diff options
Diffstat (limited to 'nuttx/fs/fat/fs_fat32util.c')
| -rw-r--r-- | nuttx/fs/fat/fs_fat32util.c | 1856 |
1 files changed, 1856 insertions, 0 deletions
diff --git a/nuttx/fs/fat/fs_fat32util.c b/nuttx/fs/fat/fs_fat32util.c new file mode 100644 index 000000000..397467c41 --- /dev/null +++ b/nuttx/fs/fat/fs_fat32util.c @@ -0,0 +1,1856 @@ +/**************************************************************************** + * fs/fat/fs_fat32util.c + * + * Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved. + * Author: Gregory Nutt <gnutt@nuttx.org> + * + * References: + * Microsoft FAT documentation + * Some good ideas were leveraged from the FAT implementation: + * 'Copyright (C) 2007, ChaN, all right reserved.' + * which has an unrestricted license. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include <nuttx/config.h> + +#include <sys/types.h> +#include <stdint.h> +#include <stdbool.h> +#include <stdlib.h> +#include <string.h> +#include <time.h> +#include <semaphore.h> +#include <assert.h> +#include <errno.h> +#include <debug.h> + +#include <nuttx/kmalloc.h> +#include <nuttx/fs/fs.h> +#include <nuttx/fs/fat.h> + +#include "fs_internal.h" +#include "fs_fat32.h" + +/**************************************************************************** + * Definitions + ****************************************************************************/ + +/**************************************************************************** + * Private Types + ****************************************************************************/ + +/**************************************************************************** + * Private Function Prototypes + ****************************************************************************/ + +/**************************************************************************** + * Private Variables + ****************************************************************************/ + +/**************************************************************************** + * Public Variables + ****************************************************************************/ + +/**************************************************************************** + * Private Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: fat_checkfsinfo + * + * Desciption: Read the FAT32 FSINFO sector + * + ****************************************************************************/ + +static int fat_checkfsinfo(struct fat_mountpt_s *fs) +{ + /* Make sure that the fsinfo sector is in the cache */ + + if (fat_fscacheread(fs, fs->fs_fsinfo) == OK) + { + /* Verify that this is, indeed, an FSINFO sector */ + + if (FSI_GETLEADSIG(fs->fs_buffer) == 0x41615252 && + FSI_GETSTRUCTSIG(fs->fs_buffer) == 0x61417272 && + FSI_GETTRAILSIG(fs->fs_buffer) == BOOT_SIGNATURE32) + { + fs->fs_fsinextfree = FSI_GETFREECOUNT(fs->fs_buffer); + fs->fs_fsifreecount = FSI_GETNXTFREE(fs->fs_buffer); + return OK; + } + } + + return -ENODEV; +} + +/**************************************************************************** + * Name: fat_checkbootrecord + * + * Desciption: Read a sector and verify that it is a a FAT boot record. + * + ****************************************************************************/ + +static int fat_checkbootrecord(struct fat_mountpt_s *fs) +{ + uint32_t ndatasectors; + uint32_t ntotalfatsects; + uint16_t rootdirsectors = 0; + bool notfat32 = false; + + /* Verify the MBR signature at offset 510 in the sector (true even + * if the sector size is greater than 512. All FAT file systems have + * this signature. On a FAT32 volume, the RootEntCount , FatSz16, and + * FatSz32 values should always be zero. The FAT sector size should + * match the reported hardware sector size. + */ + + if (MBR_GETSIGNATURE(fs->fs_buffer) != BOOT_SIGNATURE16 || + MBR_GETBYTESPERSEC(fs->fs_buffer) != fs->fs_hwsectorsize) + { + fdbg("ERROR: Signature: %04x FS sectorsize: %d HW sectorsize: %d\n", + MBR_GETSIGNATURE(fs->fs_buffer), MBR_GETBYTESPERSEC(fs->fs_buffer), + fs->fs_hwsectorsize); + + return -EINVAL; + } + + /* Verify the FAT32 file system type. The determination of the file + * system type is based on the number of clusters on the volume: FAT12 + * volume has <= FAT_MAXCLUST12 (4084) clusters, a FAT16 volume has <= + * FAT_MINCLUST16 (microsfoft says < 65,525) clusters, and any larger + * is FAT32. + * + * Get the number of 32-bit directory entries in root directory (zero + * for FAT32). + */ + + fs->fs_rootentcnt = MBR_GETROOTENTCNT(fs->fs_buffer); + if (fs->fs_rootentcnt != 0) + { + notfat32 = true; /* Must be zero for FAT32 */ + rootdirsectors = (32 * fs->fs_rootentcnt + fs->fs_hwsectorsize - 1) / fs->fs_hwsectorsize; + } + + /* Determine the number of sectors in a FAT. */ + + fs->fs_nfatsects = MBR_GETFATSZ16(fs->fs_buffer); /* Should be zero */ + if (fs->fs_nfatsects) + { + notfat32 = true; /* Must be zero for FAT32 */ + } + else + { + fs->fs_nfatsects = MBR_GETFATSZ32(fs->fs_buffer); + } + + if (!fs->fs_nfatsects || fs->fs_nfatsects >= fs->fs_hwnsectors) + { + fdbg("ERROR: fs_nfatsects %d fs_hwnsectors: %d\n", + fs->fs_nfatsects, fs->fs_hwnsectors); + + return -EINVAL; + } + + /* Get the total number of sectors on the volume. */ + + fs->fs_fattotsec = MBR_GETTOTSEC16(fs->fs_buffer); /* Should be zero */ + if (fs->fs_fattotsec) + { + notfat32 = true; /* Must be zero for FAT32 */ + } + else + { + fs->fs_fattotsec = MBR_GETTOTSEC32(fs->fs_buffer); + } + + if (!fs->fs_fattotsec || fs->fs_fattotsec > fs->fs_hwnsectors) + { + fdbg("ERROR: fs_fattotsec %d fs_hwnsectors: %d\n", + fs->fs_fattotsec, fs->fs_hwnsectors); + + return -EINVAL; + } + + /* Get the total number of reserved sectors */ + + fs->fs_fatresvdseccount = MBR_GETRESVDSECCOUNT(fs->fs_buffer); + if (fs->fs_fatresvdseccount > fs->fs_hwnsectors) + { + fdbg("ERROR: fs_fatresvdseccount %d fs_hwnsectors: %d\n", + fs->fs_fatresvdseccount, fs->fs_hwnsectors); + + return -EINVAL; + } + + /* Get the number of FATs. This is probably two but could have other values */ + + fs->fs_fatnumfats = MBR_GETNUMFATS(fs->fs_buffer); + ntotalfatsects = fs->fs_fatnumfats * fs->fs_nfatsects; + + /* Get the total number of data sectors */ + + ndatasectors = fs->fs_fattotsec - fs->fs_fatresvdseccount - ntotalfatsects - rootdirsectors; + if (ndatasectors > fs->fs_hwnsectors) + { + fdbg("ERROR: ndatasectors %d fs_hwnsectors: %d\n", + ndatasectors, fs->fs_hwnsectors); + + return -EINVAL; + } + + /* Get the sectors per cluster */ + + fs->fs_fatsecperclus = MBR_GETSECPERCLUS(fs->fs_buffer); + + /* Calculate the number of clusters */ + + fs->fs_nclusters = ndatasectors / fs->fs_fatsecperclus; + + /* Finally, the test: */ + + if (fs->fs_nclusters <= FAT_MAXCLUST12) + { + fs->fs_fsinfo = 0; + fs->fs_type = FSTYPE_FAT12; + } + else if (fs->fs_nclusters <= FAT_MAXCLUST16) + { + fs->fs_fsinfo = 0; + fs->fs_type = FSTYPE_FAT16; + } + else if (!notfat32) + { + fs->fs_fsinfo = fs->fs_fatbase + MBR_GETFSINFO(fs->fs_buffer); + fs->fs_type = FSTYPE_FAT32; + } + else + { + fdbg("ERROR: notfat32: %d fs_nclusters: %d\n", + notfat32, fs->fs_nclusters); + + return -EINVAL; + } + + /* We have what appears to be a valid FAT filesystem! Save a few more things + * from the boot record that we will need later. + */ + + fs->fs_fatbase += fs->fs_fatresvdseccount; + + if (fs->fs_type == FSTYPE_FAT32) + { + fs->fs_rootbase = MBR_GETROOTCLUS(fs->fs_buffer); + } + else + { + fs->fs_rootbase = fs->fs_fatbase + ntotalfatsects; + } + + fs->fs_database = fs->fs_fatbase + ntotalfatsects + fs->fs_rootentcnt / DIRSEC_NDIRS(fs); + fs->fs_fsifreecount = 0xffffffff; + + return OK; +} + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: fat_getuint16 + ****************************************************************************/ + +uint16_t fat_getuint16(uint8_t *ptr) +{ +#ifdef CONFIG_ENDIAN_BIG + /* The bytes always have to be swapped if the target is big-endian */ + + return ((uint16_t)ptr[0] << 8) | ptr[1]; +#else + /* Byte-by-byte transfer is still necessary if the address is un-aligned */ + + return ((uint16_t)ptr[1] << 8) | ptr[0]; +#endif +} + +/**************************************************************************** + * Name: fat_getuint32 + ****************************************************************************/ + +uint32_t fat_getuint32(uint8_t *ptr) +{ +#ifdef CONFIG_ENDIAN_BIG + /* The bytes always have to be swapped if the target is big-endian */ + + return ((uint32_t)fat_getuint16(&ptr[0]) << 16) | fat_getuint16(&ptr[2]); +#else + /* Byte-by-byte transfer is still necessary if the address is un-aligned */ + + return ((uint32_t)fat_getuint16(&ptr[2]) << 16) | fat_getuint16(&ptr[0]); +#endif +} + +/**************************************************************************** + * Name: fat_putuint16 + ****************************************************************************/ + +void fat_putuint16(uint8_t *ptr, uint16_t value16) +{ + uint8_t *val = (uint8_t*)&value16; +#ifdef CONFIG_ENDIAN_BIG + /* The bytes always have to be swapped if the target is big-endian */ + + ptr[0] = val[1]; + ptr[1] = val[0]; +#else + /* Byte-by-byte transfer is still necessary if the address is un-aligned */ + + ptr[0] = val[0]; + ptr[1] = val[1]; +#endif +} + +/**************************************************************************** + * Name: fat_putuint32 + ****************************************************************************/ + +void fat_putuint32(uint8_t *ptr, uint32_t value32) +{ + uint16_t *val = (uint16_t*)&value32; +#ifdef CONFIG_ENDIAN_BIG + /* The bytes always have to be swapped if the target is big-endian */ + + fat_putuint16(&ptr[0], val[2]); + fat_putuint16(&ptr[2], val[0]); +#else + /* Byte-by-byte transfer is still necessary if the address is un-aligned */ + + fat_putuint16(&ptr[0], val[0]); + fat_putuint16(&ptr[2], val[2]); +#endif +} + +/**************************************************************************** + * Name: fat_semtake + ****************************************************************************/ + +void fat_semtake(struct fat_mountpt_s *fs) +{ + /* Take the semaphore (perhaps waiting) */ + + while (sem_wait(&fs->fs_sem) != 0) + { + /* The only case that an error should occur here is if + * the wait was awakened by a signal. + */ + + ASSERT(*get_errno_ptr() == EINTR); + } +} + +/**************************************************************************** + * Name: fat_semgive + ****************************************************************************/ + +void fat_semgive(struct fat_mountpt_s *fs) +{ + sem_post(&fs->fs_sem); +} + +/**************************************************************************** + * Name: fat_systime2fattime + * + * Desciption: Get the system time convert to a time and and date suitble + * for writing into the FAT FS. + * + * TIME in LS 16-bits: + * Bits 0:4 = 2 second count (0-29 representing 0-58 seconds) + * Bits 5-10 = minutes (0-59) + * Bits 11-15 = hours (0-23) + * DATE in MS 16-bits + * Bits 0:4 = Day of month (1-31) + * Bits 5:8 = Month of year (1-12) + * Bits 9:15 = Year from 1980 (0-127 representing 1980-2107) + * + ****************************************************************************/ + +uint32_t fat_systime2fattime(void) +{ + /* Unless you have a hardware RTC or some other to get accurate time, then + * there is no reason to support FAT time. + */ + +#ifdef CONFIG_FS_FATTIME + struct timespec ts; + struct tm tm; + int ret; + + /* Get the current time in seconds and nanoseconds */ + + ret = clock_gettime(CLOCK_REALTIME, &ts); + if (ret == OK) + { + /* Break done the seconds in date and time units */ + + if (gmtime_r((FAR const time_t *)&ts.tv_sec, &tm) != NULL) + { + /* FAT can only represent dates since 1980. struct tm can + * represent dates since 1900. + */ + + if (tm.tm_year >= 80) + { + uint16_t fattime; + uint16_t fatdate; + + fattime = (tm.tm_sec >> 1) & 0x001f; /* Bits 0-4: 2 second count (0-29) */ + fattime |= (tm.tm_min << 5) & 0x07e0; /* Bits 5-10: minutes (0-59) */ + fattime |= (tm.tm_hour << 11) & 0xf800; /* Bits 11-15: hours (0-23) */ + + fatdate = tm.tm_mday & 0x001f; /* Bits 0-4: Day of month (1-31) */ + fatdate |= ((tm.tm_mon+1) << 5) & 0x01e0; /* Bits 5-8: Month of year (1-12) */ + fatdate |= ((tm.tm_year-80) << 9) & 0xfe00; /* Bits 9-15: Year from 1980 */ + + return (uint32_t)fatdate << 16 | (uint32_t)fattime; + } + } + } +#endif + return 0; +} + +/**************************************************************************** + * Name: fat_fattime2systime + * + * Desciption: Convert FAT data and time to a system time_t + * + * 16-bit FAT time: + * Bits 0:4 = 2 second count (0-29 representing 0-58 seconds) + * Bits 5-10 = minutes (0-59) + * Bits 11-15 = hours (0-23) + * 16-bit FAT date: + * Bits 0:4 = Day of month (1-31) + * Bits 5:8 = Month of year (1-12) + * Bits 9:15 = Year from 1980 (0-127 representing 1980-2107) + * + ****************************************************************************/ + +time_t fat_fattime2systime(uint16_t fattime, uint16_t fatdate) +{ + /* Unless you have a hardware RTC or some other to get accurate time, then + * there is no reason to support FAT time. + */ + +#ifdef CONFIG_FS_FATTIME + struct tm tm; + unsigned int tmp; + + /* Break out the date and time */ + + tm.tm_sec = (fattime & 0x001f) << 1; /* Bits 0-4: 2 second count (0-29) */ + tm.tm_min = (fattime & 0x07e0) >> 5; /* Bits 5-10: minutes (0-59) */ + tm.tm_hour = (fattime & 0xf800) >> 11; /* Bits 11-15: hours (0-23) */ + + tm.tm_mday = (fatdate & 0x001f); /* Bits 0-4: Day of month (1-31) */ + tmp = ((fatdate & 0x01e0) >> 5); /* Bits 5-8: Month of year (1-12) */ + tm.tm_mon = tmp > 0 ? tmp-1 : 0; + tm.tm_year = ((fatdate & 0xfe00) >> 9) + 80; /* Bits 9-15: Year from 1980 */ + + /* Then convert the broken out time into seconds since the epoch */ + + return mktime(&tm); +#else + return 0; +#endif +} + +/**************************************************************************** + * Name: fat_mount + * + * Desciption: This function is called only when the mountpoint is first + * established. It initializes the mountpoint structure and verifies + * that a valid FAT32 filesystem is provided by the block driver. + * + * The caller should hold the mountpoint semaphore + * + ****************************************************************************/ + +int fat_mount(struct fat_mountpt_s *fs, bool writeable) +{ + FAR struct inode *inode; + struct geometry geo; + int ret; + + /* Assume that the mount is successful */ + + fs->fs_mounted = true; + + /* Check if there is media available */ + + inode = fs->fs_blkdriver; + if (!inode || !inode->u.i_bops || !inode->u.i_bops->geometry || + inode->u.i_bops->geometry(inode, &geo) != OK || !geo.geo_available) + { + ret = -ENODEV; + goto errout; + } + + /* Make sure that that the media is write-able (if write access is needed) */ + + if (writeable && !geo.geo_writeenabled) + { + ret = -EACCES; + goto errout; + } + + /* Save the hardware geometry */ + + fs->fs_hwsectorsize = geo.geo_sectorsize; + fs->fs_hwnsectors = geo.geo_nsectors; + + /* Allocate a buffer to hold one hardware sector */ + + fs->fs_buffer = (uint8_t*)kmalloc(fs->fs_hwsectorsize); + if (!fs->fs_buffer) + { + ret = -ENOMEM; + goto errout; + } + + /* Search FAT boot record on the drive. First check at sector zero. This + * could be either the boot record or a partition that refers to the boot + * record. + * + * First read sector zero. This will be the first access to the drive and a + * likely failure point. + */ + + fs->fs_fatbase = 0; + ret = fat_hwread(fs, fs->fs_buffer, 0, 1); + if (ret < 0) + { + goto errout_with_buffer; + } + + ret = fat_checkbootrecord(fs); + if (ret != OK) + { + /* The contents of sector 0 is not a boot record. It could be a + * partition, however. Assume it is a partition and get the offset + * into the partition table. This table is at offset MBR_TABLE and is + * indexed by 16x the partition number. + */ + + int i; + for (i = 0; i < 4; i++) + { + /* Check if the partition exists and, if so, get the bootsector for that + * partition and see if we can find the boot record there. + */ + + uint8_t part = PART_GETTYPE(i, fs->fs_buffer); + fvdbg("Partition %d, offset %d, type %d\n", i, PART_ENTRY(i), part); + + if (part == 0) + { + fvdbg("No partition %d\n", i); + continue; + } + + /* There appears to be a partition, get the sector number of the + * partition (LBA) + */ + + fs->fs_fatbase = PART_GETSTARTSECTOR(i, fs->fs_buffer); + + /* Read the new candidate boot sector */ + + ret = fat_hwread(fs, fs->fs_buffer, fs->fs_fatbase, 1); + if (ret < 0) + { + /* Failed to read the sector */ + + goto errout_with_buffer; + } + + /* Check if this is a boot record */ + + ret = fat_checkbootrecord(fs); + if (ret == OK) + { + /* Break out of the loop if a valid boot record is found */ + + fvdbg("MBR found in partition %d\n", i); + break; + } + + /* Re-read sector 0 so that we can check the next partition */ + + fvdbg("Partition %d is not an MBR\n", i); + ret = fat_hwread(fs, fs->fs_buffer, 0, 1); + if (ret < 0) + { + goto errout_with_buffer; + } + } + + if (i > 3) + { + fdbg("No valid MBR\n"); + goto errout_with_buffer; + } + } + + /* We have what appears to be a valid FAT filesystem! Now read the + * FSINFO sector (FAT32 only) + */ + + if (fs->fs_type == FSTYPE_FAT32) + { + ret = fat_checkfsinfo(fs); + if (ret != OK) + { + goto errout_with_buffer; + } + } + + /* We did it! */ + + fdbg("FAT%d:\n", fs->fs_type == 0 ? 12 : fs->fs_type == 1 ? 16 : 32); + fdbg("\tHW sector size: %d\n", fs->fs_hwsectorsize); + fdbg("\t sectors: %d\n", fs->fs_hwnsectors); + fdbg("\tFAT reserved: %d\n", fs->fs_fatresvdseccount); + fdbg("\t sectors: %d\n", fs->fs_fattotsec); + fdbg("\t start sector: %d\n", fs->fs_fatbase); + fdbg("\t root sector: %d\n", fs->fs_rootbase); + fdbg("\t root entries: %d\n", fs->fs_rootentcnt); + fdbg("\t data sector: %d\n", fs->fs_database); + fdbg("\t FSINFO sector: %d\n", fs->fs_fsinfo); + fdbg("\t Num FATs: %d\n", fs->fs_fatnumfats); + fdbg("\t FAT sectors: %d\n", fs->fs_nfatsects); + fdbg("\t sectors/cluster: %d\n", fs->fs_fatsecperclus); + fdbg("\t max clusters: %d\n", fs->fs_nclusters); + fdbg("\tFSI free count %d\n", fs->fs_fsifreecount); + fdbg("\t next free %d\n", fs->fs_fsinextfree); + + return OK; + + errout_with_buffer: + kfree(fs->fs_buffer); + fs->fs_buffer = 0; + errout: + fs->fs_mounted = false; + return ret; +} + +/**************************************************************************** + * Name: fat_checkmount + * + * Desciption: Check if the mountpoint is still valid. + * + * The caller should hold the mountpoint semaphore + * + ****************************************************************************/ + +int fat_checkmount(struct fat_mountpt_s *fs) +{ + /* If the fs_mounted flag is false, then we have already handled the loss + * of the mount. + */ + + if (fs && fs->fs_mounted) + { + struct fat_file_s *file; + + /* We still think the mount is healthy. Check an see if this is + * still the case + */ + + if (fs->fs_blkdriver) + { + struct inode *inode = fs->fs_blkdriver; + if (inode && inode->u.i_bops && inode->u.i_bops->geometry) + { + struct geometry geo; + int errcode = inode->u.i_bops->geometry(inode, &geo); + if (errcode == OK && geo.geo_available && !geo.geo_mediachanged) + { + return OK; + } + } + } + + /* If we get here, the mount is NOT healthy */ + + fs->fs_mounted = false; + + /* Make sure that this is flagged in every opened file */ + + for (file = fs->fs_head; file; file = file->ff_next) + { + file->ff_open = false; + } + } + return -ENODEV; +} + +/**************************************************************************** + * Name: fat_hwread + * + * Desciption: Read the specified sector into the sector buffer + * + ****************************************************************************/ + +int fat_hwread(struct fat_mountpt_s *fs, uint8_t *buffer, off_t sector, + unsigned int nsectors) +{ + int ret = -ENODEV; + if (fs && fs->fs_blkdriver ) + { + struct inode *inode = fs->fs_blkdriver; + if (inode && inode->u.i_bops && inode->u.i_bops->read) + { + ssize_t nSectorsRead = inode->u.i_bops->read(inode, buffer, + sector, nsectors); + if (nSectorsRead == nsectors) + { + ret = OK; + } + else if (nSectorsRead < 0) + { + ret = nSectorsRead; + } + } + } + return ret; +} + +/**************************************************************************** + * Name: fat_hwwrite + * + * Desciption: Write the sector buffer to the specified sector + * + ****************************************************************************/ + +int fat_hwwrite(struct fat_mountpt_s *fs, uint8_t *buffer, off_t sector, + unsigned int nsectors) +{ + int ret = -ENODEV; + if (fs && fs->fs_blkdriver ) + { + struct inode *inode = fs->fs_blkdriver; + if (inode && inode->u.i_bops && inode->u.i_bops->write) + { + ssize_t nSectorsWritten = + inode->u.i_bops->write(inode, buffer, sector, nsectors); + + if (nSectorsWritten == nsectors) + { + ret = OK; + } + else if (nSectorsWritten < 0) + { + ret = nSectorsWritten; + } + } + } + return ret; +} + +/**************************************************************************** + * Name: fat_cluster2sector + * + * Desciption: Convert a cluster number to a start sector number + * + ****************************************************************************/ + +off_t fat_cluster2sector(struct fat_mountpt_s *fs, uint32_t cluster ) +{ + cluster -= 2; + if (cluster >= fs->fs_nclusters - 2) + { + return -EINVAL; + } + return cluster * fs->fs_fatsecperclus + fs->fs_database; +} + +/**************************************************************************** + * Name: fat_getcluster + * + * Desciption: Get the next cluster start from the FAT. + * + * Return: <0: error, 0:cluster unassigned, >=0: start sector of cluster + * + ****************************************************************************/ + +off_t fat_getcluster(struct fat_mountpt_s *fs, uint32_t clusterno) +{ + /* Verify that the cluster number is within range */ + + if (clusterno >= 2 && clusterno < fs->fs_nclusters) + { + /* Okay.. Read the next cluster from the FAT. The way we will do + * this depends on the type of FAT filesystm we are dealing with. + */ + + switch (fs->fs_type) + { + case FSTYPE_FAT12 : + { + off_t fatsector; + unsigned int fatoffset; + unsigned int cluster; + unsigned int fatindex; + + /* FAT12 is more complex because it has 12-bits (1.5 bytes) + * per FAT entry. Get the offset to the first byte: + */ + + fatoffset = (clusterno * 3) / 2; + fatsector = fs->fs_fatbase + SEC_NSECTORS(fs, fatoffset); + + /* Read the sector at this offset */ + + if (fat_fscacheread(fs, fatsector) < 0) + { + /* Read error */ + + break; + } + + /* Get the first, LS byte of the cluster from the FAT */ + + fatindex = fatoffset & SEC_NDXMASK(fs); + cluster = fs->fs_buffer[fatindex]; + + /* With FAT12, the second byte of the cluster number may lie in + * a different sector than the first byte. + */ + + fatindex++; + if (fatindex >= fs->fs_hwsectorsize) + { + fatsector++; + fatindex = 0; + + if (fat_fscacheread(fs, fatsector) < 0) + { + /* Read error */ + + break; + } + } + + /* Get the second, MS byte of the cluster for 16-bits. The + * does not depend on the endian-ness of the target, but only + * on the fact that the byte stream is little-endian. + */ + + cluster |= (unsigned int)fs->fs_buffer[fatindex] << 8; + + /* Now, pick out the correct 12 bit cluster start sector value */ + + if ((clusterno & 1) != 0) + { + /* Odd.. take the MS 12-bits */ + + cluster >>= 4; + } + else + { + /* Even.. take the LS 12-bits */ + + cluster &= 0x0fff; + } + return cluster; + } + + case FSTYPE_FAT16 : + { + unsigned int fatoffset = 2 * clusterno; + off_t fatsector = fs->fs_fatbase + SEC_NSECTORS(fs, fatoffset); + unsigned int fatindex = fatoffset & SEC_NDXMASK(fs); + + if (fat_fscacheread(fs, fatsector) < 0) + { + /* Read error */ + break; + } + return FAT_GETFAT16(fs->fs_buffer, fatindex); + } + + case FSTYPE_FAT32 : + { + unsigned int fatoffset = 4 * clusterno; + off_t fatsector = fs->fs_fatbase + SEC_NSECTORS(fs, fatoffset); + unsigned int fatindex = fatoffset & SEC_NDXMASK(fs); + + if (fat_fscacheread(fs, fatsector) < 0) + { + /* Read error */ + break; + } + return FAT_GETFAT32(fs->fs_buffer, fatindex) & 0x0fffffff; + } + default: + break; + } + } + + /* There is no cluster information, or an error occured */ + + return (off_t)-EINVAL; +} + +/**************************************************************************** + * Name: fat_putcluster + * + * Desciption: Write a new cluster into the FAT + * + ****************************************************************************/ + +int fat_putcluster(struct fat_mountpt_s *fs, uint32_t clusterno, off_t nextcluster) +{ + /* Verify that the cluster number is within range. Zero erases the cluster. */ + + if (clusterno == 0 || (clusterno >= 2 && clusterno < fs->fs_nclusters)) + { + /* Okay.. Write the next cluster into the FAT. The way we will do + * this depends on the type of FAT filesystm we are dealing with. + */ + + switch (fs->fs_type) + { + case FSTYPE_FAT12 : + { + off_t fatsector; + unsigned int fatoffset; + unsigned int fatindex; + uint8_t value; + + /* FAT12 is more complex because it has 12-bits (1.5 bytes) + * per FAT entry. Get the offset to the first byte: + */ + + fatoffset = (clusterno * 3) / 2; + fatsector = fs->fs_fatbase + SEC_NSECTORS(fs, fatoffset); + + /* Make sure that the sector at this offset is in the cache */ + + if (fat_fscacheread(fs, fatsector)< 0) + { + /* Read error */ + + break; + } + + /* Get the LS byte first handling the 12-bit alignment within + * the 16-bits + */ + + fatindex = fatoffset & SEC_NDXMASK(fs); + if ((clusterno & 1) != 0) + { + /* Save the LS four bits of the next cluster */ + + value = (fs->fs_buffer[fatindex] & 0x0f) | nextcluster << 4; + } + else + { + /* Save the LS eight bits of the next cluster */ + + value = (uint8_t)nextcluster; + } + + fs->fs_buffer[fatindex] = value; + + /* With FAT12, the second byte of the cluster number may lie in + * a different sector than the first byte. + */ + + fatindex++; + if (fatindex >= fs->fs_hwsectorsize) + { + /* Read the next sector */ + + fatsector++; + fatindex = 0; + + /* Set the dirty flag to make sure the sector that we + * just modified is written out. + */ + + fs->fs_dirty = true; + if (fat_fscacheread(fs, fatsector) < 0) + { + /* Read error */ + + break; + } + } + + /* Output the MS byte first handling the 12-bit alignment within + * the 16-bits + */ + + if ((clusterno & 1) != 0) + { + /* Save the MS eight bits of the next cluster */ + + value = (uint8_t)(nextcluster >> 4); + } + else + { + /* Save the MS four bits of the next cluster */ + + value = (fs->fs_buffer[fatindex] & 0xf0) | ((nextcluster >> 8) & 0x0f); + } + + fs->fs_buffer[fatindex] = value; + } + break; + + case FSTYPE_FAT16 : + { + unsigned int fatoffset = 2 * clusterno; + off_t fatsector = fs->fs_fatbase + SEC_NSECTORS(fs, fatoffset); + unsigned int fatindex = fatoffset & SEC_NDXMASK(fs); + + if (fat_fscacheread(fs, fatsector) < 0) + { + /* Read error */ + + break; + } + FAT_PUTFAT16(fs->fs_buffer, fatindex, nextcluster & 0xffff); + } + break; + + case FSTYPE_FAT32 : + { + unsigned int fatoffset = 4 * clusterno; + off_t fatsector = fs->fs_fatbase + SEC_NSECTORS(fs, fatoffset); + unsigned int fatindex = fatoffset & SEC_NDXMASK(fs); + + if (fat_fscacheread(fs, fatsector) < 0) + { + /* Read error */ + + break; + } + FAT_PUTFAT32(fs->fs_buffer, fatindex, nextcluster & 0x0fffffff); + } + break; + + default: + return -EINVAL; + } + + /* Mark the modified sector as "dirty" and return success */ + + fs->fs_dirty = true; + return OK; + } + + return -EINVAL; +} + +/**************************************************************************** + * Name: fat_removechain + * + * Desciption: Remove an entire chain of clusters, starting with 'cluster' + * + ****************************************************************************/ + +int fat_removechain(struct fat_mountpt_s *fs, uint32_t cluster) +{ + int32_t nextcluster; + int ret; + + /* Loop while there are clusters in the chain */ + + while (cluster >= 2 && cluster < fs->fs_nclusters) + { + /* Get the next cluster after the current one */ + + nextcluster = fat_getcluster(fs, cluster); + if (nextcluster < 0) + { + /* Error! */ + return nextcluster; + } + + /* Then nullify current cluster -- removing it from the chain */ + + ret = fat_putcluster(fs, cluster, 0); + if (ret < 0) + { + return ret; + } + + /* Update FSINFINFO data */ + + if (fs->fs_fsifreecount != 0xffffffff) + { + fs->fs_fsifreecount++; + fs->fs_fsidirty = 1; + } + + /* Then set up to remove the next cluster */ + + cluster = nextcluster; + } + + return OK; +} + +/**************************************************************************** + * Name: fat_extendchain + * + * Desciption: Add a new cluster to the chain following cluster (if cluster + * is non-NULL). if cluster is zero, then a new chain is created. + * + * Return: <0:error, 0: no free cluster, >=2: new cluster number + * + ****************************************************************************/ + +int32_t fat_extendchain(struct fat_mountpt_s *fs, uint32_t cluster) +{ + off_t startsector; + uint32_t newcluster; + uint32_t startcluster; + int ret; + + /* The special value 0 is used when the new chain should start */ + + if (cluster == 0) + { + /* The FSINFO NextFree entry should be a good starting point + * in the search for a new cluster + */ + + startcluster = fs->fs_fsinextfree; + if (startcluster == 0 || startcluster >= fs->fs_nclusters) + { + /* But it is bad.. we have to start at the beginning */ + startcluster = 1; + } + } + else + { + /* We are extending an existing chain. Verify that this + * is a valid cluster by examining its start sector. + */ + + startsector = fat_getcluster(fs, cluster); + if (startsector < 0) + { + /* An error occurred, return the error value */ + + return startsector; + } + else if (startsector < 2) + { + /* Oops.. this cluster does not exist. */ + + return 0; + } + else if (startsector < fs->fs_nclusters) + { + /* It is already followed by next cluster */ + + return startsector; + } + + /* Okay.. it checks out */ + + startcluster = cluster; + } + + /* Loop until (1) we discover that there are not free clusters + * (return 0), an errors occurs (return -errno), or (3) we find + * the next cluster (return the new cluster number). + */ + + newcluster = startcluster; + for (;;) + { + /* Examine the next cluster in the FAT */ + + newcluster++; + if (newcluster >= fs->fs_nclusters) + { + /* If we hit the end of the available clusters, then + * wrap back to the beginning because we might have + * started at a non-optimal place. But don't continue + * past the start cluster. + */ + + newcluster = 2; + if (newcluster > startcluster) + { + /* We are back past the starting cluster, then there + * is no free cluster. + */ + + return 0; + } + } + + /* We have a candidate cluster. Check if the cluster number is + * mapped to a group of sectors. + */ + + startsector = fat_getcluster(fs, newcluster); + if (startsector == 0) + { + /* Found have found a free cluster break out*/ + break; + } + else if (startsector < 0) + { + /* Some error occurred, return the error number */ + return startsector; + } + + /* We wrap all the back to the starting cluster? If so, then + * there are no free clusters. + */ + + if (newcluster == startcluster) + { + return 0; + } + } + + /* We get here only if we break out with an available cluster + * number in 'newcluster' Now mark that cluster as in-use. + */ + + ret = fat_putcluster(fs, newcluster, 0x0fffffff); + if (ret < 0) + { + /* An error occurred */ + return ret; + } + + /* And link if to the start cluster (if any)*/ + + if (cluster) + { + /* There is a start cluster -- link it */ + + ret = fat_putcluster(fs, cluster, newcluster); + if (ret < 0) + { + return ret; + } + } + + /* And update the FINSINFO for the next time we have to search */ + + fs->fs_fsinextfree = newcluster; + if (fs->fs_fsifreecount != 0xffffffff) + { + fs->fs_fsifreecount--; + fs->fs_fsidirty = 1; + } + + /* Return then number of the new cluster that was added to the chain */ + + return newcluster; +} + +/**************************************************************************** + * Name: fat_nextdirentry + * + * Desciption: Read the next directory entry from the sector in cache, + * reading the next sector(s) in the cluster as necessary. This function + * must return -ENOSPC if if fails because there are no further entries + * available in the directory. + * + ****************************************************************************/ + +int fat_nextdirentry(struct fat_mountpt_s *fs, struct fs_fatdir_s *dir) +{ + unsigned int cluster; + unsigned int ndx; + + /* Increment the index to the next 32-byte directory entry */ + + ndx = dir->fd_index + 1; + + /* Check if all of the directory entries in this sectory have + * been examined. + */ + + if ((ndx & (DIRSEC_NDIRS(fs)-1)) == 0) + { + /* Yes, then we will have to read the next sector */ + + dir->fd_currsector++; + + /* For FAT12/16, the root directory is a group of sectors relative + * to the first sector of the fat volume. + */ + + if (!dir->fd_currcluster) + { + /* For FAT12/16, the boot record tells us number of 32-bit directories + * that are contained in the root directory. This should correspond to + * an even number of sectors. + */ + + if (ndx >= fs->fs_rootentcnt) + { + /* When we index past this count, we have examined all of the entries in + * the root directory. + */ + + return -ENOSPC; + } + } + else + { + /* Not a FAT12/16 root directory, check if we have examined the entire + * cluster comprising the directory. + * + * The current sector within the cluster is the entry number divided + * byte the number of entries per sector + */ + + int sector = ndx / DIRSEC_NDIRS(fs); + + /* We are finished with the cluster when the last sector of the cluster + * has been examined. + */ + + if ((sector & (fs->fs_fatsecperclus-1)) == 0) + { + /* Get next cluster */ + + cluster = fat_getcluster(fs, dir->fd_currcluster); + + /* Check if a valid cluster was obtained. */ + + if (cluster < 2 || cluster >= fs->fs_nclusters) + { + /* No, we have probably reached the end of the cluster list */ + + return -ENOSPC; + } + + /* Initialize for new cluster */ + + dir->fd_currcluster = cluster; + dir->fd_currsector = fat_cluster2sector(fs, cluster); + } + } + } + + /* Save the new index into dir->fd_currsector */ + + dir->fd_index = ndx; + return OK; +} + +/**************************************************************************** + * Name: fat_dirtruncate + * + * Desciption: Truncate an existing file to zero length + * + * Assumptions: The caller holds mountpoint semaphore, fs_buffer holds + * the directory entry, the directory entry sector (fd_sector) is + * currently in the sector cache. + * + ****************************************************************************/ + +int fat_dirtruncate(struct fat_mountpt_s *fs, struct fat_dirinfo_s *dirinfo) +{ + unsigned int startcluster; + uint32_t writetime; + uint8_t *direntry; + off_t savesector; + int ret; + + /* Get start cluster of the file to truncate */ + + direntry = &fs->fs_buffer[dirinfo->fd_seq.ds_offset]; + startcluster = + ((uint32_t)DIR_GETFSTCLUSTHI(direntry) << 16) | + DIR_GETFSTCLUSTLO(direntry); + + /* Clear the cluster start value in the directory and set the file size + * to zero. This makes the file look empty but also have to dispose of + * all of the clusters in the chain. + */ + + DIR_PUTFSTCLUSTHI(direntry, 0); + DIR_PUTFSTCLUSTLO(direntry, 0); + DIR_PUTFILESIZE(direntry, 0); + + /* Set the ARCHIVE attribute and update the write time */ + + DIR_PUTATTRIBUTES(direntry, FATATTR_ARCHIVE); + + writetime = fat_systime2fattime(); + DIR_PUTWRTTIME(direntry, writetime & 0xffff); + DIR_PUTWRTDATE(direntry, writetime > 16); + + /* This sector needs to be written back to disk eventually */ + + fs->fs_dirty = true; + + /* Now remove the entire cluster chain comprising the file */ + + savesector = fs->fs_currentsector; + ret = fat_removechain(fs, startcluster); + if (ret < 0) + { + return ret; + } + + /* Setup FSINFO to resuse this cluster next */ + + fs->fs_fsinextfree = startcluster - 1; + + /* Make sure that the directory is still in the cache */ + + return fat_fscacheread(fs, savesector); +} + +/**************************************************************************** + * Name: fat_fscacheflush + * + * Desciption: Flush any dirty sector if fs_buffer as necessary + * + ****************************************************************************/ + +int fat_fscacheflush(struct fat_mountpt_s *fs) +{ + int ret; + + /* Check if the fs_buffer is dirty. In this case, we will write back the + * contents of fs_buffer. + */ + + if (fs->fs_dirty) + { + /* Write the dirty sector */ + + ret = fat_hwwrite(fs, fs->fs_buffer, fs->fs_currentsector, 1); + if (ret < 0) + { + return ret; + } + + /* Does the sector lie in the FAT region? */ + + if (fs->fs_currentsector >= fs->fs_fatbase && + fs->fs_currentsector < fs->fs_fatbase + fs->fs_nfatsects) + { + /* Yes, then make the change in the FAT copy as well */ + int i; + + for (i = fs->fs_fatnumfats; i >= 2; i--) + { + fs->fs_currentsector += fs->fs_nfatsects; + ret = fat_hwwrite(fs, fs->fs_buffer, fs->fs_currentsector, 1); + if (ret < 0) + { + return ret; + } + } + } + + /* No longer dirty */ + + fs->fs_dirty = false; + } + return OK; +} + +/**************************************************************************** + * Name: fat_fscacheread + * + * Desciption: Read the specified sector into the sector cache, flushing any + * existing dirty sectors as necessary. + * + ****************************************************************************/ + +int fat_fscacheread(struct fat_mountpt_s *fs, off_t sector) +{ + int ret; + + /* fs->fs_currentsector holds the current sector that is buffered in + * fs->fs_buffer. If the requested sector is the same as this sector, then + * we do nothing. Otherwise, we will have to read the new sector. + */ + + if (fs->fs_currentsector != sector) + { + /* We will need to read the new sector. First, flush the cached + * sector if it is dirty. + */ + + ret = fat_fscacheflush(fs); + if (ret < 0) + { + return ret; + } + + /* Then read the specified sector into the cache */ + + ret = fat_hwread(fs, fs->fs_buffer, sector, 1); + if (ret < 0) + { + return ret; + } + + /* Update the cached sector number */ + + fs->fs_currentsector = sector; + } + + return OK; +} + +/**************************************************************************** + * Name: fat_ffcacheflush + * + * Desciption: Flush any dirty sectors as necessary + * + ****************************************************************************/ + +int fat_ffcacheflush(struct fat_mountpt_s *fs, struct fat_file_s *ff) +{ + int ret; + + /* Check if the ff_buffer is dirty. In this case, we will write back the + * contents of ff_buffer. + */ + + if (ff->ff_cachesector && + ff->ff_bflags && (FFBUFF_DIRTY|FFBUFF_VALID) == (FFBUFF_DIRTY|FFBUFF_VALID)) + { + /* Write the dirty sector */ + + ret = fat_hwwrite(fs, ff->ff_buffer, ff->ff_cachesector, 1); + if (ret < 0) + { + return ret; + } + + /* No longer dirty, but still valid */ + + ff->ff_bflags &= ~FFBUFF_DIRTY; + } + + return OK; +} + +/**************************************************************************** + * Name: fat_ffcacheread + * + * Desciption: Read the specified sector into the sector cache, flushing any + * existing dirty sectors as necessary. + * + ****************************************************************************/ + +int fat_ffcacheread(struct fat_mountpt_s *fs, struct fat_file_s *ff, off_t sector) +{ + int ret; + + /* ff->ff_cachesector holds the current sector that is buffered in + * ff->ff_buffer. If the requested sector is the same as this sector, then + * we do nothing. Otherwise, we will have to read the new sector. + */ + + if (ff->ff_cachesector != sector || (ff->ff_bflags & FFBUFF_VALID) == 0) + { + /* We will need to read the new sector. First, flush the cached + * sector if it is dirty. + */ + + ret = fat_ffcacheflush(fs, ff); + if (ret < 0) + { + return ret; + } + + /* Then read the specified sector into the cache */ + + ret = fat_hwread(fs, ff->ff_buffer, sector, 1); + if (ret < 0) + { + return ret; + } + + /* Update the cached sector number */ + + ff->ff_cachesector = sector; + ff->ff_bflags |= FFBUFF_VALID; + } + return OK; +} + +/**************************************************************************** + * Name: fat_ffcacheread + * + * Desciption: Invalidate the current file buffer contents + * + ****************************************************************************/ + +int fat_ffcacheinvalidate(struct fat_mountpt_s *fs, struct fat_file_s *ff) +{ + int ret; + + /* Is there anything valid in the buffer now? */ + + if ((ff->ff_bflags & FFBUFF_VALID) != 0) + { + /* We will invalidate the buffered sector */ + + ret = fat_ffcacheflush(fs, ff); + if (ret < 0) + { + return ret; + } + + /* Then discard the current cache contents */ + + ff->ff_bflags &= ~FFBUFF_VALID; + ff->ff_cachesector = 0; + } + return OK; +} + +/**************************************************************************** + * Name: fat_updatefsinfo + * + * Desciption: Flush evertyhing buffered for the mountpoint and update + * the FSINFO sector, if appropriate + * + ****************************************************************************/ + +int fat_updatefsinfo(struct fat_mountpt_s *fs) +{ + int ret; + + /* Flush the fs_buffer if it is dirty */ + + ret = fat_fscacheflush(fs); + if (ret == OK) + { + /* The FSINFO sector only has to be update for the case of a FAT32 file + * system. Check if the file system type.. If this is a FAT32 file + * system then the fs_fsidirty flag will indicate if the FSINFO sector + * needs to be re-written. + */ + + if (fs->fs_type == FSTYPE_FAT32 && fs->fs_fsidirty) + { + /* Create an image of the FSINFO sector in the fs_buffer */ + + memset(fs->fs_buffer, 0, fs->fs_hwsectorsize); + FSI_PUTLEADSIG(fs->fs_buffer, 0x41615252); + FSI_PUTSTRUCTSIG(fs->fs_buffer, 0x61417272); + FSI_PUTFREECOUNT(fs->fs_buffer, fs->fs_fsifreecount); + FSI_PUTNXTFREE(fs->fs_buffer, fs->fs_fsinextfree); + FSI_PUTTRAILSIG(fs->fs_buffer, BOOT_SIGNATURE32); + + /* Then flush this to disk */ + + fs->fs_currentsector = fs->fs_fsinfo; + fs->fs_dirty = true; + ret = fat_fscacheflush(fs); + + /* No longer dirty */ + + fs->fs_fsidirty = false; + } + } + return ret; +} + +/**************************************************************************** + * Name: fat_nfreeclusters + * + * Desciption: Get the number of free clusters + * + ****************************************************************************/ + +int fat_nfreeclusters(struct fat_mountpt_s *fs, off_t *pfreeclusters) +{ + uint32_t nfreeclusters; + + /* If number of the first free cluster is valid, then just return that value. */ + + if (fs->fs_fsifreecount <= fs->fs_nclusters - 2) + { + *pfreeclusters = fs->fs_fsifreecount; + return OK; + } + + /* Otherwise, we will have to count the number of free clusters */ + + nfreeclusters = 0; + if (fs->fs_type == FSTYPE_FAT12) + { + off_t sector; + + /* Examine every cluster in the fat */ + + for (sector = 2; sector < fs->fs_nclusters; sector++) + { + + /* If the cluster is unassigned, then increment the count of free clusters */ + + if ((uint16_t)fat_getcluster(fs, sector) == 0) + { + nfreeclusters++; + } + } + } + else + { + unsigned int cluster; + off_t fatsector; + unsigned int offset; + int ret; + + fatsector = fs->fs_fatbase; + offset = fs->fs_hwsectorsize; + + /* Examine each cluster in the fat */ + + for (cluster = fs->fs_nclusters; cluster > 0; cluster--) + { + /* If we are starting a new sector, then read the new sector in fs_buffer */ + + if (offset >= fs->fs_hwsectorsize) + { + ret = fat_fscacheread(fs, fatsector++); + if (ret < 0) + { + return ret; + } + + /* Reset the offset to the next FAT entry. + * Increment the sector number to read next time around. + */ + + offset = 0; + fatsector++; + } + + /* FAT16 and FAT32 differ only on the size of each cluster start + * sector number in the FAT. + */ + + if (fs->fs_type == FSTYPE_FAT16) + { + if (FAT_GETFAT16(fs->fs_buffer, offset) == 0) + { + nfreeclusters++; + } + offset += 2; + } + else + { + if (FAT_GETFAT32(fs->fs_buffer, offset) == 0) + { + nfreeclusters++; + } + + offset += 4; + } + } + } + + fs->fs_fsifreecount = nfreeclusters; + if (fs->fs_type == FSTYPE_FAT32) + { + fs->fs_fsidirty = true; + } + + *pfreeclusters = nfreeclusters; + return OK; +} + +/**************************************************************************** + * Name: fat_nfreeclusters + * + * Desciption: + * Given the file position, set the correct current sector to access. + * + ****************************************************************************/ + +int fat_currentsector(struct fat_mountpt_s *fs, struct fat_file_s *ff, + off_t position) +{ + int sectoroffset; + + if (position <= ff->ff_size ) + { + /* sectoroffset is the sector number offset into the current cluster */ + + sectoroffset = SEC_NSECTORS(fs, position) & CLUS_NDXMASK(fs); + + /* The current cluster is the first sector of the cluster plus + * the sector offset + */ + + ff->ff_currentsector = fat_cluster2sector(fs, ff->ff_currentcluster) + + sectoroffset; + + /* The remainder is the number of sectors left in the cluster to be + * read/written + */ + + ff->ff_sectorsincluster = fs->fs_fatsecperclus - sectoroffset; + + fvdbg("position=%d currentsector=%d sectorsincluster=%d\n", + position, ff->ff_currentsector, ff->ff_sectorsincluster); + + return OK; + } + + /* The position does not lie within the file */ + + return -ENOSPC; +} + + |