fat_standard.h

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/*
 * This file is part of Ninjaflight.
 *
 * Ninjaflight is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Ninjaflight is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Ninjaflight.  If not, see <http://www.gnu.org/licenses/>.
 */

#pragma once

#include <stdint.h>
#include <stdbool.h>

#define MBR_PARTITION_TYPE_FAT16     0x06
#define MBR_PARTITION_TYPE_FAT32     0x0B
#define MBR_PARTITION_TYPE_FAT32_LBA 0x0C
#define MBR_PARTITION_TYPE_FAT16_LBA 0x0E

// Signature bytes found at index 510 and 511 in the volume ID sector
#define FAT_VOLUME_ID_SIGNATURE_1 0x55
#define FAT_VOLUME_ID_SIGNATURE_2 0xAA

#define FAT_DIRECTORY_ENTRY_SIZE 32
#define FAT_SMALLEST_LEGAL_CLUSTER_NUMBER 2

#define FAT_MAXIMUM_FILESIZE 0xFFFFFFFF

#define FAT12_MAX_CLUSTERS 4084
#define FAT16_MAX_CLUSTERS 65524

#define FAT_FILE_ATTRIBUTE_READ_ONLY 0x01
#define FAT_FILE_ATTRIBUTE_HIDDEN    0x02
#define FAT_FILE_ATTRIBUTE_SYSTEM    0x04
#define FAT_FILE_ATTRIBUTE_VOLUME_ID 0x08
#define FAT_FILE_ATTRIBUTE_DIRECTORY 0x10
#define FAT_FILE_ATTRIBUTE_ARCHIVE   0x20

#define FAT_FILENAME_LENGTH 11
#define FAT_DELETED_FILE_MARKER 0xE5

#define FAT_MAKE_DATE(year, month, day)     (day | (month << 5) | ((year - 1980) << 9))
#define FAT_MAKE_TIME(hour, minute, second) ((second / 2) | (minute << 5) | (hour << 11))

typedef enum {
    FAT_FILESYSTEM_TYPE_INVALID,
    FAT_FILESYSTEM_TYPE_FAT12,
    FAT_FILESYSTEM_TYPE_FAT16,
    FAT_FILESYSTEM_TYPE_FAT32,
} fatFilesystemType_e;

typedef struct mbrPartitionEntry_t {
    uint8_t bootFlag;
    uint8_t chsBegin[3];
    uint8_t type;
    uint8_t chsEnd[3];
    uint32_t lbaBegin;
    uint32_t numSectors;
} __attribute__((packed)) mbrPartitionEntry_t;

typedef struct fat16Descriptor_t {
    uint8_t driveNumber;
    uint8_t reserved1;
    uint8_t bootSignature;
    uint32_t volumeID;
    char volumeLabel[11];
    char fileSystemType[8];
} __attribute__((packed)) fat16Descriptor_t;

typedef struct fat32Descriptor_t {
    uint32_t FATSize32;
    uint16_t extFlags;
    uint16_t fsVer;
    uint32_t rootCluster;
    uint16_t fsInfo;
    uint16_t backupBootSector;
    uint8_t reserved[12];
    uint8_t driveNumber;
    uint8_t reserved1;
    uint8_t bootSignature;
    uint32_t volumeID;
    char volumeLabel[11];
    char fileSystemType[8];
} __attribute__((packed)) fat32Descriptor_t;

typedef struct fatVolumeID_t {
    uint8_t jmpBoot[3];
    char oemName[8];
    uint16_t bytesPerSector;
    uint8_t sectorsPerCluster;
    uint16_t reservedSectorCount;
    uint8_t numFATs;
    uint16_t rootEntryCount;
    uint16_t totalSectors16;
    uint8_t media;
    uint16_t FATSize16;
    uint16_t sectorsPerTrack;
    uint16_t numHeads;
    uint32_t hiddenSectors;
    uint32_t totalSectors32;
    union {
        fat16Descriptor_t fat16;
        fat32Descriptor_t fat32;
    } fatDescriptor;
} __attribute__((packed)) fatVolumeID_t;

typedef struct fatDirectoryEntry_t {
    char filename[FAT_FILENAME_LENGTH];
    uint8_t attrib;
    uint8_t ntReserved;
    uint8_t creationTimeTenths;
    uint16_t creationTime;
    uint16_t creationDate;
    uint16_t lastAccessDate;
    uint16_t firstClusterHigh;
    uint16_t lastWriteTime;
    uint16_t lastWriteDate;
    uint16_t firstClusterLow;
    uint32_t fileSize;
} __attribute__((packed)) fatDirectoryEntry_t;

uint32_t fat32_decodeClusterNumber(uint32_t clusterNumber);

bool fat32_isEndOfChainMarker(uint32_t clusterNumber);
bool fat16_isEndOfChainMarker(uint16_t clusterNumber);

bool fat_isFreeSpace(uint32_t clusterNumber);

bool fat_isDirectoryEntryTerminator(fatDirectoryEntry_t *entry);
bool fat_isDirectoryEntryEmpty(fatDirectoryEntry_t *entry);

void fat_convertFilenameToFATStyle(const char *filename, uint8_t *fatFilename);