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 offset = this->offset_;
226 // Align non-zero length strings.
228 offset = align_address(offset, this->addralign_);
229 this->offset_ = offset + (length + 1) * sizeof(Stringpool_char);
231 this->key_to_offset_.push_back(offset);
234 template<typename Stringpool_char>
235 const Stringpool_char*
236 Stringpool_template<Stringpool_char>::add_with_length(const Stringpool_char* s,
241 typedef std::pair<typename String_set_type::iterator, bool> Insert_type;
243 // We add 1 so that 0 is always invalid.
244 const Key k = this->key_to_offset_.size() + 1;
248 // When we don't need to copy the string, we can call insert
251 std::pair<Hashkey, Hashval> element(Hashkey(s, length), k);
253 Insert_type ins = this->string_set_.insert(element);
255 typename String_set_type::const_iterator p = ins.first;
259 // We just added the string. The key value has now been
261 this->new_key_offset(length);
265 gold_assert(k != p->second);
270 return p->first.string;
273 // When we have to copy the string, we look it up twice in the hash
274 // table. The problem is that we can't insert S before we
275 // canonicalize it by copying it into the canonical list. The hash
276 // code will only be computed once.
278 Hashkey hk(s, length);
279 typename String_set_type::const_iterator p = this->string_set_.find(hk);
280 if (p != this->string_set_.end())
284 return p->first.string;
287 this->new_key_offset(length);
289 hk.string = this->add_string(s, length);
290 // The contents of the string stay the same, so we don't need to
291 // adjust hk.hash_code or hk.length.
293 std::pair<Hashkey, Hashval> element(hk, k);
295 Insert_type ins = this->string_set_.insert(element);
296 gold_assert(ins.second);
303 template<typename Stringpool_char>
304 const Stringpool_char*
305 Stringpool_template<Stringpool_char>::find(const Stringpool_char* s,
309 typename String_set_type::const_iterator p = this->string_set_.find(hk);
310 if (p == this->string_set_.end())
316 return p->first.string;
319 // Comparison routine used when sorting into an ELF strtab. We want
320 // to sort this so that when one string is a suffix of another, we
321 // always see the shorter string immediately after the longer string.
322 // For example, we want to see these strings in this order:
326 // When strings are not suffixes, we don't care what order they are
327 // in, but we need to ensure that suffixes wind up next to each other.
328 // So we do a reversed lexicographic sort on the reversed string.
330 template<typename Stringpool_char>
332 Stringpool_template<Stringpool_char>::Stringpool_sort_comparison::operator()(
333 const Stringpool_sort_info& sort_info1,
334 const Stringpool_sort_info& sort_info2) const
336 const Hashkey& h1(sort_info1->first);
337 const Hashkey& h2(sort_info2->first);
338 const Stringpool_char* s1 = h1.string;
339 const Stringpool_char* s2 = h2.string;
340 const size_t len1 = h1.length;
341 const size_t len2 = h2.length;
342 const size_t minlen = len1 < len2 ? len1 : len2;
343 const Stringpool_char* p1 = s1 + len1 - 1;
344 const Stringpool_char* p2 = s2 + len2 - 1;
345 for (size_t i = minlen; i > 0; --i, --p1, --p2)
353 // Return whether s1 is a suffix of s2.
355 template<typename Stringpool_char>
357 Stringpool_template<Stringpool_char>::is_suffix(const Stringpool_char* s1,
359 const Stringpool_char* s2,
364 return memcmp(s1, s2 + len2 - len1, len1 * sizeof(Stringpool_char)) == 0;
367 // Turn the stringpool into an ELF strtab: determine the offsets of
368 // each string in the table.
370 template<typename Stringpool_char>
372 Stringpool_template<Stringpool_char>::set_string_offsets()
374 if (this->strtab_size_ != 0)
376 // We've already computed the offsets.
380 const size_t charsize = sizeof(Stringpool_char);
382 // Offset 0 may be reserved for the empty string.
383 section_offset_type offset = this->zero_null_ ? charsize : 0;
385 // Sorting to find suffixes can take over 25% of the total CPU time
386 // used by the linker. Since it's merely an optimization to reduce
387 // the strtab size, and gives a relatively small benefit (it's
388 // typically rare for a symbol to be a suffix of another), we only
389 // take the time to sort when the user asks for heavy optimization.
390 if (!this->optimize_)
392 // If we are not optimizing, the offsets are already assigned.
393 offset = this->offset_;
397 size_t count = this->string_set_.size();
399 std::vector<Stringpool_sort_info> v;
402 for (typename String_set_type::iterator p = this->string_set_.begin();
403 p != this->string_set_.end();
405 v.push_back(Stringpool_sort_info(p));
407 std::sort(v.begin(), v.end(), Stringpool_sort_comparison());
409 section_offset_type last_offset = -1;
410 for (typename std::vector<Stringpool_sort_info>::iterator last = v.end(),
415 section_offset_type this_offset;
416 if (this->zero_null_ && (*curr)->first.string[0] == 0)
418 else if (last != v.end()
419 && is_suffix((*curr)->first.string,
420 (*curr)->first.length,
421 (*last)->first.string,
422 (*last)->first.length))
423 this_offset = (last_offset
424 + (((*last)->first.length - (*curr)->first.length)
428 this_offset = align_address(offset, this->addralign_);
429 offset = this_offset + ((*curr)->first.length + 1) * charsize;
431 this->key_to_offset_[(*curr)->second - 1] = this_offset;
432 last_offset = this_offset;
436 this->strtab_size_ = offset;
439 // Get the offset of a string in the ELF strtab. The string must
442 template<typename Stringpool_char>
444 Stringpool_template<Stringpool_char>::get_offset(const Stringpool_char* s)
447 return this->get_offset_with_length(s, string_length(s));
450 template<typename Stringpool_char>
452 Stringpool_template<Stringpool_char>::get_offset_with_length(
453 const Stringpool_char* s,
456 gold_assert(this->strtab_size_ != 0);
457 Hashkey hk(s, length);
458 typename String_set_type::const_iterator p = this->string_set_.find(hk);
459 if (p != this->string_set_.end())
460 return this->key_to_offset_[p->second - 1];
464 // Write the ELF strtab into the buffer.
466 template<typename Stringpool_char>
468 Stringpool_template<Stringpool_char>::write_to_buffer(
469 unsigned char* buffer,
470 section_size_type bufsize)
472 gold_assert(this->strtab_size_ != 0);
473 gold_assert(bufsize >= this->strtab_size_);
474 if (this->zero_null_)
476 for (typename String_set_type::const_iterator p = this->string_set_.begin();
477 p != this->string_set_.end();
480 const int len = (p->first.length + 1) * sizeof(Stringpool_char);
481 const section_offset_type offset = this->key_to_offset_[p->second - 1];
482 gold_assert(static_cast<section_size_type>(offset) + len
483 <= this->strtab_size_);
484 memcpy(buffer + offset, p->first.string, len);
488 // Write the ELF strtab into the output file at the specified offset.
490 template<typename Stringpool_char>
492 Stringpool_template<Stringpool_char>::write(Output_file* of, off_t offset)
494 gold_assert(this->strtab_size_ != 0);
495 unsigned char* view = of->get_output_view(offset, this->strtab_size_);
496 this->write_to_buffer(view, this->strtab_size_);
497 of->write_output_view(offset, this->strtab_size_, view);
500 // Print statistical information to stderr. This is used for --stats.
502 template<typename Stringpool_char>
504 Stringpool_template<Stringpool_char>::print_stats(const char* name) const
506 #if defined(HAVE_TR1_UNORDERED_MAP) || defined(HAVE_EXT_HASH_MAP)
507 fprintf(stderr, _("%s: %s entries: %zu; buckets: %zu\n"),
508 program_name, name, this->string_set_.size(),
509 this->string_set_.bucket_count());
511 fprintf(stderr, _("%s: %s entries: %zu\n"),
512 program_name, name, this->table_.size());
514 fprintf(stderr, _("%s: %s Stringdata structures: %zu\n"),
515 program_name, name, this->strings_.size());
518 // Instantiate the templates we need.
521 class Stringpool_template<char>;
524 class Stringpool_template<uint16_t>;
527 class Stringpool_template<uint32_t>;
529 } // End namespace gold.