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