#include?“stdafx.h“
#include?“buffer_manager.h“

using?namespace?std;

//CBufferManager?m_ptheblocks[MAX_BLOCKS];
CBufferManager*?CBufferManager::m_ptheblocks?=?NULL;


/*初始化buffer區(qū)，但不分配內(nèi)存*/
void?CBufferManager::initiate_blocks（）
{
	unsigned?int?i;
	m_ptheblocks?=?new?CBufferManager?[MAX_BLOCKS];
	for（i=0;i		m_ptheblocks[i].m_address?=?NULL;
		m_ptheblocks[i].m_index_table=0;
		m_ptheblocks[i].m_is_written=0;
		m_ptheblocks[i].m_being_used=0;
		m_ptheblocks[i].m_count=0;
	}
}

/*退出時(shí)調(diào)用，將所有需要寫回的塊數(shù)據(jù)寫回相應(yīng)文件，并釋放buffer區(qū)*/
void?CBufferManager::flush_all_blocks（）{???
	for（int?i=0;i		m_ptheblocks[i].flush_block（）;
		if（m_ptheblocks[i].m_address?!=?NULL）
			delete?[]?m_ptheblocks[i].m_address;
	}
}

/*使用塊函數(shù)，buffer內(nèi)部函數(shù)*/
void?CBufferManager::using_block（unsigned?int?number）
{
	unsigned?int?i;
	m_ptheblocks[number].m_being_used=1;
	for（i=0;i		if（i!=number?&&?!m_ptheblocks[number].m_being_used）
			m_ptheblocks[i].m_count++;??//所有沒(méi)正在使用的塊count加1
		else?if（i==number）
			m_ptheblocks[i].m_count=0;??//正在使用的塊count置0，使正在被使用的塊不被換出
	}
}

/*找到count值最大的塊號(hào)（即近似LRU算法中要求替換出的塊），buffer內(nèi)部函數(shù)*/	
unsigned?int?CBufferManager::max_count_number（）
{
	unsigned?int?i;
	unsigned?int?max_count=m_ptheblocks[0].m_count;
	unsigned?int?block_number=0;
	for（i=0;i		if（m_ptheblocks[i].m_count>max_count）{
			max_count=m_ptheblocks[i].m_count;
			block_number=i;
		}
	return?block_number;
}

/*若該塊需要寫回，將該塊的數(shù)據(jù)寫回相應(yīng)文件，換出時(shí)和退出時(shí)調(diào)用buffer內(nèi)部函數(shù)*/
void?CBufferManager::flush_block（）
{
	FILE?*fp;
	if（m_is_written?&&?m_index_table）?{
		if（fp=fopen（（LPCTSTR）m_name“rb+“））{??
			fseek（fpBLOCK_SIZE*m_offset_number0）;
			fwrite（m_addressBLOCK_SIZE1fp）;
			fclose（fp）;
		}
	}
}

/*為record?manager和index?manager提供塊（寫），在其初始建立時(shí)調(diào)用*/
unsigned?int?CBufferManager::get_blank_block（short?int?index_table）
{
	unsigned?int?number;
	unsigned?int?i;
	char?*p;
	for（i=0;i		if（!m_ptheblocks[i].m_index_table?&&?!m_ptheblocks[i].m_being_used）
			break;
	if（i		number=i;
		m_ptheblocks[number].m_address?=?new?char?[BLOCK_SIZE];	

????????for（p=m_ptheblocks[number].m_address;p		???*p=‘$‘;
	}
	else{?//表示無(wú)空塊，須判斷換出哪個(gè)塊和是否有必要寫回文件
		number=max_count_number（）;
		m_ptheblocks[number].flush_block（）;
	}
	using_block（number）;
	m_ptheblocks[number].m_index_table=index_table;
	return?number;
}

/*為record?manager和index?manager提供塊（讀或改）若在buffer中找不到則調(diào)用get_blank_block為其分配空間并做標(biāo)記*/
unsigned?int?CBufferManager::get_block（short?int?index_table?CString?filename?unsigned?int?offset_number）
{
	FILE?*fp;
	unsigned?int?number;
	unsigned?int?imark;
	
	for（i=0;i		if（m_ptheblocks[i].m_index_table==index_table?&&?m_ptheblocks[i].m_name?==?filename?&&?
			m_ptheblocks[i].m_offset_number==offset_number）?{?//表示在buffer中找到了該塊
			number=i;
			using_block（number）;
			return

?屬性????????????大小?????日期????時(shí)間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2018-04-22?10:17??MiniSQL\
?????文件????????2685??2005-01-12?01:56??MiniSQL\catalog_manager.h
?????目錄???????????0??2018-04-22?11:09??__MACOSX\
?????目錄???????????0??2018-04-22?11:09??__MACOSX\MiniSQL\
?????文件?????????175??2005-01-12?01:56??__MACOSX\MiniSQL\._catalog_manager.h
?????文件???????37447??2005-01-13?02:49??MiniSQL\interpret.cpp
?????文件?????????175??2005-01-13?02:49??__MACOSX\MiniSQL\._interpret.cpp
?????文件????????1457??2005-01-09?13:26??MiniSQL\MiniSQL.rc
?????文件?????????175??2005-01-09?13:26??__MACOSX\MiniSQL\._MiniSQL.rc
?????文件????????1106??2005-01-07?12:47??MiniSQL\StdAfx.h
?????文件?????????175??2005-01-07?12:47??__MACOSX\MiniSQL\._StdAfx.h
?????文件????????3599??2005-01-09?21:40??MiniSQL\buffer_manager.cpp
?????文件?????????175??2005-01-09?21:40??__MACOSX\MiniSQL\._buffer_manager.cpp
?????文件????????1251??2005-01-09?10:39??MiniSQL\index_manager.h
?????文件?????????175??2005-01-09?10:39??__MACOSX\MiniSQL\._index_manager.h
?????文件???????19591??2005-01-09?10:59??MiniSQL\catalog_manager.cpp
?????文件?????????175??2005-01-09?10:59??__MACOSX\MiniSQL\._catalog_manager.cpp
?????文件???????14825??2005-01-13?01:10??MiniSQL\record_manager.cpp
?????文件?????????175??2005-01-13?01:10??__MACOSX\MiniSQL\._record_manager.cpp
?????文件??????107520??2005-01-13?05:09??MiniSQL\MiniSQL.ncb
?????文件?????????175??2005-01-13?05:09??__MACOSX\MiniSQL\._MiniSQL.ncb
?????文件????????1229??2005-01-09?13:46??MiniSQL\buffer_manager.h
?????文件?????????175??2005-01-09?13:46??__MACOSX\MiniSQL\._buffer_manager.h
?????文件??????192576??2005-01-13?04:53??MiniSQL\MiniSQL.exe
?????文件?????????175??2005-01-13?04:53??__MACOSX\MiniSQL\._MiniSQL.exe
?????文件????????2985??2005-01-13?04:51??MiniSQL\MiniSQL.h
?????文件?????????175??2005-01-13?04:51??__MACOSX\MiniSQL\._MiniSQL.h
?????文件?????????748??2005-01-09?12:41??MiniSQL\record_manager.h
?????文件?????????175??2005-01-09?12:41??__MACOSX\MiniSQL\._record_manager.h
?????文件???????????8??2007-11-10?18:22??MiniSQL\tables.catlog
?????文件?????????175??2007-11-10?18:22??__MACOSX\MiniSQL\._tables.catlog
............此處省略26個(gè)文件信息