文件初始化简单高效的分块记录的实现-白红宇

文件初始化简单高效的分块记录的实现

阅读量：5840 次

发布时间：2019-06-18

本文共 7286 字，大约阅读时间需要 24 分钟。

每日一贴,明天的内容关键字为文件初始化

在一文中，介绍了不管文件中记载数据为多少，只要按照文中介绍的方法存储，对于文件中恣意1条记载数据，在读缓冲内存恒定不变的情况下，最多只需要读文件1次，而且定位记载的算法也超等简略，只需做1次除法运算和1次求余运算。明天我在这里介绍一下它的C++实现方法。

1.写记载

#ifndef _WRITE_RECORD_H#define _WRITE_RECORD_H#include 
    
     #include 
     
      #define  INDEX_BLK_RECORD_NUM          1000#define  RECORD_BLK_RECORD_NUM         1000#define  MAGIC                         "BETTARECORD"#define  MAGIC_LEN                     sizeof(MAGIC) - 1#pragma pack(1)typedef struct tagRecord {    quint64 id;    float cur;    float vol;    float tempe;    float resistor;} TRecord;typedef struct tagFileHead {    quint8 magic[MAGIC_LEN];    quint32 version;    quint32 indexBlkNum;} TFileHead;typedef struct tagBlkHead {    quint64 nextBlkPos;    quint32 recordNum;}TBlkHead;typedef struct tagIndexBlk {    TBlkHead head;    quint32 blkAddr[INDEX_BLK_RECORD_NUM];} TIndexBlk;typedef struct tagRecordBlk {    TBlkHead blkHead;    TRecord record[RECORD_BLK_RECORD_NUM];} TRecordBlk;#pragma pack()class CWriteRecord {public:    CWriteRecord();    ~CWriteRecord();    bool openFile(const QString &fileName);    void writeRecordHead(const TFileHead *pFileHead);    void writeRecordBlk(const TRecord *pRecord);    void flushBlk(bool bClose);private:    void writeRecordBlkHead();    void writeIndexBlk(quint64 blkPos);    void writeIndexBlkNum();    void writeIndexBlkHead();    void init();private:    QFile file;    TBlkHead indexBlkHead;    TBlkHead recordBlkHead;    quint32 validIndexBlkRecordNum;    quint32 validRecordBlkRecordNum;    quint32 indexBlkNum;    quint32 validIndexBlkNum;    quint32 index;    quint32 recordIndex;    quint64 indexBlkPos;    quint64 recordBlkPos;    quint64 nextBlkPos;};#endif

头文件提供了openFile，writeRecordHead，writeRecordBlk，flushBlk，四个公有接口，首先通过openFile打开一个文件，该文件可以是1个已存在的文件，也可以是1个不存在的文件，由fileName指定，openFile主动将文件初始化到就绪状态，打开当前，就能够使用writeRecordHead,writeRecordBlk，写记载了，flushBlk,是将文件flush到磁盘的操纵，接下来我们看看实现：

每日一道理

如果人类不好好保护我们这个赖以生存的地球，终有一天，风沙的肆虐与垃圾的堆积会吞没我们美丽的家园。我向全世界的人们呼吁：让我们从现在开始，从我做起，手挽手，肩并肩共同保护建设我们的家园吧！

#include "writerecord.h"Queue CWriteRecord::queue;CWriteRecord::CWriteRecord(){}CWriteRecord::~CWriteRecord(){}bool CWriteRecord::openFile(const QString &fileName){    if (file.isOpen())        file.close();    file.setFileName(fileName);    return file.open(QIODevice::Append | QIODevice::ReadWrite);}void CWriteRecord::writeRecordHead(const TRecordHead *pRecordHead){    file.seek(0);    file.write((const char *)pRecordFileHead, sizeof(TRecordHead));    init();   }void CWriteRecord::init(){    recordBlkHead.recordNum = 0;    indexBlkHead.recordNum = 0;    validIndexBlkRecordNum = 0;    validRecordBlkRecordNum = 0;        indexBlkNum = 1;        validIndexBlkNum = 0;        index = 0;    recordIndex = 0;        indexBlkPos = sizeof(TFileHead);    recordBlkPos = indexBlkPos + sizeof(TIndexBlk);    nextBlkPos = recordBlkPos + sizeof(TRecordBlk);}void CWriteRecord::writeRecordBlkHead(){    if (validRecordBlkRecordNum != recordBlkHead.recordNum        && recordBlkHead.recordNum != 0)    {        validRecordBlkRecordNum = recordBlkHead.recordNum;        file.seek(recordBlkPos);        file.write((const char *)&recordBlkHead, sizeof(recordBlkHead));        writeIndexBlk(recordBlkPos);    }}void CWriteRecord::writeRecordBlk(const TRecord *pRecord){    quint64 writePos = recordBlkPos + recordIndex * sizeof(TRecord) + sizeof(TBlkHead);    file.seek(writePos);    file.write((const char *)pRecord, sizeof(TRecord));    recordIndex++;    recordBlkHead.recordNum = recordIndex;    if (recordIndex == RECORD_BLK_RECORD_NUM)    {        /*写当前块*/        recordBlkHead.nextBlkPos = nextBlkPos;        writeRecordBlkHead();        /*初始化下一块*/        recordBlkHead.recordNum = 0;        recordBlkPos = nextBlkPos;        recordIndex = 0;        recordBlkNum++;        nextBlkPos = nextBlkPos + sizeof(TRecordBlk);    }}void CWriteRecord::writeIndexBlkHead(){    if (validIndexBlkRecordNum != indexBlkHead.recordNum        && indexBlkHead.recordNum != 0)    {        validIndexBlkRecordNum = indexBlkHead.recordNum;        file.seek(indexBlkPos);        file.write((const char *)&indexBlkHead, sizeof(indexBlkHead));        writeIndexBlkNum();    }}void CWriteRecord::writeIndexBlkNum(){    if (validIndexBlkNum != indexBlkNum)    {        validIndexBlkNum = indexBlkNum;        quint32 writePos = (quint32)&((TFileHead *)0)->indexBlkNum;        file.seek(writePos);        file.write((const char *)&indexBlkNum, sizeof(indexBlkNum));    }}void CWriteRecord::writeIndexBlk(quint64 blkPos){    quint64 writePos = indexBlkPos + index * sizeof(TIndex) + sizeof(TBlkHead);    file.seek(writePos);    file.write((const char *)&blkPos, sizeof(blkPos));    index++;    indexBlkHead.recordNum = index;    quint32 blkRecordNum = INDEX_BLK_RECORD_NUM;    if (index == blkRecordNum)    {        /*写当前块*/        indexBlkHead.nextBlkPos = nextBlkPos;        writeIndexBlkHead();        /*初始化下一块*/        indexBlkHead.recordNum = 0;        indexBlkPos = nextBlkPos;        index = 0;        indexBlkNum++;        nextBlkPos = nextBlkPos + sizeof(TIndexBlk);    }}void CWriteRecord::flushBlk(bool bClose){    if (file.isOpen())    {        writeRecordBlkHead();        if (bClose)            file.close();        else            file.flush();    }}

2.读记载

#ifndef _READ_RECORD_H#define _READ_RECORD_H#include 
    
     #include 
     
      class CReadRecord {public:    static CReadRecord *getInstance();    const TRecordBlk &readRecordBlk(quint64 blkPos);    bool read(const QString &fileName);    const QVector 
      
        *getRecordBlkPosList();private:    CReadRecord();    void readRecordHead();    void initBlkPosList();private:    QFile file;    TRecordBlk recordBlk;    TIndexBlk indexBlk;    TRecordHead recordHead;    QVector 
       
         recordBlkPosList;    static CReadRecord mSelf;};#endif

#include "readrecord.h"CReadRecord CReadRecord::mSelf;CReadRecord *CReadRecord::getInstance(){    return &mSelf;}CReadRecord::CReadRecord(){}bool CReadRecord::read(const QString &fileName){    if (file.isOpen())        file.close();    file.setFileName(fileName);    if (!file.open(QIODevice::ReadOnly))        return false;    readRecordHead();    if (memcmp(recordHead.magic,               FILE_MAGIC,               FILE_MAGIC_LEN) == 0)    {        initBlkPosList();        return true;    }    return false;}const QVector 
    
      *CReadRecord::getRecordBlkPosList(){    return &recordBlkPosList;}void CReadRecord::readRecordHead(){    file.seek(0);    file.read((char *)&recordHead, sizeof(TRecordHead));}const TRecordBlk &CReadRecord::readRecordBlk(quint64 blkPos){    readFile(blkPos, (quint8 *)&recordBlk, sizeof(recordBlk));    return recordBlk;}void CReadRecord::initBlkPosList(){    recordBlkPosList.clear();    int cnt = recordHead.indexBlkNum;    quint64 indexBlkPos = sizeof(TRecordHead);    for (int i = 0; i < cnt; i++)    {        readFile(indexBlkPos, (quint8 *)&indexBlk, sizeof(indexBlk));        int cnt1 = indexBlk.blkHead.recordNum;        for (int j = 0; j < cnt1; j++)        {            recordBlkPosList.append(indexBlk.index[j]);        }        indexBlkPos = indexBlk.blkHead.nextBlkPos;    }}

文章结束给大家分享下程序员的一些笑话语录： 3G普不普及现在已经不是看终端了，而是看应用，有好的，便宜实用的应用，花1000多买个能用的智能手机应该不是什么难事。反过来说，你200元拿一个智能手机，没有好的应用，看个电影要几十元，也是没人用3G。

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