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string.cc

// -*- related-file-name: "../include/lcdf/string.hh" -*-
/*
 * string.{cc,hh} -- a String class with shared substrings
 * Eddie Kohler
 *
 * Copyright (c) 1999-2000 Massachusetts Institute of Technology
 * Copyright (c) 2001-2005 Eddie Kohler
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, subject to the conditions
 * listed in the Click LICENSE file. These conditions include: you must
 * preserve this copyright notice, and you cannot mention the copyright
 * holders in advertising related to the Software without their permission.
 * The Software is provided WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED. This
 * notice is a summary of the Click LICENSE file; the license in that file is
 * legally binding.
 */

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
#include <lcdf/string.hh>
#include <lcdf/straccum.hh>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <lcdf/inttypes.h>

static String::Initializer initializer;
String::Memo *String::null_memo = 0;
String::Memo *String::permanent_memo = 0;
String::Memo *String::oom_memo = 0;
String *String::null_string_p = 0;
String *String::oom_string_p = 0;
const char String::oom_string_data = 0;

inline
String::Memo::Memo()
    : _refcount(0), _capacity(0), _dirty(0), _real_data("")
{
}

inline
String::Memo::Memo(char *data, int dirty, int capacity)
    : _refcount(0), _capacity(capacity), _dirty(dirty),
      _real_data(data)
{
}

String::Memo::Memo(int dirty, int capacity)
    : _refcount(1), _capacity(capacity), _dirty(dirty),
      _real_data(new char[capacity])
{
    assert(_capacity >= _dirty);
}

String::Memo::~Memo()
{
    if (_capacity) {
      assert(_capacity >= _dirty);
      delete[] _real_data;
    }
}


String::String(int i)
{
    char buf[128];
    sprintf(buf, "%d", i);
    assign(buf, -1);
}

String::String(unsigned u)
{
    char buf[128];
    sprintf(buf, "%u", u);
    assign(buf, -1);
}

String::String(long d)
{
    char buf[128];
    sprintf(buf, "%ld", d);
    assign(buf, -1);
}

String::String(unsigned long u)
{
    char buf[128];
    sprintf(buf, "%lu", u);
    assign(buf, -1);
}

String::String(double d)
{
    char buf[128];
    sprintf(buf, "%.12g", d);
    assign(buf, -1);
}

String
String::claim_string(char *str, int len, int capacity)
{
    assert(str && len > 0 && capacity >= len);
    Memo *new_memo = new Memo(str, len, capacity);
    if (new_memo)
      return String(str, len, new_memo);
    else
      return String(oom_memo->_real_data, 0, oom_memo);
}

String
String::stable_string(const char *str, int len)
{
    if (len < 0)
      len = (str ? strlen(str) : 0);
    if (len == 0)
      return String();
    else
      return String(str, len, permanent_memo);
}

String
String::garbage_string(int len)
{
    String s;
    s.append_garbage(len);
    return s;
}

String
String::fill_string(int c, int len)
{
    String s;
    s.append_fill(c, len);
    return s;
}

void
String::make_out_of_memory()
{
    if (_memo)
      deref();
    _memo = oom_memo;
    _memo->_refcount++;
    _data = _memo->_real_data;
    _length = 0;
}

void
String::assign(const char *str, int len)
{
    if (!str) {
      assert(len <= 0);
      len = 0;
    } else if (len < 0)
      len = strlen(str);
  
    if (len == 0) {
      _memo = (str == oom_memo->_real_data ? oom_memo : null_memo);
      _memo->_refcount++;
    
    } else {
      // Make 'capacity' a multiple of 16 characters at least as big as
      // 'len'.
      int capacity = (len + 16) & ~15;
      _memo = new Memo(len, capacity);
      if (!_memo || !_memo->_real_data) {
          make_out_of_memory();
          return;
      }
      memcpy(_memo->_real_data, str, len);
    }
  
    _data = _memo->_real_data;
    _length = len;
}

char *
String::append_garbage(int suffix_len)
{
    // Appending anything to "out of memory" leaves it as "out of memory"
    if (suffix_len <= 0 || _memo == oom_memo)
      return 0;
  
    // If we can, append into unused space. First, we check that there's
    // enough unused space for `suffix_len' characters to fit; then, we check
    // that the unused space immediately follows the data in `*this'.
    if (_memo->_capacity > _memo->_dirty + suffix_len) {
      char *real_dirty = _memo->_real_data + _memo->_dirty;
      if (real_dirty == _data + _length) {
          _length += suffix_len;
          _memo->_dirty += suffix_len;
          assert(_memo->_dirty < _memo->_capacity);
          return real_dirty;
      }
    }
  
    // Now we have to make new space. Make sure the new capacity is a
    // multiple of 16 characters and that it is at least 16.
    int new_capacity = (_length + 16) & ~15;
    while (new_capacity < _length + suffix_len)
      new_capacity *= 2;
    Memo *new_memo = new Memo(_length + suffix_len, new_capacity);
    if (!new_memo || !new_memo->_real_data) {
      delete new_memo;
      make_out_of_memory();
      return 0;
    }

    char *new_data = new_memo->_real_data;
    memcpy(new_data, _data, _length);
  
    deref();
    _data = new_data;
    new_data += _length;      // now new_data points to the garbage
    _length += suffix_len;
    _memo = new_memo;
    return new_data;
}

void
String::append(const char *suffix, int suffix_len)
{
    if (!suffix) {
      assert(suffix_len <= 0);
      suffix_len = 0;
    } else if (suffix_len < 0)
      suffix_len = strlen(suffix);

    if (char *space = append_garbage(suffix_len))
      memcpy(space, suffix, suffix_len);
    else if (suffix == oom_memo->_real_data)
      // Appending "out of memory" to a regular string makes it "out of
      // memory"
      make_out_of_memory();
}

void
String::append_fill(int c, int suffix_len)
{
    assert(suffix_len >= 0);
    if (char *space = append_garbage(suffix_len))
      memset(space, c, suffix_len);
}

char *
String::mutable_data()
{
    // If _memo has a capacity (it's not one of the special strings) and it's
    // uniquely referenced, return _data right away.
    if (_memo->_capacity && _memo->_refcount == 1)
      return const_cast<char *>(_data);
  
    // Otherwise, make a copy of it. Rely on: deref() doesn't change _data or
    // _length; and if _capacity == 0, then deref() doesn't free _real_data.
    assert(!_memo->_capacity || _memo->_refcount > 1);
    deref();
    assign(_data, _length);
    return const_cast<char *>(_data);
}

char *
String::mutable_c_str()
{
    (void) mutable_data();
    (void) c_str();
    return const_cast<char *>(_data);
}

const char *
String::c_str() const
{
    // If _memo has no capacity, then this is one of the special strings (null
    // or PermString). We are guaranteed, in these strings, that
    // _data[_length] exists. We can return _data immediately if we have a
    // '\0' in the right place.
    if (!_memo->_capacity && _data[_length] == '\0')
      return _data;
  
    // Otherwise, this invariant must hold (there's more real data in _memo
    // than in our substring).
    assert(!_memo->_capacity
         || _memo->_real_data + _memo->_dirty >= _data + _length);
  
    // Has the character after our substring been set?
    if (_memo->_real_data + _memo->_dirty == _data + _length) {
      // Character after our substring has not been set. May be able to
      // change it to '\0'. This case will never occur on special strings.
      if (_memo->_dirty < _memo->_capacity)
          goto add_final_nul;
    
    } else {
      // Character after our substring has been set. OK to return _data if
      // it is already '\0'.
      if (_data[_length] == '\0')
          return _data;
    }
  
    // If we get here, we must make a copy of our portion of the string.
    {
      String s(_data, _length);
      deref();
      assign(s);
    }
  
  add_final_nul:
    char *real_data = const_cast<char *>(_data);
    real_data[_length] = '\0';
    _memo->_dirty++;          // include '\0' in used portion of _memo
    return _data;
}

String
String::substring(int left, int len) const
{
    if (left < 0)
      left += _length;
    if (len < 0)
      len = _length - left + len;
    if (left + len > _length)
      len = _length - left;
  
    if (left < 0 || len <= 0)
      return String();
    else
      return String(_data + left, len, _memo);
}

int
String::find_left(int c, int start) const
{
  if (start < 0)
    start = 0;
  for (int i = start; i < _length; i++)
    if ((unsigned char)_data[i] == c)
      return i;
  return -1;
}

int
String::find_left(const String &s, int start) const
{
    if (start < 0)
      start = 0;
    if (start >= length())
      return -1;
    if (!s.length())
      return 0;
    int first_c = (unsigned char)s[0];
    int pos = start, max_pos = length() - s.length();
    for (pos = find_left(first_c, pos); pos >= 0 && pos <= max_pos;
       pos = find_left(first_c, pos + 1))
      if (!memcmp(_data + pos, s._data, s.length()))
          return pos;
    return -1;
}

int
String::find_right(int c, int start) const
{
    if (start >= _length)
      start = _length - 1;
    for (int i = start; i >= 0; i--)
      if ((unsigned char)_data[i] == c)
          return i;
    return -1;
}

static String
hard_lower(const String &s, int pos)
{
    String new_s(s.data(), s.length());
    char *x = const_cast<char *>(new_s.data()); // know it's mutable
    int len = s.length();
    for (; pos < len; pos++)
      x[pos] = tolower(x[pos]);
    return new_s;
}

String
String::lower() const
{
    // avoid copies
    for (int i = 0; i < _length; i++)
      if (_data[i] >= 'A' && _data[i] <= 'Z')
          return hard_lower(*this, i);
    return *this;
}

static String
hard_upper(const String &s, int pos)
{
    String new_s(s.data(), s.length());
    char *x = const_cast<char *>(new_s.data()); // know it's mutable
    int len = s.length();
    for (; pos < len; pos++)
      x[pos] = toupper(x[pos]);
    return new_s;
}

String
String::upper() const
{
    // avoid copies
    for (int i = 0; i < _length; i++)
      if (_data[i] >= 'a' && _data[i] <= 'z')
          return hard_upper(*this, i);
    return *this;
}

static String
hard_printable(const String &s, int pos)
{
    StringAccum sa(s.length() * 2);
    sa.append(s.data(), pos);
    const unsigned char *x = reinterpret_cast<const unsigned char *>(s.data());
    int len = s.length();
    for (; pos < len; pos++) {
      if (x[pos] >= 32 && x[pos] < 127)
          sa << x[pos];
      else if (x[pos] < 32)
          sa << '^' << (unsigned char)(x[pos] + 64);
      else if (char *buf = sa.extend(4, 1))
          sprintf(buf, "\\%03o", x[pos]);
    }
    return sa.take_string();
}

String
String::printable() const
{
    // avoid copies
    for (int i = 0; i < _length; i++)
      if (_data[i] < 32 || _data[i] > 126)
          return hard_printable(*this, i);
    return *this;
}

unsigned
hashcode(const String &s)
{
    int length = s.length();
    const char *data = s.data();
    if (!length)
      return 0;
    else if (length == 1)
      return data[0] | (data[0] << 8);
    else if (length < 4)
      return data[0] + (data[1] << 3) + (length << 12);
    else
      return data[0] + (data[1] << 8) + (data[2] << 16) + (data[3] << 24)
          + (length << 12) + (data[length-1] << 10);
}

bool
String::equals(const char *s, int len) const
{
    // I would like to make "out-of-memory" strings compare unequal to
    // anything, even themseleves, but this would be a bad idea for Strings
    // used as (for example) keys in hashtables. Instead, "out-of-memory"
    // strings compare unequal to other null strings, but equal to each other.
    if (len < 0)
      len = strlen(s);
    if (_length != len)
      return false;
    else if (len == 0)
      return (_data == s || (s != oom_memo->_real_data && _memo != oom_memo));
    else
      return (_data == s || memcmp(_data, s, len) == 0);
}

int
String::compare(const char *s, int len) const
{
    if (len < 0)
      len = strlen(s);
    if (_data == s && _length == len)
      return 0;
    if (_length == len)
      return memcmp(_data, s, len);
    else if (_length < len) {
      int v = memcmp(_data, s, _length);
      return (v ? v : -1);
    } else {
      int v = memcmp(_data, s, len);
      return (v ? v : 1);
    }
}

void
String::align(int n)
{
    int offset = reinterpret_cast<uintptr_t>(_data) % n;
    if (offset) {
      String s;
      s.append_garbage(_length + n + 1);
      offset = reinterpret_cast<uintptr_t>(s._data) % n;
      memcpy((char *)s._data + n - offset, _data, _length);
      s._data += n - offset;
      s._length = _length;
      *this = s;
    }
}


String::Initializer::Initializer()
{
    String::static_initialize();
}

void
String::static_initialize()
{
    // function called to initialize static globals
    if (!null_memo) {
      null_memo = new Memo;
      null_memo->_refcount++;
      permanent_memo = new Memo;
      permanent_memo->_refcount++;
      // use a separate string for oom_memo's data, so we can distinguish
      // the pointer
      oom_memo = new Memo;
      oom_memo->_refcount++;
      oom_memo->_real_data = const_cast<char*>(&oom_string_data);
      null_string_p = new String;
      oom_string_p = new String(oom_memo->_real_data, 0, oom_memo);
    }
}

void
String::static_cleanup()
{
    if (null_string_p) {
      delete null_string_p;
      null_string_p = 0;
      delete oom_string_p;
      oom_string_p = 0;
      if (--null_memo->_refcount == 0)
          delete null_memo;
      if (--permanent_memo->_refcount == 0)
          delete permanent_memo;
      if (--oom_memo->_refcount == 0)
          delete oom_memo;
      null_memo = permanent_memo = oom_memo = 0;
    }
}

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