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Added size field to entry structure
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The size field is redundant, since an entry's size can be determined
from the nlen+elen+alen+4. However, as you may have guessed from that
expression, calculating the size this way is a bit roundabout and
inefficient. Despite its redundancy, it's cheaper to store the size in the
entry, though with a minor RAM cost.

Note, extra care must now be taken to make sure these size and len fields
don't fall out of sync.
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@geky
geky committed Oct 10, 2018
1 parent 03b262b commit 9273ac7
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Showing 2 changed files with 33 additions and 52 deletions.
82 changes: 32 additions & 50 deletions lfs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -397,10 +397,6 @@ static inline bool lfs_pairsync(
(paira[0] == pairb[1] && paira[1] == pairb[0]);
}

static inline lfs_size_t lfs_entry_size(const lfs_entry_t *entry) {
return 4 + entry->d.elen + entry->d.alen + entry->d.nlen;
}

static int lfs_dir_alloc(lfs_t *lfs, lfs_dir_t *dir) {
// allocate pair of dir blocks
for (int i = 0; i < 2; i++) {
Expand Down Expand Up @@ -677,14 +673,14 @@ static int lfs_dir_commit(lfs_t *lfs, lfs_dir_t *dir,
return 0;
}

static int lfs_dir_append_(lfs_t *lfs, lfs_dir_t *dir,
lfs_off_t *off, lfs_size_t size, struct lfs_region *regions) {
static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
lfs_entry_t *entry, struct lfs_region *regions) {
// check if we fit, if top bit is set we do not and move on
while (true) {
if ((0x7fffffff & dir->d.size) + size <= lfs->cfg->block_size) {
*off = dir->d.size - 4;
if ((0x7fffffff & dir->d.size) + entry->size <= lfs->cfg->block_size) {
entry->off = dir->d.size - 4;
for (struct lfs_region *r = regions; r; r = r->next) {
r->off += *off;
r->off += entry->off;
}

return lfs_dir_commit(lfs, dir, regions);
Expand All @@ -700,9 +696,9 @@ static int lfs_dir_append_(lfs_t *lfs, lfs_dir_t *dir,

dir->d.tail[0] = olddir.d.tail[0];
dir->d.tail[1] = olddir.d.tail[1];
*off = dir->d.size - 4;
entry->off = dir->d.size - 4;
for (struct lfs_region *r = regions; r; r = r->next) {
r->off += *off;
r->off += entry->off;
}

err = lfs_dir_commit(lfs, dir, regions);
Expand All @@ -723,10 +719,10 @@ static int lfs_dir_append_(lfs_t *lfs, lfs_dir_t *dir,
}
}

static int lfs_dir_remove_(lfs_t *lfs, lfs_dir_t *dir,
lfs_off_t off, lfs_size_t size) {
static int lfs_dir_remove(lfs_t *lfs, lfs_dir_t *dir,
const lfs_entry_t *entry) {
// check if we should just drop the directory block
if ((dir->d.size & 0x7fffffff) == sizeof(dir->d)+4 + size) {
if ((dir->d.size & 0x7fffffff) == sizeof(dir->d)+4 + entry->size) {
lfs_dir_t pdir;
int res = lfs_pred(lfs, dir->pair, &pdir);
if (res < 0) {
Expand All @@ -744,7 +740,7 @@ static int lfs_dir_remove_(lfs_t *lfs, lfs_dir_t *dir,
// shift out the entry
int err = lfs_dir_commit(lfs, dir,
&(struct lfs_region){
off, -size,
entry->off, -entry->size,
lfs_commit_mem, NULL, 0});
if (err) {
return err;
Expand All @@ -753,38 +749,27 @@ static int lfs_dir_remove_(lfs_t *lfs, lfs_dir_t *dir,
// shift over any files/directories that are affected
for (lfs_file_t *f = lfs->files; f; f = f->next) {
if (lfs_paircmp(f->pair, dir->pair) == 0) {
if (f->poff == off) {
if (f->poff == entry->off) {
f->pair[0] = 0xffffffff;
f->pair[1] = 0xffffffff;
} else if (f->poff > off) {
f->poff -= size;
} else if (f->poff > entry->off) {
f->poff -= entry->size;
}
}
}

for (lfs_dir_t *d = lfs->dirs; d; d = d->next) {
if (lfs_paircmp(d->pair, dir->pair) == 0) {
if (d->off > off) {
d->off -= size;
d->pos -= size;
if (d->off > entry->off) {
d->off -= entry->size;
d->pos -= entry->size;
}
}
}

return 0;
}

static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
lfs_entry_t *entry, struct lfs_region *regions) {
return lfs_dir_append_(lfs, dir,
&entry->off, lfs_entry_size(entry), regions);
}

static int lfs_dir_remove(lfs_t *lfs, lfs_dir_t *dir, lfs_entry_t *entry) {
return lfs_dir_remove_(lfs, dir,
entry->off, lfs_entry_size(entry));
}

static int lfs_dir_update(lfs_t *lfs, lfs_dir_t *dir,
lfs_entry_t *entry, struct lfs_region *regions) {
lfs_ssize_t diff = 0;
Expand Down Expand Up @@ -823,7 +808,7 @@ static int lfs_dir_update(lfs_t *lfs, lfs_dir_t *dir,
} else {
lfs_dir_t olddir = *dir;
lfs_off_t oldoff = entry->off;
lfs_size_t oldsize = lfs_entry_size(entry) - diff;
lfs_size_t oldsize = entry->size - diff;

// mark as moving
entry->d.type |= LFS_STRUCT_MOVED;
Expand All @@ -839,21 +824,18 @@ static int lfs_dir_update(lfs_t *lfs, lfs_dir_t *dir,
// append updated entry
err = lfs_dir_append(lfs, dir, entry,
&(struct lfs_region){
0, +lfs_entry_size(entry),
0, +entry->size,
lfs_commit_disk, &(struct lfs_commit_disk){
olddir.pair[0], entry->off, regions}, oldsize});
if (err) {
return err;
}

// remove old entry
err = lfs_dir_remove_(lfs, dir, oldoff, oldsize);
err = lfs_dir_remove(lfs, dir, &(lfs_entry_t){oldoff, oldsize});
if (err) {
return err;
}

// TODO remove file under file?
// TODO need to shift entries?
}

return 0;
Expand Down Expand Up @@ -883,8 +865,9 @@ static int lfs_dir_next(lfs_t *lfs, lfs_dir_t *dir, lfs_entry_t *entry) {
}

entry->off = dir->off;
dir->off += lfs_entry_size(entry);
dir->pos += lfs_entry_size(entry);
entry->size = 4 + entry->d.elen + entry->d.alen + entry->d.nlen;
dir->off += entry->size;
dir->pos += entry->size;
return 0;
}

Expand All @@ -903,9 +886,6 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
if (pathname[0] == '\0') {
*entry = (lfs_entry_t){
.d.type = LFS_STRUCT_DIR | LFS_TYPE_DIR,
.d.elen = sizeof(entry->d) - 4,
.d.alen = 0,
.d.nlen = 0,
.d.u.dir[0] = lfs->root[0],
.d.u.dir[1] = lfs->root[1],
};
Expand Down Expand Up @@ -960,7 +940,7 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
}

int res = lfs_bd_cmp(lfs, dir->pair[0],
entry->off + 4+entry->d.elen+entry->d.alen,
entry->off + entry->size - pathlen,
pathname, pathlen);
if (res < 0) {
return res;
Expand Down Expand Up @@ -1046,6 +1026,7 @@ int lfs_mkdir(lfs_t *lfs, const char *path) {
entry.d.nlen = strlen(path);
entry.d.u.dir[0] = dir.pair[0];
entry.d.u.dir[1] = dir.pair[1];
entry.size = 4 + entry.d.elen + entry.d.alen + entry.d.nlen;

cwd.d.tail[0] = dir.pair[0];
cwd.d.tail[1] = dir.pair[1];
Expand Down Expand Up @@ -1164,7 +1145,7 @@ int lfs_dir_read(lfs_t *lfs, lfs_dir_t *dir, struct lfs_info *info) {
}

int err = lfs_bd_read(lfs, dir->pair[0],
entry.off + 4+entry.d.elen+entry.d.alen,
entry.off + entry.size - entry.d.nlen,
info->name, entry.d.nlen);
if (err) {
return err;
Expand Down Expand Up @@ -1440,6 +1421,8 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
entry.d.nlen = strlen(path);
entry.d.u.file.head = 0xffffffff;
entry.d.u.file.size = 0;
entry.size = 4 + entry.d.elen + entry.d.alen + entry.d.nlen;

err = lfs_dir_append(lfs, &cwd, &entry,
&(struct lfs_region){
0, +sizeof(entry.d),
Expand Down Expand Up @@ -1959,7 +1942,7 @@ int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info) {
strcpy(info->name, "/");
} else {
err = lfs_bd_read(lfs, cwd.pair[0],
entry.off + 4+entry.d.elen+entry.d.alen,
entry.off + entry.size - entry.d.nlen,
info->name, entry.d.nlen);
if (err) {
return err;
Expand Down Expand Up @@ -2272,7 +2255,6 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {

// write superblocks
lfs_superblock_t superblock = {
.off = sizeof(superdir.d),
.d.type = LFS_STRUCT_DIR | LFS_TYPE_SUPERBLOCK,
.d.elen = sizeof(superblock.d) - sizeof(superblock.d.magic) - 4,
.d.nlen = sizeof(superblock.d.magic),
Expand Down Expand Up @@ -2374,8 +2356,6 @@ int lfs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data) {
}

// iterate over metadata pairs
lfs_dir_t dir;
lfs_entry_t entry;
lfs_block_t cwd[2] = {0, 1};

while (true) {
Expand All @@ -2386,12 +2366,14 @@ int lfs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data) {
}
}

lfs_dir_t dir;
int err = lfs_dir_fetch(lfs, &dir, cwd);
if (err) {
return err;
}

// iterate over contents
lfs_entry_t entry;
while (dir.off + sizeof(entry.d) <= (0x7fffffff & dir.d.size)-4) {
err = lfs_bd_read(lfs, dir.pair[0], dir.off,
&entry.d, sizeof(entry.d));
Expand All @@ -2400,7 +2382,7 @@ int lfs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data) {
return err;
}

dir.off += lfs_entry_size(&entry);
dir.off += 4 + entry.d.elen + entry.d.alen + entry.d.nlen;
if ((0x70 & entry.d.type) == LFS_STRUCT_CTZ) {
err = lfs_ctz_traverse(lfs, &lfs->rcache, NULL,
entry.d.u.file.head, entry.d.u.file.size, cb, data);
Expand Down
3 changes: 1 addition & 2 deletions lfs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -196,6 +196,7 @@ struct lfs_info {
/// littlefs data structures ///
typedef struct lfs_entry {
lfs_off_t off;
lfs_size_t size;

struct lfs_disk_entry {
uint8_t type;
Expand Down Expand Up @@ -249,8 +250,6 @@ typedef struct lfs_dir {
} lfs_dir_t;

typedef struct lfs_superblock {
lfs_off_t off;

struct lfs_disk_superblock {
uint8_t type;
uint8_t elen;
Expand Down

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