987cc25110
string.
529 lines
15 KiB
C++
529 lines
15 KiB
C++
// stringpool.cc -- a string pool for gold
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// Copyright 2006, 2007 Free Software Foundation, Inc.
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// Written by Ian Lance Taylor <iant@google.com>.
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// This file is part of gold.
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// This program is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 3 of the License, or
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// (at your option) any later version.
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
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// MA 02110-1301, USA.
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#include "gold.h"
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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 "parameters.h"
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#include "stringpool.h"
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namespace gold
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{
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template<typename Stringpool_char>
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Stringpool_template<Stringpool_char>::Stringpool_template()
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: string_set_(), strings_(), strtab_size_(0), next_index_(1),
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next_uncopied_key_(-1), zero_null_(true)
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{
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}
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template<typename Stringpool_char>
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void
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Stringpool_template<Stringpool_char>::clear()
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{
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for (typename 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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this->strings_.clear();
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this->string_set_.clear();
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}
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template<typename Stringpool_char>
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Stringpool_template<Stringpool_char>::~Stringpool_template()
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{
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this->clear();
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}
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// Return the length of a string of arbitrary character type.
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template<typename Stringpool_char>
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size_t
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Stringpool_template<Stringpool_char>::string_length(const Stringpool_char* p)
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{
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size_t len = 0;
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for (; *p != 0; ++p)
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++len;
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return len;
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}
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// Specialize string_length for char. Maybe we could just use
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// std::char_traits<>::length?
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template<>
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inline size_t
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Stringpool_template<char>::string_length(const char* p)
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{
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return strlen(p);
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}
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// Compare two strings of arbitrary character type for equality.
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template<typename Stringpool_char>
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bool
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Stringpool_template<Stringpool_char>::string_equal(const Stringpool_char* s1,
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const Stringpool_char* s2)
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{
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while (*s1 != 0)
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if (*s1++ != *s2++)
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return false;
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return *s2 == 0;
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}
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// Specialize string_equal for char.
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template<>
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inline bool
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Stringpool_template<char>::string_equal(const char* s1, const char* s2)
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{
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return strcmp(s1, s2) == 0;
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}
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// Equality comparison function for the hash table.
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template<typename Stringpool_char>
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inline bool
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Stringpool_template<Stringpool_char>::Stringpool_eq::operator()(
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const Hashkey& h1,
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const Hashkey& h2) const
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{
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return (h1.hash_code == h2.hash_code
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&& h1.length == h2.length
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&& memcmp(h1.string, h2.string,
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h1.length * sizeof(Stringpool_char)) == 0);
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}
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// Hash function. The length is in characters, not bytes.
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template<typename Stringpool_char>
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size_t
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Stringpool_template<Stringpool_char>::string_hash(const Stringpool_char* s,
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size_t length)
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{
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// Fowler/Noll/Vo (FNV) hash (type FNV-1a).
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const unsigned char* p = reinterpret_cast<const unsigned char*>(s);
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if (sizeof(size_t) > 4)
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{
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size_t result = static_cast<size_t>(14695981039346656037ULL);
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for (size_t i = 0; i < length * sizeof(Stringpool_char); ++i)
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{
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result ^= static_cast<size_t>(*p++);
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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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for (size_t i = 0; i < length * sizeof(Stringpool_char); ++i)
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{
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result ^= static_cast<size_t>(*p++);
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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 the string S to the list of canonical strings. Return a
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// pointer to the canonical string. If PKEY is not NULL, set *PKEY to
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// the key. LENGTH is the length of S in characters. Note that S may
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// not be NUL terminated.
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template<typename Stringpool_char>
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const Stringpool_char*
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Stringpool_template<Stringpool_char>::add_string(const Stringpool_char* s,
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size_t len,
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Key* pkey)
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{
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// We are in trouble if we've already computed the string offsets.
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gold_assert(this->strtab_size_ == 0);
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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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gold_assert(key_mult >= buffer_size);
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// Convert len to the number of bytes we need to allocate, including
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// the null character.
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len = (len + 1) * sizeof(Stringpool_char);
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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 - sizeof(Stringpool_char));
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memset(ret + len - sizeof(Stringpool_char), 0,
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sizeof(Stringpool_char));
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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;
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return reinterpret_cast<const Stringpool_char*>(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 - sizeof(Stringpool_char));
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memset(psd->data + len - sizeof(Stringpool_char), 0,
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sizeof(Stringpool_char));
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psd->len = len;
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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 reinterpret_cast<const Stringpool_char*>(psd->data);
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}
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// Add a string to a string pool.
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template<typename Stringpool_char>
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const Stringpool_char*
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Stringpool_template<Stringpool_char>::add(const Stringpool_char* s, bool copy,
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Key* pkey)
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{
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typedef std::pair<typename String_set_type::iterator, bool> Insert_type;
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if (!copy)
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{
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// When we don't need to copy the string, we can call insert
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// directly.
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const Key k = this->next_uncopied_key_;
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const off_t ozero = 0;
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std::pair<Hashkey, Hashval> element(Hashkey(s),
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std::make_pair(k, ozero));
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Insert_type ins = this->string_set_.insert(element);
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typename String_set_type::const_iterator p = ins.first;
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if (ins.second)
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{
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// We just added the string. The key value has now been
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// used.
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--this->next_uncopied_key_;
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}
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else
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{
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gold_assert(k != p->second.first);
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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.string;
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}
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return this->add_prefix(s, string_length(s), pkey);
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}
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// Add a prefix of a string to a string pool.
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template<typename Stringpool_char>
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const Stringpool_char*
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Stringpool_template<Stringpool_char>::add_prefix(const Stringpool_char* s,
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size_t len,
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Key* pkey)
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{
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// When adding an entry, this will look it up twice in the hash
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// table. The problem is that we can't insert S before we
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// canonicalize it by copying it into the canonical list. The hash
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// code will only be computed once, so this isn't all that
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// expensive.
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Hashkey hk(s, len);
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typename String_set_type::const_iterator p = this->string_set_.find(hk);
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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.string;
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}
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Key k;
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hk.string = this->add_string(s, len, &k);
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// The contents of the string stay the same, so we don't need to
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// adjust hk.hash_code or hk.length.
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const off_t ozero = 0;
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std::pair<Hashkey, Hashval> element(hk, std::make_pair(k, ozero));
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typedef std::pair<typename String_set_type::iterator, bool> Insert_type;
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Insert_type ins = this->string_set_.insert(element);
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gold_assert(ins.second);
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if (pkey != NULL)
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*pkey = k;
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return hk.string;
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}
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template<typename Stringpool_char>
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const Stringpool_char*
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Stringpool_template<Stringpool_char>::find(const Stringpool_char* s,
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Key* pkey) const
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{
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Hashkey hk(s);
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typename String_set_type::const_iterator p = this->string_set_.find(hk);
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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.string;
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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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template<typename Stringpool_char>
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bool
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Stringpool_template<Stringpool_char>::Stringpool_sort_comparison::operator()(
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const Stringpool_sort_info& sort_info1,
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const Stringpool_sort_info& sort_info2) const
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{
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const Hashkey& h1(sort_info1->first);
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const Hashkey& h2(sort_info2->first);
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const Stringpool_char* s1 = h1.string;
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const Stringpool_char* s2 = h2.string;
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const size_t len1 = h1.length;
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const size_t len2 = h2.length;
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const size_t minlen = len1 < len2 ? len1 : len2;
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const Stringpool_char* p1 = s1 + len1 - 1;
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const Stringpool_char* p2 = s2 + len2 - 1;
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for (size_t i = minlen; 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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template<typename Stringpool_char>
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bool
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Stringpool_template<Stringpool_char>::is_suffix(const Stringpool_char* s1,
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size_t len1,
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const Stringpool_char* s2,
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size_t len2)
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{
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if (len1 > len2)
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return false;
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return memcmp(s1, s2 + len2 - len1, len1 * sizeof(Stringpool_char)) == 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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template<typename Stringpool_char>
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void
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Stringpool_template<Stringpool_char>::set_string_offsets()
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{
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if (this->strtab_size_ != 0)
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{
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// We've already computed the offsets.
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return;
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}
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const size_t charsize = sizeof(Stringpool_char);
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// Offset 0 may be reserved for the empty string.
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off_t offset = this->zero_null_ ? charsize : 0;
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// Sorting to find suffixes can take over 25% of the total CPU time
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// used by the linker. Since it's merely an optimization to reduce
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// the strtab size, and gives a relatively small benefit (it's
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// typically rare for a symbol to be a suffix of another), we only
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// take the time to sort when the user asks for heavy optimization.
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if (parameters->optimization_level() < 2)
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{
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for (typename String_set_type::iterator curr = this->string_set_.begin();
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curr != this->string_set_.end();
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curr++)
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{
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if (this->zero_null_ && curr->first.string[0] == 0)
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curr->second.second = 0;
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else
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{
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curr->second.second = offset;
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offset += (curr->first.length + 1) * charsize;
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}
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}
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}
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else
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{
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size_t count = this->string_set_.size();
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std::vector<Stringpool_sort_info> v;
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v.reserve(count);
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for (typename 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(Stringpool_sort_info(p));
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std::sort(v.begin(), v.end(), Stringpool_sort_comparison());
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for (typename std::vector<Stringpool_sort_info>::iterator last = v.end(),
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curr = v.begin();
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curr != v.end();
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last = curr++)
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{
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if (this->zero_null_ && (*curr)->first.string[0] == 0)
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(*curr)->second.second = 0;
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else if (last != v.end()
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&& is_suffix((*curr)->first.string,
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(*curr)->first.length,
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(*last)->first.string,
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(*last)->first.length))
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(*curr)->second.second = ((*last)->second.second
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+ (((*last)->first.length
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- (*curr)->first.length)
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* charsize));
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else
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{
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(*curr)->second.second = offset;
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offset += ((*curr)->first.length + 1) * charsize;
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}
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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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template<typename Stringpool_char>
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off_t
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Stringpool_template<Stringpool_char>::get_offset(const Stringpool_char* s)
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const
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{
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gold_assert(this->strtab_size_ != 0);
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typename 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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gold_unreachable();
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}
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// Write the ELF strtab into the buffer.
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template<typename Stringpool_char>
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void
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Stringpool_template<Stringpool_char>::write_to_buffer(unsigned char* buffer,
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size_t bufsize)
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{
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gold_assert(this->strtab_size_ != 0);
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// Quiet the compiler in opt mode.
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if (bufsize < static_cast<size_t>(this->strtab_size_))
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gold_assert(bufsize >= static_cast<size_t>(this->strtab_size_));
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if (this->zero_null_)
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buffer[0] = '\0';
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for (typename 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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{
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const int len = (p->first.length + 1) * sizeof(Stringpool_char);
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gold_assert(p->second.second + len <= this->strtab_size_);
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memcpy(buffer + p->second.second, p->first.string, len);
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}
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}
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// Write the ELF strtab into the output file at the specified offset.
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template<typename Stringpool_char>
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void
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Stringpool_template<Stringpool_char>::write(Output_file* of, off_t offset)
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{
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gold_assert(this->strtab_size_ != 0);
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unsigned char* view = of->get_output_view(offset, this->strtab_size_);
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this->write_to_buffer(view, this->strtab_size_);
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of->write_output_view(offset, this->strtab_size_, view);
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}
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// Print statistical information to stderr. This is used for --stats.
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template<typename Stringpool_char>
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void
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Stringpool_template<Stringpool_char>::print_stats(const char* name) const
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{
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#if defined(HAVE_TR1_UNORDERED_MAP) || defined(HAVE_EXT_HASH_MAP)
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fprintf(stderr, _("%s: %s entries: %zu; buckets: %zu\n"),
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program_name, name, this->string_set_.size(),
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this->string_set_.bucket_count());
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#else
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fprintf(stderr, _("%s: %s entries: %zu\n"),
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program_name, name, this->table_.size());
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#endif
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fprintf(stderr, _("%s: %s Stringdata structures: %zu\n"),
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program_name, name, this->strings_.size());
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}
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// Instantiate the templates we need.
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template
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class Stringpool_template<char>;
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template
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class Stringpool_template<uint16_t>;
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template
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class Stringpool_template<uint32_t>;
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} // End namespace gold.
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