pack-objects.h

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