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         z_stream *zstream;
  22         unsigned char *compressed;
  23         size_t compressed_cap;
  24
  25         uint8_t *buf;
  26         uint32_t block_size;
  27
  28         /* Offset of the global header. Nonzero in the first block only. */
  29         uint32_t header_off;
  30
  31         /* How often to restart keys. */
  32         uint16_t restart_interval;
  33         int hash_size;
  34
  35         /* Offset of next uint8_t to write. */
  36         uint32_t next;
  37         uint32_t *restarts;
  38         uint32_t restart_len;
  39         uint32_t restart_cap;
  40
  41         struct strbuf last_key;
  42         int entries;
  43 };
  44
  45 /*
  46  * initializes the blockwriter to write `typ` entries, using `buf` as temporary
  47  * storage. `buf` is not owned by the block_writer. */
  48 void block_writer_init(struct block_writer *bw, uint8_t typ, uint8_t *buf,
  49                        uint32_t block_size, uint32_t header_off, int hash_size);
  50
  51 /* returns the block type (eg. 'r' for ref records. */
  52 uint8_t block_writer_type(struct block_writer *bw);
  53
  54 /* appends the record, or -1 if it doesn't fit. */
  55 int block_writer_add(struct block_writer *w, struct reftable_record *rec);
  56
  57 /* appends the key restarts, and compress the block if necessary. */
  58 int block_writer_finish(struct block_writer *w);
  59
  60 /* clears out internally allocated block_writer members. */
  61 void block_writer_release(struct block_writer *bw);
  62
  63 struct z_stream;
  64
  65 /* Read a block. */
  66 struct block_reader {
  67         /* offset of the block header; nonzero for the first block in a
  68          * reftable. */
  69         uint32_t header_off;
  70
  71         /* the memory block */
  72         struct reftable_block block;
  73         int hash_size;
  74
  75         /* Uncompressed data for log entries. */
  76         z_stream *zstream;
  77         unsigned char *uncompressed_data;
  78         size_t uncompressed_cap;
  79
  80         /* size of the data, excluding restart data. */
  81         uint32_t block_len;
  82         uint8_t *restart_bytes;
  83         uint16_t restart_count;
  84
  85         /* size of the data in the file. For log blocks, this is the compressed
  86          * size. */
  87         uint32_t full_block_size;
  88 };
  89
  90 /* initializes a block reader. */
  91 int block_reader_init(struct block_reader *br, struct reftable_block *bl,
  92                       uint32_t header_off, uint32_t table_block_size,
  93                       int hash_size);
  94
  95 void block_reader_release(struct block_reader *br);
  96
  97 /* Returns the block type (eg. 'r' for refs) */
  98 uint8_t block_reader_type(const struct block_reader *r);
  99
 100 /* Decodes the first key in the block */
 101 int block_reader_first_key(const struct block_reader *br, struct strbuf *key);
 102
 103 /* Iterate over entries in a block */
 104 struct block_iter {
 105         /* offset within the block of the next entry to read. */
 106         uint32_t next_off;
 107         const unsigned char *block;
 108         size_t block_len;
 109         int hash_size;
 110
 111         /* key for last entry we read. */
 112         struct strbuf last_key;
 113         struct strbuf scratch;
 114 };
 115
 116 #define BLOCK_ITER_INIT { \
 117         .last_key = STRBUF_INIT, \
 118         .scratch = STRBUF_INIT, \
 119 }
 120
 121 /* Position `it` at start of the block */
 122 void block_iter_seek_start(struct block_iter *it, const struct block_reader *br);
 123
 124 /* Position `it` to the `want` key in the block */
 125 int block_iter_seek_key(struct block_iter *it, const struct block_reader *br,
 126                         struct strbuf *want);
 127
 128 /* return < 0 for error, 0 for OK, > 0 for EOF. */
 129 int block_iter_next(struct block_iter *it, struct reftable_record *rec);
 130
 131 /* Reset the block iterator to pristine state without releasing its memory. */
 132 void block_iter_reset(struct block_iter *it);
 133
 134 /* deallocate memory for `it`. The block reader and its block is left intact. */
 135 void block_iter_close(struct block_iter *it);
 136
 137 /* size of file header, depending on format version */
 138 int header_size(int version);
 139
 140 /* size of file footer, depending on format version */
 141 int footer_size(int version);
 142
 143 /* returns a block to its source. */
 144 void reftable_block_done(struct reftable_block *ret);
 145
 146 #endif