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Merge branch 'ds/clarify-hashwrite'

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The hashwrite() API uses a buffering mechanism to avoid calling
write(2) too frequently. This logic has been refactored to be
easier to understand.

* ds/clarify-hashwrite:
  csum-file: make hashwrite() more readable
This commit is contained in:
Junio C Hamano 2021-04-07 16:54:08 -07:00
parent 642a40019c ddaf1f62e3
commit 573c5e50ab
1 changed files with 18 additions and 15 deletions
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33
csum-file.c
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@ -89,32 +89,35 @@ int finalize_hashfile(struct hashfile *f, unsigned char *result, unsigned int fl
void hashwrite(struct hashfile *f, const void *buf, unsigned int count)
{
while (count) {
unsigned offset = f->offset;
unsigned left = sizeof(f->buffer) - offset;
unsigned left = sizeof(f->buffer) - f->offset;
unsigned nr = count > left ? left : count;
const void *data;
if (f->do_crc)
f->crc32 = crc32(f->crc32, buf, nr);
if (nr == sizeof(f->buffer)) {
/* process full buffer directly without copy */
data = buf;
/*
* Flush a full batch worth of data directly
* from the input, skipping the memcpy() to
* the hashfile's buffer. In this block,
* f->offset is necessarily zero.
*/
the_hash_algo->update_fn(&f->ctx, buf, nr);
flush(f, buf, nr);
} else {
memcpy(f->buffer + offset, buf, nr);
data = f->buffer;
/*
* Copy to the hashfile's buffer, flushing only
* if it became full.
*/
memcpy(f->buffer + f->offset, buf, nr);
f->offset += nr;
left -= nr;
if (!left)
hashflush(f);
}
count -= nr;
offset += nr;
buf = (char *) buf + nr;
left -= nr;
if (!left) {
the_hash_algo->update_fn(&f->ctx, data, offset);
flush(f, data, offset);
offset = 0;
}
f->offset = offset;
}
}