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   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 */
  23enum 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 */
  81struct 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
 123struct 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
 144void prepare_packing_data(struct packing_data *pdata);
 145struct object_entry *packlist_alloc(struct packing_data *pdata,
 146                                    const unsigned char *sha1,
 147                                    uint32_t index_pos);
 148
 149struct object_entry *packlist_find(struct packing_data *pdata,
 150                                   const unsigned char *sha1,
 151                                   uint32_t *index_pos);
 152
 153static 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
 173static inline enum object_type oe_type(const struct object_entry *e)
 174{
 175        return e->type_valid ? e->type_ : OBJ_BAD;
 176}
 177
 178static 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
 188static 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
 194static 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
 201static 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
 210void oe_map_new_pack(struct packing_data *pack,
 211                     struct packed_git *p);
 212static 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
 224static 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
 233static 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
 243static 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
 252static 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
 262static 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
 271static 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
 281unsigned long oe_get_size_slow(struct packing_data *pack,
 282                               const struct object_entry *e);
 283static 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
 292static 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
 303static 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
 314static 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
 328static 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
 336static 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