pack-objects.h

   1 #ifndef PACK_OBJECTS_H
   2 #define PACK_OBJECTS_H
   3
   4 #include "object-store.h"
   5 #include "thread-utils.h"
   6 #include "pack.h"
   7
   8 #define DEFAULT_DELTA_CACHE_SIZE (256 * 1024 * 1024)
   9
  10 #define OE_DFS_STATE_BITS       2
  11 #define OE_DEPTH_BITS           12
  12 #define OE_IN_PACK_BITS         10
  13 #define OE_Z_DELTA_BITS         20
  14 /*
  15  * Note that oe_set_size() becomes expensive when the given size is
  16  * above this limit. Don't lower it too much.
  17  */
  18 #define OE_SIZE_BITS            31
  19 #define OE_DELTA_SIZE_BITS      23
  20
  21 /*
  22  * State flags for depth-first search used for analyzing delta cycles.
  23  *
  24  * The depth is measured in delta-links to the base (so if A is a delta
  25  * against B, then A has a depth of 1, and B a depth of 0).
  26  */
  27 enum dfs_state {
  28         DFS_NONE = 0,
  29         DFS_ACTIVE,
  30         DFS_DONE,
  31         DFS_NUM_STATES
  32 };
  33
  34 /*
  35  * The size of struct nearly determines pack-objects's memory
  36  * consumption. This struct is packed tight for that reason. When you
  37  * add or reorder something in this struct, think a bit about this.
  38  *
  39  * basic object info
  40  * -----------------
  41  * idx.oid is filled up before delta searching starts. idx.crc32 is
  42  * only valid after the object is written out and will be used for
  43  * generating the index. idx.offset will be both gradually set and
  44  * used in writing phase (base objects get offset first, then deltas
  45  * refer to them)
  46  *
  47  * "size" is the uncompressed object size. Compressed size of the raw
  48  * data for an object in a pack is not stored anywhere but is computed
  49  * and made available when reverse .idx is made. Note that when a
  50  * delta is reused, "size" is the uncompressed _delta_ size, not the
  51  * canonical one after the delta has been applied.
  52  *
  53  * "hash" contains a path name hash which is used for sorting the
  54  * delta list and also during delta searching. Once prepare_pack()
  55  * returns it's no longer needed.
  56  *
  57  * source pack info
  58  * ----------------
  59  * The (in_pack, in_pack_offset) tuple contains the location of the
  60  * object in the source pack. in_pack_header_size allows quickly
  61  * skipping the header and going straight to the zlib stream.
  62  *
  63  * "type" and "in_pack_type" both describe object type. in_pack_type
  64  * may contain a delta type, while type is always the canonical type.
  65  *
  66  * deltas
  67  * ------
  68  * Delta links (delta, delta_child and delta_sibling) are created to
  69  * reflect that delta graph from the source pack then updated or added
  70  * during delta searching phase when we find better deltas.
  71  *
  72  * delta_child and delta_sibling are last needed in
  73  * compute_write_order(). "delta" and "delta_size" must remain valid
  74  * at object writing phase in case the delta is not cached.
  75  *
  76  * If a delta is cached in memory and is compressed, delta_data points
  77  * to the data and z_delta_size contains the compressed size. If it's
  78  * uncompressed [1], z_delta_size must be zero. delta_size is always
  79  * the uncompressed size and must be valid even if the delta is not
  80  * cached.
  81  *
  82  * [1] during try_delta phase we don't bother with compressing because
  83  * the delta could be quickly replaced with a better one.
  84  */
  85 struct object_entry {
  86         struct pack_idx_entry idx;
  87         void *delta_data;       /* cached delta (uncompressed) */
  88         off_t in_pack_offset;
  89         uint32_t hash;                  /* name hint hash */
  90         unsigned size_:OE_SIZE_BITS;
  91         unsigned size_valid:1;
  92         uint32_t delta_idx;     /* delta base object */
  93         uint32_t delta_child_idx; /* deltified objects who bases me */
  94         uint32_t delta_sibling_idx; /* other deltified objects who
  95                                      * uses the same base as me
  96                                      */
  97         unsigned delta_size_:OE_DELTA_SIZE_BITS; /* delta data size (uncompressed) */
  98         unsigned delta_size_valid:1;
  99         unsigned char in_pack_header_size;
 100         unsigned in_pack_idx:OE_IN_PACK_BITS;   /* already in pack */
 101         unsigned z_delta_size:OE_Z_DELTA_BITS;
 102         unsigned type_valid:1;
 103         unsigned no_try_delta:1;
 104         unsigned type_:TYPE_BITS;
 105         unsigned in_pack_type:TYPE_BITS; /* could be delta */
 106         unsigned preferred_base:1; /*
 107                                     * we do not pack this, but is available
 108                                     * to be used as the base object to delta
 109                                     * objects against.
 110                                     */
 111         unsigned tagged:1; /* near the very tip of refs */
 112         unsigned filled:1; /* assigned write-order */
 113         unsigned dfs_state:OE_DFS_STATE_BITS;
 114         unsigned depth:OE_DEPTH_BITS;
 115         unsigned ext_base:1; /* delta_idx points outside packlist */
 116
 117         /*
 118          * pahole results on 64-bit linux (gcc and clang)
 119          *
 120          *   size: 80, bit_padding: 9 bits
 121          *
 122          * and on 32-bit (gcc)
 123          *
 124          *   size: 76, bit_padding: 9 bits
 125          */
 126 };
 127
 128 struct packing_data {
 129         struct object_entry *objects;
 130         uint32_t nr_objects, nr_alloc;
 131
 132         int32_t *index;
 133         uint32_t index_size;
 134
 135         unsigned int *in_pack_pos;
 136         unsigned long *delta_size;
 137
 138         /*
 139          * Only one of these can be non-NULL and they have different
 140          * sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
 141          * the pack of an object using in_pack_idx field. If not,
 142          * in_pack[] array is used the same way as in_pack_pos[]
 143          */
 144         struct packed_git **in_pack_by_idx;
 145         struct packed_git **in_pack;
 146
 147 #ifndef NO_PTHREADS
 148         pthread_mutex_t lock;
 149 #endif
 150
 151         /*
 152          * This list contains entries for bases which we know the other side
 153          * has (e.g., via reachability bitmaps), but which aren't in our
 154          * "objects" list.
 155          */
 156         struct object_entry *ext_bases;
 157         uint32_t nr_ext, alloc_ext;
 158
 159         uintmax_t oe_size_limit;
 160         uintmax_t oe_delta_size_limit;
 161 };
 162
 163 void prepare_packing_data(struct packing_data *pdata);
 164
 165 static inline void packing_data_lock(struct packing_data *pdata)
 166 {
 167 #ifndef NO_PTHREADS
 168         pthread_mutex_lock(&pdata->lock);
 169 #endif
 170 }
 171 static inline void packing_data_unlock(struct packing_data *pdata)
 172 {
 173 #ifndef NO_PTHREADS
 174         pthread_mutex_unlock(&pdata->lock);
 175 #endif
 176 }
 177
 178 struct object_entry *packlist_alloc(struct packing_data *pdata,
 179                                     const unsigned char *sha1,
 180                                     uint32_t index_pos);
 181
 182 struct object_entry *packlist_find(struct packing_data *pdata,
 183                                    const unsigned char *sha1,
 184                                    uint32_t *index_pos);
 185
 186 static inline uint32_t pack_name_hash(const char *name)
 187 {
 188         uint32_t c, hash = 0;
 189
 190         if (!name)
 191                 return 0;
 192
 193         /*
 194          * This effectively just creates a sortable number from the
 195          * last sixteen non-whitespace characters. Last characters
 196          * count "most", so things that end in ".c" sort together.
 197          */
 198         while ((c = *name++) != 0) {
 199                 if (isspace(c))
 200                         continue;
 201                 hash = (hash >> 2) + (c << 24);
 202         }
 203         return hash;
 204 }
 205
 206 static inline enum object_type oe_type(const struct object_entry *e)
 207 {
 208         return e->type_valid ? e->type_ : OBJ_BAD;
 209 }
 210
 211 static inline void oe_set_type(struct object_entry *e,
 212                                enum object_type type)
 213 {
 214         if (type >= OBJ_ANY)
 215                 BUG("OBJ_ANY cannot be set in pack-objects code");
 216
 217         e->type_valid = type >= OBJ_NONE;
 218         e->type_ = (unsigned)type;
 219 }
 220
 221 static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
 222                                           const struct object_entry *e)
 223 {
 224         return pack->in_pack_pos[e - pack->objects];
 225 }
 226
 227 static inline void oe_set_in_pack_pos(const struct packing_data *pack,
 228                                       const struct object_entry *e,
 229                                       unsigned int pos)
 230 {
 231         pack->in_pack_pos[e - pack->objects] = pos;
 232 }
 233
 234 static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
 235                                             const struct object_entry *e)
 236 {
 237         if (pack->in_pack_by_idx)
 238                 return pack->in_pack_by_idx[e->in_pack_idx];
 239         else
 240                 return pack->in_pack[e - pack->objects];
 241 }
 242
 243 void oe_map_new_pack(struct packing_data *pack,
 244                      struct packed_git *p);
 245 static inline void oe_set_in_pack(struct packing_data *pack,
 246                                   struct object_entry *e,
 247                                   struct packed_git *p)
 248 {
 249         if (!p->index)
 250                 oe_map_new_pack(pack, p);
 251         if (pack->in_pack_by_idx)
 252                 e->in_pack_idx = p->index;
 253         else
 254                 pack->in_pack[e - pack->objects] = p;
 255 }
 256
 257 static inline struct object_entry *oe_delta(
 258                 const struct packing_data *pack,
 259                 const struct object_entry *e)
 260 {
 261         if (!e->delta_idx)
 262                 return NULL;
 263         if (e->ext_base)
 264                 return &pack->ext_bases[e->delta_idx - 1];
 265         else
 266                 return &pack->objects[e->delta_idx - 1];
 267 }
 268
 269 static inline void oe_set_delta(struct packing_data *pack,
 270                                 struct object_entry *e,
 271                                 struct object_entry *delta)
 272 {
 273         if (delta)
 274                 e->delta_idx = (delta - pack->objects) + 1;
 275         else
 276                 e->delta_idx = 0;
 277 }
 278
 279 void oe_set_delta_ext(struct packing_data *pack,
 280                       struct object_entry *e,
 281                       const unsigned char *sha1);
 282
 283 static inline struct object_entry *oe_delta_child(
 284                 const struct packing_data *pack,
 285                 const struct object_entry *e)
 286 {
 287         if (e->delta_child_idx)
 288                 return &pack->objects[e->delta_child_idx - 1];
 289         return NULL;
 290 }
 291
 292 static inline void oe_set_delta_child(struct packing_data *pack,
 293                                       struct object_entry *e,
 294                                       struct object_entry *delta)
 295 {
 296         if (delta)
 297                 e->delta_child_idx = (delta - pack->objects) + 1;
 298         else
 299                 e->delta_child_idx = 0;
 300 }
 301
 302 static inline struct object_entry *oe_delta_sibling(
 303                 const struct packing_data *pack,
 304                 const struct object_entry *e)
 305 {
 306         if (e->delta_sibling_idx)
 307                 return &pack->objects[e->delta_sibling_idx - 1];
 308         return NULL;
 309 }
 310
 311 static inline void oe_set_delta_sibling(struct packing_data *pack,
 312                                         struct object_entry *e,
 313                                         struct object_entry *delta)
 314 {
 315         if (delta)
 316                 e->delta_sibling_idx = (delta - pack->objects) + 1;
 317         else
 318                 e->delta_sibling_idx = 0;
 319 }
 320
 321 unsigned long oe_get_size_slow(struct packing_data *pack,
 322                                const struct object_entry *e);
 323 static inline unsigned long oe_size(struct packing_data *pack,
 324                                     const struct object_entry *e)
 325 {
 326         if (e->size_valid)
 327                 return e->size_;
 328
 329         return oe_get_size_slow(pack, e);
 330 }
 331
 332 static inline int oe_size_less_than(struct packing_data *pack,
 333                                     const struct object_entry *lhs,
 334                                     unsigned long rhs)
 335 {
 336         if (lhs->size_valid)
 337                 return lhs->size_ < rhs;
 338         if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
 339                 return 0;
 340         return oe_get_size_slow(pack, lhs) < rhs;
 341 }
 342
 343 static inline int oe_size_greater_than(struct packing_data *pack,
 344                                        const struct object_entry *lhs,
 345                                        unsigned long rhs)
 346 {
 347         if (lhs->size_valid)
 348                 return lhs->size_ > rhs;
 349         if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
 350                 return 1;
 351         return oe_get_size_slow(pack, lhs) > rhs;
 352 }
 353
 354 static inline void oe_set_size(struct packing_data *pack,
 355                                struct object_entry *e,
 356                                unsigned long size)
 357 {
 358         if (size < pack->oe_size_limit) {
 359                 e->size_ = size;
 360                 e->size_valid = 1;
 361         } else {
 362                 e->size_valid = 0;
 363                 if (oe_get_size_slow(pack, e) != size)
 364                         BUG("'size' is supposed to be the object size!");
 365         }
 366 }
 367
 368 static inline unsigned long oe_delta_size(struct packing_data *pack,
 369                                           const struct object_entry *e)
 370 {
 371         if (e->delta_size_valid)
 372                 return e->delta_size_;
 373
 374         /*
 375          * pack->detla_size[] can't be NULL because oe_set_delta_size()
 376          * must have been called when a new delta is saved with
 377          * oe_set_delta().
 378          * If oe_delta() returns NULL (i.e. default state, which means
 379          * delta_size_valid is also false), then the caller must never
 380          * call oe_delta_size().
 381          */
 382         return pack->delta_size[e - pack->objects];
 383 }
 384
 385 static inline void oe_set_delta_size(struct packing_data *pack,
 386                                      struct object_entry *e,
 387                                      unsigned long size)
 388 {
 389         if (size < pack->oe_delta_size_limit) {
 390                 e->delta_size_ = size;
 391                 e->delta_size_valid = 1;
 392         } else {
 393                 packing_data_lock(pack);
 394                 if (!pack->delta_size)
 395                         ALLOC_ARRAY(pack->delta_size, pack->nr_alloc);
 396                 packing_data_unlock(pack);
 397
 398                 pack->delta_size[e - pack->objects] = size;
 399                 e->delta_size_valid = 0;
 400         }
 401 }
 402
 403 #endif