377 lines
13 KiB
C
377 lines
13 KiB
C
#include <fs/fat32.h>
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#include <lib/blib.h>
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#include <drivers/disk.h>
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#include <lib/libc.h>
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#include <lib/print.h>
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#include <mm/pmm.h>
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#include <stdbool.h>
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#define FAT32_LFN_MAX_ENTRIES 20
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#define FAT32_LFN_MAX_FILENAME_LENGTH (FAT32_LFN_MAX_ENTRIES * 13 + 1)
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#define FAT32_VALID_SIGNATURE_1 0x28
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#define FAT32_VALID_SIGNATURE_2 0x29
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#define FAT32_VALID_SYSTEM_IDENTIFIER "FAT32 "
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#define FAT16_VALID_SYSTEM_IDENTIFIER "FAT16 "
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#define FAT32_SECTOR_SIZE 512
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#define FAT32_ATTRIBUTE_SUBDIRECTORY 0x10
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#define FAT32_LFN_ATTRIBUTE 0x0F
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struct fat32_bpb {
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uint8_t jump[3];
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char oem[8];
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uint16_t bytes_per_sector;
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uint8_t sectors_per_cluster;
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uint16_t reserved_sectors;
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uint8_t fats_count;
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uint16_t directory_entries_count;
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uint16_t sector_totals;
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uint8_t media_descriptor_type;
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uint16_t sectors_per_fat_16;
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uint16_t sectors_per_track;
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uint16_t heads_count;
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uint32_t hidden_sectors_count;
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uint32_t large_sectors_count;
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uint32_t sectors_per_fat_32;
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uint16_t flags;
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uint16_t fat_version_number;
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uint32_t root_directory_cluster;
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uint16_t fs_info_sector;
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uint16_t backup_boot_sector;
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uint8_t reserved[12];
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uint8_t drive_number;
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uint8_t nt_flags;
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uint8_t signature;
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uint32_t volume_serial_number;
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char label[11];
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char system_identifier[8];
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} __attribute__((packed));
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struct fat32_directory_entry {
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char file_name_and_ext[8 + 3];
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uint8_t attribute;
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uint8_t file_data_1[8];
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uint16_t cluster_num_high;
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uint8_t file_data_2[4];
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uint16_t cluster_num_low;
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uint32_t file_size_bytes;
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} __attribute__((packed));
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struct fat32_lfn_entry {
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uint8_t sequence_number;
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char name1[10];
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uint8_t attribute;
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uint8_t type;
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uint8_t dos_checksum;
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char name2[12];
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uint16_t first_cluster;
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char name3[4];
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} __attribute__((packed));
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static int fat32_init_context(struct fat32_context* context, struct volume *part) {
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context->part = part;
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struct fat32_bpb bpb;
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volume_read(context->part, &bpb, 0, sizeof(struct fat32_bpb));
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if (strncmp(bpb.system_identifier, FAT32_VALID_SYSTEM_IDENTIFIER, SIZEOF_ARRAY(bpb.system_identifier)) == 0) {
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if (bpb.signature == FAT32_VALID_SIGNATURE_1 || bpb.signature == FAT32_VALID_SIGNATURE_2) {
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context->type = 32;
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goto valid;
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}
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}
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if (strncmp((((void *)&bpb) + 0x36), FAT16_VALID_SYSTEM_IDENTIFIER, SIZEOF_ARRAY(bpb.system_identifier)) == 0) {
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context->type = 16;
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goto valid;
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}
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return 1;
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valid:
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context->sectors_per_cluster = bpb.sectors_per_cluster;
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context->reserved_sectors = bpb.reserved_sectors;
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context->number_of_fats = bpb.fats_count;
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context->hidden_sectors = bpb.hidden_sectors_count;
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context->sectors_per_fat = context->type == 32 ? bpb.sectors_per_fat_32 : bpb.sectors_per_fat_16;
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context->root_directory_cluster = bpb.root_directory_cluster;
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context->fat_start_lba = bpb.reserved_sectors;
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context->root_entries = bpb.directory_entries_count;
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context->root_start = context->reserved_sectors + context->number_of_fats * context->sectors_per_fat;
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context->root_size = DIV_ROUNDUP(context->root_entries * sizeof(struct fat32_directory_entry), FAT32_SECTOR_SIZE);
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switch (context->type) {
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case 16:
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context->data_start_lba = context->root_start + context->root_size;
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break;
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case 32:
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context->data_start_lba = context->root_start;
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break;
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default:
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__builtin_unreachable();
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}
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return 0;
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}
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static int read_cluster_from_map(struct fat32_context *context, uint32_t cluster, uint32_t *out) {
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switch (context->type) {
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case 16:
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*out = 0;
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volume_read(context->part, out, context->fat_start_lba * FAT32_SECTOR_SIZE + cluster * sizeof(uint16_t), sizeof(uint16_t));
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break;
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case 32:
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volume_read(context->part, out, context->fat_start_lba * FAT32_SECTOR_SIZE + cluster * sizeof(uint32_t), sizeof(uint32_t));
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*out &= 0x0fffffff;
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break;
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default:
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__builtin_unreachable();
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}
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return 0;
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}
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static uint32_t *cache_cluster_chain(struct fat32_context *context,
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uint32_t initial_cluster,
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size_t *_chain_length) {
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uint32_t cluster_limit = (context->type == 16 ? 0xffef : 0)
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| (context->type == 32 ? 0xfffffef : 0);
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if (initial_cluster < 0x2 || initial_cluster > cluster_limit)
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return NULL;
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uint32_t cluster = initial_cluster;
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size_t chain_length;
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for (chain_length = 1; ; chain_length++) {
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read_cluster_from_map(context, cluster, &cluster);
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if (cluster < 0x2 || cluster > cluster_limit)
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break;
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}
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uint32_t *cluster_chain = ext_mem_alloc(chain_length * sizeof(uint32_t));
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cluster = initial_cluster;
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for (size_t i = 0; i < chain_length; i++) {
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cluster_chain[i] = cluster;
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read_cluster_from_map(context, cluster, &cluster);
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}
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*_chain_length = chain_length;
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return cluster_chain;
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}
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static bool read_cluster_chain(struct fat32_context *context,
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uint32_t *cluster_chain,
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void *buf, uint64_t loc, uint64_t count) {
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size_t block_size = context->sectors_per_cluster * FAT32_SECTOR_SIZE;
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for (uint64_t progress = 0; progress < count;) {
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uint64_t block = (loc + progress) / block_size;
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uint64_t chunk = count - progress;
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uint64_t offset = (loc + progress) % block_size;
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if (chunk > block_size - offset)
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chunk = block_size - offset;
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uint64_t base = ((uint64_t)context->data_start_lba + (cluster_chain[block] - 2) * context->sectors_per_cluster) * FAT32_SECTOR_SIZE;
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volume_read(context->part, buf + progress, base + offset, chunk);
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progress += chunk;
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}
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return true;
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}
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// Copy ucs-2 characters to char*
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static void fat32_lfncpy(char* destination, const void* source, unsigned int size) {
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for (unsigned int i = 0; i < size; i++) {
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// ignore high bytes
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*(((uint8_t*) destination) + i) = *(((uint8_t*) source) + (i * 2));
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}
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}
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static bool fat32_filename_to_8_3(char *dest, const char *src) {
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int i = 0, j = 0;
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bool ext = false;
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for (size_t i = 0; i < 8+3; i++)
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dest[i] = ' ';
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while (src[i]) {
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if (src[i] == '.') {
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if (ext) {
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// This is a double extension here, just give up.
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return false;
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}
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ext = true;
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j = 8;
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i++;
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continue;
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}
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if (j >= 8+3 || (j >= 8 && !ext)) {
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// Filename too long, give up.
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return false;
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}
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dest[j++] = toupper(src[i++]);
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}
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return true;
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}
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static int fat32_open_in(struct fat32_context* context, struct fat32_directory_entry* directory, struct fat32_directory_entry* file, const char* name) {
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size_t block_size = context->sectors_per_cluster * FAT32_SECTOR_SIZE;
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char current_lfn[FAT32_LFN_MAX_FILENAME_LENGTH] = {0};
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size_t dir_chain_len;
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struct fat32_directory_entry *directory_entries;
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if (directory != NULL) {
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uint32_t current_cluster_number = directory->cluster_num_high << 16 | directory->cluster_num_low;
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uint32_t *directory_cluster_chain = cache_cluster_chain(context, current_cluster_number, &dir_chain_len);
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if (directory_cluster_chain == NULL)
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return -1;
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directory_entries = ext_mem_alloc(dir_chain_len * block_size);
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if (!read_cluster_chain(context, directory_cluster_chain, directory_entries, 0, dir_chain_len * block_size))
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return -1;
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} else {
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dir_chain_len = DIV_ROUNDUP(context->root_entries * sizeof(struct fat32_directory_entry), block_size);
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directory_entries = ext_mem_alloc(dir_chain_len * block_size);
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volume_read(context->part, directory_entries, context->root_start * FAT32_SECTOR_SIZE, context->root_entries * sizeof(struct fat32_directory_entry));
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}
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for (size_t i = 0; i < (dir_chain_len * block_size) / sizeof(struct fat32_directory_entry); i++) {
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if (directory_entries[i].file_name_and_ext[0] == 0x00) {
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// no more entries here
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break;
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}
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if (directory_entries[i].attribute == FAT32_LFN_ATTRIBUTE) {
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struct fat32_lfn_entry* lfn = (struct fat32_lfn_entry*) &directory_entries[i];
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if (lfn->sequence_number & 0b01000000) {
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// this lfn is the first entry in the table, clear the lfn buffer
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memset(current_lfn, ' ', sizeof(current_lfn));
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}
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const unsigned int lfn_index = ((lfn->sequence_number & 0b00011111) - 1U) * 13U;
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if (lfn_index >= FAT32_LFN_MAX_ENTRIES * 13) {
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continue;
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}
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fat32_lfncpy(current_lfn + lfn_index + 00, lfn->name1, 5);
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fat32_lfncpy(current_lfn + lfn_index + 05, lfn->name2, 6);
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fat32_lfncpy(current_lfn + lfn_index + 11, lfn->name3, 2);
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if (lfn_index != 0)
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continue;
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// remove trailing spaces
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for (int j = SIZEOF_ARRAY(current_lfn) - 2; j >= -1; j--) {
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if (j == -1 || current_lfn[j] != ' ') {
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current_lfn[j + 1] = 0;
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break;
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}
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}
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if (!strcmp(current_lfn, name)) {
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*file = directory_entries[i+1];
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return 0;
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}
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} else {
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char fn[8+3];
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if (!fat32_filename_to_8_3(fn, name)) {
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continue;
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}
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if (!strncmp(directory_entries[i].file_name_and_ext, fn, 8+3)) {
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*file = directory_entries[i];
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return 0;
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}
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}
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}
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// file not found
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return -1;
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}
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int fat32_check_signature(struct volume *part) {
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struct fat32_context context;
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return fat32_init_context(&context, part) == 0;
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}
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int fat32_open(struct fat32_file_handle* ret, struct volume *part, const char* path) {
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struct fat32_context context;
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int r = fat32_init_context(&context, part);
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if (r) {
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print("fat32: context init failure (%d)\n", r);
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return r;
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}
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struct fat32_directory_entry _current_directory;
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struct fat32_directory_entry *current_directory;
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struct fat32_directory_entry current_file;
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unsigned int current_index = 0;
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char current_part[FAT32_LFN_MAX_FILENAME_LENGTH];
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// skip trailing slashes
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while (path[current_index] == '/') {
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current_index++;
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}
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// walk down the directory tree
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switch (context.type) {
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case 16:
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current_directory = NULL;
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break;
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case 32:
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_current_directory.cluster_num_low = context.root_directory_cluster & 0xFFFF;
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_current_directory.cluster_num_high = context.root_directory_cluster >> 16;
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current_directory = &_current_directory;
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break;
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default:
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__builtin_unreachable();
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}
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for (;;) {
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bool expect_directory = false;
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for (unsigned int i = 0; i < SIZEOF_ARRAY(current_part); i++) {
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if (path[i + current_index] == 0) {
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memcpy(current_part, path + current_index, i);
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current_part[i] = 0;
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expect_directory = false;
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break;
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}
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if (path[i + current_index] == '/') {
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memcpy(current_part, path + current_index, i);
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current_part[i] = 0;
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current_index += i + 1;
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expect_directory = true;
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break;
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}
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}
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if ((r = fat32_open_in(&context, current_directory, ¤t_file, current_part)) != 0) {
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return r;
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}
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if (expect_directory) {
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_current_directory = current_file;
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current_directory = &_current_directory;
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} else {
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ret->context = context;
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ret->first_cluster = current_file.cluster_num_high << 16 | current_file.cluster_num_low;
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ret->size_clusters = DIV_ROUNDUP(current_file.file_size_bytes, FAT32_SECTOR_SIZE);
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ret->size_bytes = current_file.file_size_bytes;
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uint32_t file_cluster = current_file.cluster_num_high << 16 | current_file.cluster_num_low;
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size_t file_chain_len;
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ret->cluster_chain = cache_cluster_chain(&context, file_cluster, &file_chain_len);
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return 0;
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}
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}
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}
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int fat32_read(struct fat32_file_handle* file, void* buf, uint64_t loc, uint64_t count) {
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return !read_cluster_chain(&file->context, file->cluster_chain, buf, loc, count);
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}
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