reftable/block.h

   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-blocksource.h"
  15
  16 /*
  17  * Writes reftable blocks. The block_writer is reused across blocks to minimize
  18  * allocation overhead.
  19  */
  20 struct block_writer {
  21         uint8_t *buf;
  22         uint32_t block_size;
  23
  24         /* Offset of the global header. Nonzero in the first block only. */
  25         uint32_t header_off;
  26
  27         /* How often to restart keys. */
  28         int restart_interval;
  29         int hash_size;
  30
  31         /* Offset of next uint8_t to write. */
  32         uint32_t next;
  33         uint32_t *restarts;
  34         uint32_t restart_len;
  35         uint32_t restart_cap;
  36
  37         struct strbuf last_key;
  38         int entries;
  39 };
  40
  41 /*
  42  * initializes the blockwriter to write `typ` entries, using `buf` as temporary
  43  * storage. `buf` is not owned by the block_writer. */
  44 void block_writer_init(struct block_writer *bw, uint8_t typ, uint8_t *buf,
  45                        uint32_t block_size, uint32_t header_off, int hash_size);
  46
  47 /* returns the block type (eg. 'r' for ref records. */
  48 uint8_t block_writer_type(struct block_writer *bw);
  49
  50 /* appends the record, or -1 if it doesn't fit. */
  51 int block_writer_add(struct block_writer *w, struct reftable_record *rec);
  52
  53 /* appends the key restarts, and compress the block if necessary. */
  54 int block_writer_finish(struct block_writer *w);
  55
  56 /* clears out internally allocated block_writer members. */
  57 void block_writer_release(struct block_writer *bw);
  58
  59 /* Read a block. */
  60 struct block_reader {
  61         /* offset of the block header; nonzero for the first block in a
  62          * reftable. */
  63         uint32_t header_off;
  64
  65         /* the memory block */
  66         struct reftable_block block;
  67         int hash_size;
  68
  69         /* size of the data, excluding restart data. */
  70         uint32_t block_len;
  71         uint8_t *restart_bytes;
  72         uint16_t restart_count;
  73
  74         /* size of the data in the file. For log blocks, this is the compressed
  75          * size. */
  76         uint32_t full_block_size;
  77 };
  78
  79 /* Iterate over entries in a block */
  80 struct block_iter {
  81         /* offset within the block of the next entry to read. */
  82         uint32_t next_off;
  83         struct block_reader *br;
  84
  85         /* key for last entry we read. */
  86         struct strbuf last_key;
  87 };
  88
  89 /* initializes a block reader. */
  90 int block_reader_init(struct block_reader *br, struct reftable_block *bl,
  91                       uint32_t header_off, uint32_t table_block_size,
  92                       int hash_size);
  93
  94 /* Position `it` at start of the block */
  95 void block_reader_start(struct block_reader *br, struct block_iter *it);
  96
  97 /* Position `it` to the `want` key in the block */
  98 int block_reader_seek(struct block_reader *br, struct block_iter *it,
  99                       struct strbuf *want);
 100
 101 /* Returns the block type (eg. 'r' for refs) */
 102 uint8_t block_reader_type(struct block_reader *r);
 103
 104 /* Decodes the first key in the block */
 105 int block_reader_first_key(struct block_reader *br, struct strbuf *key);
 106
 107 void block_iter_copy_from(struct block_iter *dest, struct block_iter *src);
 108
 109 /* return < 0 for error, 0 for OK, > 0 for EOF. */
 110 int block_iter_next(struct block_iter *it, struct reftable_record *rec);
 111
 112 /* Seek to `want` with in the block pointed to by `it` */
 113 int block_iter_seek(struct block_iter *it, struct strbuf *want);
 114
 115 /* deallocate memory for `it`. The block reader and its block is left intact. */
 116 void block_iter_close(struct block_iter *it);
 117
 118 /* size of file header, depending on format version */
 119 int header_size(int version);
 120
 121 /* size of file footer, depending on format version */
 122 int footer_size(int version);
 123
 124 /* returns a block to its source. */
 125 void reftable_block_done(struct reftable_block *ret);
 126
 127 #endif