diff options
Diffstat (limited to 'reftable/reader.c')
-rw-r--r-- | reftable/reader.c | 176 |
1 files changed, 92 insertions, 84 deletions
diff --git a/reftable/reader.c b/reftable/reader.c index b113daab77..481dff10d4 100644 --- a/reftable/reader.c +++ b/reftable/reader.c @@ -220,6 +220,7 @@ struct table_iter { struct reftable_reader *r; uint8_t typ; uint64_t block_off; + struct block_reader br; struct block_iter bi; int is_finished; }; @@ -227,16 +228,6 @@ struct table_iter { .bi = BLOCK_ITER_INIT \ } -static void table_iter_copy_from(struct table_iter *dest, - struct table_iter *src) -{ - dest->r = src->r; - dest->typ = src->typ; - dest->block_off = src->block_off; - dest->is_finished = src->is_finished; - block_iter_copy_from(&dest->bi, &src->bi); -} - static int table_iter_next_in_block(struct table_iter *ti, struct reftable_record *rec) { @@ -250,14 +241,8 @@ static int table_iter_next_in_block(struct table_iter *ti, static void table_iter_block_done(struct table_iter *ti) { - if (!ti->bi.br) { - return; - } - reftable_block_done(&ti->bi.br->block); - FREE_AND_NULL(ti->bi.br); - - ti->bi.last_key.len = 0; - ti->bi.next_off = 0; + block_reader_release(&ti->br); + block_iter_reset(&ti->bi); } static int32_t extract_block_size(uint8_t *data, uint8_t *typ, uint64_t off, @@ -321,32 +306,27 @@ done: return err; } -static int table_iter_next_block(struct table_iter *dest, - struct table_iter *src) +static void table_iter_close(struct table_iter *ti) { - uint64_t next_block_off = src->block_off + src->bi.br->full_block_size; - struct block_reader br = { 0 }; - int err = 0; + table_iter_block_done(ti); + block_iter_close(&ti->bi); +} - dest->r = src->r; - dest->typ = src->typ; - dest->block_off = next_block_off; +static int table_iter_next_block(struct table_iter *ti) +{ + uint64_t next_block_off = ti->block_off + ti->br.full_block_size; + int err; - err = reader_init_block_reader(src->r, &br, next_block_off, src->typ); - if (err > 0) { - dest->is_finished = 1; - return 1; - } - if (err != 0) + err = reader_init_block_reader(ti->r, &ti->br, next_block_off, ti->typ); + if (err > 0) + ti->is_finished = 1; + if (err) return err; - else { - struct block_reader *brp = - reftable_malloc(sizeof(struct block_reader)); - *brp = br; - dest->is_finished = 0; - block_reader_start(brp, &dest->bi); - } + ti->block_off = next_block_off; + ti->is_finished = 0; + block_iter_seek_start(&ti->bi, &ti->br); + return 0; } @@ -356,7 +336,6 @@ static int table_iter_next(struct table_iter *ti, struct reftable_record *rec) return REFTABLE_API_ERROR; while (1) { - struct table_iter next = TABLE_ITER_INIT; int err; if (ti->is_finished) @@ -376,15 +355,11 @@ static int table_iter_next(struct table_iter *ti, struct reftable_record *rec) * table and retry. If there are no more blocks then the * iterator is drained. */ - err = table_iter_next_block(&next, ti); - table_iter_block_done(ti); + err = table_iter_next_block(ti); if (err) { ti->is_finished = 1; return err; } - - table_iter_copy_from(ti, &next); - block_iter_close(&next.bi); } } @@ -393,16 +368,14 @@ static int table_iter_next_void(void *ti, struct reftable_record *rec) return table_iter_next(ti, rec); } -static void table_iter_close(void *p) +static void table_iter_close_void(void *ti) { - struct table_iter *ti = p; - table_iter_block_done(ti); - block_iter_close(&ti->bi); + table_iter_close(ti); } static struct reftable_iterator_vtable table_iter_vtable = { .next = &table_iter_next_void, - .close = &table_iter_close, + .close = &table_iter_close_void, }; static void iterator_from_table_iter(struct reftable_iterator *it, @@ -417,19 +390,16 @@ static int reader_table_iter_at(struct reftable_reader *r, struct table_iter *ti, uint64_t off, uint8_t typ) { - struct block_reader br = { 0 }; - struct block_reader *brp = NULL; + int err; - int err = reader_init_block_reader(r, &br, off, typ); + err = reader_init_block_reader(r, &ti->br, off, typ); if (err != 0) return err; - brp = reftable_malloc(sizeof(struct block_reader)); - *brp = br; ti->r = r; - ti->typ = block_reader_type(brp); + ti->typ = block_reader_type(&ti->br); ti->block_off = off; - block_reader_start(brp, &ti->bi); + block_iter_seek_start(&ti->bi, &ti->br); return 0; } @@ -454,23 +424,52 @@ static int reader_seek_linear(struct table_iter *ti, { struct strbuf want_key = STRBUF_INIT; struct strbuf got_key = STRBUF_INIT; - struct table_iter next = TABLE_ITER_INIT; struct reftable_record rec; int err = -1; reftable_record_init(&rec, reftable_record_type(want)); reftable_record_key(want, &want_key); + /* + * First we need to locate the block that must contain our record. To + * do so we scan through blocks linearly until we find the first block + * whose first key is bigger than our wanted key. Once we have found + * that block we know that the key must be contained in the preceding + * block. + * + * This algorithm is somewhat unfortunate because it means that we + * always have to seek one block too far and then back up. But as we + * can only decode the _first_ key of a block but not its _last_ key we + * have no other way to do this. + */ while (1) { - err = table_iter_next_block(&next, ti); + struct table_iter next = *ti; + + /* + * We must be careful to not modify underlying data of `ti` + * because we may find that `next` does not contain our desired + * block, but that `ti` does. In that case, we would discard + * `next` and continue with `ti`. + * + * This also means that we cannot reuse allocated memory for + * `next` here. While it would be great if we could, it should + * in practice not be too bad given that we should only ever + * end up doing linear seeks with at most three blocks. As soon + * as we have more than three blocks we would have an index, so + * we would not do a linear search there anymore. + */ + memset(&next.br.block, 0, sizeof(next.br.block)); + next.br.zstream = NULL; + next.br.uncompressed_data = NULL; + next.br.uncompressed_cap = 0; + + err = table_iter_next_block(&next); if (err < 0) goto done; - - if (err > 0) { + if (err > 0) break; - } - err = block_reader_first_key(next.bi.br, &got_key); + err = block_reader_first_key(&next.br, &got_key); if (err < 0) goto done; @@ -480,16 +479,20 @@ static int reader_seek_linear(struct table_iter *ti, } table_iter_block_done(ti); - table_iter_copy_from(ti, &next); + *ti = next; } - err = block_iter_seek(&ti->bi, &want_key); + /* + * We have located the block that must contain our record, so we seek + * the wanted key inside of it. If the block does not contain our key + * we know that the corresponding record does not exist. + */ + err = block_iter_seek_key(&ti->bi, &ti->br, &want_key); if (err < 0) goto done; err = 0; done: - block_iter_close(&next.bi); reftable_record_release(&rec); strbuf_release(&want_key); strbuf_release(&got_key); @@ -508,6 +511,7 @@ static int reader_seek_indexed(struct reftable_reader *r, .u.idx = { .last_key = STRBUF_INIT }, }; struct table_iter index_iter = TABLE_ITER_INIT; + struct table_iter empty = TABLE_ITER_INIT; struct table_iter next = TABLE_ITER_INIT; int err = 0; @@ -549,7 +553,6 @@ static int reader_seek_indexed(struct reftable_reader *r, * not exist. */ err = table_iter_next(&index_iter, &index_result); - table_iter_block_done(&index_iter); if (err != 0) goto done; @@ -558,7 +561,7 @@ static int reader_seek_indexed(struct reftable_reader *r, if (err != 0) goto done; - err = block_iter_seek(&next.bi, &want_index.u.idx.last_key); + err = block_iter_seek_key(&next.bi, &next.br, &want_index.u.idx.last_key); if (err < 0) goto done; @@ -572,18 +575,20 @@ static int reader_seek_indexed(struct reftable_reader *r, break; } - table_iter_copy_from(&index_iter, &next); + table_iter_close(&index_iter); + index_iter = next; + next = empty; } if (err == 0) { - struct table_iter empty = TABLE_ITER_INIT; struct table_iter *malloced = reftable_calloc(1, sizeof(*malloced)); - *malloced = empty; - table_iter_copy_from(malloced, &next); + *malloced = next; + next = empty; iterator_from_table_iter(it, malloced); } + done: - block_iter_close(&next.bi); + table_iter_close(&next); table_iter_close(&index_iter); reftable_record_release(&want_index); reftable_record_release(&index_result); @@ -597,25 +602,28 @@ static int reader_seek_internal(struct reftable_reader *r, struct reftable_reader_offsets *offs = reader_offsets_for(r, reftable_record_type(rec)); uint64_t idx = offs->index_offset; - struct table_iter ti = TABLE_ITER_INIT; - int err = 0; + struct table_iter ti = TABLE_ITER_INIT, *p; + int err; + if (idx > 0) return reader_seek_indexed(r, it, rec); err = reader_start(r, &ti, reftable_record_type(rec), 0); if (err < 0) - return err; + goto out; + err = reader_seek_linear(&ti, rec); if (err < 0) - return err; - else { - struct table_iter *p = - reftable_malloc(sizeof(struct table_iter)); - *p = ti; - iterator_from_table_iter(it, p); - } + goto out; - return 0; + REFTABLE_ALLOC_ARRAY(p, 1); + *p = ti; + iterator_from_table_iter(it, p); + +out: + if (err) + table_iter_close(&ti); + return err; } static int reader_seek(struct reftable_reader *r, struct reftable_iterator *it, |