reftable/block.c

   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 #include "block.h"
  10
  11 #include "blocksource.h"
  12 #include "constants.h"
  13 #include "record.h"
  14 #include "reftable-error.h"
  15 #include "system.h"
  16 #include <zlib.h>
  17
  18 int header_size(int version)
  19 {
  20         switch (version) {
  21         case 1:
  22                 return 24;
  23         case 2:
  24                 return 28;
  25         }
  26         abort();
  27 }
  28
  29 int footer_size(int version)
  30 {
  31         switch (version) {
  32         case 1:
  33                 return 68;
  34         case 2:
  35                 return 72;
  36         }
  37         abort();
  38 }
  39
  40 static int block_writer_register_restart(struct block_writer *w, int n,
  41                                          int is_restart, struct strbuf *key)
  42 {
  43         int rlen = w->restart_len;
  44         if (rlen >= MAX_RESTARTS) {
  45                 is_restart = 0;
  46         }
  47
  48         if (is_restart) {
  49                 rlen++;
  50         }
  51         if (2 + 3 * rlen + n > w->block_size - w->next)
  52                 return -1;
  53         if (is_restart) {
  54                 if (w->restart_len == w->restart_cap) {
  55                         w->restart_cap = w->restart_cap * 2 + 1;
  56                         w->restarts = reftable_realloc(
  57                                 w->restarts, sizeof(uint32_t) * w->restart_cap);
  58                 }
  59
  60                 w->restarts[w->restart_len++] = w->next;
  61         }
  62
  63         w->next += n;
  64
  65         strbuf_reset(&w->last_key);
  66         strbuf_addbuf(&w->last_key, key);
  67         w->entries++;
  68         return 0;
  69 }
  70
  71 void block_writer_init(struct block_writer *bw, uint8_t typ, uint8_t *buf,
  72                        uint32_t block_size, uint32_t header_off, int hash_size)
  73 {
  74         bw->buf = buf;
  75         bw->hash_size = hash_size;
  76         bw->block_size = block_size;
  77         bw->header_off = header_off;
  78         bw->buf[header_off] = typ;
  79         bw->next = header_off + 4;
  80         bw->restart_interval = 16;
  81         bw->entries = 0;
  82         bw->restart_len = 0;
  83         bw->last_key.len = 0;
  84 }
  85
  86 uint8_t block_writer_type(struct block_writer *bw)
  87 {
  88         return bw->buf[bw->header_off];
  89 }
  90
  91 /* Adds the reftable_record to the block. Returns -1 if it does not fit, 0 on
  92    success. Returns REFTABLE_API_ERROR if attempting to write a record with
  93    empty key. */
  94 int block_writer_add(struct block_writer *w, struct reftable_record *rec)
  95 {
  96         struct strbuf empty = STRBUF_INIT;
  97         struct strbuf last =
  98                 w->entries % w->restart_interval == 0 ? empty : w->last_key;
  99         struct string_view out = {
 100                 .buf = w->buf + w->next,
 101                 .len = w->block_size - w->next,
 102         };
 103
 104         struct string_view start = out;
 105
 106         int is_restart = 0;
 107         struct strbuf key = STRBUF_INIT;
 108         int n = 0;
 109         int err = -1;
 110
 111         reftable_record_key(rec, &key);
 112         if (!key.len) {
 113                 err = REFTABLE_API_ERROR;
 114                 goto done;
 115         }
 116
 117         n = reftable_encode_key(&is_restart, out, last, key,
 118                                 reftable_record_val_type(rec));
 119         if (n < 0)
 120                 goto done;
 121         string_view_consume(&out, n);
 122
 123         n = reftable_record_encode(rec, out, w->hash_size);
 124         if (n < 0)
 125                 goto done;
 126         string_view_consume(&out, n);
 127
 128         err = block_writer_register_restart(w, start.len - out.len, is_restart,
 129                                             &key);
 130 done:
 131         strbuf_release(&key);
 132         return err;
 133 }
 134
 135 int block_writer_finish(struct block_writer *w)
 136 {
 137         int i;
 138         for (i = 0; i < w->restart_len; i++) {
 139                 put_be24(w->buf + w->next, w->restarts[i]);
 140                 w->next += 3;
 141         }
 142
 143         put_be16(w->buf + w->next, w->restart_len);
 144         w->next += 2;
 145         put_be24(w->buf + 1 + w->header_off, w->next);
 146
 147         if (block_writer_type(w) == BLOCK_TYPE_LOG) {
 148                 int block_header_skip = 4 + w->header_off;
 149                 uLongf src_len = w->next - block_header_skip;
 150                 uLongf dest_cap = src_len * 1.001 + 12;
 151
 152                 uint8_t *compressed = reftable_malloc(dest_cap);
 153                 while (1) {
 154                         uLongf out_dest_len = dest_cap;
 155                         int zresult = compress2(compressed, &out_dest_len,
 156                                                 w->buf + block_header_skip,
 157                                                 src_len, 9);
 158                         if (zresult == Z_BUF_ERROR && dest_cap < LONG_MAX) {
 159                                 dest_cap *= 2;
 160                                 compressed =
 161                                         reftable_realloc(compressed, dest_cap);
 162                                 if (compressed)
 163                                         continue;
 164                         }
 165
 166                         if (Z_OK != zresult) {
 167                                 reftable_free(compressed);
 168                                 return REFTABLE_ZLIB_ERROR;
 169                         }
 170
 171                         memcpy(w->buf + block_header_skip, compressed,
 172                                out_dest_len);
 173                         w->next = out_dest_len + block_header_skip;
 174                         reftable_free(compressed);
 175                         break;
 176                 }
 177         }
 178         return w->next;
 179 }
 180
 181 uint8_t block_reader_type(struct block_reader *r)
 182 {
 183         return r->block.data[r->header_off];
 184 }
 185
 186 int block_reader_init(struct block_reader *br, struct reftable_block *block,
 187                       uint32_t header_off, uint32_t table_block_size,
 188                       int hash_size)
 189 {
 190         uint32_t full_block_size = table_block_size;
 191         uint8_t typ = block->data[header_off];
 192         uint32_t sz = get_be24(block->data + header_off + 1);
 193         int err = 0;
 194         uint16_t restart_count = 0;
 195         uint32_t restart_start = 0;
 196         uint8_t *restart_bytes = NULL;
 197         uint8_t *uncompressed = NULL;
 198
 199         if (!reftable_is_block_type(typ)) {
 200                 err =  REFTABLE_FORMAT_ERROR;
 201                 goto done;
 202         }
 203
 204         if (typ == BLOCK_TYPE_LOG) {
 205                 int block_header_skip = 4 + header_off;
 206                 uLongf dst_len = sz - block_header_skip; /* total size of dest
 207                                                             buffer. */
 208                 uLongf src_len = block->len - block_header_skip;
 209                 /* Log blocks specify the *uncompressed* size in their header.
 210                  */
 211                 uncompressed = reftable_malloc(sz);
 212
 213                 /* Copy over the block header verbatim. It's not compressed. */
 214                 memcpy(uncompressed, block->data, block_header_skip);
 215
 216                 /* Uncompress */
 217                 if (Z_OK !=
 218                     uncompress2(uncompressed + block_header_skip, &dst_len,
 219                                 block->data + block_header_skip, &src_len)) {
 220                         err = REFTABLE_ZLIB_ERROR;
 221                         goto done;
 222                 }
 223
 224                 if (dst_len + block_header_skip != sz) {
 225                         err = REFTABLE_FORMAT_ERROR;
 226                         goto done;
 227                 }
 228
 229                 /* We're done with the input data. */
 230                 reftable_block_done(block);
 231                 block->data = uncompressed;
 232                 uncompressed = NULL;
 233                 block->len = sz;
 234                 block->source = malloc_block_source();
 235                 full_block_size = src_len + block_header_skip;
 236         } else if (full_block_size == 0) {
 237                 full_block_size = sz;
 238         } else if (sz < full_block_size && sz < block->len &&
 239                    block->data[sz] != 0) {
 240                 /* If the block is smaller than the full block size, it is
 241                    padded (data followed by '\0') or the next block is
 242                    unaligned. */
 243                 full_block_size = sz;
 244         }
 245
 246         restart_count = get_be16(block->data + sz - 2);
 247         restart_start = sz - 2 - 3 * restart_count;
 248         restart_bytes = block->data + restart_start;
 249
 250         /* transfer ownership. */
 251         br->block = *block;
 252         block->data = NULL;
 253         block->len = 0;
 254
 255         br->hash_size = hash_size;
 256         br->block_len = restart_start;
 257         br->full_block_size = full_block_size;
 258         br->header_off = header_off;
 259         br->restart_count = restart_count;
 260         br->restart_bytes = restart_bytes;
 261
 262 done:
 263         reftable_free(uncompressed);
 264         return err;
 265 }
 266
 267 static uint32_t block_reader_restart_offset(struct block_reader *br, int i)
 268 {
 269         return get_be24(br->restart_bytes + 3 * i);
 270 }
 271
 272 void block_reader_start(struct block_reader *br, struct block_iter *it)
 273 {
 274         it->br = br;
 275         strbuf_reset(&it->last_key);
 276         it->next_off = br->header_off + 4;
 277 }
 278
 279 struct restart_find_args {
 280         int error;
 281         struct strbuf key;
 282         struct block_reader *r;
 283 };
 284
 285 static int restart_key_less(size_t idx, void *args)
 286 {
 287         struct restart_find_args *a = args;
 288         uint32_t off = block_reader_restart_offset(a->r, idx);
 289         struct string_view in = {
 290                 .buf = a->r->block.data + off,
 291                 .len = a->r->block_len - off,
 292         };
 293
 294         /* the restart key is verbatim in the block, so this could avoid the
 295            alloc for decoding the key */
 296         struct strbuf rkey = STRBUF_INIT;
 297         struct strbuf last_key = STRBUF_INIT;
 298         uint8_t unused_extra;
 299         int n = reftable_decode_key(&rkey, &unused_extra, last_key, in);
 300         int result;
 301         if (n < 0) {
 302                 a->error = 1;
 303                 return -1;
 304         }
 305
 306         result = strbuf_cmp(&a->key, &rkey);
 307         strbuf_release(&rkey);
 308         return result;
 309 }
 310
 311 void block_iter_copy_from(struct block_iter *dest, struct block_iter *src)
 312 {
 313         dest->br = src->br;
 314         dest->next_off = src->next_off;
 315         strbuf_reset(&dest->last_key);
 316         strbuf_addbuf(&dest->last_key, &src->last_key);
 317 }
 318
 319 int block_iter_next(struct block_iter *it, struct reftable_record *rec)
 320 {
 321         struct string_view in = {
 322                 .buf = it->br->block.data + it->next_off,
 323                 .len = it->br->block_len - it->next_off,
 324         };
 325         struct string_view start = in;
 326         uint8_t extra = 0;
 327         int n = 0;
 328
 329         if (it->next_off >= it->br->block_len)
 330                 return 1;
 331
 332         n = reftable_decode_key(&it->key, &extra, it->last_key, in);
 333         if (n < 0)
 334                 return -1;
 335
 336         if (!it->key.len)
 337                 return REFTABLE_FORMAT_ERROR;
 338
 339         string_view_consume(&in, n);
 340         n = reftable_record_decode(rec, it->key, extra, in, it->br->hash_size);
 341         if (n < 0)
 342                 return -1;
 343         string_view_consume(&in, n);
 344
 345         strbuf_reset(&it->last_key);
 346         strbuf_addbuf(&it->last_key, &it->key);
 347         it->next_off += start.len - in.len;
 348         return 0;
 349 }
 350
 351 int block_reader_first_key(struct block_reader *br, struct strbuf *key)
 352 {
 353         struct strbuf empty = STRBUF_INIT;
 354         int off = br->header_off + 4;
 355         struct string_view in = {
 356                 .buf = br->block.data + off,
 357                 .len = br->block_len - off,
 358         };
 359
 360         uint8_t extra = 0;
 361         int n = reftable_decode_key(key, &extra, empty, in);
 362         if (n < 0)
 363                 return n;
 364         if (!key->len)
 365                 return REFTABLE_FORMAT_ERROR;
 366
 367         return 0;
 368 }
 369
 370 int block_iter_seek(struct block_iter *it, struct strbuf *want)
 371 {
 372         return block_reader_seek(it->br, it, want);
 373 }
 374
 375 void block_iter_close(struct block_iter *it)
 376 {
 377         strbuf_release(&it->last_key);
 378         strbuf_release(&it->key);
 379 }
 380
 381 int block_reader_seek(struct block_reader *br, struct block_iter *it,
 382                       struct strbuf *want)
 383 {
 384         struct restart_find_args args = {
 385                 .key = *want,
 386                 .r = br,
 387         };
 388         struct reftable_record rec = reftable_new_record(block_reader_type(br));
 389         int err = 0;
 390         struct block_iter next = BLOCK_ITER_INIT;
 391
 392         int i = binsearch(br->restart_count, &restart_key_less, &args);
 393         if (args.error) {
 394                 err = REFTABLE_FORMAT_ERROR;
 395                 goto done;
 396         }
 397
 398         it->br = br;
 399         if (i > 0) {
 400                 i--;
 401                 it->next_off = block_reader_restart_offset(br, i);
 402         } else {
 403                 it->next_off = br->header_off + 4;
 404         }
 405
 406         /* We're looking for the last entry less/equal than the wanted key, so
 407            we have to go one entry too far and then back up.
 408         */
 409         while (1) {
 410                 block_iter_copy_from(&next, it);
 411                 err = block_iter_next(&next, &rec);
 412                 if (err < 0)
 413                         goto done;
 414
 415                 reftable_record_key(&rec, &it->key);
 416                 if (err > 0 || strbuf_cmp(&it->key, want) >= 0) {
 417                         err = 0;
 418                         goto done;
 419                 }
 420
 421                 block_iter_copy_from(it, &next);
 422         }
 423
 424 done:
 425         block_iter_close(&next);
 426         reftable_record_release(&rec);
 427
 428         return err;
 429 }
 430
 431 void block_writer_release(struct block_writer *bw)
 432 {
 433         FREE_AND_NULL(bw->restarts);
 434         strbuf_release(&bw->last_key);
 435         /* the block is not owned. */
 436 }
 437
 438 void reftable_block_done(struct reftable_block *blockp)
 439 {
 440         struct reftable_block_source source = blockp->source;
 441         if (blockp && source.ops)
 442                 source.ops->return_block(source.arg, blockp);
 443         blockp->data = NULL;
 444         blockp->len = 0;
 445         blockp->source.ops = NULL;
 446         blockp->source.arg = NULL;
 447 }