alloc.h

用c语言编程

void update_group_desc()//更新组描述符,超级块super_block和组描述符group_desc重合 
{
    fseek(fp,DISK_START,SEEK_SET);
    fwrite(super_block,BLOCK_SIZE,1,fp);
}
void reload_group_desc()//载入组描述符
{
    fseek(fp,DISK_START,SEEK_SET);
    fread(super_block,BLOCK_SIZE,1,fp);
}
void update_inode_bitmap()//更新inode位图 
{
    fseek(fp,INODE_BITMAP,SEEK_SET);
    fwrite(bitbuf,BLOCK_SIZE,1,fp);
}
void reload_inode_bitmap()//载入inode位图 
{
    fseek(fp,INODE_BITMAP,SEEK_SET);
    fread(bitbuf,BLOCK_SIZE,1,fp);
}
void update_block_bitmap()//更新block位图 
{
    fseek(fp,BLOCK_BITMAP,SEEK_SET);
    fwrite(bitbuf,BLOCK_SIZE,1,fp);
}
void reload_block_bitmap()//载入block位图 
{
    fseek(fp,BLOCK_BITMAP,SEEK_SET);
    fread(bitbuf,BLOCK_SIZE,1,fp);
}
void update_inode_entry(unsigned short i)//更新第i个inode入口 
{
    fseek(fp,INODE_TABLE+(i-1)*INODE_SIZE,SEEK_SET);
    fwrite(inode_area,INODE_SIZE,1,fp);
}
void reload_inode_entry(unsigned short i)//载入第i个inode入口
{
    fseek(fp,INODE_TABLE+(i-1)*INODE_SIZE,SEEK_SET);
    fread(inode_area,INODE_SIZE,1,fp);
}

void reload_dir(unsigned short i)//更新第i个目录 
{
    fseek(fp,DATA_BLOCK+i*BLOCK_SIZE,SEEK_SET);
    fread(dir,BLOCK_SIZE,1,fp);
}
void update_dir(unsigned short i)//载入第i个目录 
{
    fseek(fp,DATA_BLOCK+i*BLOCK_SIZE,SEEK_SET);
    fwrite(dir,BLOCK_SIZE,1,fp);
}
void reload_block(unsigned short i)//载入第i个数据块 
{
    fseek(fp,DATA_BLOCK+i*BLOCK_SIZE,SEEK_SET);
    fread(Buffer,BLOCK_SIZE,1,fp);
}
void update_block(unsigned short i)//更新第i个数据块
{
    fseek(fp,DATA_BLOCK+i*BLOCK_SIZE,SEEK_SET);
    fwrite(Buffer,BLOCK_SIZE,1,fp);
}
void reload_index_block(unsigned short i)//载入索引数据块
{
    fseek(fp,DATA_BLOCK+i*BLOCK_SIZE,SEEK_SET);
    fread(index_buf,BLOCK_SIZE,1,fp);
}
void update_index_block(unsigned short i)//更新索引数据块
{
    fseek(fp,DATA_BLOCK+i*BLOCK_SIZE,SEEK_SET);
    fwrite(index_buf,BLOCK_SIZE,1,fp);
}
void reload_index1_block(unsigned short i)//载入二级索引数据块
{
    fseek(fp,DATA_BLOCK+i*BLOCK_SIZE,SEEK_SET);
    fread(index_buf1,BLOCK_SIZE,1,fp);
}
void update_index1_block(unsigned short i)//更新二级索引数据块
{
    fseek(fp,DATA_BLOCK+i*BLOCK_SIZE,SEEK_SET);
    fwrite(index_buf1,BLOCK_SIZE,1,fp);
}
unsigned short alloc_block()//分配一个数据块,返回数据块号;
{
    unsigned short cur=last_alloc_block;
    unsigned char con=128;
    int flag=0;
    if(super_block[0].bg_free_blocks_count==0)
    {
        printf("There is no block to be alloced!\n");
        return(0);
    }
    reload_block_bitmap();
    cur=cur/8;
    while(bitbuf[cur]==255)
    {
        if(cur==511)cur=0;
        else cur++;
    }
    //printf("block:    %x  %d\n",bitbuf[cur],cur);
    while(bitbuf[cur]&con)
    {
        con=con/2;
        flag++;
    }
    bitbuf[cur]=bitbuf[cur]+con;
    last_alloc_block=cur*8+flag;
    //printf("          %x  %d\n",bitbuf[cur],last_alloc_block);
    update_block_bitmap();
    super_block[0].bg_free_blocks_count--;
    update_group_desc();
    return last_alloc_block;
}
void remove_block(unsigned short del_num)//删除一个block 
{
    unsigned short tmp;
    tmp=del_num/8;
    reload_block_bitmap();
    switch(del_num%8)//更改block位图 
    {
        case 0:bitbuf[tmp]=bitbuf[tmp]&127;break;
        case 1:bitbuf[tmp]=bitbuf[tmp]&191;break;
        case 2:bitbuf[tmp]=bitbuf[tmp]&223;break;
        case 3:bitbuf[tmp]=bitbuf[tmp]&239;break;
        case 4:bitbuf[tmp]=bitbuf[tmp]&247;break;
        case 5:bitbuf[tmp]=bitbuf[tmp]&251;break;
        case 6:bitbuf[tmp]=bitbuf[tmp]&253;break;
        case 7:bitbuf[tmp]=bitbuf[tmp]&254;break;
    }
    //printf("%x  \n",bitbuf[tmp]);
    update_block_bitmap();
    super_block[0].bg_free_blocks_count++;
    update_group_desc();
}
//
unsigned short get_inode()//分配一个inode,返回序号
{
    unsigned short cur=last_alloc_inode;
    unsigned char con=128;
    int flag=0;
    if(super_block[0].bg_free_inodes_count==0)
    {
        printf("There is no Inode to be alloced!\n");
        return 0;
    }
    reload_inode_bitmap();
    cur=(cur-1)/8;
    while(bitbuf[cur]==255)//比较结果永远为假--------------
    {
        if(cur==511)cur=0;
        else cur++;
    }
    //printf("inode     %x   %d\n",bitbuf[cur],cur);
    while(bitbuf[cur]&con)
    {
        con=con/2;
        flag++;
    }
    bitbuf[cur]=bitbuf[cur]+con;
    last_alloc_inode=cur*8+flag+1;
    //printf("          %x  %d\n",bitbuf[cur],last_alloc_inode);
    update_inode_bitmap();
    super_block[0].bg_free_inodes_count--;
    update_group_desc();
    return last_alloc_inode;
}
//
void remove_inode(unsigned short del_num)
{
    unsigned short tmp;
    tmp=(del_num-1)/8;
    reload_inode_bitmap();
    switch((del_num-1)%8)//更改block位图
    {
        case 0:bitbuf[tmp]=bitbuf[tmp]&127;break;
        case 1:bitbuf[tmp]=bitbuf[tmp]&191;break;
        case 2:bitbuf[tmp]=bitbuf[tmp]&223;break;
        case 3:bitbuf[tmp]=bitbuf[tmp]&239;break;
        case 4:bitbuf[tmp]=bitbuf[tmp]&247;break;
        case 5:bitbuf[tmp]=bitbuf[tmp]&251;break;
        case 6:bitbuf[tmp]=bitbuf[tmp]&253;break;
        case 7:bitbuf[tmp]=bitbuf[tmp]&254;break;
    }
    update_inode_bitmap();
    super_block[0].bg_free_inodes_count++;
    update_group_desc();
}