pack-objects.h

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