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lfs_bd_cmp() compares more bytes at one time #395

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Merged
merged 1 commit into from
Dec 4, 2020
Merged

lfs_bd_cmp() compares more bytes at one time #395

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20 changes: 12 additions & 8 deletions lfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -103,18 +103,22 @@ static int lfs_bd_cmp(lfs_t *lfs,
lfs_block_t block, lfs_off_t off,
const void *buffer, lfs_size_t size) {
const uint8_t *data = buffer;
lfs_size_t diff = 0;

for (lfs_off_t i = 0; i < size; i++) {
uint8_t dat;
int err = lfs_bd_read(lfs,
for (lfs_off_t i = 0; i < size; i += diff) {
uint8_t dat[8];
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Why was 8 chosen.
Remember that this is being stored on the stack.
Any thoughts on making this configurable or reasons why it shouldn't be configurable?

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Too many configurations can be confusing.
I think 8 bytes is the best balance between performance and used space.


diff = lfs_min(size-i, sizeof(dat));
int res = lfs_bd_read(lfs,
pcache, rcache, hint-i,
block, off+i, &dat, 1);
if (err) {
return err;
block, off+i, &dat, diff);
if (res) {
return res;
}

if (dat != data[i]) {
return (dat < data[i]) ? LFS_CMP_LT : LFS_CMP_GT;
res = memcmp(dat, data + i, diff);
if (res) {
return res < 0 ? LFS_CMP_LT : LFS_CMP_GT;
}
}

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