FATFS 初学之 f_getfree

 1 /*-----------------------------------------------------------------------*/
 2 /* Get Number of Free Clusters                                           */
 3 /*-----------------------------------------------------------------------*/
 4 
 5 FRESULT f_getfree (
 6     const TCHAR *path,    /* Pointer to the logical drive number (root dir) */
 7     DWORD *nclst,        /* Pointer to the variable to return number of free clusters */
 8     FATFS **fatfs        /* Pointer to pointer to corresponding file system object to return */
 9 )
10 {
11     FRESULT res;
12     DWORD n, clst, sect, stat;
13     UINT i;
14     BYTE fat, *p;
15 
16 
17     /* Get drive number */
18     res = chk_mounted(&path, fatfs, 0);
19     if (res == FR_OK) {
20         /* If free_clust is valid, return it without full cluster scan */
21         if ((*fatfs)->free_clust <= (*fatfs)->n_fatent - 2) {
22             *nclst = (*fatfs)->free_clust;
23         } else {
24             /* Get number of free clusters */
25             fat = (*fatfs)->fs_type;
26             n = 0;
27             if (fat == FS_FAT12) {
28                 clst = 2;
29                 do {
30                     stat = get_fat(*fatfs, clst);
31                     if (stat == 0xFFFFFFFF) { res = FR_DISK_ERR; break; }
32                     if (stat == 1) { res = FR_INT_ERR; break; }
33                     if (stat == 0) n++;
34                 } while (++clst < (*fatfs)->n_fatent);
35             } else {
36                 clst = (*fatfs)->n_fatent;
37                 sect = (*fatfs)->fatbase;
38                 i = 0; p = 0;
39                 do {
40                     if (!i) {
41                         res = move_window(*fatfs, sect++);
42                         if (res != FR_OK) break;
43                         p = (*fatfs)->win;
44                         i = SS(*fatfs);
45                     }
46                     if (fat == FS_FAT16) {
47                         if (LD_WORD(p) == 0) n++;
48                         p += 2; i -= 2;
49                     } else {
50                         if ((LD_DWORD(p) & 0x0FFFFFFF) == 0) n++;
51                         p += 4; i -= 4;
52                     }
53                 } while (--clst);
54             }
55             (*fatfs)->free_clust = n;
56             if (fat == FS_FAT32) (*fatfs)->fsi_flag = 1;
57             *nclst = n;
58         }
59     }
60     LEAVE_FF(*fatfs, res);
61 }
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函数功能:获取空闲簇的数目

描述:

f_getfree函数当 _FS_READONLY == 0并且 _FS_MINIMIZE == 0时有效。
f_getfree函数获取驱动器上空闲簇的数目。文件系统对象中的成员csize是每簇中的扇区数,因此,以扇区为单位的空闲空间可以被计算出来。当FAT32卷上的FSInfo结构不同步时,该函数返回一个错误的空闲簇计数。

例:

unsigned long total,free;

if(exf_getfree("0",&total,&free))
{
    // 错误代码...
}
 1 //得到磁盘剩余容量
 2 //drv:磁盘编号("0:"/"1:")
 3 //total:总容量     (单位KB)
 4 //free:剩余容量     (单位KB)
 5 //返回值:0,正常.其他,错误代码
 6 u8 exf_getfree(u8 *drv,u32 *total,u32 *free)
 7 {
 8     FATFS *fs1;
 9     u8 res;
10     DWORD fre_clust=0, fre_sect=0, tot_sect=0;
11     //得到磁盘信息及空闲簇数量
12     res = f_getfree((const TCHAR*)drv, &fre_clust, &fs1);
13     if(res==0)
14     {
15         tot_sect=(fs1->n_fatent-2)*fs1->csize;    //得到总扇区数
16         fre_sect=fre_clust*fs1->csize;            //得到空闲扇区数
17 #if _MAX_SS!=512                                  //扇区大小不是512字节,则转换为512字节
18         tot_sect*=fs1->ssize/512;
19         fre_sect*=fs1->ssize/512;
20 #endif      
21         *total=tot_sect>>1;    //单位为KB
22         *free=fre_sect>>1;    //单位为KB 
23      }
24     return res;
25 }
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原文地址:https://www.cnblogs.com/Danhuise/p/3910516.html