reftable/record.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 RECORD_H
  10 #define RECORD_H
  11
  12 #include "system.h"
  13
  14 #include <stdint.h>
  15
  16 #include "reftable-record.h"
  17
  18 /*
  19  * A substring of existing string data. This structure takes no responsibility
  20  * for the lifetime of the data it points to.
  21  */
  22 struct string_view {
  23         uint8_t *buf;
  24         size_t len;
  25 };
  26
  27 /* Advance `s.buf` by `n`, and decrease length. */
  28 void string_view_consume(struct string_view *s, int n);
  29
  30 /* utilities for de/encoding varints */
  31
  32 int get_var_int(uint64_t *dest, struct string_view *in);
  33 int put_var_int(struct string_view *dest, uint64_t val);
  34
  35 /* Methods for records. */
  36 struct reftable_record_vtable {
  37         /* encode the key of to a uint8_t strbuf. */
  38         void (*key)(const void *rec, struct strbuf *dest);
  39
  40         /* The record type of ('r' for ref). */
  41         uint8_t type;
  42
  43         void (*copy_from)(void *dest, const void *src, int hash_size);
  44
  45         /* a value of [0..7], indicating record subvariants (eg. ref vs. symref
  46          * vs ref deletion) */
  47         uint8_t (*val_type)(const void *rec);
  48
  49         /* encodes rec into dest, returning how much space was used. */
  50         int (*encode)(const void *rec, struct string_view dest, int hash_size);
  51
  52         /* decode data from `src` into the record. */
  53         int (*decode)(void *rec, struct strbuf key, uint8_t extra,
  54                       struct string_view src, int hash_size);
  55
  56         /* deallocate and null the record. */
  57         void (*release)(void *rec);
  58
  59         /* is this a tombstone? */
  60         int (*is_deletion)(const void *rec);
  61
  62         /* Are two records equal? This assumes they have the same type. Returns 0 for non-equal. */
  63         int (*equal)(const void *a, const void *b, int hash_size);
  64
  65         /*
  66          * Compare keys of two records with each other. The records must have
  67          * the same type.
  68          */
  69         int (*cmp)(const void *a, const void *b);
  70
  71         /* Print on stdout, for debugging. */
  72         void (*print)(const void *rec, int hash_size);
  73 };
  74
  75 /* returns true for recognized block types. Block start with the block type. */
  76 int reftable_is_block_type(uint8_t typ);
  77
  78 /* return an initialized record for the given type */
  79 struct reftable_record reftable_new_record(uint8_t typ);
  80
  81 /* Encode `key` into `dest`. Sets `is_restart` to indicate a restart. Returns
  82  * number of bytes written. */
  83 int reftable_encode_key(int *is_restart, struct string_view dest,
  84                         struct strbuf prev_key, struct strbuf key,
  85                         uint8_t extra);
  86
  87 /* Decode into `key` and `extra` from `in` */
  88 int reftable_decode_key(struct strbuf *key, uint8_t *extra,
  89                         struct strbuf last_key, struct string_view in);
  90
  91 /* reftable_index_record are used internally to speed up lookups. */
  92 struct reftable_index_record {
  93         uint64_t offset; /* Offset of block */
  94         struct strbuf last_key; /* Last key of the block. */
  95 };
  96
  97 /* reftable_obj_record stores an object ID => ref mapping. */
  98 struct reftable_obj_record {
  99         uint8_t *hash_prefix; /* leading bytes of the object ID */
 100         int hash_prefix_len; /* number of leading bytes. Constant
 101                               * across a single table. */
 102         uint64_t *offsets; /* a vector of file offsets. */
 103         int offset_len;
 104 };
 105
 106 /* record is a generic wrapper for different types of records. It is normally
 107  * created on the stack, or embedded within another struct. If the type is
 108  * known, a fresh instance can be initialized explicitly. Otherwise, use
 109  * reftable_new_record() to initialize generically (as the index_record is not
 110  * valid as 0-initialized structure)
 111  */
 112 struct reftable_record {
 113         uint8_t type;
 114         union {
 115                 struct reftable_ref_record ref;
 116                 struct reftable_log_record log;
 117                 struct reftable_obj_record obj;
 118                 struct reftable_index_record idx;
 119         } u;
 120 };
 121
 122 /* see struct record_vtable */
 123 int reftable_record_cmp(struct reftable_record *a, struct reftable_record *b);
 124 int reftable_record_equal(struct reftable_record *a, struct reftable_record *b, int hash_size);
 125 void reftable_record_print(struct reftable_record *rec, int hash_size);
 126 void reftable_record_key(struct reftable_record *rec, struct strbuf *dest);
 127 uint8_t reftable_record_type(struct reftable_record *rec);
 128 void reftable_record_copy_from(struct reftable_record *rec,
 129                                struct reftable_record *src, int hash_size);
 130 uint8_t reftable_record_val_type(struct reftable_record *rec);
 131 int reftable_record_encode(struct reftable_record *rec, struct string_view dest,
 132                            int hash_size);
 133 int reftable_record_decode(struct reftable_record *rec, struct strbuf key,
 134                            uint8_t extra, struct string_view src,
 135                            int hash_size);
 136 int reftable_record_is_deletion(struct reftable_record *rec);
 137
 138 /* frees and zeroes out the embedded record */
 139 void reftable_record_release(struct reftable_record *rec);
 140
 141 /* for qsort. */
 142 int reftable_ref_record_compare_name(const void *a, const void *b);
 143
 144 /* for qsort. */
 145 int reftable_log_record_compare_key(const void *a, const void *b);
 146
 147 #endif