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1 /*
2 * Copyright 2020 Google LLC
3 *
4 * Use of this source code is governed by a BSD-style
5 * license that can be found in the LICENSE file or at
6 * https://developers.google.com/open-source/licenses/bsd
7 */
8
9 #ifndef BLOCK_H
10 #define BLOCK_H
11
12 #include "basics.h"
13 #include "record.h"
14 #include "reftable-block.h"
15 #include "reftable-blocksource.h"
16
17 /*
18 * Writes reftable blocks. The block_writer is reused across blocks to minimize
19 * allocation overhead.
20 */
21 struct block_writer {
22 struct z_stream_s *zstream;
23 unsigned char *compressed;
24 size_t compressed_cap;
25
26 uint8_t *block;
27 uint32_t block_size;
28
29 /* Offset of the global header. Nonzero in the first block only. */
30 uint32_t header_off;
31
32 /* How often to restart keys. */
33 uint16_t restart_interval;
34 uint32_t hash_size;
35
36 /* Offset of next uint8_t to write. */
37 uint32_t next;
38 uint32_t *restarts;
39 uint32_t restart_len;
40 uint32_t restart_cap;
41
42 struct reftable_buf last_key;
43 /* Scratch buffer used to avoid allocations. */
44 struct reftable_buf scratch;
45 int entries;
46 };
47
48 /*
49 * initializes the blockwriter to write `typ` entries, using `block` as temporary
50 * storage. `block` is not owned by the block_writer. */
51 int block_writer_init(struct block_writer *bw, uint8_t typ, uint8_t *block,
52 uint32_t block_size, uint32_t header_off, uint32_t hash_size);
53
54 /* returns the block type (eg. 'r' for ref records. */
55 uint8_t block_writer_type(struct block_writer *bw);
56
57 /* Attempts to append the record. Returns 0 on success or error code on failure. */
58 int block_writer_add(struct block_writer *w, struct reftable_record *rec);
59
60 /* appends the key restarts, and compress the block if necessary. */
61 int block_writer_finish(struct block_writer *w);
62
63 /* clears out internally allocated block_writer members. */
64 void block_writer_release(struct block_writer *bw);
65
66 /* Iterator for records contained in a single block. */
67 struct block_iter {
68 /* offset within the block of the next entry to read. */
69 uint32_t next_off;
70 const struct reftable_block *block;
71
72 /* key for last entry we read. */
73 struct reftable_buf last_key;
74 struct reftable_buf scratch;
75 };
76
77 #define BLOCK_ITER_INIT { \
78 .last_key = REFTABLE_BUF_INIT, \
79 .scratch = REFTABLE_BUF_INIT, \
80 }
81
82 /*
83 * Initialize the block iterator with the given block. The iterator will be
84 * positioned at the first record contained in the block. The block must remain
85 * valid until the end of the iterator's lifetime. It is valid to re-initialize
86 * iterators multiple times.
87 */
88 void block_iter_init(struct block_iter *it, const struct reftable_block *block);
89
90 /* Position the initialized iterator at the first record of its block. */
91 void block_iter_seek_start(struct block_iter *it);
92
93 /*
94 * Position the initialized iterator at the desired record key. It is not an
95 * error in case the record cannot be found. If so, a subsequent call to
96 * `block_iter_next()` will indicate that the iterator is exhausted.
97 */
98 int block_iter_seek_key(struct block_iter *it, struct reftable_buf *want);
99
100 /* return < 0 for error, 0 for OK, > 0 for EOF. */
101 int block_iter_next(struct block_iter *it, struct reftable_record *rec);
102
103 /* Reset the block iterator to pristine state without releasing its memory. */
104 void block_iter_reset(struct block_iter *it);
105
106 /* deallocate memory for `it`. The block reader and its block is left intact. */
107 void block_iter_close(struct block_iter *it);
108
109 /* size of file header, depending on format version */
110 size_t header_size(int version);
111
112 /* size of file footer, depending on format version */
113 size_t footer_size(int version);
114
115 #endif