src/main/msc/emfat.c

   1 /*
   2  * Derived from
   3  * https://github.com/fetisov/emfat/blob/master/project/emfat.c
   4  * version: 1.1 (2.04.2017)
   5  */
   6
   7 /*
   8  * The MIT License (MIT)
   9  *
  10  * Copyright (c) 2015 by Sergey Fetisov <fsenok@gmail.com>
  11  *
  12  * Permission is hereby granted, free of charge, to any person obtaining a copy
  13  * of this software and associated documentation files (the "Software"), to deal
  14  * in the Software without restriction, including without limitation the rights
  15  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  16  * copies of the Software, and to permit persons to whom the Software is
  17  * furnished to do so, subject to the following conditions:
  18  *
  19  * The above copyright notice and this permission notice shall be included in all
  20  * copies or substantial portions of the Software.
  21  *
  22  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  23  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  25  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  26  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  27  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  28  * SOFTWARE.
  29  */
  30
  31 #include "common/utils.h"
  32
  33 #include "emfat.h"
  34
  35 #ifdef __cplusplus
  36 extern "C" {
  37 #endif
  38
  39 #define SECT              512
  40 #define CLUST             4096
  41 #define SECT_PER_CLUST    (CLUST / SECT)
  42 #define SIZE_TO_NSECT(s)  ((s) == 0 ? 1 : ((s) + SECT - 1) / SECT)
  43 #define SIZE_TO_NCLUST(s) ((s) == 0 ? 1 : ((s) + CLUST - 1) / CLUST)
  44
  45 #define CLUST_FREE     0x00000000
  46 #define CLUST_RESERVED 0x00000001
  47 #define CLUST_BAD      0x0FFFFFF7
  48 #define CLUST_ROOT_END 0X0FFFFFF8
  49 #define CLUST_EOF      0x0FFFFFFF
  50
  51 #define MAX_DIR_ENTRY_CNT 16
  52 #define FILE_SYS_TYPE_OFF 82
  53 #define BYTES_PER_SEC_OFF 11
  54 #define SEC_PER_CLUS_OFF 13
  55 #define RES_SEC_CNT_OFF 14
  56 #define FAT_CNT_OFF 16
  57 #define TOT_SEC_CNT_OFF 32
  58 #define SEC_PER_FAT 36
  59 #define ROOT_DIR_STRT_CLUS_OFF 44
  60 #define FS_INFOSECTOR_OFF 48
  61 #define BACKUP_BOOT_SEC_OFF 50
  62 #define NXT_FREE_CLUS_OFF 492
  63 #define FILE_SYS_TYPE_LENGTH 8
  64 #define SHRT_FILE_NAME_LEN 11
  65 #define STRT_CLUS_LOW_OFF 26
  66 #define STRT_CLUS_HIGH_OFF 20
  67 #define FILE_SIZE_OFF 28
  68 #define ATTR_OFF 11
  69 #define FILE_STAT_LEN 21
  70 #define CHECK_SUM_OFF 13
  71 #define FILE_NAME_SHRT_LEN 8
  72 #define FILE_NAME_EXTN_LEN 3
  73 #define LONG_FILE_NAME_LEN 255
  74 #define LOW_CLUSWORD_MASK 0x0000FFFF
  75 #define HIGH_CLUSWORD_MASK 0xFFFF0000
  76 #define LONG_FNAME_MASK 0x0F
  77 #define LAST_ORD_FIELD_SEQ 0x40
  78 #define LFN_END_MARK 0xFFFF
  79 #define LFN_TERM_MARK 0x0000
  80 #define LFN_FIRST_OFF 0x01
  81 #define LFN_SIXTH_OFF 0x0E
  82 #define LFN_TWELVETH_OFF 0x1C
  83 #define LFN_FIRST_SET_CNT 5
  84 #define LFN_SEC_SET_CNT 6
  85 #define LFN_THIRD_SET_CNT 2
  86 #define LFN_FIRST_SET_LEN 10
  87 #define LFN_SEC_SET_LEN 12
  88 #define LFN_THIRD_SET_LEN 4
  89 #define LFN_EMPTY_LEN 2
  90 #define LFN_LEN_PER_ENTRY 13
  91 #define FNAME_EXTN_SEP_OFF 6
  92 #define FNAME_SEQ_NUM_OFF 7
  93 #define BYTES_PER_CLUSTER_ENTRY 4
  94 #define DIR_ENTRY_LEN 32
  95 #define VOL_ID_LEN 4
  96 #define VOL_LABEL_LEN 11
  97 #define RESERV_LEN 12
  98 #define FS_VER_LEN 2
  99 #define OEM_NAME_LEN 8
 100 #define JUMP_INS_LEN 3
 101 #define MAX_FAT_CNT 2
 102 #define SPACE_VAL 32
 103 #define FILE_READ 0x01
 104 #define FILE_WRITE 0X02
 105 #define FILE_CREATE_NEW 0x04
 106 #define FILE_CREATE_ALWAYS 0x08
 107 #define FILE_APPEND 0x10
 108 #define FREE_DIR_ENTRY 0x00
 109 #define DEL_DIR_ENTRY 0xE5
 110 #define DOT_DIR_ENTRY 0x2E
 111 #define ASCII_DIFF 32
 112 #define FILE_SEEK_SET 0
 113 #define FILE_SEEK_CUR 1
 114 #define FILE_SEEK_END 2
 115 #define DELIMITER '/'
 116 #define EXTN_DELIMITER '.'
 117 #define TILDE '~'
 118 #define FULL_SHRT_NAME_LEN 13
 119
 120 #pragma pack(push, 1)
 121
 122 typedef struct
 123 {
 124     uint8_t  status;          // 0x80 for bootable, 0x00 for not bootable, anything else for invalid
 125     uint8_t  start_head;      // The head of the start
 126     uint8_t  start_sector;    // (S | ((C >> 2) & 0xC0)) where S is the sector of the start and C is the cylinder of the start. Note that S is counted from one.
 127     uint8_t  start_cylinder;  // (C & 0xFF) where C is the cylinder of the start
 128     uint8_t  PartType;
 129     uint8_t  end_head;
 130     uint8_t  end_sector;
 131     uint8_t  end_cylinder;
 132     uint32_t StartLBA;        // linear address of first sector in partition. Multiply by sector size (usually 512) for real offset
 133     uint32_t EndLBA;          // linear address of last sector in partition. Multiply by sector size (usually 512) for real offset
 134 } mbr_part_t;
 135
 136 typedef struct
 137 {
 138     uint8_t    Code[440];
 139     uint32_t   DiskSig;  //This is optional
 140     uint16_t   Reserved; //Usually 0x0000
 141     mbr_part_t PartTable[4];
 142     uint8_t    BootSignature[2]; //0x55 0xAA for bootable
 143 } mbr_t;
 144
 145 typedef struct
 146 {
 147     uint8_t jump[JUMP_INS_LEN];
 148     uint8_t OEM_name[OEM_NAME_LEN];
 149     uint16_t bytes_per_sec;
 150     uint8_t sec_per_clus;
 151     uint16_t reserved_sec_cnt;
 152     uint8_t fat_cnt;
 153     uint16_t root_dir_max_cnt;
 154     uint16_t tot_sectors;
 155     uint8_t media_desc;
 156     uint16_t sec_per_fat_fat16;
 157     uint16_t sec_per_track;
 158     uint16_t number_of_heads;
 159     uint32_t hidden_sec_cnt;
 160     uint32_t tol_sector_cnt;
 161     uint32_t sectors_per_fat;
 162     uint16_t ext_flags;
 163     uint8_t fs_version[FS_VER_LEN];
 164     uint32_t root_dir_strt_cluster;
 165     uint16_t fs_info_sector;
 166     uint16_t backup_boot_sector;
 167     uint8_t reserved[RESERV_LEN];
 168     uint8_t drive_number;
 169     uint8_t reserved1;
 170     uint8_t boot_sig;
 171     uint8_t volume_id[VOL_ID_LEN];
 172     uint8_t volume_label[VOL_LABEL_LEN];
 173     uint8_t file_system_type[FILE_SYS_TYPE_LENGTH];
 174 } boot_sector;
 175
 176 typedef struct
 177 {
 178     uint32_t signature1;     /* 0x41615252L */
 179     uint32_t reserved1[120]; /* Nothing as far as I can tell */
 180     uint32_t signature2;     /* 0x61417272L */
 181     uint32_t free_clusters;  /* Free cluster count.  -1 if unknown */
 182     uint32_t next_cluster;   /* Most recently allocated cluster */
 183     uint32_t reserved2[3];
 184     uint32_t signature3;
 185 } fsinfo_t;
 186
 187 typedef struct
 188 {
 189     uint8_t name[FILE_NAME_SHRT_LEN];
 190     uint8_t extn[FILE_NAME_EXTN_LEN];
 191     uint8_t attr;
 192     uint8_t reserved;
 193     uint8_t crt_time_tenth;
 194     uint16_t crt_time;
 195     uint16_t crt_date;
 196     uint16_t lst_access_date;
 197     uint16_t strt_clus_hword;
 198     uint16_t lst_mod_time;
 199     uint16_t lst_mod_date;
 200     uint16_t strt_clus_lword;
 201     uint32_t size;
 202 } dir_entry;
 203
 204 typedef struct
 205 {
 206     uint8_t ord_field;
 207     uint8_t fname0_4[LFN_FIRST_SET_LEN];
 208     uint8_t flag;
 209     uint8_t reserved;
 210     uint8_t chksum;
 211     uint8_t fname6_11[LFN_SEC_SET_LEN];
 212     uint8_t empty[LFN_EMPTY_LEN];
 213     uint8_t fname12_13[LFN_THIRD_SET_LEN];
 214 } lfn_entry;
 215
 216 #pragma pack(pop)
 217
 218 bool emfat_init_entries(emfat_entry_t *entries)
 219 {
 220     emfat_entry_t *e;
 221     int i, n;
 222
 223     e = &entries[0];
 224     if (e->level != 0 || !e->dir || e->name == NULL) return false;
 225
 226     e->priv.top = NULL;
 227     e->priv.next = NULL;
 228     e->priv.sub = NULL;
 229     e->priv.num_subentry = 0;
 230
 231     n = 0;
 232     for (i = 1; entries[i].name != NULL; i++) {
 233         entries[i].priv.top = NULL;
 234         entries[i].priv.next = NULL;
 235         entries[i].priv.sub = NULL;
 236         entries[i].priv.num_subentry = 0;
 237         if (entries[i].level == n - 1) {
 238             if (n == 0) return false;
 239             e = e->priv.top;
 240             n--;
 241         }
 242
 243         if (entries[i].level == n + 1) {
 244             if (!e->dir) return false;
 245             e->priv.sub = &entries[i];
 246             entries[i].priv.top = e;
 247             e = &entries[i];
 248             n++;
 249             continue;
 250         }
 251
 252         if (entries[i].level == n) {
 253             if (n == 0) return false;
 254             e->priv.top->priv.num_subentry++;
 255             entries[i].priv.top = e->priv.top;
 256             e->priv.next = &entries[i];
 257             e = &entries[i];
 258             continue;
 259         }
 260
 261         return false;
 262     }
 263
 264     return true;
 265 }
 266
 267 static void lba_to_chs(int lba, uint8_t *cl, uint8_t *ch, uint8_t *dh)
 268 {
 269     int cylinder, head, sector;
 270     int sectors = 63;
 271     int heads = 255;
 272     int cylinders = 1024;
 273     sector = lba % sectors + 1;
 274     head = (lba / sectors) % heads;
 275     cylinder = lba / (sectors * heads);
 276     if (cylinder >= cylinders) {
 277       *cl = *ch = *dh = 0xff;
 278       return;
 279     }
 280     *cl = sector | ((cylinder & 0x300) >> 2);
 281     *ch = cylinder & 0xFF;
 282     *dh = head;
 283 }
 284
 285 bool emfat_init(emfat_t *emfat, const char *label, emfat_entry_t *entries)
 286 {
 287     uint32_t sect_per_fat;
 288     uint32_t clust;
 289     uint32_t reserved_clust = 0;
 290     emfat_entry_t *e;
 291     int i;
 292
 293     if (emfat == NULL || label == NULL || entries == NULL) {
 294         return false;
 295     }
 296
 297     if (!emfat_init_entries(entries)) {
 298         return false;
 299     }
 300
 301     clust = 2;
 302     for (i = 0; entries[i].name != NULL; i++) {
 303         e = &entries[i];
 304         if (e->dir) {
 305             e->curr_size = 0;
 306             e->max_size = 0;
 307             e->priv.first_clust = clust;
 308             e->priv.last_clust = clust + SIZE_TO_NCLUST(e->priv.num_subentry * sizeof(dir_entry)) - 1;
 309             e->priv.last_reserved = e->priv.last_clust;
 310         } else {
 311             e->priv.first_clust = clust;
 312             e->priv.last_clust = e->priv.first_clust + SIZE_TO_NCLUST(entries[i].curr_size) - 1;
 313             e->priv.last_reserved = e->priv.first_clust + SIZE_TO_NCLUST(entries[i].max_size) - 1;
 314         }
 315         reserved_clust += e->priv.last_reserved - e->priv.last_clust;
 316         clust = e->priv.last_reserved + 1;
 317     }
 318     clust -= 2;
 319
 320     emfat->vol_label = label;
 321     emfat->priv.num_entries = i;
 322     emfat->priv.boot_lba = 62;
 323     emfat->priv.fsinfo_lba = emfat->priv.boot_lba + 1;
 324     emfat->priv.fat1_lba = emfat->priv.fsinfo_lba + 1;
 325     emfat->priv.num_clust = clust;
 326     emfat->priv.free_clust = reserved_clust;
 327     sect_per_fat = SIZE_TO_NSECT((uint64_t)emfat->priv.num_clust * 4);
 328     emfat->priv.fat2_lba = emfat->priv.fat1_lba + sect_per_fat;
 329     emfat->priv.root_lba = emfat->priv.fat2_lba + sect_per_fat;
 330     emfat->priv.entries = entries;
 331     emfat->priv.last_entry = entries;
 332     emfat->disk_sectors = clust * SECT_PER_CLUST + emfat->priv.root_lba;
 333     emfat->vol_size = (uint64_t)emfat->disk_sectors * SECT;
 334     /* calc cyl number */
 335 //    i = ((emfat->disk_sectors + 63*255 - 1) / (63*255));
 336 //    emfat->disk_sectors = i * 63*255;
 337     return true;
 338 }
 339
 340 void read_mbr_sector(const emfat_t *emfat, uint8_t *sect)
 341 {
 342     mbr_t *mbr;
 343     memset(sect, 0, SECT);
 344     mbr = (mbr_t *)sect;
 345     mbr->DiskSig = 0;
 346     mbr->Reserved = 0;
 347     mbr->PartTable[0].status = 0x80;
 348     mbr->PartTable[0].PartType = 0x0C;
 349     mbr->PartTable[0].StartLBA = emfat->priv.boot_lba;
 350     mbr->PartTable[0].EndLBA = emfat->disk_sectors;
 351     lba_to_chs(mbr->PartTable[0].StartLBA, &mbr->PartTable[0].start_sector, &mbr->PartTable[0].start_cylinder, &mbr->PartTable[0].start_head);
 352     lba_to_chs(emfat->disk_sectors - 1, &mbr->PartTable[0].end_sector, &mbr->PartTable[0].end_cylinder, &mbr->PartTable[0].end_head);
 353     mbr->BootSignature[0] = 0x55;
 354     mbr->BootSignature[1] = 0xAA;
 355 }
 356
 357 void read_boot_sector(const emfat_t *emfat, uint8_t *sect)
 358 {
 359     boot_sector *bs;
 360     memset(sect, 0, SECT);
 361     bs = (boot_sector *)sect;
 362     bs->jump[0] = 0xEB;
 363     bs->jump[1] = 0x58;
 364     bs->jump[2] = 0x90;
 365     memcpy(bs->OEM_name, "MSDOS5.0", 8);
 366     bs->bytes_per_sec = SECT;
 367     bs->sec_per_clus = 8;     /* 4 kb per cluster */
 368     bs->reserved_sec_cnt = 2; /* boot sector & fsinfo sector */
 369     bs->fat_cnt = 2;          /* two tables */
 370     bs->root_dir_max_cnt = 0;
 371     bs->tot_sectors = 0;
 372     bs->media_desc = 0xF8;
 373     bs->sec_per_fat_fat16 = 0;
 374     bs->sec_per_track = 63;
 375     bs->number_of_heads = 0xFF;
 376     bs->hidden_sec_cnt = 62;
 377     bs->tol_sector_cnt = emfat->disk_sectors - emfat->priv.boot_lba;
 378     bs->sectors_per_fat = emfat->priv.fat2_lba - emfat->priv.fat1_lba;
 379     bs->ext_flags = 0;
 380     bs->fs_version[0] = 0;
 381     bs->fs_version[1] = 0;
 382     bs->root_dir_strt_cluster = 2;
 383     bs->fs_info_sector = 1;
 384     bs->backup_boot_sector = 0; /* not used */
 385     bs->drive_number = 128;
 386     bs->boot_sig = 0x29;
 387     bs->volume_id[0] = 148;
 388     bs->volume_id[1] = 14;
 389     bs->volume_id[2] = 13;
 390     bs->volume_id[3] = 8;
 391     memcpy(bs->volume_label, "NO NAME    ", VOL_LABEL_LEN);
 392     memcpy(bs->file_system_type, "FAT32   ", FILE_SYS_TYPE_LENGTH);
 393     sect[SECT - 2] = 0x55;
 394     sect[SECT - 1] = 0xAA;
 395 }
 396
 397 #define IS_CLUST_OF(clust, entry) ((clust) >= (entry)->priv.first_clust && (clust) <= (entry)->priv.last_reserved)
 398
 399 emfat_entry_t *find_entry(const emfat_t *emfat, uint32_t clust, emfat_entry_t *nearest)
 400 {
 401     if (nearest == NULL) {
 402         nearest = emfat->priv.entries;
 403     }
 404
 405     if (nearest->priv.first_clust > clust) {
 406         while (nearest >= emfat->priv.entries) { // backward finding
 407             if (IS_CLUST_OF(clust, nearest))
 408                 return nearest;
 409             nearest--;
 410         }
 411     } else {
 412         while (nearest->name != NULL) { // forward finding
 413             if (IS_CLUST_OF(clust, nearest))
 414                 return nearest;
 415             nearest++;
 416         }
 417     }
 418     return NULL;
 419 }
 420
 421 void read_fsinfo_sector(const emfat_t *emfat, uint8_t *sect)
 422 {
 423     UNUSED(emfat);
 424
 425     fsinfo_t *info = (fsinfo_t *)sect;
 426     info->signature1 = 0x41615252L;
 427     info->signature2 = 0x61417272L;
 428     //info->free_clusters = 0;
 429     info->free_clusters = emfat->priv.free_clust;
 430     //info->next_cluster = emfat->priv.num_clust + 2;
 431     info->next_cluster = 0xffffffff;
 432     memset(info->reserved1, 0, sizeof(info->reserved1));
 433     memset(info->reserved2, 0, sizeof(info->reserved2));
 434     info->signature3 = 0xAA550000;
 435 }
 436
 437 void read_fat_sector(emfat_t *emfat, uint8_t *sect, uint32_t index)
 438 {
 439     emfat_entry_t *le;
 440     uint32_t *values;
 441     uint32_t count;
 442     uint32_t curr;
 443
 444     values = (uint32_t *)sect;
 445     curr = index * 128;
 446     count = 128;
 447
 448     if (curr == 0) {
 449         *values++ = CLUST_ROOT_END;
 450         *values++ = 0xFFFFFFFF;
 451         count -= 2;
 452         curr += 2;
 453     }
 454
 455     le = emfat->priv.last_entry;
 456     while (count != 0) {
 457         if (!IS_CLUST_OF(curr, le)) {
 458             le = find_entry(emfat, curr, le);
 459             if (le == NULL) {
 460                 le = emfat->priv.last_entry;
 461                 *values = CLUST_RESERVED;
 462                 values++;
 463                 count--;
 464                 curr++;
 465                 continue;
 466             }
 467         }
 468         if (le->dir) {
 469             if (curr == le->priv.last_clust) {
 470                 *values = CLUST_EOF;
 471             } else {
 472                 *values = curr + 1;
 473             }
 474         } else {
 475             if (curr == le->priv.last_clust) {
 476                 *values = CLUST_EOF;
 477             } else if (curr > le->priv.last_clust) {
 478                 *values = CLUST_FREE;
 479             } else {
 480                 *values = curr + 1;
 481             }
 482         }
 483         values++;
 484         count--;
 485         curr++;
 486     }
 487     emfat->priv.last_entry = le;
 488 }
 489
 490 void fill_entry(dir_entry *entry, const char *name, uint8_t attr, uint32_t clust, const uint32_t cma[3], uint32_t size)
 491 {
 492     int i, l, l1, l2;
 493     int dot_pos;
 494
 495     memset(entry, 0, sizeof(dir_entry));
 496
 497     if (cma) {
 498         entry->crt_date = cma[0] >> 16;
 499         entry->crt_time = cma[0] & 0xFFFF;
 500         entry->lst_mod_date = cma[1] >> 16;
 501         entry->lst_mod_time = cma[1] & 0xFFFF;
 502         entry->lst_access_date = cma[2] >> 16;
 503     }
 504
 505     l = strlen(name);
 506     dot_pos = -1;
 507
 508     if ((attr & ATTR_DIR) == 0) {
 509         for (i = l - 1; i >= 0; i--) {
 510             if (name[i] == '.')
 511             {
 512                 dot_pos = i;
 513                 break;
 514             }
 515         }
 516     }
 517
 518     if (dot_pos == -1) {
 519         l1 = l > FILE_NAME_SHRT_LEN ? FILE_NAME_SHRT_LEN : l;
 520         l2 = 0;
 521     } else {
 522         l1 = dot_pos;
 523         l1 = l1 > FILE_NAME_SHRT_LEN ? FILE_NAME_SHRT_LEN : l1;
 524         l2 = l - dot_pos - 1;
 525         l2 = l2 > FILE_NAME_EXTN_LEN ? FILE_NAME_EXTN_LEN : l2;
 526     }
 527
 528     memset(entry->name, ' ', FILE_NAME_SHRT_LEN);
 529     memcpy(entry->name, name, l1);
 530     memset(entry->extn, ' ', FILE_NAME_EXTN_LEN);
 531     memcpy(entry->extn, name + dot_pos + 1, l2);
 532
 533     for (i = 0; i < FILE_NAME_SHRT_LEN; i++) {
 534         if (entry->name[i] >= 'a' && entry->name[i] <= 'z') {
 535             entry->name[i] -= 0x20;
 536         }
 537     }
 538
 539     for (i = 0; i < FILE_NAME_EXTN_LEN; i++) {
 540         if (entry->extn[i] >= 'a' && entry->extn[i] <= 'z') {
 541             entry->extn[i] -= 0x20;
 542         }
 543     }
 544
 545     entry->attr = attr;
 546     entry->reserved = 24;
 547     entry->strt_clus_hword = clust >> 16;
 548     entry->strt_clus_lword = clust;
 549     entry->size = size;
 550
 551     return;
 552 }
 553
 554 void fill_dir_sector(emfat_t *emfat, uint8_t *data, emfat_entry_t *entry, uint32_t rel_sect)
 555 {
 556     dir_entry *de;
 557     uint32_t avail;
 558
 559     memset(data, 0, SECT);
 560     de = (dir_entry *)data;
 561     avail = SECT;
 562
 563     if (rel_sect == 0) { // 1. first sector of directory
 564         if (entry->priv.top == NULL) {
 565             fill_entry(de++, emfat->vol_label, ATTR_VOL_LABEL, 0, 0, 0);
 566             avail -= sizeof(dir_entry);
 567         } else {
 568             fill_entry(de++, ".", ATTR_DIR | ATTR_READ, entry->priv.first_clust, 0, 0);
 569             if (entry->priv.top->priv.top == NULL) {
 570                 fill_entry(de++, "..", ATTR_DIR | ATTR_READ, 0, 0, 0);
 571             } else {
 572                 fill_entry(de++, "..", ATTR_DIR | ATTR_READ, entry->priv.top->priv.first_clust, 0, 0);
 573             }
 574             avail -= sizeof(dir_entry) * 2;
 575         }
 576         entry = entry->priv.sub;
 577     } else { // 2. not a first sector
 578         int n;
 579         n = rel_sect * (SECT / sizeof(dir_entry));
 580         n -= entry->priv.top == NULL ? 1 : 2;
 581         entry = entry->priv.sub;
 582
 583         while (n > 0 && entry != NULL) {
 584             entry = entry->priv.next;
 585             n--;
 586         }
 587     }
 588
 589     while (entry != NULL && avail >= sizeof(dir_entry)) {
 590         if (entry->dir) {
 591             fill_entry(de++, entry->name, ATTR_DIR | ATTR_READ, entry->priv.first_clust, entry->cma_time, 0);
 592         } else {
 593             //fill_entry(de++, entry->name, ATTR_ARCHIVE | ATTR_READ, entry->priv.first_clust, entry->cma_time, entry->curr_size);
 594             fill_entry(de++, entry->name, ATTR_ARCHIVE | ATTR_READ | entry->attr, entry->priv.first_clust, entry->cma_time, entry->curr_size);
 595         }
 596         entry = entry->priv.next;
 597         avail -= sizeof(dir_entry);
 598     }
 599 }
 600
 601 void read_data_sector(emfat_t *emfat, uint8_t *data, uint32_t rel_sect)
 602 {
 603     emfat_entry_t *le;
 604     uint32_t cluster;
 605     cluster = rel_sect / 8 + 2;
 606     rel_sect = rel_sect % 8;
 607
 608     le = emfat->priv.last_entry;
 609     if (!IS_CLUST_OF(cluster, le)) {
 610         le = find_entry(emfat, cluster, le);
 611         if (le == NULL) {
 612             int i;
 613             for (i = 0; i < SECT / 4; i++)
 614                 ((uint32_t *)data)[i] = 0xEFBEADDE;
 615             return;
 616         }
 617         emfat->priv.last_entry = le;
 618     }
 619
 620     if (le->dir) {
 621         fill_dir_sector(emfat, data, le, rel_sect);
 622         return;
 623     }
 624
 625     if (le->readcb == NULL) {
 626         memset(data, 0, SECT);
 627     } else {
 628         uint32_t offset = cluster - le->priv.first_clust;
 629         offset = offset * CLUST + rel_sect * SECT;
 630         le->readcb(data, SECT, offset + le->offset, le);
 631     }
 632
 633     return;
 634 }
 635
 636 void emfat_read(emfat_t *emfat, uint8_t *data, uint32_t sector, int num_sectors)
 637 {
 638     while (num_sectors > 0) {
 639         if (sector >= emfat->priv.root_lba) {
 640             read_data_sector(emfat, data, sector - emfat->priv.root_lba);
 641         } else if (sector == 0) {
 642             read_mbr_sector(emfat, data);
 643         } else if (sector == emfat->priv.fsinfo_lba) {
 644             read_fsinfo_sector(emfat, data);
 645         } else if (sector == emfat->priv.boot_lba) {
 646             read_boot_sector(emfat, data);
 647         } else if (sector >= emfat->priv.fat1_lba && sector < emfat->priv.fat2_lba) {
 648             read_fat_sector(emfat, data, sector - emfat->priv.fat1_lba);
 649         } else if (sector >= emfat->priv.fat2_lba && sector < emfat->priv.root_lba) {
 650             read_fat_sector(emfat, data, sector - emfat->priv.fat2_lba);
 651         } else {
 652             memset(data, 0, SECT);
 653         }
 654         data += SECT;
 655         num_sectors--;
 656         sector++;
 657     }
 658 }
 659
 660 void write_data_sector(emfat_t *emfat, const uint8_t *data, uint32_t rel_sect)
 661 {
 662     emfat_entry_t *le;
 663     uint32_t cluster;
 664     cluster = rel_sect / 8 + 2;
 665     rel_sect = rel_sect % 8;
 666
 667     le = emfat->priv.last_entry;
 668
 669     if (!IS_CLUST_OF(cluster, le)) {
 670         le = find_entry(emfat, cluster, le);
 671         if (le == NULL) return;
 672         emfat->priv.last_entry = le;
 673     }
 674
 675     if (le->dir) {
 676         // TODO: handle changing a filesize
 677         return;
 678     }
 679
 680     if (le->writecb != NULL) {
 681         le->writecb(data, SECT, rel_sect * SECT + le->offset, le);
 682     }
 683 }
 684
 685 #define FEBRUARY        2
 686 #define    STARTOFTIME        1970
 687 #define SECDAY            86400L
 688 #define SECYR            (SECDAY * 365)
 689 #define    leapyear(year)        ((year) % 4 == 0)
 690 #define    days_in_year(a)        (leapyear(a) ? 366 : 365)
 691 #define    days_in_month(a)    (month_days[(a) - 1])
 692
 693 static int month_days[12] = {
 694     31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
 695 };
 696
 697 uint32_t emfat_cma_time_from_unix(uint32_t tim)
 698 {
 699     register int i;
 700     register long tmp, day;
 701     int ymd[3];
 702     int hms[3];
 703
 704     day = tim / SECDAY;
 705     tmp = tim % SECDAY;
 706
 707     /* Hours, minutes, seconds are easy */
 708
 709     hms[0] = tmp / 3600;
 710     hms[1] = (tmp % 3600) / 60;
 711     hms[2] = (tmp % 3600) % 60;
 712
 713     /* Number of years in days */
 714     for (i = STARTOFTIME; day >= days_in_year(i); i++)
 715         day -= days_in_year(i);
 716     ymd[0] = i;
 717
 718     /* Number of months in days left */
 719     if (leapyear(ymd[0])) {
 720         days_in_month(FEBRUARY) = 29;
 721     }
 722     for (i = 1; day >= days_in_month(i); i++) {
 723         day -= days_in_month(i);
 724     }
 725     days_in_month(FEBRUARY) = 28;
 726     ymd[1] = i;
 727
 728     /* Days are what is left over (+1) from all that. */
 729     ymd[2] = day + 1;
 730
 731     return EMFAT_ENCODE_CMA_TIME(ymd[2], ymd[1], ymd[0], hms[0], hms[1], hms[2]);
 732 }
 733
 734 #ifdef __cplusplus
 735 }
 736 #endif