fat.c

AVR 单片机上实现SD卡的读写

/* 
 * Copyright (c) 2006-2008 by Roland Riegel <[e-mail]>
 *
 * This file is free software; you can redistribute it and/or modify
 * it under the terms of either the GNU General Public License version 2
 * or the GNU Lesser General Public License version 2.1, both as
 * published by the Free Software Foundation.
 */

#include "byteordering.h"
#include "partition.h"
#include "fat.h"
#include "fat_config.h"
#include "sd-reader_config.h"

#include <string.h>

#if USE_DYNAMIC_MEMORY
    #include <stdlib.h>
#endif

/**
 * \addtogroup fat FAT support
 *
 * This module implements FAT16/FAT32 read and write access.
 * 
 * The following features are supported:
 * - File names up to 31 characters long.
 * - Unlimited depth of subdirectories.
 * - Short 8.3 and long filenames.
 * - Creating and deleting files.
 * - Reading and writing from and to files.
 * - File resizing.
 * - File sizes of up to 4 gigabytes.
 * 
 * @{
 */
/**
 * \file
 * FAT implementation (license: GPLv2 or LGPLv2.1)
 *
 * \author Roland Riegel
 */

/**
 * \addtogroup fat_config FAT configuration
 * Preprocessor defines to configure the FAT implementation.
 */

/**
 * \addtogroup fat_fs FAT access
 * Basic functions for handling a FAT filesystem.
 */

/**
 * \addtogroup fat_file FAT file functions
 * Functions for managing files.
 */

/**
 * \addtogroup fat_dir FAT directory functions
 * Functions for managing directories.
 */

/**
 * @}
 */

#define FAT16_CLUSTER_FREE 0x0000
#define FAT16_CLUSTER_RESERVED_MIN 0xfff0
#define FAT16_CLUSTER_RESERVED_MAX 0xfff6
#define FAT16_CLUSTER_BAD 0xfff7
#define FAT16_CLUSTER_LAST_MIN 0xfff8
#define FAT16_CLUSTER_LAST_MAX 0xffff

#define FAT32_CLUSTER_FREE 0x00000000
#define FAT32_CLUSTER_RESERVED_MIN 0x0ffffff0
#define FAT32_CLUSTER_RESERVED_MAX 0x0ffffff6
#define FAT32_CLUSTER_BAD 0x0ffffff7
#define FAT32_CLUSTER_LAST_MIN 0x0ffffff8
#define FAT32_CLUSTER_LAST_MAX 0x0fffffff

#define FAT_DIRENTRY_DELETED 0xe5
#define FAT_DIRENTRY_LFNLAST (1 << 6)
#define FAT_DIRENTRY_LFNSEQMASK ((1 << 6) - 1)

/* Each entry within the directory table has a size of 32 bytes
 * and either contains a 8.3 DOS-style file name or a part of a
 * long file name, which may consist of several directory table
 * entries at once.
 *
 * multi-byte integer values are stored little-endian!
 *
 * 8.3 file name entry:
 * ====================
 * offset  length  description
 *      0       8  name (space padded)
 *      8       3  extension (space padded)
 *     11       1  attributes (FAT_ATTRIB_*)
 *
 * long file name (lfn) entry ordering for a single file name:
 * ===========================================================
 * LFN entry n
 *     ...
 * LFN entry 2
 * LFN entry 1
 * 8.3 entry (see above)
 * 
 * lfn entry:
 * ==========
 * offset  length  description
 *      0       1  ordinal field
 *      1       2  unicode character 1
 *      3       3  unicode character 2
 *      5       3  unicode character 3
 *      7       3  unicode character 4
 *      9       3  unicode character 5
 *     11       1  attribute (always 0x0f)
 *     12       1  type (reserved, always 0)
 *     13       1  checksum
 *     14       2  unicode character 6
 *     16       2  unicode character 7
 *     18       2  unicode character 8
 *     20       2  unicode character 9
 *     22       2  unicode character 10
 *     24       2  unicode character 11
 *     26       2  cluster (unused, always 0)
 *     28       2  unicode character 12
 *     30       2  unicode character 13
 * 
 * The ordinal field contains a descending number, from n to 1.
 * For the n'th lfn entry the ordinal field is or'ed with 0x40.
 * For deleted lfn entries, the ordinal field is set to 0xe5.
 */

struct fat_header_struct
{
    offset_t size;

    offset_t fat_offset;
    uint32_t fat_size;

    uint16_t sector_size;
    uint16_t cluster_size;

    offset_t cluster_zero_offset;

    offset_t root_dir_offset;
#if FAT_FAT32_SUPPORT
    cluster_t root_dir_cluster;
#endif
};

struct fat_fs_struct
{
    struct partition_struct* partition;
    struct fat_header_struct header;
};

struct fat_file_struct
{
    struct fat_fs_struct* fs;
    struct fat_dir_entry_struct dir_entry;
    offset_t pos;
    cluster_t pos_cluster;
};

struct fat_dir_struct
{
    struct fat_fs_struct* fs;
    struct fat_dir_entry_struct dir_entry;
    cluster_t entry_cluster;
    uint16_t entry_offset;
};

struct fat_read_dir_callback_arg
{
    struct fat_dir_entry_struct* dir_entry;
    uintptr_t bytes_read;
    uint8_t finished;
};

struct fat_usage_count_callback_arg
{
    cluster_t cluster_count;
    uintptr_t buffer_size;
};

#if !USE_DYNAMIC_MEMORY
static struct fat_fs_struct fat_fs_handles[FAT_FS_COUNT];
static struct fat_file_struct fat_file_handles[FAT_FILE_COUNT];
static struct fat_dir_struct fat_dir_handles[FAT_DIR_COUNT];
#endif

static uint8_t fat_read_header(struct fat_fs_struct* fs);
static cluster_t fat_get_next_cluster(const struct fat_fs_struct* fs, cluster_t cluster_num);
static offset_t fat_cluster_offset(const struct fat_fs_struct* fs, cluster_t cluster_num);
static uint8_t fat_dir_entry_read_callback(uint8_t* buffer, offset_t offset, void* p);
static uint8_t fat_interpret_dir_entry(struct fat_dir_entry_struct* dir_entry, const uint8_t* raw_entry);

static uint8_t fat_get_fs_free_16_callback(uint8_t* buffer, offset_t offset, void* p);
#if FAT_FAT32_SUPPORT
static uint8_t fat_get_fs_free_32_callback(uint8_t* buffer, offset_t offset, void* p);
#endif

#if FAT_WRITE_SUPPORT
static cluster_t fat_append_clusters(const struct fat_fs_struct* fs, cluster_t cluster_num, cluster_t count);
static uint8_t fat_free_clusters(const struct fat_fs_struct* fs, cluster_t cluster_num);
static uint8_t fat_terminate_clusters(const struct fat_fs_struct* fs, cluster_t cluster_num);
static uint8_t fat_clear_cluster(const struct fat_fs_struct* fs, cluster_t cluster_num);
static uintptr_t fat_clear_cluster_callback(uint8_t* buffer, offset_t offset, void* p);
static offset_t fat_find_offset_for_dir_entry(const struct fat_fs_struct* fs, const struct fat_dir_struct* parent, const struct fat_dir_entry_struct* dir_entry);
static uint8_t fat_write_dir_entry(const struct fat_fs_struct* fs, struct fat_dir_entry_struct* dir_entry);
#if FAT_DATETIME_SUPPORT
static void fat_set_file_modification_date(struct fat_dir_entry_struct* dir_entry, uint16_t year, uint8_t month, uint8_t day);
static void fat_set_file_modification_time(struct fat_dir_entry_struct* dir_entry, uint8_t hour, uint8_t min, uint8_t sec);
#endif
#endif

/**
 * \ingroup fat_fs
 * Opens a FAT filesystem.
 *
 * \param[in] partition Discriptor of partition on which the filesystem resides.
 * \returns 0 on error, a FAT filesystem descriptor on success.
 * \see fat_close
 */
struct fat_fs_struct* fat_open(struct partition_struct* partition)
{
    if(!partition ||
#if FAT_WRITE_SUPPORT
       !partition->device_write ||
       !partition->device_write_interval
#else
       0
#endif
      )
        return 0;

#if USE_DYNAMIC_MEMORY
    struct fat_fs_struct* fs = malloc(sizeof(*fs));
    if(!fs)
        return 0;
#else
    struct fat_fs_struct* fs = fat_fs_handles;
    uint8_t i;
    for(i = 0; i < FAT_FS_COUNT; ++i)
    {
        if(!fs->partition)
            break;

        ++fs;
    }
    if(i >= FAT_FS_COUNT)
        return 0;
#endif

    memset(fs, 0, sizeof(*fs));

    fs->partition = partition;
    if(!fat_read_header(fs))
    {
#if USE_DYNAMIC_MEMORY
        free(fs);
#else
        fs->partition = 0;
#endif
        return 0;
    }
    
    return fs;
}

/**
 * \ingroup fat_fs
 * Closes a FAT filesystem.
 *
 * When this function returns, the given filesystem descriptor
 * will be invalid.
 *
 * \param[in] fs The filesystem to close.
 * \see fat_open
 */
void fat_close(struct fat_fs_struct* fs)
{
    if(!fs)
        return;

#if USE_DYNAMIC_MEMORY
    free(fs);
#else
    fs->partition = 0;
#endif
}

/**
 * \ingroup fat_fs
 * Reads and parses the header of a FAT filesystem.
 *
 * \param[inout] fs The filesystem for which to parse the header.
 * \returns 0 on failure, 1 on success.
 */
uint8_t fat_read_header(struct fat_fs_struct* fs)
{
    if(!fs)
        return 0;

    struct partition_struct* partition = fs->partition;
    if(!partition)
        return 0;

    /* read fat parameters */
#if FAT_FAT32_SUPPORT
    uint8_t buffer[37];
#else
    uint8_t buffer[25];
#endif
    offset_t partition_offset = (offset_t) partition->offset * 512;
    if(!partition->device_read(partition_offset + 0x0b, buffer, sizeof(buffer)))
        return 0;

    uint16_t bytes_per_sector = ltoh16(*((uint16_t*) &buffer[0x00]));
    uint16_t reserved_sectors = ltoh16(*((uint16_t*) &buffer[0x03]));
    uint8_t sectors_per_cluster = buffer[0x02];
    uint8_t fat_copies = buffer[0x05];
    uint16_t max_root_entries = ltoh16(*((uint16_t*) &buffer[0x06]));
    uint16_t sector_count_16 = ltoh16(*((uint16_t*) &buffer[0x08]));
    uint16_t sectors_per_fat = ltoh16(*((uint16_t*) &buffer[0x0b]));
    uint32_t sector_count = ltoh32(*((uint32_t*) &buffer[0x15]));
#if FAT_FAT32_SUPPORT
    uint32_t sectors_per_fat32 = ltoh32(*((uint32_t*) &buffer[0x19]));
    uint32_t cluster_root_dir = ltoh32(*((uint32_t*) &buffer[0x21]));
#endif

    if(sector_count == 0)
    {
        if(sector_count_16 == 0)
            /* illegal volume size */
            return 0;
        else
            sector_count = sector_count_16;
    }
#if FAT_FAT32_SUPPORT
    if(sectors_per_fat != 0)
        sectors_per_fat32 = sectors_per_fat;
    else if(sectors_per_fat32 == 0)
        /* this is neither FAT16 nor FAT32 */
        return 0;
#else
    if(sectors_per_fat == 0)
        /* this is not a FAT16 */
        return 0;
#endif

    /* determine the type of FAT we have here */
    uint32_t data_sector_count = sector_count
                                 - reserved_sectors
#if FAT_FAT32_SUPPORT
                                 - sectors_per_fat32 * fat_copies
#else
                                 - (uint32_t) sectors_per_fat * fat_copies
#endif
                                 - ((max_root_entries * 32 + bytes_per_sector - 1) / bytes_per_sector);
    uint32_t data_cluster_count = data_sector_count / sectors_per_cluster;
    if(data_cluster_count < 4085)
        /* this is a FAT12, not supported */
        return 0;
    else if(data_cluster_count < 65525)
        /* this is a FAT16 */
        partition->type = PARTITION_TYPE_FAT16;
    else
        /* this is a FAT32 */
        partition->type = PARTITION_TYPE_FAT32;

    /* fill header information */
    struct fat_header_struct* header = &fs->header;
    memset(header, 0, sizeof(*header));
    
    header->size = (offset_t) sector_count * bytes_per_sector;

    header->fat_offset = /* jump to partition */
                         partition_offset +
                         /* jump to fat */
                         (offset_t) reserved_sectors * bytes_per_sector;
    header->fat_size = (data_cluster_count + 2) * sizeof(cluster_t);

    header->sector_size = bytes_per_sector;
    header->cluster_size = (uint16_t) bytes_per_sector * sectors_per_cluster;

#if FAT_FAT32_SUPPORT
    if(partition->type == PARTITION_TYPE_FAT16)
#endif
    {
        header->root_dir_offset = /* jump to fats */
                                  header->fat_offset +
                                  /* jump to root directory entries */
                                  (offset_t) fat_copies * sectors_per_fat * bytes_per_sector;

        header->cluster_zero_offset = /* jump to root directory entries */
                                      header->root_dir_offset +
                                      /* skip root directory entries */
                                      (offset_t) max_root_entries * 32;
    }
#if FAT_FAT32_SUPPORT
    else
    {
        header->cluster_zero_offset = /* jump to fats */
                                      header->fat_offset +
                                      /* skip fats */
                                      (offset_t) fat_copies * sectors_per_fat32 * bytes_per_sector;

        header->root_dir_cluster = cluster_root_dir;
    }
#endif

    return 1;
}

/**
 * \ingroup fat_fs
 * Retrieves the next following cluster of a given cluster.
 *
 * Using the filesystem file allocation table, this function returns
 * the number of the cluster containing the data directly following
 * the data within the cluster with the given number.
 *
 * \param[in] fs The filesystem for which to determine the next cluster.
 * \param[in] cluster_num The number of the cluster for which to determine its successor.
 * \returns The wanted cluster number, or 0 on error.
 */
cluster_t fat_get_next_cluster(const struct fat_fs_struct* fs, cluster_t cluster_num)
{
    if(!fs || cluster_num < 2)
        return 0;