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 // Resize the internal hashtable with the expectation we'll get n new
62 // elements. Note that the hashtable constructor takes a "number of
63 // buckets you'd like," rather than "number of elements you'd like,"
64 // but that's the best we can do.
66 template<typename Stringpool_char
>
68 Stringpool_template
<Stringpool_char
>::reserve(unsigned int n
)
70 #if defined(HAVE_TR1_UNORDERED_MAP)
71 // rehash() implementation is broken in gcc 4.0.3's stl
72 //this->string_set_.rehash(this->string_set_.size() + n);
74 #elif defined(HAVE_EXT_HASH_MAP)
75 this->string_set_
.resize(this->string_set_
.size() + n
);
79 // This is the generic "reserve" code, if no #ifdef above triggers.
80 String_set_type
new_string_set(this->string_set_
.size() + n
);
81 new_string_set
.insert(this->string_set_
.begin(), this->string_set_
.end());
82 this->string_set_
.swap(new_string_set
);
85 // Return the length of a string of arbitrary character type.
87 template<typename Stringpool_char
>
89 Stringpool_template
<Stringpool_char
>::string_length(const Stringpool_char
* p
)
97 // Specialize string_length for char. Maybe we could just use
98 // std::char_traits<>::length?
102 Stringpool_template
<char>::string_length(const char* p
)
107 // Compare two strings of arbitrary character type for equality.
109 template<typename Stringpool_char
>
111 Stringpool_template
<Stringpool_char
>::string_equal(const Stringpool_char
* s1
,
112 const Stringpool_char
* s2
)
120 // Specialize string_equal for char.
124 Stringpool_template
<char>::string_equal(const char* s1
, const char* s2
)
126 return strcmp(s1
, s2
) == 0;
129 // Equality comparison function for the hash table.
131 template<typename Stringpool_char
>
133 Stringpool_template
<Stringpool_char
>::Stringpool_eq::operator()(
135 const Hashkey
& h2
) const
137 return (h1
.hash_code
== h2
.hash_code
138 && h1
.length
== h2
.length
139 && memcmp(h1
.string
, h2
.string
,
140 h1
.length
* sizeof(Stringpool_char
)) == 0);
143 // Hash function. The length is in characters, not bytes.
145 template<typename Stringpool_char
>
147 Stringpool_template
<Stringpool_char
>::string_hash(const Stringpool_char
* s
,
150 // Fowler/Noll/Vo (FNV) hash (type FNV-1a).
151 const unsigned char* p
= reinterpret_cast<const unsigned char*>(s
);
152 if (sizeof(size_t) > 4)
154 size_t result
= static_cast<size_t>(14695981039346656037ULL);
155 for (size_t i
= 0; i
< length
* sizeof(Stringpool_char
); ++i
)
157 result
^= static_cast<size_t>(*p
++);
158 result
*= 1099511628211ULL;
164 size_t result
= 2166136261UL;
165 for (size_t i
= 0; i
< length
* sizeof(Stringpool_char
); ++i
)
167 result
^= static_cast<size_t>(*p
++);
168 result
*= 16777619UL;
174 // Add the string S to the list of canonical strings. Return a
175 // pointer to the canonical string. If PKEY is not NULL, set *PKEY to
176 // the key. LENGTH is the length of S in characters. Note that S may
177 // not be NUL terminated.
179 template<typename Stringpool_char
>
180 const Stringpool_char
*
181 Stringpool_template
<Stringpool_char
>::add_string(const Stringpool_char
* s
,
185 // We are in trouble if we've already computed the string offsets.
186 gold_assert(this->strtab_size_
== 0);
188 // The size we allocate for a new Stringdata.
189 const size_t buffer_size
= 1000;
190 // The amount we multiply the Stringdata index when calculating the
192 const size_t key_mult
= 1024;
193 gold_assert(key_mult
>= buffer_size
);
195 // Convert len to the number of bytes we need to allocate, including
196 // the null character.
197 len
= (len
+ 1) * sizeof(Stringpool_char
);
201 if (len
> buffer_size
)
203 alc
= sizeof(Stringdata
) + len
;
206 else if (this->strings_
.empty())
207 alc
= sizeof(Stringdata
) + buffer_size
;
210 Stringdata
*psd
= this->strings_
.front();
211 if (len
> psd
->alc
- psd
->len
)
212 alc
= sizeof(Stringdata
) + buffer_size
;
215 char* ret
= psd
->data
+ psd
->len
;
216 memcpy(ret
, s
, len
- sizeof(Stringpool_char
));
217 memset(ret
+ len
- sizeof(Stringpool_char
), 0,
218 sizeof(Stringpool_char
));
221 *pkey
= psd
->index
* key_mult
+ psd
->len
;
225 return reinterpret_cast<const Stringpool_char
*>(ret
);
229 Stringdata
*psd
= reinterpret_cast<Stringdata
*>(new char[alc
]);
230 psd
->alc
= alc
- sizeof(Stringdata
);
231 memcpy(psd
->data
, s
, len
- sizeof(Stringpool_char
));
232 memset(psd
->data
+ len
- sizeof(Stringpool_char
), 0,
233 sizeof(Stringpool_char
));
235 psd
->index
= this->next_index_
;
240 *pkey
= psd
->index
* key_mult
;
241 // Ensure there was no overflow.
242 gold_assert(*pkey
/ key_mult
== psd
->index
);
246 this->strings_
.push_front(psd
);
248 this->strings_
.push_back(psd
);
250 return reinterpret_cast<const Stringpool_char
*>(psd
->data
);
253 // Add a string to a string pool.
255 template<typename Stringpool_char
>
256 const Stringpool_char
*
257 Stringpool_template
<Stringpool_char
>::add(const Stringpool_char
* s
, bool copy
,
260 typedef std::pair
<typename
String_set_type::iterator
, bool> Insert_type
;
264 // When we don't need to copy the string, we can call insert
267 const Key k
= this->next_uncopied_key_
;
268 const section_offset_type ozero
= 0;
269 std::pair
<Hashkey
, Hashval
> element(Hashkey(s
),
270 std::make_pair(k
, ozero
));
272 Insert_type ins
= this->string_set_
.insert(element
);
274 typename
String_set_type::const_iterator p
= ins
.first
;
278 // We just added the string. The key value has now been
280 --this->next_uncopied_key_
;
284 gold_assert(k
!= p
->second
.first
);
288 *pkey
= p
->second
.first
;
289 return p
->first
.string
;
292 return this->add_prefix(s
, string_length(s
), pkey
);
295 // Add a prefix of a string to a string pool.
297 template<typename Stringpool_char
>
298 const Stringpool_char
*
299 Stringpool_template
<Stringpool_char
>::add_prefix(const Stringpool_char
* s
,
303 // When adding an entry, this will look it up twice in the hash
304 // table. The problem is that we can't insert S before we
305 // canonicalize it by copying it into the canonical list. The hash
306 // code will only be computed once, so this isn't all that
310 typename
String_set_type::const_iterator p
= this->string_set_
.find(hk
);
311 if (p
!= this->string_set_
.end())
314 *pkey
= p
->second
.first
;
315 return p
->first
.string
;
319 hk
.string
= this->add_string(s
, len
, &k
);
320 // The contents of the string stay the same, so we don't need to
321 // adjust hk.hash_code or hk.length.
323 const section_offset_type ozero
= 0;
324 std::pair
<Hashkey
, Hashval
> element(hk
, std::make_pair(k
, ozero
));
326 typedef std::pair
<typename
String_set_type::iterator
, bool> Insert_type
;
327 Insert_type ins
= this->string_set_
.insert(element
);
328 gold_assert(ins
.second
);
335 template<typename Stringpool_char
>
336 const Stringpool_char
*
337 Stringpool_template
<Stringpool_char
>::find(const Stringpool_char
* s
,
341 typename
String_set_type::const_iterator p
= this->string_set_
.find(hk
);
342 if (p
== this->string_set_
.end())
346 *pkey
= p
->second
.first
;
348 return p
->first
.string
;
351 // Comparison routine used when sorting into an ELF strtab. We want
352 // to sort this so that when one string is a suffix of another, we
353 // always see the shorter string immediately after the longer string.
354 // For example, we want to see these strings in this order:
358 // When strings are not suffixes, we don't care what order they are
359 // in, but we need to ensure that suffixes wind up next to each other.
360 // So we do a reversed lexicographic sort on the reversed string.
362 template<typename Stringpool_char
>
364 Stringpool_template
<Stringpool_char
>::Stringpool_sort_comparison::operator()(
365 const Stringpool_sort_info
& sort_info1
,
366 const Stringpool_sort_info
& sort_info2
) const
368 const Hashkey
& h1(sort_info1
->first
);
369 const Hashkey
& h2(sort_info2
->first
);
370 const Stringpool_char
* s1
= h1
.string
;
371 const Stringpool_char
* s2
= h2
.string
;
372 const size_t len1
= h1
.length
;
373 const size_t len2
= h2
.length
;
374 const size_t minlen
= len1
< len2
? len1
: len2
;
375 const Stringpool_char
* p1
= s1
+ len1
- 1;
376 const Stringpool_char
* p2
= s2
+ len2
- 1;
377 for (size_t i
= minlen
; i
> 0; --i
, --p1
, --p2
)
385 // Return whether s1 is a suffix of s2.
387 template<typename Stringpool_char
>
389 Stringpool_template
<Stringpool_char
>::is_suffix(const Stringpool_char
* s1
,
391 const Stringpool_char
* s2
,
396 return memcmp(s1
, s2
+ len2
- len1
, len1
* sizeof(Stringpool_char
)) == 0;
399 // Turn the stringpool into an ELF strtab: determine the offsets of
400 // each string in the table.
402 template<typename Stringpool_char
>
404 Stringpool_template
<Stringpool_char
>::set_string_offsets()
406 if (this->strtab_size_
!= 0)
408 // We've already computed the offsets.
412 const size_t charsize
= sizeof(Stringpool_char
);
414 // Offset 0 may be reserved for the empty string.
415 section_offset_type offset
= this->zero_null_
? charsize
: 0;
417 // Sorting to find suffixes can take over 25% of the total CPU time
418 // used by the linker. Since it's merely an optimization to reduce
419 // the strtab size, and gives a relatively small benefit (it's
420 // typically rare for a symbol to be a suffix of another), we only
421 // take the time to sort when the user asks for heavy optimization.
422 if (parameters
->optimization_level() < 2)
424 for (typename
String_set_type::iterator curr
= this->string_set_
.begin();
425 curr
!= this->string_set_
.end();
428 if (this->zero_null_
&& curr
->first
.string
[0] == 0)
429 curr
->second
.second
= 0;
432 curr
->second
.second
= offset
;
433 offset
+= (curr
->first
.length
+ 1) * charsize
;
439 size_t count
= this->string_set_
.size();
441 std::vector
<Stringpool_sort_info
> v
;
444 for (typename
String_set_type::iterator p
= this->string_set_
.begin();
445 p
!= this->string_set_
.end();
447 v
.push_back(Stringpool_sort_info(p
));
449 std::sort(v
.begin(), v
.end(), Stringpool_sort_comparison());
451 for (typename
std::vector
<Stringpool_sort_info
>::iterator last
= v
.end(),
456 if (this->zero_null_
&& (*curr
)->first
.string
[0] == 0)
457 (*curr
)->second
.second
= 0;
458 else if (last
!= v
.end()
459 && is_suffix((*curr
)->first
.string
,
460 (*curr
)->first
.length
,
461 (*last
)->first
.string
,
462 (*last
)->first
.length
))
463 (*curr
)->second
.second
= ((*last
)->second
.second
464 + (((*last
)->first
.length
465 - (*curr
)->first
.length
)
469 (*curr
)->second
.second
= offset
;
470 offset
+= ((*curr
)->first
.length
+ 1) * charsize
;
475 this->strtab_size_
= offset
;
478 // Get the offset of a string in the ELF strtab. The string must
481 template<typename Stringpool_char
>
483 Stringpool_template
<Stringpool_char
>::get_offset(const Stringpool_char
* s
)
486 gold_assert(this->strtab_size_
!= 0);
487 typename
String_set_type::const_iterator p
= this->string_set_
.find(s
);
488 if (p
!= this->string_set_
.end())
489 return p
->second
.second
;
493 // Write the ELF strtab into the buffer.
495 template<typename Stringpool_char
>
497 Stringpool_template
<Stringpool_char
>::write_to_buffer(
498 unsigned char* buffer
,
499 section_size_type bufsize
)
501 gold_assert(this->strtab_size_
!= 0);
502 gold_assert(bufsize
>= this->strtab_size_
);
503 if (this->zero_null_
)
505 for (typename
String_set_type::const_iterator p
= this->string_set_
.begin();
506 p
!= this->string_set_
.end();
509 const int len
= (p
->first
.length
+ 1) * sizeof(Stringpool_char
);
510 gold_assert(static_cast<section_size_type
>(p
->second
.second
) + len
511 <= this->strtab_size_
);
512 memcpy(buffer
+ p
->second
.second
, p
->first
.string
, len
);
516 // Write the ELF strtab into the output file at the specified offset.
518 template<typename Stringpool_char
>
520 Stringpool_template
<Stringpool_char
>::write(Output_file
* of
, off_t offset
)
522 gold_assert(this->strtab_size_
!= 0);
523 unsigned char* view
= of
->get_output_view(offset
, this->strtab_size_
);
524 this->write_to_buffer(view
, this->strtab_size_
);
525 of
->write_output_view(offset
, this->strtab_size_
, view
);
528 // Print statistical information to stderr. This is used for --stats.
530 template<typename Stringpool_char
>
532 Stringpool_template
<Stringpool_char
>::print_stats(const char* name
) const
534 #if defined(HAVE_TR1_UNORDERED_MAP) || defined(HAVE_EXT_HASH_MAP)
535 fprintf(stderr
, _("%s: %s entries: %zu; buckets: %zu\n"),
536 program_name
, name
, this->string_set_
.size(),
537 this->string_set_
.bucket_count());
539 fprintf(stderr
, _("%s: %s entries: %zu\n"),
540 program_name
, name
, this->table_
.size());
542 fprintf(stderr
, _("%s: %s Stringdata structures: %zu\n"),
543 program_name
, name
, this->strings_
.size());
546 // Instantiate the templates we need.
549 class Stringpool_template
<char>;
552 class Stringpool_template
<uint16_t>;
555 class Stringpool_template
<uint32_t>;
557 } // End namespace gold.