首页 > 代码库 > FATFS 初学之 f_open/ f_close
FATFS 初学之 f_open/ f_close
f_open：
1 /*-----------------------------------------------------------------------*/ 2 /* Open or Create a File */ 3 /*-----------------------------------------------------------------------*/ 4 5 FRESULT f_open ( 6 FIL *fp, /* Pointer to the blank file object */ 7 const TCHAR *path, /* Pointer to the file name */ 8 BYTE mode /* Access mode and file open mode flags */ 9 ) 10 { 11 FRESULT res; 12 DIR dj; 13 BYTE *dir; 14 DEF_NAMEBUF; 15 16 17 fp->fs = 0; /* Clear file object */ 18 19 #if !_FS_READONLY 20 mode &= FA_READ | FA_WRITE | FA_CREATE_ALWAYS | FA_OPEN_ALWAYS | FA_CREATE_NEW; 21 res = chk_mounted(&path, &dj.fs, (BYTE)(mode & ~FA_READ)); 22 #else 23 mode &= FA_READ; 24 res = chk_mounted(&path, &dj.fs, 0); 25 #endif 26 INIT_BUF(dj); 27 if (res == FR_OK) 28 res = follow_path(&dj, path); /* Follow the file path */ 29 dir = dj.dir; 30 31 #if !_FS_READONLY /* R/W configuration */ 32 if (res == FR_OK) { 33 if (!dir) /* Current dir itself */ 34 res = FR_INVALID_NAME; 35 #if _FS_SHARE 36 else 37 res = chk_lock(&dj, (mode & ~FA_READ) ? 1 : 0); 38 #endif 39 } 40 /* Create or Open a file */ 41 if (mode & (FA_CREATE_ALWAYS | FA_OPEN_ALWAYS | FA_CREATE_NEW)) { 42 DWORD dw, cl; 43 44 if (res != FR_OK) { /* No file, create new */ 45 if (res == FR_NO_FILE) /* There is no file to open, create a new entry */ 46 #if _FS_SHARE 47 res = enq_lock() ? dir_register(&dj) : FR_TOO_MANY_OPEN_FILES; 48 #else 49 res = dir_register(&dj); 50 #endif 51 mode |= FA_CREATE_ALWAYS; /* File is created */ 52 dir = dj.dir; /* New entry */ 53 } 54 else { /* Any object is already existing */ 55 if (dir[DIR_Attr] & (AM_RDO | AM_DIR)) { /* Cannot overwrite it (R/O or DIR) */ 56 res = FR_DENIED; 57 } else { 58 if (mode & FA_CREATE_NEW) /* Cannot create as new file */ 59 res = FR_EXIST; 60 } 61 } 62 if (res == FR_OK && (mode & FA_CREATE_ALWAYS)) { /* Truncate it if overwrite mode */ 63 dw = get_fattime(); /* Created time */ 64 ST_DWORD(dir+DIR_CrtTime, dw); 65 dir[DIR_Attr] = 0; /* Reset attribute */ 66 ST_DWORD(dir+DIR_FileSize, 0); /* size = 0 */ 67 cl = LD_CLUST(dir); /* Get start cluster */ 68 ST_CLUST(dir, 0); /* cluster = 0 */ 69 dj.fs->wflag = 1; 70 if (cl) { /* Remove the cluster chain if exist */ 71 dw = dj.fs->winsect; 72 res = remove_chain(dj.fs, cl); 73 if (res == FR_OK) { 74 dj.fs->last_clust = cl - 1; /* Reuse the cluster hole */ 75 res = move_window(dj.fs, dw); 76 } 77 } 78 } 79 } 80 else { /* Open an existing file */ 81 if (res == FR_OK) { /* Follow succeeded */ 82 if (dir[DIR_Attr] & AM_DIR) { /* It is a directory */ 83 res = FR_NO_FILE; 84 } else { 85 if ((mode & FA_WRITE) && (dir[DIR_Attr] & AM_RDO)) /* R/O violation */ 86 res = FR_DENIED; 87 } 88 } 89 } 90 if (res == FR_OK) { 91 if (mode & FA_CREATE_ALWAYS) /* Set file change flag if created or overwritten */ 92 mode |= FA__WRITTEN; 93 fp->dir_sect = dj.fs->winsect; /* Pointer to the directory entry */ 94 fp->dir_ptr = dir; 95 #if _FS_SHARE 96 fp->lockid = inc_lock(&dj, (mode & ~FA_READ) ? 1 : 0); 97 if (!fp->lockid) res = FR_INT_ERR; 98 #endif 99 }100 101 #else /* R/O configuration */102 if (res == FR_OK) { /* Follow succeeded */103 if (!dir) { /* Current dir itself */104 res = FR_INVALID_NAME;105 } else {106 if (dir[DIR_Attr] & AM_DIR) /* It is a directory */107 res = FR_NO_FILE;108 }109 }110 #endif111 FREE_BUF();112 113 if (res == FR_OK) {114 fp->flag = mode; /* File access mode */115 fp->sclust = LD_CLUST(dir); /* File start cluster */116 fp->fsize = LD_DWORD(dir+DIR_FileSize); /* File size */117 fp->fptr = 0; /* File pointer */118 fp->dsect = 0;119 #if _USE_FASTSEEK120 fp->cltbl = 0; /* Normal seek mode */121 #endif122 fp->fs = dj.fs; fp->id = dj.fs->id; /* Validate file object */123 }124 125 LEAVE_FF(dj.fs, res);126 }
函数功能：创建/打开一个用于访问文件的文件对象
描述：如果函数成功，则创建一个文件对象。该文件对象被后续的读/写函数用来访问文件。如果想要关闭一个打开的文件对象，则使用f_close函数。如果不关闭修改后的文件，那么文件可能会崩溃。
在使用任何文件函数之前，必须使用 f_mount函数为驱动器注册一个工作区。只有这样，其他文件函数才能正常工作。
将打开的文件名、文件目录及读写属性等装入 fp，为后续操作做准备。
f_close：
1 /*-----------------------------------------------------------------------*/ 2 /* Close File */ 3 /*-----------------------------------------------------------------------*/ 4 5 FRESULT f_close ( 6 FIL *fp /* Pointer to the file object to be closed */ 7 ) 8 { 9 FRESULT res;10 11 #if _FS_READONLY12 FATFS *fs = fp->fs;13 res = validate(fs, fp->id);14 if (res == FR_OK) fp->fs = 0; /* Discard file object */15 LEAVE_FF(fs, res);16 17 #else18 res = f_sync(fp); /* Flush cached data */19 #if _FS_SHARE20 if (res == FR_OK) { /* Decrement open counter */21 #if _FS_REENTRANT22 res = validate(fp->fs, fp->id);23 if (res == FR_OK) {24 res = dec_lock(fp->lockid); 25 unlock_fs(fp->fs, FR_OK);26 }27 #else28 res = dec_lock(fp->lockid);29 #endif30 }31 #endif32 if (res == FR_OK) fp->fs = 0; /* Discard file object */33 return res;34 #endif35 }
函数功能：关闭一个已打开的文件
描述：f_close函数关闭一个打开的文件对象。无论向文件写入任何数据，文件的缓存信息都将被写回到磁盘。该函数成功后，文件对象不再有效，并且可以被丢弃。如果文件对象是在只读模式下打开的，不需要使用该函数，也能被丢弃。
例：
1 FATFS fs; /* 逻辑驱动器的工作区(文件系统对象) */ 2 FIL fsrc; /* 文件对象 */ 3 FRESULT res; /* FatFs 函数公共结果代码 */ 4 5 void main(void) 6 { 7 // 设备初始化... 8 9 f_mount(0,&fs);10 res = f_open(&fdst,"0:/Demo.TXT", FA_WRITE | FA_READ);11 if(FR_OK == res)12 {13 // ...14 f_close(&fdst);15 }16 else17 {18 // ...19 }20 21 f_mount(0, NULL);22 }
声明：以上内容来自用户投稿及互联网公开渠道收集整理发布，本网站不拥有所有权，未作人工编辑处理，也不承担相关法律责任，若内容有误或涉及侵权可进行投诉： 投诉/举报 工作人员会在5个工作日内联系你，一经查实，本站将立刻删除涉嫌侵权内容。