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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KB22         *free=fre_sect>>1;    //单位为KB 23      }24     return res;25 }
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