Fifth batch for 2.19 cycle
[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 unsigned preferred_base:1; /*
104 * we do not pack this, but is available
105 * to be used as the base object to delta
106 * objects against.
107 */
108 unsigned tagged:1; /* near the very tip of refs */
109 unsigned filled:1; /* assigned write-order */
110 unsigned dfs_state:OE_DFS_STATE_BITS;
111 unsigned char in_pack_header_size;
112 unsigned depth:OE_DEPTH_BITS;
113
114 /*
115 * pahole results on 64-bit linux (gcc and clang)
116 *
117 * size: 80, bit_padding: 20 bits, holes: 8 bits
118 *
119 * and on 32-bit (gcc)
120 *
121 * size: 76, bit_padding: 20 bits, holes: 8 bits
122 */
123 };
124
125 struct packing_data {
126 struct object_entry *objects;
127 uint32_t nr_objects, nr_alloc;
128
129 int32_t *index;
130 uint32_t index_size;
131
132 unsigned int *in_pack_pos;
133
134 /*
135 * Only one of these can be non-NULL and they have different
136 * sizes. if in_pack_by_idx is allocated, oe_in_pack() returns
137 * the pack of an object using in_pack_idx field. If not,
138 * in_pack[] array is used the same way as in_pack_pos[]
139 */
140 struct packed_git **in_pack_by_idx;
141 struct packed_git **in_pack;
142
143 uintmax_t oe_size_limit;
144 };
145
146 void prepare_packing_data(struct packing_data *pdata);
147 struct object_entry *packlist_alloc(struct packing_data *pdata,
148 const unsigned char *sha1,
149 uint32_t index_pos);
150
151 struct object_entry *packlist_find(struct packing_data *pdata,
152 const unsigned char *sha1,
153 uint32_t *index_pos);
154
155 static inline uint32_t pack_name_hash(const char *name)
156 {
157 uint32_t c, hash = 0;
158
159 if (!name)
160 return 0;
161
162 /*
163 * This effectively just creates a sortable number from the
164 * last sixteen non-whitespace characters. Last characters
165 * count "most", so things that end in ".c" sort together.
166 */
167 while ((c = *name++) != 0) {
168 if (isspace(c))
169 continue;
170 hash = (hash >> 2) + (c << 24);
171 }
172 return hash;
173 }
174
175 static inline enum object_type oe_type(const struct object_entry *e)
176 {
177 return e->type_valid ? e->type_ : OBJ_BAD;
178 }
179
180 static inline void oe_set_type(struct object_entry *e,
181 enum object_type type)
182 {
183 if (type >= OBJ_ANY)
184 BUG("OBJ_ANY cannot be set in pack-objects code");
185
186 e->type_valid = type >= OBJ_NONE;
187 e->type_ = (unsigned)type;
188 }
189
190 static inline unsigned int oe_in_pack_pos(const struct packing_data *pack,
191 const struct object_entry *e)
192 {
193 return pack->in_pack_pos[e - pack->objects];
194 }
195
196 static inline void oe_set_in_pack_pos(const struct packing_data *pack,
197 const struct object_entry *e,
198 unsigned int pos)
199 {
200 pack->in_pack_pos[e - pack->objects] = pos;
201 }
202
203 static inline struct packed_git *oe_in_pack(const struct packing_data *pack,
204 const struct object_entry *e)
205 {
206 if (pack->in_pack_by_idx)
207 return pack->in_pack_by_idx[e->in_pack_idx];
208 else
209 return pack->in_pack[e - pack->objects];
210 }
211
212 void oe_map_new_pack(struct packing_data *pack,
213 struct packed_git *p);
214 static inline void oe_set_in_pack(struct packing_data *pack,
215 struct object_entry *e,
216 struct packed_git *p)
217 {
218 if (!p->index)
219 oe_map_new_pack(pack, p);
220 if (pack->in_pack_by_idx)
221 e->in_pack_idx = p->index;
222 else
223 pack->in_pack[e - pack->objects] = p;
224 }
225
226 static inline struct object_entry *oe_delta(
227 const struct packing_data *pack,
228 const struct object_entry *e)
229 {
230 if (e->delta_idx)
231 return &pack->objects[e->delta_idx - 1];
232 return NULL;
233 }
234
235 static inline void oe_set_delta(struct packing_data *pack,
236 struct object_entry *e,
237 struct object_entry *delta)
238 {
239 if (delta)
240 e->delta_idx = (delta - pack->objects) + 1;
241 else
242 e->delta_idx = 0;
243 }
244
245 static inline struct object_entry *oe_delta_child(
246 const struct packing_data *pack,
247 const struct object_entry *e)
248 {
249 if (e->delta_child_idx)
250 return &pack->objects[e->delta_child_idx - 1];
251 return NULL;
252 }
253
254 static inline void oe_set_delta_child(struct packing_data *pack,
255 struct object_entry *e,
256 struct object_entry *delta)
257 {
258 if (delta)
259 e->delta_child_idx = (delta - pack->objects) + 1;
260 else
261 e->delta_child_idx = 0;
262 }
263
264 static inline struct object_entry *oe_delta_sibling(
265 const struct packing_data *pack,
266 const struct object_entry *e)
267 {
268 if (e->delta_sibling_idx)
269 return &pack->objects[e->delta_sibling_idx - 1];
270 return NULL;
271 }
272
273 static inline void oe_set_delta_sibling(struct packing_data *pack,
274 struct object_entry *e,
275 struct object_entry *delta)
276 {
277 if (delta)
278 e->delta_sibling_idx = (delta - pack->objects) + 1;
279 else
280 e->delta_sibling_idx = 0;
281 }
282
283 unsigned long oe_get_size_slow(struct packing_data *pack,
284 const struct object_entry *e);
285 static inline unsigned long oe_size(struct packing_data *pack,
286 const struct object_entry *e)
287 {
288 if (e->size_valid)
289 return e->size_;
290
291 return oe_get_size_slow(pack, e);
292 }
293
294 static inline int oe_size_less_than(struct packing_data *pack,
295 const struct object_entry *lhs,
296 unsigned long rhs)
297 {
298 if (lhs->size_valid)
299 return lhs->size_ < rhs;
300 if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
301 return 0;
302 return oe_get_size_slow(pack, lhs) < rhs;
303 }
304
305 static inline int oe_size_greater_than(struct packing_data *pack,
306 const struct object_entry *lhs,
307 unsigned long rhs)
308 {
309 if (lhs->size_valid)
310 return lhs->size_ > rhs;
311 if (rhs < pack->oe_size_limit) /* rhs < 2^x <= lhs ? */
312 return 1;
313 return oe_get_size_slow(pack, lhs) > rhs;
314 }
315
316 static inline void oe_set_size(struct packing_data *pack,
317 struct object_entry *e,
318 unsigned long size)
319 {
320 if (size < pack->oe_size_limit) {
321 e->size_ = size;
322 e->size_valid = 1;
323 } else {
324 e->size_valid = 0;
325 if (oe_get_size_slow(pack, e) != size)
326 BUG("'size' is supposed to be the object size!");
327 }
328 }
329
330 static inline unsigned long oe_delta_size(struct packing_data *pack,
331 const struct object_entry *e)
332 {
333 if (e->delta_size_valid)
334 return e->delta_size_;
335 return oe_size(pack, e);
336 }
337
338 static inline void oe_set_delta_size(struct packing_data *pack,
339 struct object_entry *e,
340 unsigned long size)
341 {
342 e->delta_size_ = size;
343 e->delta_size_valid = e->delta_size_ == size;
344 if (!e->delta_size_valid && size != oe_size(pack, e))
345 BUG("this can only happen in check_object() "
346 "where delta size is the same as entry size");
347 }
348
349 #endif