// stringpool.cc -- a string pool for gold
// Copyright (C) 2006-2018 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
#include "gold.h"
#include <cstring>
#include <algorithm>
#include <vector>
#include "output.h"
#include "parameters.h"
#include "stringpool.h"
namespace gold
{
template<typename Stringpool_char>
Stringpool_template<Stringpool_char>::Stringpool_template(uint64_t addralign)
: string_set_(), key_to_offset_(), strings_(), strtab_size_(0),
zero_null_(true), optimize_(false), offset_(sizeof(Stringpool_char)),
addralign_(addralign)
{
if (parameters->options_valid()
&& parameters->options().optimize() >= 2
&& addralign <= sizeof(Stringpool_char))
this->optimize_ = true;
}
template<typename Stringpool_char>
void
Stringpool_template<Stringpool_char>::clear()
{
for (typename std::list<Stringdata*>::iterator p = this->strings_.begin();
p != this->strings_.end();
++p)
delete[] reinterpret_cast<char*>(*p);
this->strings_.clear();
this->key_to_offset_.clear();
this->string_set_.clear();
}
template<typename Stringpool_char>
Stringpool_template<Stringpool_char>::~Stringpool_template()
{
this->clear();
}
// Resize the internal hashtable with the expectation we'll get n new
// elements. Note that the hashtable constructor takes a "number of
// buckets you'd like," rather than "number of elements you'd like,"
// but that's the best we can do.
template<typename Stringpool_char>
void
Stringpool_template<Stringpool_char>::reserve(unsigned int n)
{
this->key_to_offset_.reserve(n);
#if defined(HAVE_UNORDERED_MAP)
this->string_set_.rehash(this->string_set_.size() + n);
return;
#elif defined(HAVE_TR1_UNORDERED_MAP)
// rehash() implementation is broken in gcc 4.0.3's stl
//this->string_set_.rehash(this->string_set_.size() + n);
//return;
#elif defined(HAVE_EXT_HASH_MAP)
this->string_set_.resize(this->string_set_.size() + n);
return;
#endif
// This is the generic "reserve" code, if no #ifdef above triggers.
String_set_type new_string_set(this->string_set_.size() + n);
new_string_set.insert(this->string_set_.begin(), this->string_set_.end());
this->string_set_.swap(new_string_set);
}
// Compare two strings of arbitrary character type for equality.
template<typename Stringpool_char>
bool
Stringpool_template<Stringpool_char>::string_equal(const Stringpool_char* s1,
const Stringpool_char* s2)
{
while (*s1 != 0)
if (*s1++ != *s2++)
return false;
return *s2 == 0;
}
// Specialize string_equal for char.
template<>
inline bool
Stringpool_template<char>::string_equal(const char* s1, const char* s2)
{
return strcmp(s1, s2) == 0;
}
// Equality comparison function for the hash table.
template<typename Stringpool_char>
inline bool
Stringpool_template<Stringpool_char>::Stringpool_eq::operator()(
const Hashkey& h1,
const Hashkey& h2) const
{
return (h1.hash_code == h2.hash_code
&& h1.length == h2.length
&& (h1.string == h2.string
|| memcmp(h1.string, h2.string,
h1.length * sizeof(Stringpool_char)) == 0));
}
// Hash function. The length is in characters, not bytes.
template<typename Stringpool_char>
size_t
Stringpool_template<Stringpool_char>::string_hash(const Stringpool_char* s,
size_t length)
{
return gold::string_hash<Stringpool_char>(s, length);
}
// Add the string S to the list of canonical strings. Return a
// pointer to the canonical string. If PKEY is not NULL, set *PKEY to
// the key. LENGTH is the length of S in characters. Note that S may
// not be NUL terminated.
template<typename Stringpool_char>
const Stringpool_char*
Stringpool_template<Stringpool_char>::add_string(const Stringpool_char* s,
size_t len)
{
// We are in trouble if we've already computed the string offsets.
gold_assert(this->strtab_size_ == 0);
// The size we allocate for a new Stringdata.
const size_t buffer_size = 1000;
// The amount we multiply the Stringdata index when calculating the
// key.
const size_t key_mult = 1024;
gold_assert(key_mult >= buffer_size);
// Convert len to the number of bytes we need to allocate, including
// the null character.
len = (len + 1) * sizeof(Stringpool_char);
size_t alc;
bool front = true;
if (len > buffer_size)
{
alc = sizeof(Stringdata) + len;
front = false;
}
else if (this->strings_.empty())
alc = sizeof(Stringdata) + buffer_size;
else
{
Stringdata* psd = this->strings_.front();
if (len > psd->alc - psd->len)
alc = sizeof(Stringdata) + buffer_size;
else
{
char* ret = psd->data + psd->len;
memcpy(ret, s, len - sizeof(Stringpool_char));
memset(ret + len - sizeof(Stringpool_char), 0,
sizeof(Stringpool_char));
psd->len += len;
return reinterpret_cast<const Stringpool_char*>(ret);
}
}
Stringdata* psd = reinterpret_cast<Stringdata*>(new char[alc]);
psd->alc = alc - sizeof(Stringdata);
memcpy(psd->data, s, len - sizeof(Stringpool_char));
memset(psd->data + len - sizeof(Stringpool_char), 0,
sizeof(Stringpool_char));
psd->len = len;
if (front)
this->strings_.push_front(psd);
else
this->strings_.push_back(psd);
return reinterpret_cast<const Stringpool_char*>(psd->data);
}
// Add a string to a string pool.
template<typename Stringpool_char>
const Stringpool_char*
Stringpool_template<Stringpool_char>::add(const Stringpool_char* s, bool copy,
Key* pkey)
{
return this->add_with_length(s, string_length(s), copy, pkey);
}
// Add a new key offset entry.
template<typename Stringpool_char>
void
Stringpool_template<Stringpool_char>::new_key_offset(size_t length)
{
section_offset_type offset;
if (this->zero_null_ && length == 0)
offset = 0;
else
{
offset = this->offset_;
// Align strings.
offset = align_address(offset, this->addralign_);
this->offset_ = offset + (length + 1) * sizeof(Stringpool_char);
}
this->key_to_offset_.push_back(offset);
}
template<typename Stringpool_char>
const Stringpool_char*
Stringpool_template<Stringpool_char>::add_with_length(const Stringpool_char* s,
size_t length,
bool copy,
Key* pkey)
{
typedef std::pair<typename String_set_type::iterator, bool> Insert_type;
// We add 1 so that 0 is always invalid.
const Key k = this->key_to_offset_.size() + 1;
if (!copy)
{
// When we don't need to copy the string, we can call insert
// directly.
std::pair<Hashkey, Hashval> element(Hashkey(s, length), k);
Insert_type ins = this->string_set_.insert(element);
typename String_set_type::const_iterator p = ins.first;
if (ins.second)
{
// We just added the string. The key value has now been
// used.
this->new_key_offset(length);
}
else
{
gold_assert(k != p->second);
}
if (pkey != NULL)
*pkey = p->second;
return p->first.string;
}
// When we have to copy the string, we look it up twice in the hash
// table. The problem is that we can't insert S before we
// canonicalize it by copying it into the canonical list. The hash
// code will only be computed once.
Hashkey hk(s, length);
typename String_set_type::const_iterator p = this->string_set_.find(hk);
if (p != this->string_set_.end())
{
if (pkey != NULL)
*pkey = p->second;
return p->first.string;
}
this->new_key_offset(length);
hk.string = this->add_string(s, length);
// The contents of the string stay the same, so we don't need to
// adjust hk.hash_code or hk.length.
std::pair<Hashkey, Hashval> element(hk, k);
Insert_type ins = this->string_set_.insert(element);
gold_assert(ins.second);
if (pkey != NULL)
*pkey = k;
return hk.string;
}
template<typename Stringpool_char>
const Stringpool_char*
Stringpool_template<Stringpool_char>::find(const Stringpool_char* s,
Key* pkey) const
{
Hashkey hk(s);
typename String_set_type::const_iterator p = this->string_set_.find(hk);
if (p == this->string_set_.end())
return NULL;
if (pkey != NULL)
*pkey = p->second;
return p->first.string;
}
// Comparison routine used when sorting into an ELF strtab. We want
// to sort this so that when one string is a suffix of another, we
// always see the shorter string immediately after the longer string.
// For example, we want to see these strings in this order:
// abcd
// cd
// d
// When strings are not suffixes, we don't care what order they are
// in, but we need to ensure that suffixes wind up next to each other.
// So we do a reversed lexicographic sort on the reversed string.
template<typename Stringpool_char>
bool
Stringpool_template<Stringpool_char>::Stringpool_sort_comparison::operator()(
const Stringpool_sort_info& sort_info1,
const Stringpool_sort_info& sort_info2) const
{
const Hashkey& h1(sort_info1->first);
const Hashkey& h2(sort_info2->first);
const Stringpool_char* s1 = h1.string;
const Stringpool_char* s2 = h2.string;
const size_t len1 = h1.length;
const size_t len2 = h2.length;
const size_t minlen = len1 < len2 ? len1 : len2;
const Stringpool_char* p1 = s1 + len1 - 1;
const Stringpool_char* p2 = s2 + len2 - 1;
for (size_t i = minlen; i > 0; --i, --p1, --p2)
{
if (*p1 != *p2)
return *p1 > *p2;
}
return len1 > len2;
}
// Return whether s1 is a suffix of s2.
template<typename Stringpool_char>
bool
Stringpool_template<Stringpool_char>::is_suffix(const Stringpool_char* s1,
size_t len1,
const Stringpool_char* s2,
size_t len2)
{
if (len1 > len2)
return false;
return memcmp(s1, s2 + len2 - len1, len1 * sizeof(Stringpool_char)) == 0;
}
// Turn the stringpool into an ELF strtab: determine the offsets of
// each string in the table.
template<typename Stringpool_char>
void
Stringpool_template<Stringpool_char>::set_string_offsets()
{
if (this->strtab_size_ != 0)
{
// We've already computed the offsets.
return;
}
const size_t charsize = sizeof(Stringpool_char);
// Offset 0 may be reserved for the empty string.
section_offset_type offset = this->zero_null_ ? charsize : 0;
// Sorting to find suffixes can take over 25% of the total CPU time
// used by the linker. Since it's merely an optimization to reduce
// the strtab size, and gives a relatively small benefit (it's
// typically rare for a symbol to be a suffix of another), we only
// take the time to sort when the user asks for heavy optimization.
if (!this->optimize_)
{
// If we are not optimizing, the offsets are already assigned.
offset = this->offset_;
}
else
{
size_t count = this->string_set_.size();
std::vector<Stringpool_sort_info> v;
v.reserve(count);
for (typename String_set_type::iterator p = this->string_set_.begin();
p != this->string_set_.end();
++p)
v.push_back(Stringpool_sort_info(p));
std::sort(v.begin(), v.end(), Stringpool_sort_comparison());
section_offset_type last_offset = -1;
for (typename std::vector<Stringpool_sort_info>::iterator last = v.end(),
curr = v.begin();
curr != v.end();
last = curr++)
{
section_offset_type this_offset;
if (this->zero_null_ && (*curr)->first.string[0] == 0)
this_offset = 0;
else if (last != v.end()
&& ((((*curr)->first.length - (*last)->first.length)
% this->addralign_) == 0)
&& is_suffix((*curr)->first.string,
(*curr)->first.length,
(*last)->first.string,
(*last)->first.length))
this_offset = (last_offset
+ (((*last)->first.length - (*curr)->first.length)
* charsize));
else
{
this_offset = align_address(offset, this->addralign_);
offset = this_offset + ((*curr)->first.length + 1) * charsize;
}
this->key_to_offset_[(*curr)->second - 1] = this_offset;
last_offset = this_offset;
}
}
this->strtab_size_ = offset;
}
// Get the offset of a string in the ELF strtab. The string must
// exist.
template<typename Stringpool_char>
section_offset_type
Stringpool_template<Stringpool_char>::get_offset(const Stringpool_char* s)
const
{
return this->get_offset_with_length(s, string_length(s));
}
template<typename Stringpool_char>
section_offset_type
Stringpool_template<Stringpool_char>::get_offset_with_length(
const Stringpool_char* s,
size_t length) const
{
gold_assert(this->strtab_size_ != 0);
Hashkey hk(s, length);
typename String_set_type::const_iterator p = this->string_set_.find(hk);
if (p != this->string_set_.end())
return this->key_to_offset_[p->second - 1];
gold_unreachable();
}
// Write the ELF strtab into the buffer.
template<typename Stringpool_char>
void
Stringpool_template<Stringpool_char>::write_to_buffer(
unsigned char* buffer,
section_size_type bufsize)
{
gold_assert(this->strtab_size_ != 0);
gold_assert(bufsize >= this->strtab_size_);
if (this->zero_null_)
buffer[0] = '\0';
for (typename String_set_type::const_iterator p = this->string_set_.begin();
p != this->string_set_.end();
++p)
{
const int len = (p->first.length + 1) * sizeof(Stringpool_char);
const section_offset_type offset = this->key_to_offset_[p->second - 1];
gold_assert(static_cast<section_size_type>(offset) + len
<= this->strtab_size_);
memcpy(buffer + offset, p->first.string, len);
}
}
// Write the ELF strtab into the output file at the specified offset.
template<typename Stringpool_char>
void
Stringpool_template<Stringpool_char>::write(Output_file* of, off_t offset)
{
gold_assert(this->strtab_size_ != 0);
unsigned char* view = of->get_output_view(offset, this->strtab_size_);
this->write_to_buffer(view, this->strtab_size_);
of->write_output_view(offset, this->strtab_size_, view);
}
// Print statistical information to stderr. This is used for --stats.
template<typename Stringpool_char>
void
Stringpool_template<Stringpool_char>::print_stats(const char* name) const
{
#if defined(HAVE_UNORDERED_MAP) || defined(HAVE_TR1_UNORDERED_MAP) || defined(HAVE_EXT_HASH_MAP)
fprintf(stderr, _("%s: %s entries: %zu; buckets: %zu\n"),
program_name, name, this->string_set_.size(),
this->string_set_.bucket_count());
#else
fprintf(stderr, _("%s: %s entries: %zu\n"),
program_name, name, this->table_.size());
#endif
fprintf(stderr, _("%s: %s Stringdata structures: %zu\n"),
program_name, name, this->strings_.size());
}
// Instantiate the templates we need.
template
class Stringpool_template<char>;
template
class Stringpool_template<uint16_t>;
template
class Stringpool_template<uint32_t>;
} // End namespace gold.