1 // stringpool.cc -- a string pool for gold
3 // Copyright (C) 2006-2015 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()
43 && parameters->options().optimize() >= 2
44 && addralign <= sizeof(Stringpool_char))
45 this->optimize_ = true;
48 template<typename Stringpool_char>
50 Stringpool_template<Stringpool_char>::clear()
52 for (typename std::list<Stringdata*>::iterator p = this->strings_.begin();
53 p != this->strings_.end();
55 delete[] reinterpret_cast<char*>(*p);
56 this->strings_.clear();
57 this->key_to_offset_.clear();
58 this->string_set_.clear();
61 template<typename Stringpool_char>
62 Stringpool_template<Stringpool_char>::~Stringpool_template()
67 // Resize the internal hashtable with the expectation we'll get n new
68 // elements. Note that the hashtable constructor takes a "number of
69 // buckets you'd like," rather than "number of elements you'd like,"
70 // but that's the best we can do.
72 template<typename Stringpool_char>
74 Stringpool_template<Stringpool_char>::reserve(unsigned int n)
76 this->key_to_offset_.reserve(n);
78 #if defined(HAVE_UNORDERED_MAP)
79 this->string_set_.rehash(this->string_set_.size() + n);
81 #elif defined(HAVE_TR1_UNORDERED_MAP)
82 // rehash() implementation is broken in gcc 4.0.3's stl
83 //this->string_set_.rehash(this->string_set_.size() + n);
85 #elif defined(HAVE_EXT_HASH_MAP)
86 this->string_set_.resize(this->string_set_.size() + n);
90 // This is the generic "reserve" code, if no #ifdef above triggers.
91 String_set_type new_string_set(this->string_set_.size() + n);
92 new_string_set.insert(this->string_set_.begin(), this->string_set_.end());
93 this->string_set_.swap(new_string_set);
96 // Compare two strings of arbitrary character type for equality.
98 template<typename Stringpool_char>
100 Stringpool_template<Stringpool_char>::string_equal(const Stringpool_char* s1,
101 const Stringpool_char* s2)
109 // Specialize string_equal for char.
113 Stringpool_template<char>::string_equal(const char* s1, const char* s2)
115 return strcmp(s1, s2) == 0;
118 // Equality comparison function for the hash table.
120 template<typename Stringpool_char>
122 Stringpool_template<Stringpool_char>::Stringpool_eq::operator()(
124 const Hashkey& h2) const
126 return (h1.hash_code == h2.hash_code
127 && h1.length == h2.length
128 && (h1.string == h2.string
129 || memcmp(h1.string, h2.string,
130 h1.length * sizeof(Stringpool_char)) == 0));
133 // Hash function. The length is in characters, not bytes.
135 template<typename Stringpool_char>
137 Stringpool_template<Stringpool_char>::string_hash(const Stringpool_char* s,
140 return gold::string_hash<Stringpool_char>(s, length);
143 // Add the string S to the list of canonical strings. Return a
144 // pointer to the canonical string. If PKEY is not NULL, set *PKEY to
145 // the key. LENGTH is the length of S in characters. Note that S may
146 // not be NUL terminated.
148 template<typename Stringpool_char>
149 const Stringpool_char*
150 Stringpool_template<Stringpool_char>::add_string(const Stringpool_char* s,
153 // We are in trouble if we've already computed the string offsets.
154 gold_assert(this->strtab_size_ == 0);
156 // The size we allocate for a new Stringdata.
157 const size_t buffer_size = 1000;
158 // The amount we multiply the Stringdata index when calculating the
160 const size_t key_mult = 1024;
161 gold_assert(key_mult >= buffer_size);
163 // Convert len to the number of bytes we need to allocate, including
164 // the null character.
165 len = (len + 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;
184 memcpy(ret, s, len - sizeof(Stringpool_char));
185 memset(ret + len - sizeof(Stringpool_char), 0,
186 sizeof(Stringpool_char));
190 return reinterpret_cast<const Stringpool_char*>(ret);
194 Stringdata* psd = reinterpret_cast<Stringdata*>(new char[alc]);
195 psd->alc = alc - sizeof(Stringdata);
196 memcpy(psd->data, s, len - sizeof(Stringpool_char));
197 memset(psd->data + len - sizeof(Stringpool_char), 0,
198 sizeof(Stringpool_char));
202 this->strings_.push_front(psd);
204 this->strings_.push_back(psd);
206 return reinterpret_cast<const Stringpool_char*>(psd->data);
209 // Add a string to a string pool.
211 template<typename Stringpool_char>
212 const Stringpool_char*
213 Stringpool_template<Stringpool_char>::add(const Stringpool_char* s, bool copy,
216 return this->add_with_length(s, string_length(s), copy, pkey);
219 // Add a new key offset entry.
221 template<typename Stringpool_char>
223 Stringpool_template<Stringpool_char>::new_key_offset(size_t length)
225 section_offset_type offset;
226 if (this->zero_null_ && length == 0)
230 offset = this->offset_;
231 // Align non-zero length strings.
233 offset = align_address(offset, this->addralign_);
234 this->offset_ = offset + (length + 1) * sizeof(Stringpool_char);
236 this->key_to_offset_.push_back(offset);
239 template<typename Stringpool_char>
240 const Stringpool_char*
241 Stringpool_template<Stringpool_char>::add_with_length(const Stringpool_char* s,
246 typedef std::pair<typename String_set_type::iterator, bool> Insert_type;
248 // We add 1 so that 0 is always invalid.
249 const Key k = this->key_to_offset_.size() + 1;
253 // When we don't need to copy the string, we can call insert
256 std::pair<Hashkey, Hashval> element(Hashkey(s, length), k);
258 Insert_type ins = this->string_set_.insert(element);
260 typename String_set_type::const_iterator p = ins.first;
264 // We just added the string. The key value has now been
266 this->new_key_offset(length);
270 gold_assert(k != p->second);
275 return p->first.string;
278 // When we have to copy the string, we look it up twice in the hash
279 // table. The problem is that we can't insert S before we
280 // canonicalize it by copying it into the canonical list. The hash
281 // code will only be computed once.
283 Hashkey hk(s, length);
284 typename String_set_type::const_iterator p = this->string_set_.find(hk);
285 if (p != this->string_set_.end())
289 return p->first.string;
292 this->new_key_offset(length);
294 hk.string = this->add_string(s, length);
295 // The contents of the string stay the same, so we don't need to
296 // adjust hk.hash_code or hk.length.
298 std::pair<Hashkey, Hashval> element(hk, k);
300 Insert_type ins = this->string_set_.insert(element);
301 gold_assert(ins.second);
308 template<typename Stringpool_char>
309 const Stringpool_char*
310 Stringpool_template<Stringpool_char>::find(const Stringpool_char* s,
314 typename String_set_type::const_iterator p = this->string_set_.find(hk);
315 if (p == this->string_set_.end())
321 return p->first.string;
324 // Comparison routine used when sorting into an ELF strtab. We want
325 // to sort this so that when one string is a suffix of another, we
326 // always see the shorter string immediately after the longer string.
327 // For example, we want to see these strings in this order:
331 // When strings are not suffixes, we don't care what order they are
332 // in, but we need to ensure that suffixes wind up next to each other.
333 // So we do a reversed lexicographic sort on the reversed string.
335 template<typename Stringpool_char>
337 Stringpool_template<Stringpool_char>::Stringpool_sort_comparison::operator()(
338 const Stringpool_sort_info& sort_info1,
339 const Stringpool_sort_info& sort_info2) const
341 const Hashkey& h1(sort_info1->first);
342 const Hashkey& h2(sort_info2->first);
343 const Stringpool_char* s1 = h1.string;
344 const Stringpool_char* s2 = h2.string;
345 const size_t len1 = h1.length;
346 const size_t len2 = h2.length;
347 const size_t minlen = len1 < len2 ? len1 : len2;
348 const Stringpool_char* p1 = s1 + len1 - 1;
349 const Stringpool_char* p2 = s2 + len2 - 1;
350 for (size_t i = minlen; i > 0; --i, --p1, --p2)
358 // Return whether s1 is a suffix of s2.
360 template<typename Stringpool_char>
362 Stringpool_template<Stringpool_char>::is_suffix(const Stringpool_char* s1,
364 const Stringpool_char* s2,
369 return memcmp(s1, s2 + len2 - len1, len1 * sizeof(Stringpool_char)) == 0;
372 // Turn the stringpool into an ELF strtab: determine the offsets of
373 // each string in the table.
375 template<typename Stringpool_char>
377 Stringpool_template<Stringpool_char>::set_string_offsets()
379 if (this->strtab_size_ != 0)
381 // We've already computed the offsets.
385 const size_t charsize = sizeof(Stringpool_char);
387 // Offset 0 may be reserved for the empty string.
388 section_offset_type offset = this->zero_null_ ? charsize : 0;
390 // Sorting to find suffixes can take over 25% of the total CPU time
391 // used by the linker. Since it's merely an optimization to reduce
392 // the strtab size, and gives a relatively small benefit (it's
393 // typically rare for a symbol to be a suffix of another), we only
394 // take the time to sort when the user asks for heavy optimization.
395 if (!this->optimize_)
397 // If we are not optimizing, the offsets are already assigned.
398 offset = this->offset_;
402 size_t count = this->string_set_.size();
404 std::vector<Stringpool_sort_info> v;
407 for (typename String_set_type::iterator p = this->string_set_.begin();
408 p != this->string_set_.end();
410 v.push_back(Stringpool_sort_info(p));
412 std::sort(v.begin(), v.end(), Stringpool_sort_comparison());
414 section_offset_type last_offset = -1;
415 for (typename std::vector<Stringpool_sort_info>::iterator last = v.end(),
420 section_offset_type this_offset;
421 if (this->zero_null_ && (*curr)->first.string[0] == 0)
423 else if (last != v.end()
424 && is_suffix((*curr)->first.string,
425 (*curr)->first.length,
426 (*last)->first.string,
427 (*last)->first.length))
428 this_offset = (last_offset
429 + (((*last)->first.length - (*curr)->first.length)
433 this_offset = align_address(offset, this->addralign_);
434 offset = this_offset + ((*curr)->first.length + 1) * charsize;
436 this->key_to_offset_[(*curr)->second - 1] = this_offset;
437 last_offset = this_offset;
441 this->strtab_size_ = offset;
444 // Get the offset of a string in the ELF strtab. The string must
447 template<typename Stringpool_char>
449 Stringpool_template<Stringpool_char>::get_offset(const Stringpool_char* s)
452 return this->get_offset_with_length(s, string_length(s));
455 template<typename Stringpool_char>
457 Stringpool_template<Stringpool_char>::get_offset_with_length(
458 const Stringpool_char* s,
461 gold_assert(this->strtab_size_ != 0);
462 Hashkey hk(s, length);
463 typename String_set_type::const_iterator p = this->string_set_.find(hk);
464 if (p != this->string_set_.end())
465 return this->key_to_offset_[p->second - 1];
469 // Write the ELF strtab into the buffer.
471 template<typename Stringpool_char>
473 Stringpool_template<Stringpool_char>::write_to_buffer(
474 unsigned char* buffer,
475 section_size_type bufsize)
477 gold_assert(this->strtab_size_ != 0);
478 gold_assert(bufsize >= this->strtab_size_);
479 if (this->zero_null_)
481 for (typename String_set_type::const_iterator p = this->string_set_.begin();
482 p != this->string_set_.end();
485 const int len = (p->first.length + 1) * sizeof(Stringpool_char);
486 const section_offset_type offset = this->key_to_offset_[p->second - 1];
487 gold_assert(static_cast<section_size_type>(offset) + len
488 <= this->strtab_size_);
489 memcpy(buffer + offset, p->first.string, len);
493 // Write the ELF strtab into the output file at the specified offset.
495 template<typename Stringpool_char>
497 Stringpool_template<Stringpool_char>::write(Output_file* of, off_t offset)
499 gold_assert(this->strtab_size_ != 0);
500 unsigned char* view = of->get_output_view(offset, this->strtab_size_);
501 this->write_to_buffer(view, this->strtab_size_);
502 of->write_output_view(offset, this->strtab_size_, view);
505 // Print statistical information to stderr. This is used for --stats.
507 template<typename Stringpool_char>
509 Stringpool_template<Stringpool_char>::print_stats(const char* name) const
511 #if defined(HAVE_UNORDERED_MAP) || defined(HAVE_TR1_UNORDERED_MAP) || defined(HAVE_EXT_HASH_MAP)
512 fprintf(stderr, _("%s: %s entries: %zu; buckets: %zu\n"),
513 program_name, name, this->string_set_.size(),
514 this->string_set_.bucket_count());
516 fprintf(stderr, _("%s: %s entries: %zu\n"),
517 program_name, name, this->table_.size());
519 fprintf(stderr, _("%s: %s Stringdata structures: %zu\n"),
520 program_name, name, this->strings_.size());
523 // Instantiate the templates we need.
526 class Stringpool_template<char>;
529 class Stringpool_template<uint16_t>;
532 class Stringpool_template<uint32_t>;
534 } // End namespace gold.