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 struct z_stream;
  60
  61 /* Read a block. */
  62 struct block_reader {
  63         /* offset of the block header; nonzero for the first block in a
  64          * reftable. */
  65         uint32_t header_off;
  66
  67         /* the memory block */
  68         struct reftable_block block;
  69         int hash_size;
  70
  71         /* Uncompressed data for log entries. */
  72         z_stream *zstream;
  73         unsigned char *uncompressed_data;
  74         size_t uncompressed_cap;
  75
  76         /* size of the data, excluding restart data. */
  77         uint32_t block_len;
  78         uint8_t *restart_bytes;
  79         uint16_t restart_count;
  80
  81         /* size of the data in the file. For log blocks, this is the compressed
  82          * size. */
  83         uint32_t full_block_size;
  84 };
  85
  86 /* initializes a block reader. */
  87 int block_reader_init(struct block_reader *br, struct reftable_block *bl,
  88                       uint32_t header_off, uint32_t table_block_size,
  89                       int hash_size);
  90
  91 void block_reader_release(struct block_reader *br);
  92
  93 /* Returns the block type (eg. 'r' for refs) */
  94 uint8_t block_reader_type(const struct block_reader *r);
  95
  96 /* Decodes the first key in the block */
  97 int block_reader_first_key(const struct block_reader *br, struct strbuf *key);
  98
  99 /* Iterate over entries in a block */
 100 struct block_iter {
 101         /* offset within the block of the next entry to read. */
 102         uint32_t next_off;
 103         const unsigned char *block;
 104         size_t block_len;
 105         int hash_size;
 106
 107         /* key for last entry we read. */
 108         struct strbuf last_key;
 109         struct strbuf scratch;
 110 };
 111
 112 #define BLOCK_ITER_INIT { \
 113         .last_key = STRBUF_INIT, \
 114         .scratch = STRBUF_INIT, \
 115 }
 116
 117 /* Position `it` at start of the block */
 118 void block_iter_seek_start(struct block_iter *it, const struct block_reader *br);
 119
 120 /* Position `it` to the `want` key in the block */
 121 int block_iter_seek_key(struct block_iter *it, const struct block_reader *br,
 122                         struct strbuf *want);
 123
 124 /* return < 0 for error, 0 for OK, > 0 for EOF. */
 125 int block_iter_next(struct block_iter *it, struct reftable_record *rec);
 126
 127 /* Reset the block iterator to pristine state without releasing its memory. */
 128 void block_iter_reset(struct block_iter *it);
 129
 130 /* deallocate memory for `it`. The block reader and its block is left intact. */
 131 void block_iter_close(struct block_iter *it);
 132
 133 /* size of file header, depending on format version */
 134 int header_size(int version);
 135
 136 /* size of file footer, depending on format version */
 137 int footer_size(int version);
 138
 139 /* returns a block to its source. */
 140 void reftable_block_done(struct reftable_block *ret);
 141
 142 #endif