pack-objects: fix tree_depth and layer invariants
[git/git.git] / pack-objects.h
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1#ifndef PACK_OBJECTS_H
2#define PACK_OBJECTS_H
3
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4#include "object-store.h"
5
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6#define DEFAULT_DELTA_CACHE_SIZE (256 * 1024 * 1024)
7
0c6804ab 8#define OE_DFS_STATE_BITS 2
b5c0cbd8 9#define OE_DEPTH_BITS 12
43fa44fa 10#define OE_IN_PACK_BITS 10
0cb3c142 11#define OE_Z_DELTA_BITS 20
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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
0aca34e8 17#define OE_DELTA_SIZE_BITS 20
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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
8d6ccce1 32/*
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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 *
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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
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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.
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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 */
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83struct object_entry {
84 struct pack_idx_entry idx;
2834bc27 85 void *delta_data; /* cached delta (uncompressed) */
3b13a5f2 86 off_t in_pack_offset;
2834bc27 87 uint32_t hash; /* name hint hash */
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88 unsigned size_:OE_SIZE_BITS;
89 unsigned size_valid:1;
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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 */
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95 unsigned delta_size_:OE_DELTA_SIZE_BITS; /* delta data size (uncompressed) */
96 unsigned delta_size_valid:1;
3b13a5f2 97 unsigned in_pack_idx:OE_IN_PACK_BITS; /* already in pack */
0cb3c142 98 unsigned z_delta_size:OE_Z_DELTA_BITS;
3b13a5f2 99 unsigned type_valid:1;
fd9b1bae 100 unsigned type_:TYPE_BITS;
3b13a5f2 101 unsigned no_try_delta:1;
fd9b1bae 102 unsigned in_pack_type:TYPE_BITS; /* could be delta */
c8d521fa 103
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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 */
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109 unsigned tagged:1; /* near the very tip of refs */
110 unsigned filled:1; /* assigned write-order */
0c6804ab 111 unsigned dfs_state:OE_DFS_STATE_BITS;
3b13a5f2 112 unsigned char in_pack_header_size;
b5c0cbd8 113 unsigned depth:OE_DEPTH_BITS;
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114
115 /*
3b13a5f2 116 * pahole results on 64-bit linux (gcc and clang)
7dbabbbe 117 *
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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
4cf2143e 123 */
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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;
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132
133 unsigned int *in_pack_pos;
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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;
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143
144 uintmax_t oe_size_limit;
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145
146 /* delta islands */
147 unsigned int *tree_depth;
fe0ac2fb 148 unsigned char *layer;
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149};
150
43fa44fa 151void prepare_packing_data(struct packing_data *pdata);
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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
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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
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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
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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
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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
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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
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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
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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
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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)
bc35ac1a 367 ALLOC_ARRAY(pack->tree_depth, pack->nr_alloc);
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368 pack->tree_depth[e - pack->objects] = tree_depth;
369}
370
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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)
bc35ac1a 384 ALLOC_ARRAY(pack->layer, pack->nr_alloc);
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385 pack->layer[e - pack->objects] = layer;
386}
387
2834bc27 388#endif