pack-objects.h

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