h> |
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#include <sys/types.h> |
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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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#ifdef UNIX |
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#define O_BINARY 0 |
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#endif |
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#include "GiSTfile.h" |
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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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void |
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GiSTfile::Create(const char *filename) |
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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) { |
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close(fileHandle); |
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return; |
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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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/* Reserve page 0 */ |
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char *page=new char[PageSize()]; |
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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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void |
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GiSTfile::Open(const char *filename) |
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{ |
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char *page; |
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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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void |
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GiSTfile::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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void |
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GiSTfile::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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} |
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} |
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void |
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GiSTfile::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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} |
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} |
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GiSTpage |
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GiSTfile::Allocate() |
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{ |
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GiSTpage page; |
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char *buf; |
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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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void |
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GiSTfile::Deallocate(GiSTpage page) |
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{ |
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char *buf; |
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GiSTpage temp; |
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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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} |
