init.c~

模拟linux的ext3文件系统。采用位图法。用一个文件模拟硬盘。实现创建、删除目录、文件。读、写文件

#define MAIN
#include "structure.h"
//function init_FS()

int init_FS()
{
 u16  i; 
 
 u8   end[32]="this is the end of FS   2.36MB";
 u8   buf[512]={0,};
 u8   volume_name[16]="ext2_filesystem";
 u16  bg_block_bitmap[1]={1};
 u16  bg_inode_bitmap[1]={2};
 u16  bg_inode_table[1]={3};
 u16  bg_free_blocks_count[1]={4094}; //number 0 is reserved;the root dir  used one block and one inode
 u16  bg_free_inodes_count[1]={4094};
 u16  bg_used_dirs_count[1]={2};     //dirs . and ..
 u8   bitmap=0xC0;
 
  
 u16 i_mode[1]={0x26};
 u16 i_blocks[1]={1};
 u32 i_size[1]={20};
 u32 i_atime[1]={0};
 u32 i_ctime[1]={0};
 u32 i_mtime[1]={0};
 u32 i_dtime[1]={0};
 u16 i_block[1]={1};
 u16 d1_inode[1]={1};
 u16 d1_length[1]={8};
 u8 d1_name_len[1]={1};
 u8 d1_filetype[1]={2};
 u8 d1_name[EXT2_NAME_LEN];
 u16 d2_inode[1]={1};
 u16 d2_length[1]={12};
 u8 d2_name_len[1]={2};
 u8 d2_filetype[1]={2};
 u8 d2_name[EXT2_NAME_LEN];	
 for(i=0;i<EXT2_NAME_LEN;i++){
         d1_name[i]=0;
         d2_name[i]=0;
 }  
 strcpy(d1_name,".");
 strcpy(d2_name,"..");
 //create hard FS and initialize it
 FS=fopen("FS","r+t");
 if(FS==NULL)  FS=fopen("FS","w+");
 fseek(FS,0,SEEK_SET);
 for(i=0;i<512;i++)  buf[i]=0;
 for(i=0;i<4611;i++)  fwrite(buf,sizeof(u8),512,FS);
 fwrite(end,sizeof(u8),32,FS);
 //init group_desc
 fseek(FS,0,SEEK_SET);
 fwrite(volume_name,sizeof(u8),16,FS);
 fwrite(bg_block_bitmap,sizeof(u16),1,FS);
 fwrite(bg_inode_bitmap,sizeof(u16),1,FS);
 fwrite(bg_inode_table,sizeof(u16),1,FS);
 fwrite(bg_free_blocks_count,sizeof(u16),1,FS);
 fwrite(bg_free_inodes_count,sizeof(u16),1,FS);
 fwrite(bg_used_dirs_count,sizeof(u16),1,FS);
 //init block_bitmap
 fseek(FS,BLOCK_BITMAP,SEEK_SET);
 fprintf(FS,"%c",bitmap);
 //init inode_bitmap
 fseek(FS,INODE_BITMAP,SEEK_SET);
 fprintf(FS,"%c",bitmap);
 //init inode_table 
 fseek(FS,INODE_TABLE,SEEK_SET);
 fprintf(FS,"inode_table start from here \n");
 fseek(FS,INODE_TABLE+64,SEEK_SET);

 fwrite(i_mode,sizeof(u16),1,FS);
 fwrite(i_blocks,sizeof(u16),1,FS);
 fwrite(i_size,sizeof(u32),1,FS);
 fwrite(i_atime,sizeof(u32),1,FS);
 fwrite(i_ctime,sizeof(u32),1,FS);
 fwrite(i_mtime,sizeof(u32),1,FS);
 fwrite(i_dtime,sizeof(u32),1,FS);
 fwrite(i_block,sizeof(u16),1,FS);
 //init data_block
 fseek(FS,DATA_BLOCK+512,SEEK_SET);
 fwrite(d1_inode,sizeof(u16),1,FS);
 fwrite(d1_length,sizeof(u16),1,FS);
 fwrite(d1_name_len,sizeof(u8),1,FS);
 fwrite(d1_filetype,sizeof(u8),1,FS);
 fwrite(d1_name,sizeof(u8),d1_name_len[1],FS);
 //fwrite(dir_entry1,sizeof(struct ext2_dir_entry),1,FS);
 fseek(FS,DATA_BLOCK+512+32,SEEK_SET);
 //fwrite(dir_entry2,sizeof(struct ext2_dir_entry),1,FS);
  fwrite(d2_inode,sizeof(u16),1,FS);
  fwrite(d2_length,sizeof(u16),1,FS);
  fwrite(d2_name_len,sizeof(u8),1,FS);
  fwrite(d2_filetype,sizeof(u8),1,FS);
  fwrite(d2_name,sizeof(u8),d2_name_len[1],FS);
  fseek(FS,DATA_BLOCK,SEEK_SET);
  fprintf(FS,"data_block start from here");
  fclose(FS);      
 printf("FS has been formatted sucessfully!\n");
 return 1;
}

//function init_memory()

int init_memory()
{
 int i;
 u8 buffer[512];
 for(i=0;i<MAX_OPEN_FILE;i++)   file_open_table[i]=0;
 last_alloc_inode=0;
 last_alloc_block=0;
 current_dir=1;
 strcpy(current_path,"/");
 FS=fopen("FS","r+");
 if(FS==NULL) {
	 printf("FS not exits or not format \n");
	 return 0;
 }
 fseek(FS,0,SEEK_SET);
 fread(buffer,sizeof(u8),512,FS);
 for(i=0;i<16;i++)  group_desc.bg_volume_name[i]=buffer[i];
 group_desc.bg_block_bitmap=buffer[16];
 group_desc.bg_inode_bitmap=buffer[18];
 group_desc.bg_inode_table=buffer[20];
 group_desc.bg_free_blocks_count=buffer[23]*0x100+buffer[22];
 group_desc.bg_free_inodes_count=buffer[25]*0x100+buffer[24];
 group_desc.bg_used_dirs_count=buffer[26];

 return 1;
}