C语言版Mysql存储块（page）格式读取工具（源代码）

清疚 2022-08-10 00:59 27阅读 0赞

C版本的Mysql存储块格式读取工具源代码如下：

其中mysql块存储采用大端字节，所以需要做一定的转换，C语言指针强力转换方式如下：

#include <stdio.h>
    #include <stdlib.h>
    
    int readpage(unsigned char * page_hdr,int page_off,FILE *fd) {
      int ret = -1;
      if((ret = fseek(fd,page_off,SEEK_SET)) != 0) {	//fseek error may not be caught successfully here
        printf("fseek failed\n");
        exit(-1);
      }
      printf("now from our calclation page_off is %d\n",page_off);
      if(!(ret = fread(page_hdr,62,1,fd))) {
        printf("read page failed! ret is %d\n",ret);
        return -1;
      }
      return 1;
    }
    
    int main() {
      unsigned char page_hdr_tmp[62];
      unsigned char * tmp;
      unsigned int page_offset = 0;
      unsigned short page_type = 0;
      unsigned int tab_space_id = 0;
      unsigned short page_level = 0;
      int ret = -1;
      int page_count = 0;
      int filesize = 0;
      FILE *fd;
      if(!freopen("C:\\MinGW\\bin\\log.txt", "w", stdout)) {
        printf("log file created failed!\n");
      }
      
      if(!(fd = fopen("C:\\MinGW\\bin\\payment.ibd","rb"))) {
        printf("fopen failed!\n");
        return -1;
      } 
      if((ret = fseek(fd,0,SEEK_END)) != 0) {
        printf("fseek failed\n");
        exit(-1);
      }
      filesize = ftell(fd);
      
      printf("filesize is %d\n",filesize);
      
      while (page_count < filesize/1024/16) {
        printf("processing the %d [rd] page\n",page_count);
        if(ret = readpage(page_hdr_tmp, page_count*16*1024, fd)) {
          page_count++;
        } else {
          printf("readpage failed!\n");
          system("pause");
          exit -1;
        }
        //for page_offset
        tmp = (unsigned char *)&page_offset;
        tmp[0] = page_hdr_tmp[7];
        tmp[1] = page_hdr_tmp[6];
        tmp[2] = page_hdr_tmp[5];
        tmp[3] = page_hdr_tmp[4];
        
        //for page_type
        tmp = (unsigned char *)&page_type;
        tmp[0] = page_hdr_tmp[25];
        tmp[1] = page_hdr_tmp[24];
        
        //for tab_space_id
        tmp = (unsigned char *)&tab_space_id;
        tmp[0] = page_hdr_tmp[37];
        tmp[1] = page_hdr_tmp[36];
        tmp[2] = page_hdr_tmp[35];
        tmp[3] = page_hdr_tmp[34];
        
        //for page_level
        tmp = (unsigned char *)&page_level;
        tmp[0] = page_hdr_tmp[61];
        tmp[1] = page_hdr_tmp[60];
        
        printf("page_offset is %d\n",page_offset);
        printf("page_type is %x\n",page_type);
        printf("tab_space_id is %x\n",tab_space_id);
        printf("page_level is %x\n\n",page_level);
      }
      fclose(fd);
      system("pause");
      return 0;
    }

我们打开程序输出的log来看，信息如下：

filesize is 10485760
    processing the 0 [rd] page
    now from our calclation page_off is 0
    page_offset is 0
    page_type is 8
    tab_space_id is 11
    page_level is b
    
    processing the 1 [rd] page
    now from our calclation page_off is 16384
    page_offset is 1
    page_type is 5
    tab_space_id is 11
    page_level is 0
    
    processing the 2 [rd] page
    now from our calclation page_off is 32768
    page_offset is 2
    page_type is 3
    tab_space_id is 11
    page_level is 0
    
    processing the 3 [rd] page
    now from our calclation page_off is 49152
    page_offset is 3
    page_type is 45bf
    tab_space_id is 11
    page_level is 0

其中page\_type的45bf代表的是索引节点。而page\_level是0，意思是，索引节点的层级为0。

到了第75 \[rd\]块的时候，所有块都是空白块了。

processing the 74 [rd] page
    now from our calclation page_off is 1212416
    page_offset is 74
    page_type is 45bf
    tab_space_id is 11
    page_level is 0
    
    processing the 75 [rd] page
    now from our calclation page_off is 1228800
    page_offset is 0
    page_type is 0
    tab_space_id is 0
    page_level is 0
    
    processing the 76 [rd] page
    now from our calclation page_off is 1245184
    page_offset is 0
    page_type is 0
    tab_space_id is 0
    page_level is 0

测试的ibd文件是mysql 5.6自带的sakila库下的payment.ibd。