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1 : : /* File caching.
2 : : Copyright (C) 2023-2025 Free Software Foundation, Inc.
3 : :
4 : : This file is part of GCC.
5 : :
6 : : GCC is free software; you can redistribute it and/or modify it under
7 : : the terms of the GNU General Public License as published by the Free
8 : : Software Foundation; either version 3, or (at your option) any later
9 : : version.
10 : :
11 : : GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 : : WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 : : FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 : : for more details.
15 : :
16 : : You should have received a copy of the GNU General Public License
17 : : along with GCC; see the file COPYING3. If not see
18 : : <http://www.gnu.org/licenses/>. */
19 : :
20 : : #ifndef GCC_LTO_LTRANS_CACHE_H
21 : : #define GCC_LTO_LTRANS_CACHE_H
22 : :
23 : : #include "lockfile.h"
24 : :
25 : : using checksum_t = std::array<uint8_t, 32>;
26 : :
27 : : class ltrans_file_cache
28 : : {
29 : : public:
30 : : /* Cache item representing input/output filename pair. */
31 : : struct item
32 : : {
33 : : item (std::string input, std::string output,
34 : : checksum_t input_checksum, uint32_t last_used);
35 : : ~item ();
36 : :
37 : : /* Full path to input filename. */
38 : : const std::string input;
39 : : /* Full path to output filename. */
40 : : const std::string output;
41 : : /* Checksum of input file. */
42 : : const checksum_t input_checksum;
43 : :
44 : : /* Larger last_used corresponds to later usage. */
45 : : uint32_t last_used;
46 : :
47 : : /* Lockfile so that output file can be created later than input file. */
48 : : lockfile lock;
49 : : };
50 : :
51 : : /* Constructor. Resulting cache item filenames will be
52 : : in format `prefix%d[.ltrans]suffix`. */
53 : : ltrans_file_cache (const char* dir, const char* prefix, const char* suffix,
54 : : size_t soft_cache_size);
55 : : /* Destructor. */
56 : : ~ltrans_file_cache ();
57 : :
58 : : /* Loads data about previously cached items from cachedata file.
59 : :
60 : : Must be called with creation_lock or deletion_lock held to
61 : : prevent data race. */
62 : : void load_cache ();
63 : :
64 : : /* Rewrites data about cache items into cachedata file.
65 : :
66 : : Must be only called when creation_lock or deletion_lock was held since last
67 : : call to load_cache. */
68 : : void save_cache ();
69 : :
70 : :
71 : : /* Adds input file into cache. Cache item with input file identical to
72 : : added input file will be returned as _item.
73 : : If the file was already cached, `true` is returned, `false` otherwise.
74 : : The added input file is deleted (or moved).
75 : :
76 : : Must be called with creation_lock held to prevent data race. */
77 : : bool add_to_cache (const char* filename, item*& _item);
78 : :
79 : : /* If exists, returns cache item corresponding to cached input file. */
80 : : item* get_item (const char* input);
81 : :
82 : : /* If no other process holds the deletion_lock, prunes oldest unused cache
83 : : items over limit. */
84 : : void try_prune ();
85 : :
86 : : /* Clears cache class, as if only constructor was called. */
87 : : void cleanup ();
88 : :
89 : : /* Cache is enabled if true. */
90 : 60738 : operator bool ()
91 : : {
92 : 60738 : return dir;
93 : : }
94 : :
95 : : /* Access to already created items can be concurrent with item creation. */
96 : : lockfile creation_lock;
97 : : /* Access to already created items cannot be concurrent
98 : : with item deletion. */
99 : : lockfile deletion_lock;
100 : :
101 : : /* Directory of cache. NULL if cache is disabled. */
102 : : const char* dir;
103 : : private:
104 : : /* Adds given cache item to all relevant datastructures. */
105 : : void add_item (item* item);
106 : :
107 : : /* Creates new cache item with given checksum.
108 : : New input/output files are chosen to not collide with other items.
109 : :
110 : : Must be called with creation_lock held to prevent data race. */
111 : : item* create_item (const checksum_t& checksum);
112 : :
113 : : /* Prunes oldest unused cache items over limit.
114 : : Must be called with deletion_lock held to prevent data race. */
115 : : void prune ();
116 : :
117 : : /* Creates cachedata filename for save/load. */
118 : : std::string filename_cachedata ();
119 : :
120 : : /* All cache items in current cache. */
121 : : std::vector<item*> items;
122 : : std::map<checksum_t, item*> map_checksum;
123 : : std::map<std::string, item*> map_input;
124 : :
125 : : /* Cached filenames are in format "prefix%d[.ltrans]suffix". */
126 : : const char* prefix;
127 : : const char* suffix;
128 : :
129 : : /* If cache items count is larger, prune deletes old items. */
130 : : size_t soft_cache_size;
131 : :
132 : : /* Counter used to populate last_used of items. */
133 : : uint32_t usage_counter;
134 : :
135 : : /* String in format "dir/prefix". */
136 : : std::string cache_prefix;
137 : : /* Lower indices are occupied. */
138 : : uint32_t cache_free_idx;
139 : :
140 : : /* Buffer for sprintf. */
141 : : char* str_buffer;
142 : : };
143 : :
144 : : #endif
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