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// stringpool.cc -- a string pool for gold

// Copyright 2006, 2007, 2008 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()

  : string_set_(), key_to_offset_(), strings_(), strtab_size_(0),

    zero_null_(true), optimize_(false)

{

  if (parameters->options_valid() && parameters->options().optimize() >= 2)

    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_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);

}

// Return the length of a string of arbitrary character type.

template<typename Stringpool_char>

size_t

Stringpool_template<Stringpool_char>::string_length(const Stringpool_char* p)

{

  size_t len = 0;

  for (; *p != 0; ++p)

    ++len;

  return len;

}

// Specialize string_length for char.  Maybe we could just use

// std::char_traits<>::length?

template<>

inline size_t

Stringpool_template<char>::string_length(const char* p)

{

  return strlen(p);

}

// 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)

{

  // This is the hash function used by the dynamic linker for

  // DT_GNU_HASH entries.  I compared this to a Fowler/Noll/Vo hash

  // for a C++ program with 385,775 global symbols.  This hash

  // function was very slightly worse.  However, it is much faster to

  // compute.  Overall wall clock time was a win.

  const unsigned char* p = reinterpret_cast<const unsigned char*>(s);

  size_t h = 5381;

  for (size_t i = 0; i < length * sizeof(Stringpool_char); ++i)

    h = h * 33 + *p++;

  return h;

}

// 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);

}

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->key_to_offset_.push_back(0);

        }

      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->key_to_offset_.push_back(0);

  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_)

    {

      for (typename String_set_type::iterator curr = this->string_set_.begin();

           curr != this->string_set_.end();

           curr++)

        {

          section_offset_type* poff = &this->key_to_offset_[curr->second - 1];

          if (this->zero_null_ && curr->first.string[0] == 0)

            *poff = 0;

          else

            {

              *poff = offset;

              offset += (curr->first.length + 1) * charsize;

            }

        }

    }

  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()

                   && 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 = offset;

              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_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.