diff options
Diffstat (limited to 'reftable/table.c')
| -rw-r--r-- | reftable/table.c | 779 |
1 files changed, 779 insertions, 0 deletions
diff --git a/reftable/table.c b/reftable/table.c new file mode 100644 index 0000000000..56362df0ed --- /dev/null +++ b/reftable/table.c @@ -0,0 +1,779 @@ +/* + * Copyright 2020 Google LLC + * + * Use of this source code is governed by a BSD-style + * license that can be found in the LICENSE file or at + * https://developers.google.com/open-source/licenses/bsd + */ + +#include "table.h" + +#include "system.h" +#include "block.h" +#include "blocksource.h" +#include "constants.h" +#include "iter.h" +#include "record.h" +#include "reftable-error.h" + +static struct reftable_table_offsets * +table_offsets_for(struct reftable_table *t, uint8_t typ) +{ + switch (typ) { + case REFTABLE_BLOCK_TYPE_REF: + return &t->ref_offsets; + case REFTABLE_BLOCK_TYPE_LOG: + return &t->log_offsets; + case REFTABLE_BLOCK_TYPE_OBJ: + return &t->obj_offsets; + } + abort(); +} + +enum reftable_hash reftable_table_hash_id(struct reftable_table *t) +{ + return t->hash_id; +} + +const char *reftable_table_name(struct reftable_table *t) +{ + return t->name; +} + +static int parse_footer(struct reftable_table *t, uint8_t *footer, + uint8_t *header) +{ + uint8_t *f = footer; + uint8_t first_block_typ; + int err = 0; + uint32_t computed_crc; + uint32_t file_crc; + + if (memcmp(f, "REFT", 4)) { + err = REFTABLE_FORMAT_ERROR; + goto done; + } + f += 4; + + if (memcmp(footer, header, header_size(t->version))) { + err = REFTABLE_FORMAT_ERROR; + goto done; + } + + f++; + t->block_size = reftable_get_be24(f); + + f += 3; + t->min_update_index = reftable_get_be64(f); + f += 8; + t->max_update_index = reftable_get_be64(f); + f += 8; + + if (t->version == 1) { + t->hash_id = REFTABLE_HASH_SHA1; + } else { + switch (reftable_get_be32(f)) { + case REFTABLE_FORMAT_ID_SHA1: + t->hash_id = REFTABLE_HASH_SHA1; + break; + case REFTABLE_FORMAT_ID_SHA256: + t->hash_id = REFTABLE_HASH_SHA256; + break; + default: + err = REFTABLE_FORMAT_ERROR; + goto done; + } + + f += 4; + } + + t->ref_offsets.index_offset = reftable_get_be64(f); + f += 8; + + t->obj_offsets.offset = reftable_get_be64(f); + f += 8; + + t->object_id_len = t->obj_offsets.offset & ((1 << 5) - 1); + t->obj_offsets.offset >>= 5; + + t->obj_offsets.index_offset = reftable_get_be64(f); + f += 8; + t->log_offsets.offset = reftable_get_be64(f); + f += 8; + t->log_offsets.index_offset = reftable_get_be64(f); + f += 8; + + computed_crc = crc32(0, footer, f - footer); + file_crc = reftable_get_be32(f); + f += 4; + if (computed_crc != file_crc) { + err = REFTABLE_FORMAT_ERROR; + goto done; + } + + first_block_typ = header[header_size(t->version)]; + t->ref_offsets.is_present = (first_block_typ == REFTABLE_BLOCK_TYPE_REF); + t->ref_offsets.offset = 0; + t->log_offsets.is_present = (first_block_typ == REFTABLE_BLOCK_TYPE_LOG || + t->log_offsets.offset > 0); + t->obj_offsets.is_present = t->obj_offsets.offset > 0; + if (t->obj_offsets.is_present && !t->object_id_len) { + err = REFTABLE_FORMAT_ERROR; + goto done; + } + + err = 0; +done: + return err; +} + +struct table_iter { + struct reftable_table *table; + uint8_t typ; + uint64_t block_off; + struct reftable_block block; + struct block_iter bi; + int is_finished; +}; + +static int table_iter_init(struct table_iter *ti, struct reftable_table *t) +{ + struct block_iter bi = BLOCK_ITER_INIT; + memset(ti, 0, sizeof(*ti)); + reftable_table_incref(t); + ti->table = t; + ti->bi = bi; + return 0; +} + +static int table_iter_next_in_block(struct table_iter *ti, + struct reftable_record *rec) +{ + int res = block_iter_next(&ti->bi, rec); + if (res == 0 && reftable_record_type(rec) == REFTABLE_BLOCK_TYPE_REF) { + rec->u.ref.update_index += ti->table->min_update_index; + } + + return res; +} + +static void table_iter_block_done(struct table_iter *ti) +{ + reftable_block_release(&ti->block); + block_iter_reset(&ti->bi); +} + +int table_init_block(struct reftable_table *t, struct reftable_block *block, + uint64_t next_off, uint8_t want_typ) +{ + uint32_t header_off = next_off ? 0 : header_size(t->version); + int err; + + if (next_off >= t->size) + return 1; + + err = reftable_block_init(block, &t->source, next_off, header_off, + t->block_size, hash_size(t->hash_id), want_typ); + if (err) + reftable_block_release(block); + return err; +} + +static void table_iter_close(struct table_iter *ti) +{ + table_iter_block_done(ti); + block_iter_close(&ti->bi); + reftable_table_decref(ti->table); +} + +static int table_iter_next_block(struct table_iter *ti) +{ + uint64_t next_block_off = ti->block_off + ti->block.full_block_size; + int err; + + err = table_init_block(ti->table, &ti->block, next_block_off, ti->typ); + if (err > 0) + ti->is_finished = 1; + if (err) + return err; + + ti->block_off = next_block_off; + ti->is_finished = 0; + block_iter_init(&ti->bi, &ti->block); + + return 0; +} + +static int table_iter_next(struct table_iter *ti, struct reftable_record *rec) +{ + if (reftable_record_type(rec) != ti->typ) + return REFTABLE_API_ERROR; + + while (1) { + int err; + + if (ti->is_finished) + return 1; + + /* + * Check whether the current block still has more records. If + * so, return it. If the iterator returns positive then the + * current block has been exhausted. + */ + err = table_iter_next_in_block(ti, rec); + if (err <= 0) + return err; + + /* + * Otherwise, we need to continue to the next block in the + * table and retry. If there are no more blocks then the + * iterator is drained. + */ + err = table_iter_next_block(ti); + if (err) { + ti->is_finished = 1; + return err; + } + } +} + +static int table_iter_seek_to(struct table_iter *ti, uint64_t off, uint8_t typ) +{ + int err; + + err = table_init_block(ti->table, &ti->block, off, typ); + if (err != 0) + return err; + + ti->typ = reftable_block_type(&ti->block); + ti->block_off = off; + block_iter_init(&ti->bi, &ti->block); + ti->is_finished = 0; + return 0; +} + +static int table_iter_seek_start(struct table_iter *ti, uint8_t typ, int index) +{ + struct reftable_table_offsets *offs = table_offsets_for(ti->table, typ); + uint64_t off = offs->offset; + if (index) { + off = offs->index_offset; + if (off == 0) { + return 1; + } + typ = REFTABLE_BLOCK_TYPE_INDEX; + } + + return table_iter_seek_to(ti, off, typ); +} + +static int table_iter_seek_linear(struct table_iter *ti, + struct reftable_record *want) +{ + struct reftable_buf want_key = REFTABLE_BUF_INIT; + struct reftable_buf got_key = REFTABLE_BUF_INIT; + struct reftable_record rec; + int err; + + err = reftable_record_init(&rec, reftable_record_type(want)); + if (err < 0) + goto done; + + err = reftable_record_key(want, &want_key); + if (err < 0) + goto done; + + /* + * 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) { + 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.block.block_data, 0, sizeof(next.block.block_data)); + next.block.zstream = NULL; + next.block.uncompressed_data = NULL; + next.block.uncompressed_cap = 0; + + err = table_iter_next_block(&next); + if (err < 0) + goto done; + if (err > 0) + break; + + err = reftable_block_first_key(&next.block, &got_key); + if (err < 0) + goto done; + + if (reftable_buf_cmp(&got_key, &want_key) > 0) { + table_iter_block_done(&next); + break; + } + + table_iter_block_done(ti); + *ti = next; + } + + /* + * 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. + */ + block_iter_init(&ti->bi, &ti->block); + err = block_iter_seek_key(&ti->bi, &want_key); + if (err < 0) + goto done; + err = 0; + +done: + reftable_record_release(&rec); + reftable_buf_release(&want_key); + reftable_buf_release(&got_key); + return err; +} + +static int table_iter_seek_indexed(struct table_iter *ti, + struct reftable_record *rec) +{ + struct reftable_record want_index = { + .type = REFTABLE_BLOCK_TYPE_INDEX, .u.idx = { .last_key = REFTABLE_BUF_INIT } + }; + struct reftable_record index_result = { + .type = REFTABLE_BLOCK_TYPE_INDEX, + .u.idx = { .last_key = REFTABLE_BUF_INIT }, + }; + int err; + + err = reftable_record_key(rec, &want_index.u.idx.last_key); + if (err < 0) + goto done; + + /* + * The index may consist of multiple levels, where each level may have + * multiple index blocks. We start by doing a linear search in the + * highest layer that identifies the relevant index block as well as + * the record inside that block that corresponds to our wanted key. + */ + err = table_iter_seek_linear(ti, &want_index); + if (err < 0) + goto done; + + /* + * Traverse down the levels until we find a non-index entry. + */ + while (1) { + /* + * In case we seek a record that does not exist the index iter + * will tell us that the iterator is over. This works because + * the last index entry of the current level will contain the + * last key it knows about. So in case our seeked key is larger + * than the last indexed key we know that it won't exist. + * + * There is one subtlety in the layout of the index section + * that makes this work as expected: the highest-level index is + * at end of the section and will point backwards and thus we + * start reading from the end of the index section, not the + * beginning. + * + * If that wasn't the case and the order was reversed then the + * linear seek would seek into the lower levels and traverse + * all levels of the index only to find out that the key does + * not exist. + */ + err = table_iter_next(ti, &index_result); + if (err != 0) + goto done; + + err = table_iter_seek_to(ti, index_result.u.idx.offset, 0); + if (err != 0) + goto done; + + block_iter_init(&ti->bi, &ti->block); + + err = block_iter_seek_key(&ti->bi, &want_index.u.idx.last_key); + if (err < 0) + goto done; + + if (ti->typ == reftable_record_type(rec)) { + err = 0; + break; + } + + if (ti->typ != REFTABLE_BLOCK_TYPE_INDEX) { + err = REFTABLE_FORMAT_ERROR; + goto done; + } + } + +done: + reftable_record_release(&want_index); + reftable_record_release(&index_result); + return err; +} + +static int table_iter_seek(struct table_iter *ti, + struct reftable_record *want) +{ + uint8_t typ = reftable_record_type(want); + struct reftable_table_offsets *offs = table_offsets_for(ti->table, typ); + int err; + + err = table_iter_seek_start(ti, reftable_record_type(want), + !!offs->index_offset); + if (err < 0) + goto out; + + if (offs->index_offset) + err = table_iter_seek_indexed(ti, want); + else + err = table_iter_seek_linear(ti, want); + if (err) + goto out; + +out: + return err; +} + +static int table_iter_seek_void(void *ti, struct reftable_record *want) +{ + return table_iter_seek(ti, want); +} + +static int table_iter_next_void(void *ti, struct reftable_record *rec) +{ + return table_iter_next(ti, rec); +} + +static void table_iter_close_void(void *ti) +{ + table_iter_close(ti); +} + +static struct reftable_iterator_vtable table_iter_vtable = { + .seek = &table_iter_seek_void, + .next = &table_iter_next_void, + .close = &table_iter_close_void, +}; + +static void iterator_from_table_iter(struct reftable_iterator *it, + struct table_iter *ti) +{ + assert(!it->ops); + it->iter_arg = ti; + it->ops = &table_iter_vtable; +} + +int table_init_iter(struct reftable_table *t, + struct reftable_iterator *it, + uint8_t typ) +{ + struct reftable_table_offsets *offs = table_offsets_for(t, typ); + + if (offs->is_present) { + struct table_iter *ti; + REFTABLE_ALLOC_ARRAY(ti, 1); + if (!ti) + return REFTABLE_OUT_OF_MEMORY_ERROR; + + table_iter_init(ti, t); + iterator_from_table_iter(it, ti); + } else { + iterator_set_empty(it); + } + + return 0; +} + +int reftable_table_init_ref_iterator(struct reftable_table *t, + struct reftable_iterator *it) +{ + return table_init_iter(t, it, REFTABLE_BLOCK_TYPE_REF); +} + +int reftable_table_init_log_iterator(struct reftable_table *t, + struct reftable_iterator *it) +{ + return table_init_iter(t, it, REFTABLE_BLOCK_TYPE_LOG); +} + +int reftable_table_new(struct reftable_table **out, + struct reftable_block_source *source, char const *name) +{ + struct reftable_block_data footer = { 0 }; + struct reftable_block_data header = { 0 }; + struct reftable_table *t; + uint64_t file_size = block_source_size(source); + uint32_t read_size; + ssize_t bytes_read; + int err; + + REFTABLE_CALLOC_ARRAY(t, 1); + if (!t) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + + /* + * We need one extra byte to read the type of first block. We also + * pretend to always be reading v2 of the format because it is larger. + */ + read_size = header_size(2) + 1; + if (read_size > file_size) { + err = REFTABLE_FORMAT_ERROR; + goto done; + } + + bytes_read = block_source_read_data(source, &header, 0, read_size); + if (bytes_read < 0 || (size_t)bytes_read != read_size) { + err = REFTABLE_IO_ERROR; + goto done; + } + + if (memcmp(header.data, "REFT", 4)) { + err = REFTABLE_FORMAT_ERROR; + goto done; + } + t->version = header.data[4]; + if (t->version != 1 && t->version != 2) { + err = REFTABLE_FORMAT_ERROR; + goto done; + } + + t->size = file_size - footer_size(t->version); + t->source = *source; + t->name = reftable_strdup(name); + if (!t->name) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto done; + } + t->hash_id = 0; + t->refcount = 1; + + bytes_read = block_source_read_data(source, &footer, t->size, + footer_size(t->version)); + if (bytes_read < 0 || (size_t)bytes_read != footer_size(t->version)) { + err = REFTABLE_IO_ERROR; + goto done; + } + + err = parse_footer(t, footer.data, header.data); + if (err) + goto done; + + *out = t; + +done: + block_source_release_data(&footer); + block_source_release_data(&header); + if (err) { + if (t) + reftable_free(t->name); + reftable_free(t); + block_source_close(source); + } + return err; +} + +void reftable_table_incref(struct reftable_table *t) +{ + t->refcount++; +} + +void reftable_table_decref(struct reftable_table *t) +{ + if (!t) + return; + if (--t->refcount) + return; + block_source_close(&t->source); + REFTABLE_FREE_AND_NULL(t->name); + reftable_free(t); +} + +static int reftable_table_refs_for_indexed(struct reftable_table *t, + struct reftable_iterator *it, + uint8_t *oid) +{ + struct reftable_record want = { + .type = REFTABLE_BLOCK_TYPE_OBJ, + .u.obj = { + .hash_prefix = oid, + .hash_prefix_len = t->object_id_len, + }, + }; + struct reftable_iterator oit = { NULL }; + struct reftable_record got = { + .type = REFTABLE_BLOCK_TYPE_OBJ, + .u.obj = { 0 }, + }; + int err = 0; + struct indexed_table_ref_iter *itr = NULL; + + /* Look through the reverse index. */ + err = table_init_iter(t, &oit, REFTABLE_BLOCK_TYPE_OBJ); + if (err < 0) + goto done; + + err = iterator_seek(&oit, &want); + if (err != 0) + goto done; + + /* read out the reftable_obj_record */ + err = iterator_next(&oit, &got); + if (err < 0) + goto done; + + if (err > 0 || memcmp(want.u.obj.hash_prefix, got.u.obj.hash_prefix, + t->object_id_len)) { + /* didn't find it; return empty iterator */ + iterator_set_empty(it); + err = 0; + goto done; + } + + err = indexed_table_ref_iter_new(&itr, t, oid, hash_size(t->hash_id), + got.u.obj.offsets, + got.u.obj.offset_len); + if (err < 0) + goto done; + got.u.obj.offsets = NULL; + iterator_from_indexed_table_ref_iter(it, itr); + +done: + reftable_iterator_destroy(&oit); + reftable_record_release(&got); + return err; +} + +static int reftable_table_refs_for_unindexed(struct reftable_table *t, + struct reftable_iterator *it, + uint8_t *oid) +{ + struct table_iter *ti; + struct filtering_ref_iterator *filter = NULL; + struct filtering_ref_iterator empty = FILTERING_REF_ITERATOR_INIT; + uint32_t oid_len = hash_size(t->hash_id); + int err; + + REFTABLE_ALLOC_ARRAY(ti, 1); + if (!ti) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto out; + } + + table_iter_init(ti, t); + err = table_iter_seek_start(ti, REFTABLE_BLOCK_TYPE_REF, 0); + if (err < 0) + goto out; + + filter = reftable_malloc(sizeof(*filter)); + if (!filter) { + err = REFTABLE_OUT_OF_MEMORY_ERROR; + goto out; + } + *filter = empty; + + err = reftable_buf_add(&filter->oid, oid, oid_len); + if (err < 0) + goto out; + + iterator_from_table_iter(&filter->it, ti); + + iterator_from_filtering_ref_iterator(it, filter); + + err = 0; + +out: + if (err < 0) { + if (ti) + table_iter_close(ti); + reftable_free(ti); + } + return err; +} + +int reftable_table_refs_for(struct reftable_table *t, + struct reftable_iterator *it, uint8_t *oid) +{ + if (t->obj_offsets.is_present) + return reftable_table_refs_for_indexed(t, it, oid); + return reftable_table_refs_for_unindexed(t, it, oid); +} + +uint64_t reftable_table_max_update_index(struct reftable_table *t) +{ + return t->max_update_index; +} + +uint64_t reftable_table_min_update_index(struct reftable_table *t) +{ + return t->min_update_index; +} + +int reftable_table_iterator_init(struct reftable_table_iterator *it, + struct reftable_table *t) +{ + struct table_iter *ti; + int err; + + REFTABLE_ALLOC_ARRAY(ti, 1); + if (!ti) + return REFTABLE_OUT_OF_MEMORY_ERROR; + + err = table_iter_init(ti, t); + if (err < 0) + goto out; + + it->iter_arg = ti; + err = 0; + +out: + if (err < 0) + reftable_free(ti); + return err; +} + +void reftable_table_iterator_release(struct reftable_table_iterator *it) +{ + if (!it->iter_arg) + return; + table_iter_close(it->iter_arg); + reftable_free(it->iter_arg); + it->iter_arg = NULL; +} + +int reftable_table_iterator_next(struct reftable_table_iterator *it, + const struct reftable_block **out) +{ + struct table_iter *ti = it->iter_arg; + int err; + + err = table_iter_next_block(ti); + if (err) + return err; + + *out = &ti->block; + + return 0; +} |