Add delta-islands.{c,h}
[git/git.git] / 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