1 // stringpool.cc -- a string pool for gold
3 // Copyright 2006, 2007, 2008 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(uint64_t addralign
)
38 : string_set_(), key_to_offset_(), strings_(), strtab_size_(0),
39 zero_null_(true), optimize_(false), offset_(sizeof(Stringpool_char
)),
42 if (parameters
->options_valid() && parameters
->options().optimize() >= 2)
43 this->optimize_
= true;
46 template<typename Stringpool_char
>
48 Stringpool_template
<Stringpool_char
>::clear()
50 for (typename
std::list
<Stringdata
*>::iterator p
= this->strings_
.begin();
51 p
!= this->strings_
.end();
53 delete[] reinterpret_cast<char*>(*p
);
54 this->strings_
.clear();
55 this->key_to_offset_
.clear();
56 this->string_set_
.clear();
59 template<typename Stringpool_char
>
60 Stringpool_template
<Stringpool_char
>::~Stringpool_template()
65 // Resize the internal hashtable with the expectation we'll get n new
66 // elements. Note that the hashtable constructor takes a "number of
67 // buckets you'd like," rather than "number of elements you'd like,"
68 // but that's the best we can do.
70 template<typename Stringpool_char
>
72 Stringpool_template
<Stringpool_char
>::reserve(unsigned int n
)
74 this->key_to_offset_
.reserve(n
);
76 #if defined(HAVE_TR1_UNORDERED_MAP)
77 // rehash() implementation is broken in gcc 4.0.3's stl
78 //this->string_set_.rehash(this->string_set_.size() + n);
80 #elif defined(HAVE_EXT_HASH_MAP)
81 this->string_set_
.resize(this->string_set_
.size() + n
);
85 // This is the generic "reserve" code, if no #ifdef above triggers.
86 String_set_type
new_string_set(this->string_set_
.size() + n
);
87 new_string_set
.insert(this->string_set_
.begin(), this->string_set_
.end());
88 this->string_set_
.swap(new_string_set
);
91 // Compare two strings of arbitrary character type for equality.
93 template<typename Stringpool_char
>
95 Stringpool_template
<Stringpool_char
>::string_equal(const Stringpool_char
* s1
,
96 const Stringpool_char
* s2
)
104 // Specialize string_equal for char.
108 Stringpool_template
<char>::string_equal(const char* s1
, const char* s2
)
110 return strcmp(s1
, s2
) == 0;
113 // Equality comparison function for the hash table.
115 template<typename Stringpool_char
>
117 Stringpool_template
<Stringpool_char
>::Stringpool_eq::operator()(
119 const Hashkey
& h2
) const
121 return (h1
.hash_code
== h2
.hash_code
122 && h1
.length
== h2
.length
123 && (h1
.string
== h2
.string
124 || memcmp(h1
.string
, h2
.string
,
125 h1
.length
* sizeof(Stringpool_char
)) == 0));
128 // Hash function. The length is in characters, not bytes.
130 template<typename Stringpool_char
>
132 Stringpool_template
<Stringpool_char
>::string_hash(const Stringpool_char
* s
,
135 return gold::string_hash
<Stringpool_char
>(s
, length
);
138 // Add the string S to the list of canonical strings. Return a
139 // pointer to the canonical string. If PKEY is not NULL, set *PKEY to
140 // the key. LENGTH is the length of S in characters. Note that S may
141 // not be NUL terminated.
143 template<typename Stringpool_char
>
144 const Stringpool_char
*
145 Stringpool_template
<Stringpool_char
>::add_string(const Stringpool_char
* s
,
148 // We are in trouble if we've already computed the string offsets.
149 gold_assert(this->strtab_size_
== 0);
151 // The size we allocate for a new Stringdata.
152 const size_t buffer_size
= 1000;
153 // The amount we multiply the Stringdata index when calculating the
155 const size_t key_mult
= 1024;
156 gold_assert(key_mult
>= buffer_size
);
158 // Convert len to the number of bytes we need to allocate, including
159 // the null character.
160 len
= (len
+ 1) * sizeof(Stringpool_char
);
164 if (len
> buffer_size
)
166 alc
= sizeof(Stringdata
) + len
;
169 else if (this->strings_
.empty())
170 alc
= sizeof(Stringdata
) + buffer_size
;
173 Stringdata
* psd
= this->strings_
.front();
174 if (len
> psd
->alc
- psd
->len
)
175 alc
= sizeof(Stringdata
) + buffer_size
;
178 char* ret
= psd
->data
+ psd
->len
;
179 memcpy(ret
, s
, len
- sizeof(Stringpool_char
));
180 memset(ret
+ len
- sizeof(Stringpool_char
), 0,
181 sizeof(Stringpool_char
));
185 return reinterpret_cast<const Stringpool_char
*>(ret
);
189 Stringdata
* psd
= reinterpret_cast<Stringdata
*>(new char[alc
]);
190 psd
->alc
= alc
- sizeof(Stringdata
);
191 memcpy(psd
->data
, s
, len
- sizeof(Stringpool_char
));
192 memset(psd
->data
+ len
- sizeof(Stringpool_char
), 0,
193 sizeof(Stringpool_char
));
197 this->strings_
.push_front(psd
);
199 this->strings_
.push_back(psd
);
201 return reinterpret_cast<const Stringpool_char
*>(psd
->data
);
204 // Add a string to a string pool.
206 template<typename Stringpool_char
>
207 const Stringpool_char
*
208 Stringpool_template
<Stringpool_char
>::add(const Stringpool_char
* s
, bool copy
,
211 return this->add_with_length(s
, string_length(s
), copy
, pkey
);
214 // Add a new key offset entry.
216 template<typename Stringpool_char
>
218 Stringpool_template
<Stringpool_char
>::new_key_offset(size_t length
)
220 section_offset_type offset
;
221 if (this->zero_null_
&& length
== 0)
225 // Align non-zero length strings.
227 offset
= align_address(this->offset_
, this->addralign_
);
228 this->offset_
= offset
+ (length
+ 1) * sizeof(Stringpool_char
);
230 this->key_to_offset_
.push_back(offset
);
233 template<typename Stringpool_char
>
234 const Stringpool_char
*
235 Stringpool_template
<Stringpool_char
>::add_with_length(const Stringpool_char
* s
,
240 typedef std::pair
<typename
String_set_type::iterator
, bool> Insert_type
;
242 // We add 1 so that 0 is always invalid.
243 const Key k
= this->key_to_offset_
.size() + 1;
247 // When we don't need to copy the string, we can call insert
250 std::pair
<Hashkey
, Hashval
> element(Hashkey(s
, length
), k
);
252 Insert_type ins
= this->string_set_
.insert(element
);
254 typename
String_set_type::const_iterator p
= ins
.first
;
258 // We just added the string. The key value has now been
260 this->new_key_offset(length
);
264 gold_assert(k
!= p
->second
);
269 return p
->first
.string
;
272 // When we have to copy the string, we look it up twice in the hash
273 // table. The problem is that we can't insert S before we
274 // canonicalize it by copying it into the canonical list. The hash
275 // code will only be computed once.
277 Hashkey
hk(s
, length
);
278 typename
String_set_type::const_iterator p
= this->string_set_
.find(hk
);
279 if (p
!= this->string_set_
.end())
283 return p
->first
.string
;
286 this->new_key_offset(length
);
288 hk
.string
= this->add_string(s
, length
);
289 // The contents of the string stay the same, so we don't need to
290 // adjust hk.hash_code or hk.length.
292 std::pair
<Hashkey
, Hashval
> element(hk
, k
);
294 Insert_type ins
= this->string_set_
.insert(element
);
295 gold_assert(ins
.second
);
302 template<typename Stringpool_char
>
303 const Stringpool_char
*
304 Stringpool_template
<Stringpool_char
>::find(const Stringpool_char
* s
,
308 typename
String_set_type::const_iterator p
= this->string_set_
.find(hk
);
309 if (p
== this->string_set_
.end())
315 return p
->first
.string
;
318 // Comparison routine used when sorting into an ELF strtab. We want
319 // to sort this so that when one string is a suffix of another, we
320 // always see the shorter string immediately after the longer string.
321 // For example, we want to see these strings in this order:
325 // When strings are not suffixes, we don't care what order they are
326 // in, but we need to ensure that suffixes wind up next to each other.
327 // So we do a reversed lexicographic sort on the reversed string.
329 template<typename Stringpool_char
>
331 Stringpool_template
<Stringpool_char
>::Stringpool_sort_comparison::operator()(
332 const Stringpool_sort_info
& sort_info1
,
333 const Stringpool_sort_info
& sort_info2
) const
335 const Hashkey
& h1(sort_info1
->first
);
336 const Hashkey
& h2(sort_info2
->first
);
337 const Stringpool_char
* s1
= h1
.string
;
338 const Stringpool_char
* s2
= h2
.string
;
339 const size_t len1
= h1
.length
;
340 const size_t len2
= h2
.length
;
341 const size_t minlen
= len1
< len2
? len1
: len2
;
342 const Stringpool_char
* p1
= s1
+ len1
- 1;
343 const Stringpool_char
* p2
= s2
+ len2
- 1;
344 for (size_t i
= minlen
; i
> 0; --i
, --p1
, --p2
)
352 // Return whether s1 is a suffix of s2.
354 template<typename Stringpool_char
>
356 Stringpool_template
<Stringpool_char
>::is_suffix(const Stringpool_char
* s1
,
358 const Stringpool_char
* s2
,
363 return memcmp(s1
, s2
+ len2
- len1
, len1
* sizeof(Stringpool_char
)) == 0;
366 // Turn the stringpool into an ELF strtab: determine the offsets of
367 // each string in the table.
369 template<typename Stringpool_char
>
371 Stringpool_template
<Stringpool_char
>::set_string_offsets()
373 if (this->strtab_size_
!= 0)
375 // We've already computed the offsets.
379 const size_t charsize
= sizeof(Stringpool_char
);
381 // Offset 0 may be reserved for the empty string.
382 section_offset_type offset
= this->zero_null_
? charsize
: 0;
384 // Sorting to find suffixes can take over 25% of the total CPU time
385 // used by the linker. Since it's merely an optimization to reduce
386 // the strtab size, and gives a relatively small benefit (it's
387 // typically rare for a symbol to be a suffix of another), we only
388 // take the time to sort when the user asks for heavy optimization.
389 if (!this->optimize_
)
391 // If we are not optimizing, the offsets are already assigned.
392 offset
= this->offset_
;
396 size_t count
= this->string_set_
.size();
398 std::vector
<Stringpool_sort_info
> v
;
401 for (typename
String_set_type::iterator p
= this->string_set_
.begin();
402 p
!= this->string_set_
.end();
404 v
.push_back(Stringpool_sort_info(p
));
406 std::sort(v
.begin(), v
.end(), Stringpool_sort_comparison());
408 section_offset_type last_offset
= -1;
409 for (typename
std::vector
<Stringpool_sort_info
>::iterator last
= v
.end(),
414 section_offset_type this_offset
;
415 if (this->zero_null_
&& (*curr
)->first
.string
[0] == 0)
417 else if (last
!= v
.end()
418 && is_suffix((*curr
)->first
.string
,
419 (*curr
)->first
.length
,
420 (*last
)->first
.string
,
421 (*last
)->first
.length
))
422 this_offset
= (last_offset
423 + (((*last
)->first
.length
- (*curr
)->first
.length
)
427 this_offset
= align_address(offset
, this->addralign_
);
428 offset
= this_offset
+ ((*curr
)->first
.length
+ 1) * charsize
;
430 this->key_to_offset_
[(*curr
)->second
- 1] = this_offset
;
431 last_offset
= this_offset
;
435 this->strtab_size_
= offset
;
438 // Get the offset of a string in the ELF strtab. The string must
441 template<typename Stringpool_char
>
443 Stringpool_template
<Stringpool_char
>::get_offset(const Stringpool_char
* s
)
446 return this->get_offset_with_length(s
, string_length(s
));
449 template<typename Stringpool_char
>
451 Stringpool_template
<Stringpool_char
>::get_offset_with_length(
452 const Stringpool_char
* s
,
455 gold_assert(this->strtab_size_
!= 0);
456 Hashkey
hk(s
, length
);
457 typename
String_set_type::const_iterator p
= this->string_set_
.find(hk
);
458 if (p
!= this->string_set_
.end())
459 return this->key_to_offset_
[p
->second
- 1];
463 // Write the ELF strtab into the buffer.
465 template<typename Stringpool_char
>
467 Stringpool_template
<Stringpool_char
>::write_to_buffer(
468 unsigned char* buffer
,
469 section_size_type bufsize
)
471 gold_assert(this->strtab_size_
!= 0);
472 gold_assert(bufsize
>= this->strtab_size_
);
473 if (this->zero_null_
)
475 for (typename
String_set_type::const_iterator p
= this->string_set_
.begin();
476 p
!= this->string_set_
.end();
479 const int len
= (p
->first
.length
+ 1) * sizeof(Stringpool_char
);
480 const section_offset_type offset
= this->key_to_offset_
[p
->second
- 1];
481 gold_assert(static_cast<section_size_type
>(offset
) + len
482 <= this->strtab_size_
);
483 memcpy(buffer
+ offset
, p
->first
.string
, len
);
487 // Write the ELF strtab into the output file at the specified offset.
489 template<typename Stringpool_char
>
491 Stringpool_template
<Stringpool_char
>::write(Output_file
* of
, off_t offset
)
493 gold_assert(this->strtab_size_
!= 0);
494 unsigned char* view
= of
->get_output_view(offset
, this->strtab_size_
);
495 this->write_to_buffer(view
, this->strtab_size_
);
496 of
->write_output_view(offset
, this->strtab_size_
, view
);
499 // Print statistical information to stderr. This is used for --stats.
501 template<typename Stringpool_char
>
503 Stringpool_template
<Stringpool_char
>::print_stats(const char* name
) const
505 #if defined(HAVE_TR1_UNORDERED_MAP) || defined(HAVE_EXT_HASH_MAP)
506 fprintf(stderr
, _("%s: %s entries: %zu; buckets: %zu\n"),
507 program_name
, name
, this->string_set_
.size(),
508 this->string_set_
.bucket_count());
510 fprintf(stderr
, _("%s: %s entries: %zu\n"),
511 program_name
, name
, this->table_
.size());
513 fprintf(stderr
, _("%s: %s Stringdata structures: %zu\n"),
514 program_name
, name
, this->strings_
.size());
517 // Instantiate the templates we need.
520 class Stringpool_template
<char>;
523 class Stringpool_template
<uint16_t>;
526 class Stringpool_template
<uint32_t>;
528 } // End namespace gold.