fsctl/src/fugue/core/dirent.c

#include "fsctl/fugue/dirent.h"
#include "fsctl/fugue/cluster.h"
#include "fsctl/fugue/logger.h"
#include "fsctl/fugue/bits/fat.h"

//---
// Internals
//---

/* _fugue_dirent_checksum() : Fugue checksum handling */
static uint8_t _fugue_dirent_checksum(uintptr_t directory)
{
    uint8_t *block;
    uint8_t checksum;
    int a;
    int b;

    checksum = 0;
    block = (void *)directory;
    for (int i = 0 ; i < 11 ; ++i)
    {
        checksum = checksum & 0xff;
        a = checksum / 2;
        b = checksum * 128;
        checksum = a | b;
        checksum = checksum + block[i];
    }
    checksum = checksum & 0xff;
    return checksum;
}

/* _fugue_dirent_frag_dump() : decode name fragment */
static int _fugue_dirent_frag_dump(fugue_file_t *file, uint8_t *frag, int n)
{
    while (--n >= 0)
    {
        file->name[file->name_len] = frag[0];
        if ((frag[0] & 0x80) != 0) {
            file->name[file->name_len] = frag[1];
            file->name_len += 1;
        }
        file->name_len += 1;
        frag = &frag[2];
    }
    file->name[file->name_len] = '\0';
    return 0;
}

//---
// Public
//---

/* fugue_dirent_init() : init dirent object */
int fugue_dirent_init(fugue_dirent_t *dirent, fugue_fs_t *fs)
{
    if (fs == NULL || dirent == NULL)
        return -1;
    memset(dirent, 0x00, sizeof(fugue_dirent_t));
    memcpy(&dirent->_private.fs, fs, sizeof(fugue_fs_t));
    dirent->current_dir_addr   = (uintptr_t)fs->_private.root;
    dirent->cluster_addr_start = (uintptr_t)fs->_private.root;
    dirent->cluster_addr_end   = (uintptr_t)fs->_private.root;
    dirent->cluster_addr_end  += fs->props.sector_root_nb * 512;
    return 0;
}

/* fugue_dirent_dir_fetch() : fetch the current dir blob and walk to next */
void *fugue_dirent_dir_fetch(fugue_dirent_t *dirent)
{
    void *dir;

    dir = (void*)dirent->current_dir_addr;
    if (dir == NULL)
        return NULL;

    dirent->current_dir_addr += 32;
    if (dirent->current_dir_addr < dirent->cluster_addr_end)
        return dir;

    dirent->cluster_addr_start = fugue_cluster_find_next(
        &dirent->_private.fs,
        dirent->cluster_idx
    );
    dirent->cluster_addr_end = dirent->cluster_addr_start;
    if (dirent->cluster_addr_start != 0x00000000)
        dirent->cluster_addr_end += dirent->_private.fs.props.cluster_size;
    return dir;
}

/* fugue_dirent_name_fetch() : fetch fragment */
int fugue_dirent_name_fetch(
    fugue_dirent_t *dirent,
    fugue_file_t *file,
    void *dir
) {
    fugue_logger_t *log;
    struct fugue_fat_dir_name *lfn;

    lfn = (void *)dir;
    log = dirent->_private.fs._private.logger;

    //---
    // check directory block validity
    //---

    if (lfn->DIR_Attr != FUGUE_DIR_ATTR_LFN) {
        fugue_logger_write(log, "[WARN] %p: LFN type error\n", lfn);
        return -1;
    }
    if (lfn->DIR_Type != 0x00) {
        fugue_logger_write(log, "[WARN] %p: LFN attribute error\n", lfn);
        return -2;
    }
    if (lfn->DIR_FstClus != 0x0000) {
        fugue_logger_write(log, "[WARN] %p: cluster info error\n", lfn);
        return -3;
    }
    if (lfn->DIR_Sequence._low0 != 0 || lfn->DIR_Sequence._low1 != 0) {
        fugue_logger_write(log, "[WARN] %p: dirty sequence\n", lfn);
        return -4;
    }
    if (lfn->checksum != _fugue_dirent_checksum(dirent->current_dir_addr)) {
        fugue_logger_write(log, "[WARN] %p: checksum error\n", lfn);
        return -5;
    }

    //---
    // check sequence validity
    //---

    if (lfn->DIR_Sequence.last != 0)
    {
        if (dirent->_private.lfn_prev_idx != 0)
            fugue_logger_write(log, "[WARN] %p: multiple LFN entry\n", lfn);
        dirent->_private.lfn_prev_idx = lfn->DIR_Sequence.id + 1;
    }
    if (dirent->_private.lfn_prev_idx != lfn->DIR_Sequence.id + 1) {
        fugue_logger_write(log, "[WARN] %p: LFN sequence error\n", lfn);
        return -6;
    }
    dirent->_private.lfn_prev_idx = lfn->DIR_Sequence.id;

    //---
    // Dump name fragment
    //---

    _fugue_dirent_frag_dump(file, (uint8_t*)&lfn->DIR_Char0, 5);
    _fugue_dirent_frag_dump(file, (uint8_t*)&lfn->DIR_Char5, 5);
    _fugue_dirent_frag_dump(file, (uint8_t*)&lfn->DIR_Char11,2);
    return -1;
}