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f0641a0b38
output regardless of randomize_va_space.
285 lines
6.7 KiB
C++
285 lines
6.7 KiB
C++
// stringpool.cc -- a string pool for gold
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#include "gold.h"
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#include <cassert>
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#include <cstring>
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#include <algorithm>
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#include <vector>
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#include "output.h"
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#include "stringpool.h"
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namespace gold
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{
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Stringpool::Stringpool()
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: string_set_(), strings_(), strtab_size_(0), next_index_(1)
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{
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}
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Stringpool::~Stringpool()
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{
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for (std::list<Stringdata*>::iterator p = this->strings_.begin();
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p != this->strings_.end();
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++p)
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delete[] reinterpret_cast<char*>(*p);
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}
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// Hash function.
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size_t
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Stringpool::Stringpool_hash::operator()(const char* s) const
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{
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// Fowler/Noll/Vo (FNV) hash (type FNV-1a).
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if (sizeof(size_t) == 8)
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{
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size_t result = static_cast<size_t>(14695981039346656037ULL);
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while (*s != '\0')
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{
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result &= (size_t) *s++;
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result *= 1099511628211ULL;
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}
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return result;
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}
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else
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{
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size_t result = 2166136261UL;
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while (*s != '\0')
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{
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result ^= (size_t) *s++;
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result *= 16777619UL;
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}
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return result;
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}
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}
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// Add a string to the list of canonical strings. Return a pointer to
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// the canonical string. If PKEY is not NULL, set *PKEY to the key.
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const char*
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Stringpool::add_string(const char* s, Key* pkey)
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{
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// The size we allocate for a new Stringdata.
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const size_t buffer_size = 1000;
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// The amount we multiply the Stringdata index when calculating the
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// key.
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const size_t key_mult = 1024;
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assert(key_mult >= buffer_size);
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size_t len = strlen(s);
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size_t alc;
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bool front = true;
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if (len >= buffer_size)
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{
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alc = sizeof(Stringdata) + len;
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front = false;
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}
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else if (this->strings_.empty())
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alc = sizeof(Stringdata) + buffer_size;
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else
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{
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Stringdata *psd = this->strings_.front();
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if (len >= psd->alc - psd->len)
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alc = sizeof(Stringdata) + buffer_size;
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else
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{
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char* ret = psd->data + psd->len;
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memcpy(ret, s, len + 1);
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if (pkey != NULL)
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*pkey = psd->index * key_mult + psd->len;
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psd->len += len + 1;
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return ret;
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}
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}
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Stringdata *psd = reinterpret_cast<Stringdata*>(new char[alc]);
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psd->alc = alc - sizeof(Stringdata);
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memcpy(psd->data, s, len + 1);
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psd->len = len + 1;
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psd->index = this->next_index_;
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++this->next_index_;
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if (pkey != NULL)
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*pkey = psd->index * key_mult;
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if (front)
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this->strings_.push_front(psd);
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else
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this->strings_.push_back(psd);
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return psd->data;
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}
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// Add a string to a string pool.
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const char*
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Stringpool::add(const char* s, Key* pkey)
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{
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// FIXME: This will look up the entry twice in the hash table. The
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// problem is that we can't insert S before we canonicalize it. I
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// don't think there is a way to handle this correctly with
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// unordered_map, so this should be replaced with custom code to do
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// what we need, which is to return the empty slot.
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String_set_type::const_iterator p = this->string_set_.find(s);
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if (p != this->string_set_.end())
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{
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if (pkey != NULL)
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*pkey = p->second.first;
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return p->first;
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}
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Key k;
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const char* ret = this->add_string(s, &k);
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const off_t ozero = 0;
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std::pair<const char*, Val> element(ret, std::make_pair(k, ozero));
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std::pair<String_set_type::iterator, bool> ins =
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this->string_set_.insert(element);
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assert(ins.second);
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if (pkey != NULL)
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*pkey = k;
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return ret;
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}
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// Add a prefix of a string to a string pool.
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const char*
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Stringpool::add(const char* s, size_t len, Key* pkey)
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{
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// FIXME: This implementation should be rewritten when we rewrite
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// the hash table to avoid copying.
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std::string st(s, len);
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return this->add(st, pkey);
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}
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const char*
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Stringpool::find(const char* s, Key* pkey) const
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{
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String_set_type::const_iterator p = this->string_set_.find(s);
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if (p == this->string_set_.end())
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return NULL;
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if (pkey != NULL)
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*pkey = p->second.first;
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return p->first;
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}
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// Comparison routine used when sorting into an ELF strtab. We want
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// to sort this so that when one string is a suffix of another, we
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// always see the shorter string immediately after the longer string.
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// For example, we want to see these strings in this order:
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// abcd
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// cd
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// d
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// When strings are not suffixes, we don't care what order they are
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// in, but we need to ensure that suffixes wind up next to each other.
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// So we do a reversed lexicographic sort on the reversed string.
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bool
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Stringpool::Stringpool_sort_comparison::operator()(
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String_set_type::iterator it1,
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String_set_type::iterator it2) const
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{
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const char* s1 = it1->first;
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const char* s2 = it2->first;
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int len1 = strlen(s1);
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int len2 = strlen(s2);
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int minlen = len1 < len2 ? len1 : len2;
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const char* p1 = s1 + len1 - 1;
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const char* p2 = s2 + len2 - 1;
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for (int i = minlen - 1; i >= 0; --i, --p1, --p2)
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{
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if (*p1 != *p2)
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return *p1 > *p2;
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}
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return len1 > len2;
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}
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// Return whether s1 is a suffix of s2.
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bool
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Stringpool::is_suffix(const char* s1, const char* s2)
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{
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size_t len1 = strlen(s1);
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size_t len2 = strlen(s2);
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if (len1 > len2)
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return false;
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return strcmp(s1, s2 + len2 - len1) == 0;
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}
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// Turn the stringpool into an ELF strtab: determine the offsets of
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// each string in the table.
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void
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Stringpool::set_string_offsets()
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{
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size_t count = this->string_set_.size();
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std::vector<String_set_type::iterator> v;
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v.reserve(count);
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for (String_set_type::iterator p = this->string_set_.begin();
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p != this->string_set_.end();
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++p)
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v.push_back(p);
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std::sort(v.begin(), v.end(), Stringpool_sort_comparison());
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// Offset 0 is reserved for the empty string.
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off_t offset = 1;
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for (size_t i = 0; i < count; ++i)
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{
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if (v[i]->first[0] == '\0')
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v[i]->second.second = 0;
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else if (i > 0 && Stringpool::is_suffix(v[i]->first, v[i - 1]->first))
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v[i]->second.second = (v[i - 1]->second.second
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+ strlen(v[i - 1]->first)
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- strlen(v[i]->first));
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else
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{
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v[i]->second.second = offset;
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offset += strlen(v[i]->first) + 1;
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}
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}
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this->strtab_size_ = offset;
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}
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// Get the offset of a string in the ELF strtab. The string must
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// exist.
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off_t
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Stringpool::get_offset(const char* s) const
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{
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String_set_type::const_iterator p = this->string_set_.find(s);
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if (p != this->string_set_.end())
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return p->second.second;
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abort();
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}
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// Write the ELF strtab into the output file at the specified offset.
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void
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Stringpool::write(Output_file* of, off_t offset)
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{
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unsigned char* viewu = of->get_output_view(offset, this->strtab_size_);
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char* view = reinterpret_cast<char*>(viewu);
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view[0] = '\0';
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for (String_set_type::const_iterator p = this->string_set_.begin();
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p != this->string_set_.end();
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++p)
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strcpy(view + p->second.second, p->first);
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of->write_output_view(offset, this->strtab_size_, viewu);
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}
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} // End namespace gold.
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