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 #endif
111 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_FASTSEEK
120 fp->cltbl = 0; /* Normal seek mode */
121 #endif
122 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_READONLY
12 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 #else
18 res = f_sync(fp); /* Flush cached data */
19 #if _FS_SHARE
20 if (res == FR_OK) { /* Decrement open counter */
21 #if _FS_REENTRANT
22 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 #else
28 res = dec_lock(fp->lockid);
29 #endif
30 }
31 #endif
32 if (res == FR_OK) fp->fs = 0; /* Discard file object */
33 return res;
34 #endif
35 }
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 else
17 {
18 // ...
19 }
20
21 f_mount(0, NULL);
22 }
FATFS 初学之 f_open/ f_close
时间： 2024-10-08 01:57:41