binutils-gdb/gold/stringpool.cc

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// stringpool.cc -- a string pool for gold
#include "gold.h"
#include <cstring>
#include <algorithm>
#include <vector>
#include "output.h"
#include "stringpool.h"
namespace gold
{
Stringpool::Stringpool()
: string_set_(), strings_(), strtab_size_(0), next_index_(1)
{
}
Stringpool::~Stringpool()
{
for (std::list<Stringdata*>::iterator p = this->strings_.begin();
p != this->strings_.end();
++p)
delete[] reinterpret_cast<char*>(*p);
}
// Hash function.
size_t
Stringpool::Stringpool_hash::operator()(const char* s) const
{
// Fowler/Noll/Vo (FNV) hash (type FNV-1a).
if (sizeof(size_t) == 8)
{
2006-09-26 23:53:18 +02:00
size_t result = static_cast<size_t>(14695981039346656037ULL);
while (*s != '\0')
{
result &= (size_t) *s++;
result *= 1099511628211ULL;
}
return result;
}
else
{
size_t result = 2166136261UL;
while (*s != '\0')
{
result ^= (size_t) *s++;
result *= 16777619UL;
}
return result;
}
}
// Add a string to the list of canonical strings. Return a pointer to
// the canonical string. If PKEY is not NULL, set *PKEY to the key.
const char*
Stringpool::add_string(const char* s, Key* pkey)
{
// 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);
size_t len = strlen(s);
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 + 1);
if (pkey != NULL)
*pkey = psd->index * key_mult + psd->len;
psd->len += len + 1;
return ret;
}
}
Stringdata *psd = reinterpret_cast<Stringdata*>(new char[alc]);
psd->alc = alc - sizeof(Stringdata);
memcpy(psd->data, s, len + 1);
psd->len = len + 1;
psd->index = this->next_index_;
++this->next_index_;
if (pkey != NULL)
*pkey = psd->index * key_mult;
if (front)
this->strings_.push_front(psd);
else
this->strings_.push_back(psd);
return psd->data;
}
// Add a string to a string pool.
const char*
Stringpool::add(const char* s, Key* pkey)
{
// FIXME: This will look up the entry twice in the hash table. The
// problem is that we can't insert S before we canonicalize it. I
// don't think there is a way to handle this correctly with
// unordered_map, so this should be replaced with custom code to do
// what we need, which is to return the empty slot.
String_set_type::const_iterator p = this->string_set_.find(s);
if (p != this->string_set_.end())
{
if (pkey != NULL)
*pkey = p->second.first;
return p->first;
}
Key k;
const char* ret = this->add_string(s, &k);
const off_t ozero = 0;
std::pair<const char*, Val> element(ret, std::make_pair(k, ozero));
std::pair<String_set_type::iterator, bool> ins =
this->string_set_.insert(element);
gold_assert(ins.second);
if (pkey != NULL)
*pkey = k;
return ret;
}
// Add a prefix of a string to a string pool.
const char*
Stringpool::add(const char* s, size_t len, Key* pkey)
{
// FIXME: This implementation should be rewritten when we rewrite
// the hash table to avoid copying.
std::string st(s, len);
return this->add(st, pkey);
}
const char*
Stringpool::find(const char* s, Key* pkey) const
{
String_set_type::const_iterator p = this->string_set_.find(s);
if (p == this->string_set_.end())
return NULL;
if (pkey != NULL)
*pkey = p->second.first;
return p->first;
}
// 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.
bool
Stringpool::Stringpool_sort_comparison::operator()(
String_set_type::iterator it1,
String_set_type::iterator it2) const
{
const char* s1 = it1->first;
const char* s2 = it2->first;
int len1 = strlen(s1);
int len2 = strlen(s2);
int minlen = len1 < len2 ? len1 : len2;
const char* p1 = s1 + len1 - 1;
const char* p2 = s2 + len2 - 1;
for (int i = minlen - 1; i >= 0; --i, --p1, --p2)
{
if (*p1 != *p2)
return *p1 > *p2;
}
return len1 > len2;
}
// Return whether s1 is a suffix of s2.
bool
Stringpool::is_suffix(const char* s1, const char* s2)
{
size_t len1 = strlen(s1);
size_t len2 = strlen(s2);
if (len1 > len2)
return false;
return strcmp(s1, s2 + len2 - len1) == 0;
}
// Turn the stringpool into an ELF strtab: determine the offsets of
// each string in the table.
void
Stringpool::set_string_offsets()
{
if (this->strtab_size_ != 0)
{
// We've already computed the offsets.
return;
}
size_t count = this->string_set_.size();
std::vector<String_set_type::iterator> v;
v.reserve(count);
for (String_set_type::iterator p = this->string_set_.begin();
p != this->string_set_.end();
++p)
v.push_back(p);
std::sort(v.begin(), v.end(), Stringpool_sort_comparison());
// Offset 0 is reserved for the empty string.
off_t offset = 1;
for (size_t i = 0; i < count; ++i)
{
if (v[i]->first[0] == '\0')
v[i]->second.second = 0;
else if (i > 0 && Stringpool::is_suffix(v[i]->first, v[i - 1]->first))
v[i]->second.second = (v[i - 1]->second.second
+ strlen(v[i - 1]->first)
- strlen(v[i]->first));
else
{
v[i]->second.second = offset;
offset += strlen(v[i]->first) + 1;
}
}
this->strtab_size_ = offset;
}
// Get the offset of a string in the ELF strtab. The string must
// exist.
off_t
Stringpool::get_offset(const char* s) const
{
gold_assert(this->strtab_size_ != 0);
String_set_type::const_iterator p = this->string_set_.find(s);
if (p != this->string_set_.end())
return p->second.second;
gold_unreachable();
}
// Write the ELF strtab into the output file at the specified offset.
void
Stringpool::write(Output_file* of, off_t offset)
{
gold_assert(this->strtab_size_ != 0);
unsigned char* viewu = of->get_output_view(offset, this->strtab_size_);
char* view = reinterpret_cast<char*>(viewu);
view[0] = '\0';
for (String_set_type::const_iterator p = this->string_set_.begin();
p != this->string_set_.end();
++p)
strcpy(view + p->second.second, p->first);
of->write_output_view(offset, this->strtab_size_, viewu);
}
} // End namespace gold.