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
 104         unsigned int tree_depth; /* should be repositioned for packing? */
 105         unsigned char layer;
 106
 107         unsigned preferred_base:1; /*
 108                                     * we do not pack this, but is available
 109                                     * to be used as the base object to delta
 110                                     * objects against.
 111                                     */
 112         unsigned tagged:1; /* near the very tip of refs */
 113         unsigned filled:1; /* assigned write-order */
 114         unsigned dfs_state:OE_DFS_STATE_BITS;
 115         unsigned char in_pack_header_size;
 116         unsigned depth:OE_DEPTH_BITS;
 117
 118         /*
 119          * pahole results on 64-bit linux (gcc and clang)
 120          *
 121          *   size: 80, bit_padding: 20 bits, holes: 8 bits
 122          *
 123          * and on 32-bit (gcc)
 124          *
 125          *   size: 76, bit_padding: 20 bits, holes: 8 bits
 126          */
 127 };
 128
 129 struct packing_data {
 130         struct object_entry *objects;
 131         uint32_t nr_objects, nr_alloc;
 132
 133         int32_t *index;
 134         uint32_t index_size;
 135
 136         unsigned int *in_pack_pos;
 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         uintmax_t oe_size_limit;
 148 };
 149
 150 void prepare_packing_data(struct packing_data *pdata);
 151 struct object_entry *packlist_alloc(struct packing_data *pdata,
 152                                     const unsigned char *sha1,
 153                                     uint32_t index_pos);
 154
 155 struct object_entry *packlist_find(struct packing_data *pdata,
 156                                    const unsigned char *sha1,
 157                                    uint32_t *index_pos);
 158
 159 static inline uint32_t pack_name_hash(const char *name)
 160 {
 161         uint32_t c, hash = 0;
 162
 163         if (!name)
 164                 return 0;
 165
 166         /*
 167          * This effectively just creates a sortable number from the
 168          * last sixteen non-whitespace characters. Last characters
 169          * count "most", so things that end in ".c" sort together.
 170          */
 171         while ((c = *name++) != 0) {
 172                 if (isspace(c))
 173                         continue;
 174                 hash = (hash >> 2) + (c << 24);
 175         }
 176         return hash;
 177 }
 178
 179 static inline enum object_type oe_type(const struct object_entry *e)
 180 {
 181         return e->type_valid ? e->type_ : OBJ_BAD;
 182 }
 183
 184 static inline void oe_set_type(struct object_entry *e,
 185                                enum object_type type)
 186 {
 187         if (type >= OBJ_ANY)
 188                 BUG("OBJ_ANY cannot be set in pack-objects code");
 189
 190         e->type_valid = type >= OBJ_NONE;
 191         e->type_ = (unsigned)type;
 192 }
 193
 194 static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
 195                                           const struct object_entry *e)
 196 {
 197         return pack->in_pack_pos[e - pack->objects];
 198 }
 199
 200 static inline void oe_set_in_pack_pos(const struct packing_data *pack,
 201                                       const struct object_entry *e,
 202                                       unsigned int pos)
 203 {
 204         pack->in_pack_pos[e - pack->objects] = pos;
 205 }
 206
 207 static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
 208                                             const struct object_entry *e)
 209 {
 210         if (pack->in_pack_by_idx)
 211                 return pack->in_pack_by_idx[e->in_pack_idx];
 212         else
 213                 return pack->in_pack[e - pack->objects];
 214 }
 215
 216 void oe_map_new_pack(struct packing_data *pack,
 217                      struct packed_git *p);
 218 static inline void oe_set_in_pack(struct packing_data *pack,
 219                                   struct object_entry *e,
 220                                   struct packed_git *p)
 221 {
 222         if (!p->index)
 223                 oe_map_new_pack(pack, p);
 224         if (pack->in_pack_by_idx)
 225                 e->in_pack_idx = p->index;
 226         else
 227                 pack->in_pack[e - pack->objects] = p;
 228 }
 229
 230 static inline struct object_entry *oe_delta(
 231                 const struct packing_data *pack,
 232                 const struct object_entry *e)
 233 {
 234         if (e->delta_idx)
 235                 return &pack->objects[e->delta_idx - 1];
 236         return NULL;
 237 }
 238
 239 static inline void oe_set_delta(struct packing_data *pack,
 240                                 struct object_entry *e,
 241                                 struct object_entry *delta)
 242 {
 243         if (delta)
 244                 e->delta_idx = (delta - pack->objects) + 1;
 245         else
 246                 e->delta_idx = 0;
 247 }
 248
 249 static inline struct object_entry *oe_delta_child(
 250                 const struct packing_data *pack,
 251                 const struct object_entry *e)
 252 {
 253         if (e->delta_child_idx)
 254                 return &pack->objects[e->delta_child_idx - 1];
 255         return NULL;
 256 }
 257
 258 static inline void oe_set_delta_child(struct packing_data *pack,
 259                                       struct object_entry *e,
 260                                       struct object_entry *delta)
 261 {
 262         if (delta)
 263                 e->delta_child_idx = (delta - pack->objects) + 1;
 264         else
 265                 e->delta_child_idx = 0;
 266 }
 267
 268 static inline struct object_entry *oe_delta_sibling(
 269                 const struct packing_data *pack,
 270                 const struct object_entry *e)
 271 {
 272         if (e->delta_sibling_idx)
 273                 return &pack->objects[e->delta_sibling_idx - 1];
 274         return NULL;
 275 }
 276
 277 static inline void oe_set_delta_sibling(struct packing_data *pack,
 278                                         struct object_entry *e,
 279                                         struct object_entry *delta)
 280 {
 281         if (delta)
 282                 e->delta_sibling_idx = (delta - pack->objects) + 1;
 283         else
 284                 e->delta_sibling_idx = 0;
 285 }
 286
 287 unsigned long oe_get_size_slow(struct packing_data *pack,
 288                                const struct object_entry *e);
 289 static inline unsigned long oe_size(struct packing_data *pack,
 290                                     const struct object_entry *e)
 291 {
 292         if (e->size_valid)
 293                 return e->size_;
 294
 295         return oe_get_size_slow(pack, e);
 296 }
 297
 298 static inline int oe_size_less_than(struct packing_data *pack,
 299                                     const struct object_entry *lhs,
 300                                     unsigned long rhs)
 301 {
 302         if (lhs->size_valid)
 303                 return lhs->size_ < rhs;
 304         if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
 305                 return 0;
 306         return oe_get_size_slow(pack, lhs) < rhs;
 307 }
 308
 309 static inline int oe_size_greater_than(struct packing_data *pack,
 310                                        const struct object_entry *lhs,
 311                                        unsigned long rhs)
 312 {
 313         if (lhs->size_valid)
 314                 return lhs->size_ > rhs;
 315         if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
 316                 return 1;
 317         return oe_get_size_slow(pack, lhs) > rhs;
 318 }
 319
 320 static inline void oe_set_size(struct packing_data *pack,
 321                                struct object_entry *e,
 322                                unsigned long size)
 323 {
 324         if (size < pack->oe_size_limit) {
 325                 e->size_ = size;
 326                 e->size_valid = 1;
 327         } else {
 328                 e->size_valid = 0;
 329                 if (oe_get_size_slow(pack, e) != size)
 330                         BUG("'size' is supposed to be the object size!");
 331         }
 332 }
 333
 334 static inline unsigned long oe_delta_size(struct packing_data *pack,
 335                                           const struct object_entry *e)
 336 {
 337         if (e->delta_size_valid)
 338                 return e->delta_size_;
 339         return oe_size(pack, e);
 340 }
 341
 342 static inline void oe_set_delta_size(struct packing_data *pack,
 343                                      struct object_entry *e,
 344                                      unsigned long size)
 345 {
 346         e->delta_size_ = size;
 347         e->delta_size_valid = e->delta_size_ == size;
 348         if (!e->delta_size_valid && size != oe_size(pack, e))
 349                 BUG("this can only happen in check_object() "
 350                     "where delta size is the same as entry size");
 351 }
 352
 353 #endif