107 lines
3.6 KiB
C
107 lines
3.6 KiB
C
/*----------------------------------------------------------------------/
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/ Allocate a contiguous area to the file
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/-----------------------------------------------------------------------/
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/ This function checks if the file is contiguous with desired size.
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/ If not, a block of contiguous sectors is allocated to the file.
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/ If the file has been opened without FA_WRITE flag, it only checks if
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/ the file is contiguous and returns the resulut. */
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#if _FATFS != 32020 /* Check if R0.11 */
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#error This function may not be compatible with this revision of FatFs module.
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#endif
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/* Declarations of FatFs internal functions accessible from applications.
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/ This is intended to be used for disk checking/fixing or dirty hacks :-) */
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DWORD clust2sect (FATFS* fs, DWORD clst);
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DWORD get_fat (FATFS* fs, DWORD clst);
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FRESULT put_fat (FATFS* fs, DWORD clst, DWORD val);
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DWORD allocate_contiguous_clusters ( /* Returns the first sector in LBA (0:error or not contiguous) */
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FIL* fp, /* Pointer to the open file object */
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DWORD len /* Number of bytes to allocate */
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)
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{
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DWORD csz, tcl, ncl, ccl, cl;
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if (f_lseek(fp, 0) || !len) /* Check if the given parameters are valid */
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return 0;
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csz = 512UL * fp->fs->csize; /* Cluster size in unit of byte (assuming 512 bytes/sector) */
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tcl = (len + csz - 1) / csz; /* Total number of clusters required */
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len = tcl * csz; /* Round-up file size to the cluster boundary */
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/* Check if the existing cluster chain is contiguous */
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if (len == fp->fsize) {
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ncl = 0; ccl = fp->sclust;
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do {
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cl = get_fat(fp->fs, ccl); /* Get the cluster status */
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if (cl + 1 < 3) return 0; /* Hard error? */
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if (cl != ccl + 1 &&; cl < fp->fs->n_fatent) break; /* Not contiguous? */
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ccl = cl;
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} while (++ncl < tcl);
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if (ncl == tcl) /* Is the file contiguous? */
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return clust2sect(fp->fs, fp->sclust); /* Return file start sector */
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}
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#if _FS_READONLY
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return 0;
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#else
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if (f_truncate(fp)) return 0; /* Remove the existing chain */
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/* Find a free contiguous area */
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ccl = cl = 2; ncl = 0;
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do {
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if (cl >= fp->fs->n_fatent) return 0; /* No contiguous area is found. */
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if (get_fat(fp->fs, cl)) { /* Encounterd a cluster in use */
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do { /* Skip the block of used clusters */
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cl++;
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if (cl >= fp->fs->n_fatent) return 0; /* No contiguous area is found. */
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} while (get_fat(fp->fs, cl));
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ccl = cl; ncl = 0;
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}
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cl++; ncl++;
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} while (ncl < tcl);
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/* Create a contiguous cluster chain */
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fp->fs->last_clust = ccl - 1;
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if (f_lseek(fp, len)) return 0;
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return clust2sect(fp->fs, fp->sclust); /* Return file start sector */
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#endif
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}
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int main (void)
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{
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FRESULT fr;
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DRESULT dr;
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FATFS fs;
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FIL fil;
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DWORD org;
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/* Open or create a file */
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f_mount(&fs, "", 0);
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fr = f_open(&fil, "swapfile.sys", FA_READ | FA_WRITE | FA_OPEN_ALWAYS);
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if (fr) return 1;
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/* Check if the file is 64MB in size and occupies a contiguous area.
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/ If not, a contiguous area will be re-allocated to the file. */
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org = allocate_contiguous_clusters(&fil, 0x4000000);
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if (!org) {
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printf("Function failed due to any error or insufficient contiguous area.\n");
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f_close(&fil);
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return 1;
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}
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/* Now you can read/write the file with disk functions bypassing the file system layer. */
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dr = disk_write(fil.fs->drv, Buff, org, 1024); /* Write 512KiB from top of the file */
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...
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f_close(&fil);
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return 0;
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}
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