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
 115         /*
 116          * pahole results on 64-bit linux (gcc and clang)
 117          *
 118          *   size: 80, bit_padding: 20 bits, holes: 8 bits
 119          *
 120          * and on 32-bit (gcc)
 121          *
 122          *   size: 76, bit_padding: 20 bits, holes: 8 bits
 123          */
 124 };
 125
 126 struct packing_data {
 127         struct object_entry *objects;
 128         uint32_t nr_objects, nr_alloc;
 129
 130         int32_t *index;
 131         uint32_t index_size;
 132
 133         unsigned int *in_pack_pos;
 134
 135         /*
 136          * Only one of these can be non-NULL and they have different
 137          * sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
 138          * the pack of an object using in_pack_idx field. If not,
 139          * in_pack[] array is used the same way as in_pack_pos[]
 140          */
 141         struct packed_git **in_pack_by_idx;
 142         struct packed_git **in_pack;
 143
 144         uintmax_t oe_size_limit;
 145 };
 146
 147 void prepare_packing_data(struct packing_data *pdata);
 148 struct object_entry *packlist_alloc(struct packing_data *pdata,
 149                                     const unsigned char *sha1,
 150                                     uint32_t index_pos);
 151
 152 struct object_entry *packlist_find(struct packing_data *pdata,
 153                                    const unsigned char *sha1,
 154                                    uint32_t *index_pos);
 155
 156 static inline uint32_t pack_name_hash(const char *name)
 157 {
 158         uint32_t c, hash = 0;
 159
 160         if (!name)
 161                 return 0;
 162
 163         /*
 164          * This effectively just creates a sortable number from the
 165          * last sixteen non-whitespace characters. Last characters
 166          * count "most", so things that end in ".c" sort together.
 167          */
 168         while ((c = *name++) != 0) {
 169                 if (isspace(c))
 170                         continue;
 171                 hash = (hash >> 2) + (c << 24);
 172         }
 173         return hash;
 174 }
 175
 176 static inline enum object_type oe_type(const struct object_entry *e)
 177 {
 178         return e->type_valid ? e->type_ : OBJ_BAD;
 179 }
 180
 181 static inline void oe_set_type(struct object_entry *e,
 182                                enum object_type type)
 183 {
 184         if (type >= OBJ_ANY)
 185                 BUG("OBJ_ANY cannot be set in pack-objects code");
 186
 187         e->type_valid = type >= OBJ_NONE;
 188         e->type_ = (unsigned)type;
 189 }
 190
 191 static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
 192                                           const struct object_entry *e)
 193 {
 194         return pack->in_pack_pos[e - pack->objects];
 195 }
 196
 197 static inline void oe_set_in_pack_pos(const struct packing_data *pack,
 198                                       const struct object_entry *e,
 199                                       unsigned int pos)
 200 {
 201         pack->in_pack_pos[e - pack->objects] = pos;
 202 }
 203
 204 static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
 205                                             const struct object_entry *e)
 206 {
 207         if (pack->in_pack_by_idx)
 208                 return pack->in_pack_by_idx[e->in_pack_idx];
 209         else
 210                 return pack->in_pack[e - pack->objects];
 211 }
 212
 213 void oe_map_new_pack(struct packing_data *pack,
 214                      struct packed_git *p);
 215 static inline void oe_set_in_pack(struct packing_data *pack,
 216                                   struct object_entry *e,
 217                                   struct packed_git *p)
 218 {
 219         if (!p->index)
 220                 oe_map_new_pack(pack, p);
 221         if (pack->in_pack_by_idx)
 222                 e->in_pack_idx = p->index;
 223         else
 224                 pack->in_pack[e - pack->objects] = p;
 225 }
 226
 227 static inline struct object_entry *oe_delta(
 228                 const struct packing_data *pack,
 229                 const struct object_entry *e)
 230 {
 231         if (e->delta_idx)
 232                 return &pack->objects[e->delta_idx - 1];
 233         return NULL;
 234 }
 235
 236 static inline void oe_set_delta(struct packing_data *pack,
 237                                 struct object_entry *e,
 238                                 struct object_entry *delta)
 239 {
 240         if (delta)
 241                 e->delta_idx = (delta - pack->objects) + 1;
 242         else
 243                 e->delta_idx = 0;
 244 }
 245
 246 static inline struct object_entry *oe_delta_child(
 247                 const struct packing_data *pack,
 248                 const struct object_entry *e)
 249 {
 250         if (e->delta_child_idx)
 251                 return &pack->objects[e->delta_child_idx - 1];
 252         return NULL;
 253 }
 254
 255 static inline void oe_set_delta_child(struct packing_data *pack,
 256                                       struct object_entry *e,
 257                                       struct object_entry *delta)
 258 {
 259         if (delta)
 260                 e->delta_child_idx = (delta - pack->objects) + 1;
 261         else
 262                 e->delta_child_idx = 0;
 263 }
 264
 265 static inline struct object_entry *oe_delta_sibling(
 266                 const struct packing_data *pack,
 267                 const struct object_entry *e)
 268 {
 269         if (e->delta_sibling_idx)
 270                 return &pack->objects[e->delta_sibling_idx - 1];
 271         return NULL;
 272 }
 273
 274 static inline void oe_set_delta_sibling(struct packing_data *pack,
 275                                         struct object_entry *e,
 276                                         struct object_entry *delta)
 277 {
 278         if (delta)
 279                 e->delta_sibling_idx = (delta - pack->objects) + 1;
 280         else
 281                 e->delta_sibling_idx = 0;
 282 }
 283
 284 unsigned long oe_get_size_slow(struct packing_data *pack,
 285                                const struct object_entry *e);
 286 static inline unsigned long oe_size(struct packing_data *pack,
 287                                     const struct object_entry *e)
 288 {
 289         if (e->size_valid)
 290                 return e->size_;
 291
 292         return oe_get_size_slow(pack, e);
 293 }
 294
 295 static inline int oe_size_less_than(struct packing_data *pack,
 296                                     const struct object_entry *lhs,
 297                                     unsigned long rhs)
 298 {
 299         if (lhs->size_valid)
 300                 return lhs->size_ < rhs;
 301         if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
 302                 return 0;
 303         return oe_get_size_slow(pack, lhs) < rhs;
 304 }
 305
 306 static inline int oe_size_greater_than(struct packing_data *pack,
 307                                        const struct object_entry *lhs,
 308                                        unsigned long rhs)
 309 {
 310         if (lhs->size_valid)
 311                 return lhs->size_ > rhs;
 312         if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
 313                 return 1;
 314         return oe_get_size_slow(pack, lhs) > rhs;
 315 }
 316
 317 static inline void oe_set_size(struct packing_data *pack,
 318                                struct object_entry *e,
 319                                unsigned long size)
 320 {
 321         if (size < pack->oe_size_limit) {
 322                 e->size_ = size;
 323                 e->size_valid = 1;
 324         } else {
 325                 e->size_valid = 0;
 326                 if (oe_get_size_slow(pack, e) != size)
 327                         BUG("'size' is supposed to be the object size!");
 328         }
 329 }
 330
 331 static inline unsigned long oe_delta_size(struct packing_data *pack,
 332                                           const struct object_entry *e)
 333 {
 334         if (e->delta_size_valid)
 335                 return e->delta_size_;
 336         return oe_size(pack, e);
 337 }
 338
 339 static inline void oe_set_delta_size(struct packing_data *pack,
 340                                      struct object_entry *e,
 341                                      unsigned long size)
 342 {
 343         e->delta_size_ = size;
 344         e->delta_size_valid = e->delta_size_ == size;
 345         if (!e->delta_size_valid && size != oe_size(pack, e))
 346                 BUG("this can only happen in check_object() "
 347                     "where delta size is the same as entry size");
 348 }
 349
 350 #endif