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14bfc3f5 ILT |
1 | // stringpool.h -- a string pool for gold -*- C++ -*- |
2 | ||
6cb15b7f ILT |
3 | // Copyright 2006, 2007 Free Software Foundation, Inc. |
4 | // Written by Ian Lance Taylor <iant@google.com>. | |
5 | ||
6 | // This file is part of gold. | |
7 | ||
8 | // This program is free software; you can redistribute it and/or modify | |
9 | // it under the terms of the GNU General Public License as published by | |
10 | // the Free Software Foundation; either version 3 of the License, or | |
11 | // (at your option) any later version. | |
12 | ||
13 | // This program is distributed in the hope that it will be useful, | |
14 | // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | // GNU General Public License for more details. | |
17 | ||
18 | // You should have received a copy of the GNU General Public License | |
19 | // along with this program; if not, write to the Free Software | |
20 | // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, | |
21 | // MA 02110-1301, USA. | |
22 | ||
14bfc3f5 ILT |
23 | #include <string> |
24 | #include <list> | |
25 | ||
14bfc3f5 ILT |
26 | #ifndef GOLD_STRINGPOOL_H |
27 | #define GOLD_STRINGPOOL_H | |
28 | ||
29 | namespace gold | |
30 | { | |
31 | ||
61ba1cf9 ILT |
32 | class Output_file; |
33 | ||
835965e6 ILT |
34 | // A Stringpool is a pool of unique strings. It provides the |
35 | // following features: | |
36 | ||
37 | // Every string in the pool is unique. Thus, if you have two strings | |
38 | // in the Stringpool, you can compare them for equality by using | |
39 | // pointer comparison rather than string comparison. | |
40 | ||
41 | // There is a key associated with every string in the pool. If you | |
42 | // add strings to the Stringpool in the same order, then the key for | |
43 | // each string will always be the same for any run of the linker. | |
44 | // This is not true of the string pointers themselves, as they may | |
45 | // change due to address space randomization. Some parts of the | |
46 | // linker (e.g., the symbol table) use the key value instead of the | |
47 | // string pointer so that repeated runs of the linker will generate | |
48 | // precisely the same output. | |
49 | ||
cfd73a4e ILT |
50 | // When you add a string to a Stringpool, Stringpool will optionally |
51 | // make a copy of it. Thus there is no requirement to keep a copy | |
52 | // elsewhere. | |
bc56b3fb | 53 | |
835965e6 ILT |
54 | // A Stringpool can be turned into a string table, a sequential series |
55 | // of null terminated strings. The first string may optionally be a | |
56 | // single zero byte, as required for SHT_STRTAB sections. This | |
57 | // conversion is only permitted after all strings have been added to | |
58 | // the Stringpool. After doing this conversion, you can ask for the | |
59 | // offset of any string in the stringpool in the string table, and you | |
60 | // can write the resulting string table to an output file. | |
61 | ||
62 | // When a Stringpool is turned into a string table, then as an | |
63 | // optimization it will reuse string suffixes to avoid duplicating | |
64 | // strings. That is, given the strings "abc" and "bc", only the | |
65 | // string "abc" will be stored, and "bc" will be represented by an | |
66 | // offset into the middle of the string "abc". | |
67 | ||
68 | // Stringpools are implemented in terms of Stringpool_template, which | |
69 | // is generalized on the type of character used for the strings. Most | |
70 | // uses will want the Stringpool type which uses char. Other cases | |
71 | // are used for merging wide string constants. | |
72 | ||
b8e6aad9 ILT |
73 | template<typename Stringpool_char> |
74 | class Stringpool_template | |
14bfc3f5 ILT |
75 | { |
76 | public: | |
835965e6 ILT |
77 | // The type of a key into the stringpool. As described above, a key |
78 | // value will always be the same during any run of the linker. Zero | |
79 | // is never a valid key value. | |
f0641a0b ILT |
80 | typedef size_t Key; |
81 | ||
a8b2552e ILT |
82 | // Create a Stringpool. |
83 | Stringpool_template(); | |
14bfc3f5 | 84 | |
b8e6aad9 | 85 | ~Stringpool_template(); |
14bfc3f5 | 86 | |
a8b2552e ILT |
87 | // Indicate that we should not reserve offset 0 to hold the empty |
88 | // string when converting the stringpool to a string table. This | |
89 | // should not be called for a proper ELF SHT_STRTAB section. | |
90 | void | |
91 | set_no_zero_null() | |
92 | { this->zero_null_ = false; } | |
93 | ||
835965e6 | 94 | // Add the string S to the pool. This returns a canonical permanent |
cfd73a4e ILT |
95 | // pointer to the string in the pool. If COPY is true, the string |
96 | // is copied into permanent storage. If PKEY is not NULL, this sets | |
97 | // *PKEY to the key for the string. | |
b8e6aad9 | 98 | const Stringpool_char* |
cfd73a4e | 99 | add(const Stringpool_char* s, bool copy, Key* pkey); |
14bfc3f5 | 100 | |
835965e6 | 101 | // Add the prefix of length LEN of string S to the pool. |
b8e6aad9 | 102 | const Stringpool_char* |
cfd73a4e | 103 | add_prefix(const Stringpool_char* s, size_t len, Key* pkey); |
61ba1cf9 | 104 | |
835965e6 ILT |
105 | // If the string S is present in the pool, return the canonical |
106 | // string pointer. Otherwise, return NULL. If PKEY is not NULL, | |
107 | // set *PKEY to the key. | |
b8e6aad9 | 108 | const Stringpool_char* |
835965e6 | 109 | find(const Stringpool_char* s, Key* pkey) const; |
61ba1cf9 | 110 | |
835965e6 ILT |
111 | // Turn the stringpool into a string table: determine the offsets of |
112 | // all the strings. After this is called, no more strings may be | |
113 | // added to the stringpool. | |
61ba1cf9 ILT |
114 | void |
115 | set_string_offsets(); | |
116 | ||
835965e6 ILT |
117 | // Get the offset of the string S in the string table. This returns |
118 | // the offset in bytes, not in units of Stringpool_char. This may | |
119 | // only be called after set_string_offsets has been called. | |
61ba1cf9 | 120 | off_t |
835965e6 | 121 | get_offset(const Stringpool_char* s) const; |
61ba1cf9 | 122 | |
835965e6 | 123 | // Get the offset of the string S in the string table. |
61ba1cf9 | 124 | off_t |
b8e6aad9 | 125 | get_offset(const std::basic_string<Stringpool_char>& s) const |
61ba1cf9 ILT |
126 | { return this->get_offset(s.c_str()); } |
127 | ||
835965e6 ILT |
128 | // Get the size of the string table. This returns the number of |
129 | // bytes, not in units of Stringpool_char. | |
61ba1cf9 ILT |
130 | off_t |
131 | get_strtab_size() const | |
a3ad94ed ILT |
132 | { |
133 | gold_assert(this->strtab_size_ != 0); | |
134 | return this->strtab_size_; | |
135 | } | |
61ba1cf9 | 136 | |
835965e6 ILT |
137 | // Write the string table into the output file at the specified |
138 | // offset. | |
61ba1cf9 ILT |
139 | void |
140 | write(Output_file*, off_t offset); | |
14bfc3f5 ILT |
141 | |
142 | private: | |
b8e6aad9 ILT |
143 | Stringpool_template(const Stringpool_template&); |
144 | Stringpool_template& operator=(const Stringpool_template&); | |
145 | ||
835965e6 | 146 | // Return the length of a string in units of Stringpool_char. |
b8e6aad9 ILT |
147 | static size_t |
148 | string_length(const Stringpool_char*); | |
14bfc3f5 | 149 | |
61ba1cf9 ILT |
150 | // We store the actual data in a list of these buffers. |
151 | struct Stringdata | |
14bfc3f5 ILT |
152 | { |
153 | // Length of data in buffer. | |
154 | size_t len; | |
155 | // Allocated size of buffer. | |
156 | size_t alc; | |
f0641a0b ILT |
157 | // Buffer index. |
158 | unsigned int index; | |
14bfc3f5 ILT |
159 | // Buffer. |
160 | char data[1]; | |
161 | }; | |
162 | ||
61ba1cf9 | 163 | // Copy a string into the buffers, returning a canonical string. |
b8e6aad9 ILT |
164 | const Stringpool_char* |
165 | add_string(const Stringpool_char*, Key*); | |
14bfc3f5 | 166 | |
835965e6 | 167 | // Hash function. |
14bfc3f5 ILT |
168 | struct Stringpool_hash |
169 | { | |
170 | size_t | |
b8e6aad9 | 171 | operator()(const Stringpool_char*) const; |
14bfc3f5 ILT |
172 | }; |
173 | ||
835965e6 | 174 | // Equality comparison function for hash table. |
14bfc3f5 ILT |
175 | struct Stringpool_eq |
176 | { | |
177 | bool | |
b8e6aad9 | 178 | operator()(const Stringpool_char* p1, const Stringpool_char* p2) const; |
14bfc3f5 ILT |
179 | }; |
180 | ||
61ba1cf9 | 181 | // Return whether s1 is a suffix of s2. |
b8e6aad9 | 182 | static bool |
614f30a2 ILT |
183 | is_suffix(const Stringpool_char* s1, size_t len1, |
184 | const Stringpool_char* s2, size_t len2); | |
61ba1cf9 | 185 | |
f0641a0b | 186 | // The hash table is a map from string names to a pair of Key and |
835965e6 ILT |
187 | // string table offsets. We only use the offsets if we turn this |
188 | // into an string table section. | |
f0641a0b ILT |
189 | |
190 | typedef std::pair<Key, off_t> Val; | |
61ba1cf9 | 191 | |
274e99f9 | 192 | #ifdef HAVE_TR1_UNORDERED_SET |
b8e6aad9 | 193 | typedef Unordered_map<const Stringpool_char*, Val, Stringpool_hash, |
61ba1cf9 | 194 | Stringpool_eq, |
b8e6aad9 ILT |
195 | std::allocator<std::pair<const Stringpool_char* const, |
196 | Val> >, | |
14bfc3f5 | 197 | true> String_set_type; |
274e99f9 | 198 | #else |
b8e6aad9 | 199 | typedef Unordered_map<const Stringpool_char*, Val, Stringpool_hash, |
61ba1cf9 | 200 | Stringpool_eq> String_set_type; |
274e99f9 ILT |
201 | #endif |
202 | ||
835965e6 | 203 | // Comparison routine used when sorting into a string table. We |
614f30a2 ILT |
204 | // store string-sizes in the sort-vector so we don't have to |
205 | // recompute them log(n) times as we sort. | |
206 | struct Stringpool_sort_info | |
207 | { | |
208 | typename String_set_type::iterator it; | |
209 | size_t string_length; | |
210 | Stringpool_sort_info(typename String_set_type::iterator i, size_t s) | |
211 | : it(i), string_length(s) | |
212 | { } | |
213 | }; | |
61ba1cf9 ILT |
214 | |
215 | struct Stringpool_sort_comparison | |
216 | { | |
217 | bool | |
614f30a2 | 218 | operator()(const Stringpool_sort_info&, const Stringpool_sort_info&) const; |
61ba1cf9 ILT |
219 | }; |
220 | ||
f0641a0b ILT |
221 | // List of Stringdata structures. |
222 | typedef std::list<Stringdata*> Stringdata_list; | |
223 | ||
224 | // Mapping from const char* to namepool entry. | |
14bfc3f5 | 225 | String_set_type string_set_; |
f0641a0b ILT |
226 | // List of buffers. |
227 | Stringdata_list strings_; | |
835965e6 | 228 | // Size of string table. |
61ba1cf9 | 229 | off_t strtab_size_; |
f0641a0b ILT |
230 | // Next Stringdata index. |
231 | unsigned int next_index_; | |
cfd73a4e ILT |
232 | // Next key value for a string we don't copy. |
233 | int next_uncopied_key_; | |
b8e6aad9 ILT |
234 | // Whether to reserve offset 0 to hold the null string. |
235 | bool zero_null_; | |
14bfc3f5 ILT |
236 | }; |
237 | ||
b8e6aad9 ILT |
238 | // The most common type of Stringpool. |
239 | typedef Stringpool_template<char> Stringpool; | |
240 | ||
14bfc3f5 ILT |
241 | } // End namespace gold. |
242 | ||
243 | #endif // !defined(GOLD_STRINGPOOL_H) |