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   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 */
  25enum 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 */
  83struct 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 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
 126struct 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        /* delta islands */
 147        unsigned int *tree_depth;
 148        unsigned char *layer;
 149};
 150
 151void prepare_packing_data(struct packing_data *pdata);
 152struct object_entry *packlist_alloc(struct packing_data *pdata,
 153                                    const unsigned char *sha1,
 154                                    uint32_t index_pos);
 155
 156struct object_entry *packlist_find(struct packing_data *pdata,
 157                                   const unsigned char *sha1,
 158                                   uint32_t *index_pos);
 159
 160static inline uint32_t pack_name_hash(const char *name)
 161{
 162        uint32_t c, hash = 0;
 163
 164        if (!name)
 165                return 0;
 166
 167        /*
 168         * This effectively just creates a sortable number from the
 169         * last sixteen non-whitespace characters. Last characters
 170         * count "most", so things that end in ".c" sort together.
 171         */
 172        while ((c = *name++) != 0) {
 173                if (isspace(c))
 174                        continue;
 175                hash = (hash >> 2) + (c << 24);
 176        }
 177        return hash;
 178}
 179
 180static inline enum object_type oe_type(const struct object_entry *e)
 181{
 182        return e->type_valid ? e->type_ : OBJ_BAD;
 183}
 184
 185static inline void oe_set_type(struct object_entry *e,
 186                               enum object_type type)
 187{
 188        if (type >= OBJ_ANY)
 189                BUG("OBJ_ANY cannot be set in pack-objects code");
 190
 191        e->type_valid = type >= OBJ_NONE;
 192        e->type_ = (unsigned)type;
 193}
 194
 195static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
 196                                          const struct object_entry *e)
 197{
 198        return pack->in_pack_pos[e - pack->objects];
 199}
 200
 201static inline void oe_set_in_pack_pos(const struct packing_data *pack,
 202                                      const struct object_entry *e,
 203                                      unsigned int pos)
 204{
 205        pack->in_pack_pos[e - pack->objects] = pos;
 206}
 207
 208static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
 209                                            const struct object_entry *e)
 210{
 211        if (pack->in_pack_by_idx)
 212                return pack->in_pack_by_idx[e->in_pack_idx];
 213        else
 214                return pack->in_pack[e - pack->objects];
 215}
 216
 217void oe_map_new_pack(struct packing_data *pack,
 218                     struct packed_git *p);
 219static inline void oe_set_in_pack(struct packing_data *pack,
 220                                  struct object_entry *e,
 221                                  struct packed_git *p)
 222{
 223        if (!p->index)
 224                oe_map_new_pack(pack, p);
 225        if (pack->in_pack_by_idx)
 226                e->in_pack_idx = p->index;
 227        else
 228                pack->in_pack[e - pack->objects] = p;
 229}
 230
 231static inline struct object_entry *oe_delta(
 232                const struct packing_data *pack,
 233                const struct object_entry *e)
 234{
 235        if (e->delta_idx)
 236                return &pack->objects[e->delta_idx - 1];
 237        return NULL;
 238}
 239
 240static inline void oe_set_delta(struct packing_data *pack,
 241                                struct object_entry *e,
 242                                struct object_entry *delta)
 243{
 244        if (delta)
 245                e->delta_idx = (delta - pack->objects) + 1;
 246        else
 247                e->delta_idx = 0;
 248}
 249
 250static inline struct object_entry *oe_delta_child(
 251                const struct packing_data *pack,
 252                const struct object_entry *e)
 253{
 254        if (e->delta_child_idx)
 255                return &pack->objects[e->delta_child_idx - 1];
 256        return NULL;
 257}
 258
 259static inline void oe_set_delta_child(struct packing_data *pack,
 260                                      struct object_entry *e,
 261                                      struct object_entry *delta)
 262{
 263        if (delta)
 264                e->delta_child_idx = (delta - pack->objects) + 1;
 265        else
 266                e->delta_child_idx = 0;
 267}
 268
 269static inline struct object_entry *oe_delta_sibling(
 270                const struct packing_data *pack,
 271                const struct object_entry *e)
 272{
 273        if (e->delta_sibling_idx)
 274                return &pack->objects[e->delta_sibling_idx - 1];
 275        return NULL;
 276}
 277
 278static inline void oe_set_delta_sibling(struct packing_data *pack,
 279                                        struct object_entry *e,
 280                                        struct object_entry *delta)
 281{
 282        if (delta)
 283                e->delta_sibling_idx = (delta - pack->objects) + 1;
 284        else
 285                e->delta_sibling_idx = 0;
 286}
 287
 288unsigned long oe_get_size_slow(struct packing_data *pack,
 289                               const struct object_entry *e);
 290static inline unsigned long oe_size(struct packing_data *pack,
 291                                    const struct object_entry *e)
 292{
 293        if (e->size_valid)
 294                return e->size_;
 295
 296        return oe_get_size_slow(pack, e);
 297}
 298
 299static inline int oe_size_less_than(struct packing_data *pack,
 300                                    const struct object_entry *lhs,
 301                                    unsigned long rhs)
 302{
 303        if (lhs->size_valid)
 304                return lhs->size_ < rhs;
 305        if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
 306                return 0;
 307        return oe_get_size_slow(pack, lhs) < rhs;
 308}
 309
 310static inline int oe_size_greater_than(struct packing_data *pack,
 311                                       const struct object_entry *lhs,
 312                                       unsigned long rhs)
 313{
 314        if (lhs->size_valid)
 315                return lhs->size_ > rhs;
 316        if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
 317                return 1;
 318        return oe_get_size_slow(pack, lhs) > rhs;
 319}
 320
 321static inline void oe_set_size(struct packing_data *pack,
 322                               struct object_entry *e,
 323                               unsigned long size)
 324{
 325        if (size < pack->oe_size_limit) {
 326                e->size_ = size;
 327                e->size_valid = 1;
 328        } else {
 329                e->size_valid = 0;
 330                if (oe_get_size_slow(pack, e) != size)
 331                        BUG("'size' is supposed to be the object size!");
 332        }
 333}
 334
 335static inline unsigned long oe_delta_size(struct packing_data *pack,
 336                                          const struct object_entry *e)
 337{
 338        if (e->delta_size_valid)
 339                return e->delta_size_;
 340        return oe_size(pack, e);
 341}
 342
 343static inline void oe_set_delta_size(struct packing_data *pack,
 344                                     struct object_entry *e,
 345                                     unsigned long size)
 346{
 347        e->delta_size_ = size;
 348        e->delta_size_valid = e->delta_size_ == size;
 349        if (!e->delta_size_valid && size != oe_size(pack, e))
 350                BUG("this can only happen in check_object() "
 351                    "where delta size is the same as entry size");
 352}
 353
 354static inline unsigned int oe_tree_depth(struct packing_data *pack,
 355                                         struct object_entry *e)
 356{
 357        if (!pack->tree_depth)
 358                return 0;
 359        return pack->tree_depth[e - pack->objects];
 360}
 361
 362static inline void oe_set_tree_depth(struct packing_data *pack,
 363                                     struct object_entry *e,
 364                                     unsigned int tree_depth)
 365{
 366        if (!pack->tree_depth)
 367                ALLOC_ARRAY(pack->tree_depth, pack->nr_alloc);
 368        pack->tree_depth[e - pack->objects] = tree_depth;
 369}
 370
 371static inline unsigned char oe_layer(struct packing_data *pack,
 372                                     struct object_entry *e)
 373{
 374        if (!pack->layer)
 375                return 0;
 376        return pack->layer[e - pack->objects];
 377}
 378
 379static inline void oe_set_layer(struct packing_data *pack,
 380                                struct object_entry *e,
 381                                unsigned char layer)
 382{
 383        if (!pack->layer)
 384                ALLOC_ARRAY(pack->layer, pack->nr_alloc);
 385        pack->layer[e - pack->objects] = layer;
 386}
 387
 388#endif