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reading from a root-directory file basically works

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This commit is contained in:
Wiesner András 2023-10-03 07:04:31 +02:00
parent 46f6fe7494
commit 1e6e6253b9
2 changed files with 116 additions and 32 deletions
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101
fs/fat32/fat32.c
View File

@ -35,6 +35,7 @@ int fat32_load(Fat32_CtrlBlock *ctrl, uint32_t bpb_s, const MassStorage * mstg)
memcpy(ctrl->volume_label, bpb_obj->volume_label, 11);
ctrl->serial_number = bpb_obj->volume_serial_number;
ctrl->fat_copies = bpb_obj->n_fats;
ctrl->fat_entries_per_sector = ctrl->bytes_per_sector / sizeof(Fat32_FatTableEntry);
ctrl->fat_s = ctrl->bpb_s + bpb_obj->n_reserved_sectors; // FATs are stored on the hidden area right after the reserved sectors
ctrl->data_s = ctrl->fat_s + ctrl->fat_copies * ctrl->sectors_per_fat; // data region begins right after the FAT copies
@ -166,11 +167,11 @@ int fat32_print_file_entry(Fat32_FileEntry ** const entry) {
static inline uint16_t fat32_extract_next_basename_length(const char *path) {
uint16_t i;
for (i = 0; path[i] != FAT32_DIRECTORY_SEPARATOR && path[i] != '\0'; i++) {}
for (i = 0; (path[i] != FAT32_DIRECTORY_SEPARATOR) && (path[i] != '\0'); i++) {}
return i;
}
int fat32_locate_file(const Fat32_CtrlBlock *ctrl, const char *path) {
const Fat32_FileEntry *fat32_locate_file(const Fat32_CtrlBlock *ctrl, const char *path) {
FETCH_MSTG;
// start search in the root directory
@ -183,6 +184,8 @@ int fat32_locate_file(const Fat32_CtrlBlock *ctrl, const char *path) {
const char *path_iter = path; // path is being fetched from its beginning
char basename[FAT32_MAX_BASENAME_LENGTH + 1]; // basename
basename[FAT32_MAX_BASENAME_LENGTH] = '\0'; // NULL-termination
char entry_name[FAT32_MAX_BASENAME_LENGTH + 1]; // entry name
Fat32_FileEntry *entry = NULL; // entry iterator
while ((!file_found) && (!no_such_file)) {
// extract first basename
@ -190,10 +193,63 @@ int fat32_locate_file(const Fat32_CtrlBlock *ctrl, const char *path) {
uint16_t copy_len = MIN(basename_len, FAT32_MAX_BASENAME_LENGTH);
memcpy(basename, path_iter, copy_len); // extract basename
basename[copy_len] = '\0'; // NULL-termination
path_iter += basename_len + 1; // advance basename
path_iter += basename_len; // advance basename
// search for basename in the current directory
// acquire pointer to the beginning of the file entry table
entry = (Fat32_FileEntry *) buffer;
bool basename_entry_found = false;
while ((entry->short_fname[0] != 0x00) && (!basename_entry_found)) {
if (entry->short_fname[0] != FAT32_UNUSED_FILE_ENTRY) {
fat32_get_file_entry(&entry, entry_name);
// compare entry name
if (!strncmp(entry_name, basename, basename_len)) { // if matches...
basename_entry_found = true; // ...then the entry is found
continue;
}
}
return 0;
entry++;
// if we crossed the first buffer - second buffer border, then
// copy the second buffer to the first one and load the next sector
// to the second buffer
if ((void *) entry > (void *) (buffer + SECTOR_SIZE)) {
// copy the second buffer to the first one
fat32_copy_second_to_first_buffer();
sector++;
READ_MSTG_TO_SECOND_BUFFER(sector + 1);
// modify the entry pointer, since it's been moved
entry = (Fat32_FileEntry *) (((uint8_t *) (entry)) - SECTOR_SIZE);
}
}
// if the basename entry is found...
if (basename_entry_found) {
if (path_iter[0] == '\0') { // ...and it's the end of the path
file_found = true; // ...then the file is found
} else { // ...if it's not the end of the path, then load the cluster corresponding to the entry
// determine sector number
uint32_t next_cluster = (entry->first_cluster_high << 16) | (entry->first_cluster_low);
uint32_t next_sector = fat32_get_first_sector_of_cluster(ctrl, next_cluster);
// load sectors
READ_MSTG_TO_FIRST_BUFFER(next_sector);
READ_MSTG_TO_SECOND_BUFFER(next_sector + 1);
}
} else { // if not found...
no_such_file = true; // ...then the file could not be located
}
}
// return with appropriate value
if (!no_such_file) {
return entry;
} else {
return NULL;
}
}
int fat32_list_dir(const Fat32_CtrlBlock *ctrl, const char *dir) {
@ -234,8 +290,35 @@ static inline uint32_t fat32_get_fat_entry_sector_by_cluster_index(const Fat32_C
return cluster * sizeof(Fat32_FatTableEntry) / ctrl->bytes_per_sector + ctrl->fat_s;
}
//int fat32_read_file(const Fat32_CtrlBlock * ctrl, uint32_t pos, uint32_t len) {
// FETCH_MSTG;
// uint32_t fae_sec =
// Fat32_FatTableEntry fae =
//}
static inline uint32_t fat32_get_cluster_from_pos(const Fat32_CtrlBlock * ctrl, uint32_t first_cluster, uint32_t pos) {
FETCH_MSTG;
uint32_t cluster_link_number = pos / (ctrl->sectors_per_cluster * ctrl->bytes_per_sector); // calculate the sequence number of the FAT entry containing the reference to the desired data cluster
uint32_t fat_iter_sector = 0;
uint32_t cluster = first_cluster; // linked cluster
Fat32_FatTableEntry * fat_iter = NULL; // iterator on FAT table
for (uint32_t hop = 0; hop < cluster_link_number; hop++) {
uint32_t new_fat_iter_sector = fat32_get_fat_entry_sector_by_cluster_index(ctrl, cluster); // get the FAT sector containing the referred entry
if (new_fat_iter_sector != fat_iter_sector) {
READ_MSTG_TO_FIRST_BUFFER(new_fat_iter_sector); // read FAT sector containing the specific entry to the buffer
fat_iter_sector = new_fat_iter_sector;
}
fat_iter = ((Fat32_FatTableEntry *) buffer) + (cluster % ctrl->fat_entries_per_sector); // get FAT iter
uint32_t next_cluster = (*fat_iter) & ~(0xF << 28);
if (next_cluster >= 2 && next_cluster <= 0xFFFFFEF) {
cluster = next_cluster;
}
}
return cluster;
}
int fat32_read_file(const Fat32_CtrlBlock * ctrl, const Fat32_FileEntry * entry, uint32_t pos, uint32_t len, uint8_t * p) {
FETCH_MSTG;
uint32_t first_cluster = (entry->first_cluster_high << 16) | (entry->first_cluster_low);
uint32_t cluster = fat32_get_cluster_from_pos(ctrl, first_cluster, pos);
uint32_t sector = fat32_get_first_sector_of_cluster(ctrl, cluster);
READ_MSTG_TO_FIRST_BUFFER(sector);
uint32_t pos_in_sector = pos % ctrl->bytes_per_sector;
memcpy(p, buffer + pos_in_sector, len);
return len; // TODO
}

5
fs/fat32/fat32.h
View File

@ -50,6 +50,7 @@ typedef struct {
uint32_t sectors_per_fat; // sectors per FAT table
uint16_t bytes_per_sector; // number of bytes creating a sector
uint16_t sectors_per_cluster; // number of sectors creating a cluster
uint16_t fat_entries_per_sector; // number of FAT entries per sector
uint8_t fat_copies; // number of FAT table copies
uint8_t volume_label[11]; // pointer to volume label
} Fat32_CtrlBlock;
@ -94,8 +95,8 @@ int fat32_load(Fat32_CtrlBlock *ctrl, uint32_t bpb_s, const MassStorage * mstg);
int fat32_list_dir(const Fat32_CtrlBlock *ctrl, const char * dir);
int fat32_read_file(const Fat32_CtrlBlock * ctrl, uint32_t pos, uint32_t len);
int fat32_read_file(const Fat32_CtrlBlock * ctrl, const Fat32_FileEntry * entry, uint32_t pos, uint32_t len, uint8_t * p);
int fat32_locate_file(const Fat32_CtrlBlock *ctrl, const char *path);
const Fat32_FileEntry * fat32_locate_file(const Fat32_CtrlBlock *ctrl, const char *path);
#endif //EMBPART_FAT32_H