1 // stringpool.cc -- a string pool for gold
3 // Copyright 2006, 2007 Free Software Foundation, Inc.
4 // Written by Ian Lance Taylor <iant@google.com>.
6 // This file is part of gold.
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.
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.
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.
30 #include "parameters.h"
31 #include "stringpool.h"
36 template<typename Stringpool_char
>
37 Stringpool_template
<Stringpool_char
>::Stringpool_template()
38 : string_set_(), strings_(), strtab_size_(0), next_index_(1),
39 next_uncopied_key_(-1), zero_null_(true)
43 template<typename Stringpool_char
>
45 Stringpool_template
<Stringpool_char
>::clear()
47 for (typename
std::list
<Stringdata
*>::iterator p
= this->strings_
.begin();
48 p
!= this->strings_
.end();
50 delete[] reinterpret_cast<char*>(*p
);
51 this->strings_
.clear();
52 this->string_set_
.clear();
55 template<typename Stringpool_char
>
56 Stringpool_template
<Stringpool_char
>::~Stringpool_template()
61 // Return the length of a string of arbitrary character type.
63 template<typename Stringpool_char
>
65 Stringpool_template
<Stringpool_char
>::string_length(const Stringpool_char
* p
)
73 // Specialize string_length for char. Maybe we could just use
74 // std::char_traits<>::length?
78 Stringpool_template
<char>::string_length(const char* p
)
83 // Equality comparison function.
85 template<typename Stringpool_char
>
87 Stringpool_template
<Stringpool_char
>::Stringpool_eq::operator()(
88 const Stringpool_char
* s1
,
89 const Stringpool_char
* s2
) const
97 // Specialize equality comparison for char.
101 Stringpool_template
<char>::Stringpool_eq::operator()(const char* s1
,
102 const char* s2
) const
104 return strcmp(s1
, s2
) == 0;
109 template<typename Stringpool_char
>
111 Stringpool_template
<Stringpool_char
>::Stringpool_hash::operator()(
112 const Stringpool_char
* s
) const
114 // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
115 if (sizeof(size_t) > 4)
117 size_t result
= static_cast<size_t>(14695981039346656037ULL);
120 const char* p
= reinterpret_cast<const char*>(s
);
121 for (size_t i
= 0; i
< sizeof(Stringpool_char
); ++i
)
123 result
^= (size_t) *p
++;
124 result
*= 1099511628211ULL;
132 size_t result
= 2166136261UL;
135 const char* p
= reinterpret_cast<const char*>(s
);
136 for (size_t i
= 0; i
< sizeof(Stringpool_char
); ++i
)
138 result
^= (size_t) *p
++;
139 result
*= 16777619UL;
147 // Add a string to the list of canonical strings. Return a pointer to
148 // the canonical string. If PKEY is not NULL, set *PKEY to the key.
150 template<typename Stringpool_char
>
151 const Stringpool_char
*
152 Stringpool_template
<Stringpool_char
>::add_string(const Stringpool_char
* s
,
155 // We are in trouble if we've already computed the string offsets.
156 gold_assert(this->strtab_size_
== 0);
158 // The size we allocate for a new Stringdata.
159 const size_t buffer_size
= 1000;
160 // The amount we multiply the Stringdata index when calculating the
162 const size_t key_mult
= 1024;
163 gold_assert(key_mult
>= buffer_size
);
165 size_t len
= (string_length(s
) + 1) * sizeof(Stringpool_char
);
169 if (len
> buffer_size
)
171 alc
= sizeof(Stringdata
) + len
;
174 else if (this->strings_
.empty())
175 alc
= sizeof(Stringdata
) + buffer_size
;
178 Stringdata
*psd
= this->strings_
.front();
179 if (len
> psd
->alc
- psd
->len
)
180 alc
= sizeof(Stringdata
) + buffer_size
;
183 char* ret
= psd
->data
+ psd
->len
;
187 *pkey
= psd
->index
* key_mult
+ psd
->len
;
191 return reinterpret_cast<const Stringpool_char
*>(ret
);
195 Stringdata
*psd
= reinterpret_cast<Stringdata
*>(new char[alc
]);
196 psd
->alc
= alc
- sizeof(Stringdata
);
197 memcpy(psd
->data
, s
, len
);
199 psd
->index
= this->next_index_
;
203 *pkey
= psd
->index
* key_mult
;
206 this->strings_
.push_front(psd
);
208 this->strings_
.push_back(psd
);
210 return reinterpret_cast<const Stringpool_char
*>(psd
->data
);
213 // Add a string to a string pool.
215 template<typename Stringpool_char
>
216 const Stringpool_char
*
217 Stringpool_template
<Stringpool_char
>::add(const Stringpool_char
* s
, bool copy
,
220 // FIXME: This will look up the entry twice in the hash table. The
221 // problem is that we can't insert S before we canonicalize it. I
222 // don't think there is a way to handle this correctly with
223 // unordered_map, so this should be replaced with custom code to do
224 // what we need, which is to return the empty slot.
226 typename
String_set_type::const_iterator p
= this->string_set_
.find(s
);
227 if (p
!= this->string_set_
.end())
230 *pkey
= p
->second
.first
;
235 const Stringpool_char
* ret
;
237 ret
= this->add_string(s
, &k
);
241 k
= this->next_uncopied_key_
;
242 --this->next_uncopied_key_
;
245 const off_t ozero
= 0;
246 std::pair
<const Stringpool_char
*, Val
> element(ret
,
247 std::make_pair(k
, ozero
));
248 std::pair
<typename
String_set_type::iterator
, bool> ins
=
249 this->string_set_
.insert(element
);
250 gold_assert(ins
.second
);
258 // Add a prefix of a string to a string pool.
260 template<typename Stringpool_char
>
261 const Stringpool_char
*
262 Stringpool_template
<Stringpool_char
>::add_prefix(const Stringpool_char
* s
,
266 // FIXME: This implementation should be rewritten when we rewrite
267 // the hash table to avoid copying.
268 std::basic_string
<Stringpool_char
> st(s
, len
);
269 return this->add(st
.c_str(), true, pkey
);
272 template<typename Stringpool_char
>
273 const Stringpool_char
*
274 Stringpool_template
<Stringpool_char
>::find(const Stringpool_char
* s
,
277 typename
String_set_type::const_iterator p
= this->string_set_
.find(s
);
278 if (p
== this->string_set_
.end())
282 *pkey
= p
->second
.first
;
287 // Comparison routine used when sorting into an ELF strtab. We want
288 // to sort this so that when one string is a suffix of another, we
289 // always see the shorter string immediately after the longer string.
290 // For example, we want to see these strings in this order:
294 // When strings are not suffixes, we don't care what order they are
295 // in, but we need to ensure that suffixes wind up next to each other.
296 // So we do a reversed lexicographic sort on the reversed string.
298 template<typename Stringpool_char
>
300 Stringpool_template
<Stringpool_char
>::Stringpool_sort_comparison::operator()(
301 const Stringpool_sort_info
& sort_info1
,
302 const Stringpool_sort_info
& sort_info2
) const
304 const Stringpool_char
* s1
= sort_info1
.it
->first
;
305 const Stringpool_char
* s2
= sort_info2
.it
->first
;
306 const size_t len1
= sort_info1
.string_length
;
307 const size_t len2
= sort_info2
.string_length
;
308 const size_t minlen
= len1
< len2
? len1
: len2
;
309 const Stringpool_char
* p1
= s1
+ len1
- 1;
310 const Stringpool_char
* p2
= s2
+ len2
- 1;
311 for (size_t i
= minlen
; i
> 0; --i
, --p1
, --p2
)
319 // Return whether s1 is a suffix of s2.
321 template<typename Stringpool_char
>
323 Stringpool_template
<Stringpool_char
>::is_suffix(const Stringpool_char
* s1
,
325 const Stringpool_char
* s2
,
330 return memcmp(s1
, s2
+ len2
- len1
, len1
* sizeof(Stringpool_char
)) == 0;
333 // Turn the stringpool into an ELF strtab: determine the offsets of
334 // each string in the table.
336 template<typename Stringpool_char
>
338 Stringpool_template
<Stringpool_char
>::set_string_offsets()
340 if (this->strtab_size_
!= 0)
342 // We've already computed the offsets.
346 const size_t charsize
= sizeof(Stringpool_char
);
348 // Offset 0 may be reserved for the empty string.
349 off_t offset
= this->zero_null_
? charsize
: 0;
351 // Sorting to find suffixes can take over 25% of the total CPU time
352 // used by the linker. Since it's merely an optimization to reduce
353 // the strtab size, and gives a relatively small benefit (it's
354 // typically rare for a symbol to be a suffix of another), we only
355 // take the time to sort when the user asks for heavy optimization.
356 if (parameters
->optimization_level() < 2)
358 for (typename
String_set_type::iterator curr
= this->string_set_
.begin();
359 curr
!= this->string_set_
.end();
362 if (this->zero_null_
&& curr
->first
[0] == 0)
363 curr
->second
.second
= 0;
366 curr
->second
.second
= offset
;
367 offset
+= (string_length(curr
->first
) + 1) * charsize
;
373 size_t count
= this->string_set_
.size();
375 std::vector
<Stringpool_sort_info
> v
;
378 for (typename
String_set_type::iterator p
= this->string_set_
.begin();
379 p
!= this->string_set_
.end();
381 v
.push_back(Stringpool_sort_info(p
, string_length(p
->first
)));
383 std::sort(v
.begin(), v
.end(), Stringpool_sort_comparison());
385 for (typename
std::vector
<Stringpool_sort_info
>::iterator last
= v
.end(),
390 if (this->zero_null_
&& curr
->it
->first
[0] == 0)
391 curr
->it
->second
.second
= 0;
392 else if (last
!= v
.end()
393 && is_suffix(curr
->it
->first
, curr
->string_length
,
394 last
->it
->first
, last
->string_length
))
395 curr
->it
->second
.second
= (last
->it
->second
.second
396 + ((last
->string_length
397 - curr
->string_length
)
401 curr
->it
->second
.second
= offset
;
402 offset
+= (curr
->string_length
+ 1) * charsize
;
407 this->strtab_size_
= offset
;
410 // Get the offset of a string in the ELF strtab. The string must
413 template<typename Stringpool_char
>
415 Stringpool_template
<Stringpool_char
>::get_offset(const Stringpool_char
* s
)
418 gold_assert(this->strtab_size_
!= 0);
419 typename
String_set_type::const_iterator p
= this->string_set_
.find(s
);
420 if (p
!= this->string_set_
.end())
421 return p
->second
.second
;
425 // Write the ELF strtab into the buffer.
427 template<typename Stringpool_char
>
429 Stringpool_template
<Stringpool_char
>::write_to_buffer(char* buffer
,
432 gold_assert(this->strtab_size_
!= 0);
433 if (bufsize
< this->strtab_size_
) // Quiet the compiler in opt mode.
434 gold_assert(bufsize
>= this->strtab_size_
);
435 if (this->zero_null_
)
437 for (typename
String_set_type::const_iterator p
= this->string_set_
.begin();
438 p
!= this->string_set_
.end();
441 const int len
= (string_length(p
->first
) + 1) * sizeof(Stringpool_char
);
442 gold_assert(p
->second
.second
+ len
<= this->strtab_size_
);
443 memcpy(buffer
+ p
->second
.second
, p
->first
, len
);
447 // Write the ELF strtab into the output file at the specified offset.
449 template<typename Stringpool_char
>
451 Stringpool_template
<Stringpool_char
>::write(Output_file
* of
, off_t offset
)
453 gold_assert(this->strtab_size_
!= 0);
454 unsigned char* view
= of
->get_output_view(offset
, this->strtab_size_
);
455 this->write_to_buffer(reinterpret_cast<char*>(view
), this->strtab_size_
);
456 of
->write_output_view(offset
, this->strtab_size_
, view
);
459 // Instantiate the templates we need.
462 class Stringpool_template
<char>;
465 class Stringpool_template
<uint16_t>;
468 class Stringpool_template
<uint32_t>;
470 } // End namespace gold.
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