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https://github.com/eledio-devices/thirdparty-littlefs.git
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8a674524fc
In writing the initial allocator, I ran into the rather difficult problem of trying to iterate through the entire filesystem cheaply and with only constant memory consumption (which prohibits recursive functions). The solution was to simply thread all directory blocks onto a massive linked-list that spans the entire filesystem. With the linked-list it was easy to create a traverse function for all blocks in use on the filesystem (which has potential for other utility), and add the rudimentary block allocator using a bit-vector. While the linked-list may add complexity (especially where needing to maintain atomic operations), the linked-list helps simplify what is currently the most expensive operation in the filesystem, with no cost to space (the linked-list can reuse the pointers used for chained directory blocks).
156 lines
3.3 KiB
C
156 lines
3.3 KiB
C
/*
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* The little filesystem
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*
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* Copyright (c) 2017 Christopher Haster
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* Distributed under the MIT license
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*/
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#ifndef LFS_H
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#define LFS_H
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#include "lfs_config.h"
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#include "lfs_bd.h"
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// Data structures
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enum lfs_error {
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LFS_ERROR_OK = 0,
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LFS_ERROR_CORRUPT = -3,
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LFS_ERROR_NO_ENTRY = -4,
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LFS_ERROR_EXISTS = -5,
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LFS_ERROR_NOT_DIR = -6,
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LFS_ERROR_IS_DIR = -7,
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LFS_ERROR_INVALID = -8,
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LFS_ERROR_NO_SPACE = -9,
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};
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enum lfs_type {
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LFS_TYPE_REG = 1,
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LFS_TYPE_DIR = 2,
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};
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enum lfs_open_flags {
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LFS_O_RDONLY = 0,
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LFS_O_WRONLY = 1,
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LFS_O_RDWR = 2,
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LFS_O_CREAT = 0x020,
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LFS_O_EXCL = 0x040,
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LFS_O_TRUNC = 0x080,
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LFS_O_APPEND = 0x100,
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LFS_O_SYNC = 0x200,
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};
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struct lfs_config {
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lfs_bd_t *bd;
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const struct lfs_bd_ops *bd_ops;
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lfs_size_t read_size;
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lfs_size_t prog_size;
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lfs_size_t block_size;
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lfs_size_t block_count;
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};
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struct lfs_info {
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uint8_t type;
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lfs_size_t size;
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char name[LFS_NAME_MAX+1];
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};
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typedef struct lfs_entry {
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lfs_block_t dir[2];
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lfs_off_t off;
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struct lfs_disk_entry {
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uint16_t type;
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uint16_t len;
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union {
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struct {
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lfs_block_t head;
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lfs_size_t size;
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} file;
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lfs_block_t dir[2];
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} u;
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} d;
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} lfs_entry_t;
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typedef struct lfs_file {
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lfs_block_t head;
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lfs_size_t size;
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lfs_block_t wblock;
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uint32_t windex;
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lfs_block_t rblock;
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uint32_t rindex;
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lfs_off_t roff;
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struct lfs_entry entry;
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} lfs_file_t;
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typedef struct lfs_dir {
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lfs_block_t pair[2];
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lfs_off_t off;
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struct lfs_disk_dir {
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uint32_t rev;
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lfs_size_t size;
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lfs_block_t tail[2];
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} d;
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} lfs_dir_t;
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typedef struct lfs_superblock {
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lfs_block_t pair[2];
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struct lfs_disk_superblock {
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uint32_t rev;
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uint32_t size;
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lfs_block_t root[2];
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char magic[8];
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uint32_t block_size;
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uint32_t block_count;
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} d;
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} lfs_superblock_t;
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// Little filesystem type
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typedef struct lfs {
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lfs_size_t read_size; // size of read
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lfs_size_t prog_size; // size of program
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lfs_size_t block_size; // size of erase (block size)
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lfs_size_t block_count; // number of erasable blocks
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lfs_size_t words; // number of 32-bit words that can fit in a block
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lfs_bd_t *bd;
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const struct lfs_bd_ops *bd_ops;
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lfs_block_t root[2];
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lfs_block_t cwd[2];
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struct {
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lfs_block_t begin;
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lfs_block_t end;
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} free;
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uint32_t lookahead[LFS_CFG_LOOKAHEAD/32];
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} lfs_t;
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// Functions
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int lfs_format(lfs_t *lfs, const struct lfs_config *config);
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int lfs_mount(lfs_t *lfs, const struct lfs_config *config);
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int lfs_unmount(lfs_t *lfs);
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int lfs_remove(lfs_t *lfs, const char *path);
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int lfs_mkdir(lfs_t *lfs, const char *path);
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int lfs_dir_open(lfs_t *lfs, lfs_dir_t *dir, const char *path);
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int lfs_dir_close(lfs_t *lfs, lfs_dir_t *dir);
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int lfs_dir_read(lfs_t *lfs, lfs_dir_t *dir, struct lfs_info *info);
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int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
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const char *path, int flags);
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int lfs_file_close(lfs_t *lfs, lfs_file_t *file);
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lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
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const void *buffer, lfs_size_t size);
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lfs_ssize_t lfs_file_read(lfs_t *lfs, lfs_file_t *file,
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void *buffer, lfs_size_t size);
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#endif
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