1. FATFS 分析之——数据结构
1. FATFS 分析之——数据结构
文件系统主要数据结构全放在ff.h里面。
1. File system object structure
文件系统最主要的数据结构，用于存储文件系统的基本信息如：文件系统类型、扇区大小、簇的扇区数、FAT表的位置及大小等一些重要信息。
typedefstruct {
BYTE fs_type; /* FAT子类型，在Mount时，置0表示未挂载 */
BYTE drv; /* 物理驱动号 */
BYTE csize; /* Sectors per cluster (1,2,4...128) */ 每个簇扇区数目
BYTE n_fats; /* FAT表数目 */
BYTE wflag; /* win[] dirtyflag (1:must be written back) */ 标记文件是否被改动过
BYTE fsi_flag; /* fsinfodirty flag (1:must be written back) */标记文件系统时否被改动过
WORD id; /*File system mount ID */文件系统挂载ID
WORD n_rootdir; /* Number ofroot directory entries (FAT12/16) */ FAT12/16所用，这里不作深究
#if_MAX_SS != 512
WORD ssize; /* Bytes per sector (512,1024,2048,4096) */每个扇区字节数
#endif
#if_FS_REENTRANTfs_reentrant，允许重入
_SYNC_t sobj; /*Identifier of sync object */// 创建同步对像
#endif
#if!_FS_READONLY // 只读模式
DWORD last_clust; /* Last allocated cluster*/
DWORD free_clust; /* Number of freeclusters */
DWORD fsi_sector; /* fsinfo sector (FAT32)*/
#endif
#if_FS_RPATH // 允讲相对路径
DWORD cdir; /* Currentdirectory start cluster (0:root) */
#endif
DWORD n_fatent; /* Number ofFAT entries (= number of clusters + 2) */FAT入口
DWORD fsize; /* Sectors per FAT */每个FAT所占扇区
DWORD fatbase; /* FATstart sector */FAT表起始扇区
DWORD dirbase; /* Rootdirectory start sector (FAT32:Cluster#) */根目录扇区
DWORD database; /* Data startsector */数据目录扇区
DWORD winsect; /* Currentsector appearing in the win[] */当前缓冲区中存储的扇区号
BYTE win[_MAX_SS]; /* Disk access window forDirectory, FAT (and Data on tiny cfg) */
}FATFS;
2. File object structure
这个结构体存储一个文件的相关信息()。要调用文件系统上层接口函数必须创建的一个实体。
typedefstruct {
FATFS*fs; /*Pointer to the owner file system object */文件所在FS
WORD id; /*Owner file system mount ID */所在的FS挂载编号
BYTE flag; /* File statusflags */文件状态标志
BYTE pad1; //未查到有何作用，以前版本此位：扇区偏移
DWORD fptr; /* Fileread/write pointer */文件读写指针
DWORD fsize; /* File size */文件大小
DWORD org_clust; /* File startcluster (0 when fsize==0) */文件起始扇区
DWORD curr_clust; /* Current cluster */当前簇
DWORD dsect; /* Current data sector */数据当前扇区
#if!_FS_READONLY只读模式
DWORD dir_sect; /* Sectorcontaining the directory entry */
BYTE* dir_ptr; /* Ponter to the directory entry in the window */
#endif
#if_USE_FASTSEEK
DWORD* cltbl; /* Pointer to the cluster link map table (null on file open) */指向簇链映射表
#endif
#if_FS_SHARE
UINT lockid; /* File lock ID (index of file semaphore table) */
#endif
#if!_FS_TINY
BYTE buf[_MAX_SS]; /* File data read/write buffer*/
#endif
}FIL;
3. Directory object structure
文件目录结构体，主要作用是在文件系统处理目录操作时所用到的结构体。
typedefstruct {
FATFS*fs; /*Pointer to the owner file system object */
WORD id; /* Owner file system mount ID */
WORD index; /* Currentread/write index number */
DWORD sclust; /*Table start cluster (0:Root dir) */
DWORD clust; /* Current cluster */
DWORD sect; /* Currentsector */
BYTE* dir; /*Pointer to the current SFN entry in the win[] */
BYTE* fn; /*Pointer to the SFN (in/out) {file[8],ext[3],status[1]} */
#if_USE_LFN
WCHAR* lfn; /* Pointer to the LFN working buffer */
WORD lfn_idx; /*Last matched LFN index number (0xFFFF:No LFN) */
#endif
}DIR;
4. File status structure (FILINFO)
记录文件目录项信息的数据结构，这个结构主要描述文件的状态信息，包括文件名13个字符（8+.+3+\0）、属性、修改时间等
typedefstruct {
DWORD fsize; /* File size */
WORD fdate; /* Last modifieddate */
WORD ftime; /* Last modifiedtime */
BYTE fattrib; /*Attribute */
TCHAR fname[13]; /* Short file name(8.3 format) */
#if_USE_LFN
TCHAR* lfname; /* Pointer tothe LFN buffer */
UINT lfsize; /* Size of LFN buffer in TCHAR */
#endif
}FILINFO;
5. 用于共享控制的结构体。
typedefstruct {
FATFS*fs; /* File ID 1, volume (NULL:blank entry) */
DWORDclu; /* File ID 2, directory */
WORDidx; /* File ID 3, directory index */
WORDctr; /* File open counter, 0:none, 0x01..0xFF:read open count, 0x100:write mode */
}FILESEM;
6. File function return code
typedefenum {
FR_OK =0, /* (0) Succeeded */
FR_DISK_ERR, /* (1) A hard error occured in the low level disk I/O layer */
FR_INT_ERR, /* (2) Assertion failed */
FR_NOT_READY, /* (3) The physical drive cannot work */
FR_NO_FILE, /* (4) Could not find the file */
FR_NO_PATH, /* (5) Could not find the path */
FR_INVALID_NAME, /* (6) The path nameformat is invalid */
FR_DENIED, /* (7) Acces denied due to prohibited access or directory full */
FR_EXIST, /* (8) Acces denied due to prohibited access */
FR_INVALID_OBJECT, /* (9) The file/directoryobject is invalid */
FR_WRITE_PROTECTED, /* (10) The physical drive is writeprotected */
FR_INVALID_DRIVE, /* (11) The logical drivenumber is invalid */
FR_NOT_ENABLED, /* (12) Thevolume has no work area */
FR_NO_FILESYSTEM, /* (13) There is no validFAT volume on the physical drive */
FR_MKFS_ABORTED, /* (14) The f_mkfs()aborted due to any parameter error */
FR_TIMEOUT, /* (15) Could not get a grant to access the volume within defined period */
FR_LOCKED, /* (16) The operation is rejected according to the file shareing policy */
FR_NOT_ENOUGH_CORE, /* (17) LFN working buffer could not be allocated */
FR_TOO_MANY_OPEN_FILES /* (18) Number of open files > _FS_SHARE */
}FRESULT;