How To Write Dangerous Code 101

string is a class:
////////////////////////////////////////////////
// file name: string
#ifndef __STRING__
#define __STRING__

#include <std/bastring.h>

extern "C++" {
typedef basic_string <char> string;
// typedef basic_string <wchar_t> wstring;
} // extern "C++"

#endif

/////////////////////////////////////////////
// file name: bastring.h
template <class charT, class traits = string_char_traits<charT>,
class Allocator = alloc >
class basic_string
{
private:
struct Rep {
size_t len, res, ref;
bool selfish;

charT* data () { return reinterpret_cast<charT *>(this + 1); }
charT& operator[] (size_t s) { return data () [s]; }
charT* grab () { if (selfish) return clone (); ++ref; return data (); }
#if defined __i486__ || defined __i586__ || defined __i686__
void release ()
{
size_t __val;
// This opcode exists as a .byte instead of as a mnemonic for the
// benefit of SCO OpenServer 5. The system assembler (which is
// essentially required on this target) can't assemble xaddl in
//COFF mode.
asm (".byte 0xf0, 0x0f, 0xc1, 0x02" // lock; xaddl %eax, (%edx)
: "=a" (__val)
: "0" (-1), "m" (ref), "d" (&ref)
: "memory");

if (__val == 1)
delete this;
}
#elif defined __sparcv9__
void release ()
{
size_t __newval, __oldval = ref;
do
{
__newval = __oldval - 1;
__asm__ ("cas [%4], %2, %0"
: "=r" (__oldval), "=m" (ref)
: "r" (__oldval), "m" (ref), "r"(&(ref)), "0" (__newval));
}
while (__newval != __oldval);

if (__oldval == 0)
delete this;
}
#else
void release () { if (--ref == 0) delete this; }
#endif

inline static void * operator new (size_t, size_t);
inline static void operator delete (void *);
inline static Rep* create (size_t);
charT* clone ();

inline void copy (size_t, const charT *, size_t);
inline void move (size_t, const charT *, size_t);
inline void set (size_t, const charT, size_t);

inline static bool excess_slop (size_t, size_t);
inline static size_t frob_size (size_t);

private:
Rep &operator= (const Rep &);
};

public:
// types:
typedef traits traits_type;
typedef typename traits::char_type value_type;
typedef Allocator allocator_type;

typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef charT& reference;
typedef const charT& const_reference;
typedef charT* pointer;
typedef const charT* const_pointer;
typedef pointer iterator;
typedef const_pointer const_iterator;
typedef ::reverse_iterator<iterator> reverse_iterator;
typedef ::reverse_iterator<const_iterator> const_reverse_iterator;
static const size_type npos = static_cast<size_type>(-1);

private:
Rep *rep () const { return reinterpret_cast<Rep *>(dat) - 1; }
void repup (Rep *p) { rep ()->release (); dat = p->data (); }

public:
const charT* data () const
{ return rep ()->data(); }
size_type length () const
{ return rep ()->len; }
size_type size () const
{ return rep ()->len; }
size_type capacity () const
{ return rep ()->res; }
size_type max_size () const
{ return (npos - 1)/sizeof (charT); } // XXX
bool empty () const
{ return size () == 0; }

// _lib.string.cons_ construct/copy/destroy:
basic_string& operator= (const basic_string& str)
{
if (&str != this) { rep ()->release (); dat = str.rep ()->grab (); }
return *this;
}

explicit basic_string (): dat (nilRep.grab ()) { }
basic_string (const basic_string& str): dat (str.rep ()->grab ()) { }
basic_string (const basic_string& str, size_type pos, size_type n = npos)
: dat (nilRep.grab ()) { assign (str, pos, n); }
basic_string (const charT* s, size_type n)
: dat (nilRep.grab ()) { assign (s, n); }
basic_string (const charT* s)
: dat (nilRep.grab ()) { assign (s); }
basic_string (size_type n, charT c)
: dat (nilRep.grab ()) { assign (n, c); }
#ifdef __STL_MEMBER_TEMPLATES
template<class InputIterator>
basic_string(InputIterator __begin, InputIterator __end)
#else
basic_string(const_iterator __begin, const_iterator __end)
#endif
: dat (nilRep.grab ()) { assign (__begin, __end); }

~basic_string ()
{ rep ()->release (); }

void swap (basic_string &s) { charT *d = dat; dat = s.dat; s.dat = d; }

basic_string& append (const basic_string& str, size_type pos = 0,
size_type n = npos)
{ return replace (length (), 0, str, pos, n); }
basic_string& append (const charT* s, size_type n)
{ return replace (length (), 0, s, n); }
basic_string& append (const charT* s)
{ return append (s, traits::length (s)); }
basic_string& append (size_type n, charT c)
{ return replace (length (), 0, n, c); }
#ifdef __STL_MEMBER_TEMPLATES
template<class InputIterator>
basic_string& append(InputIterator first, InputIterator last)
#else
basic_string& append(const_iterator first, const_iterator last)
#endif
{ return replace (iend (), iend (), first, last); }

void push_back(charT __c)
{ append(1, __c); }

basic_string& assign (const basic_string& str, size_type pos = 0,
size_type n = npos)
{ return replace (0, npos, str, pos, n); }
basic_string& assign (const charT* s, size_type n)
{ return replace (0, npos, s, n); }
basic_string& assign (const charT* s)
{ return assign (s, traits::length (s)); }
basic_string& assign (size_type n, charT c)
{ return replace (0, npos, n, c); }
#ifdef __STL_MEMBER_TEMPLATES
template<class InputIterator>
basic_string& assign(InputIterator first, InputIterator last)
#else
basic_string& assign(const_iterator first, const_iterator last)
#endif
{ return replace (ibegin (), iend (), first, last); }

basic_string& operator= (const charT* s)
{ return assign (s); }
basic_string& operator= (charT c)
{ return assign (1, c); }

basic_string& operator+= (const basic_string& rhs)
{ return append (rhs); }
basic_string& operator+= (const charT* s)
{ return append (s); }
basic_string& operator+= (charT c)
{ return append (1, c); }

basic_string& insert (size_type pos1, const basic_string& str,
size_type pos2 = 0, size_type n = npos)
{ return replace (pos1, 0, str, pos2, n); }
basic_string& insert (size_type pos, const charT* s, size_type n)
{ return replace (pos, 0, s, n); }
basic_string& insert (size_type pos, const charT* s)
{ return insert (pos, s, traits::length (s)); }
basic_string& insert (size_type pos, size_type n, charT c)
{ return replace (pos, 0, n, c); }
iterator insert(iterator p, charT c)
{ size_type __o = p - ibegin ();
insert (p - ibegin (), 1, c); selfish ();
return ibegin () + __o; }
iterator insert(iterator p, size_type n, charT c)
{ size_type __o = p - ibegin ();
insert (p - ibegin (), n, c); selfish ();
return ibegin () + __o; }
#ifdef __STL_MEMBER_TEMPLATES
template<class InputIterator>
void insert(iterator p, InputIterator first, InputIterator last)
#else
void insert(iterator p, const_iterator first, const_iterator last)
#endif
{ replace (p, p, first, last); }

basic_string& erase (size_type pos = 0, size_type n = npos)
{ return replace (pos, n, (size_type)0, (charT)0); }
iterator erase(iterator p)
{ size_type __o = p - begin();
replace (__o, 1, (size_type)0, (charT)0); selfish ();
return ibegin() + __o; }
iterator erase(iterator f, iterator l)
{ size_type __o = f - ibegin();
replace (__o, l-f, (size_type)0, (charT)0);selfish ();
return ibegin() + __o; }

basic_string& replace (size_type pos1, size_type n1, const basic_string& str,
size_type pos2 = 0, size_type n2 = npos);
basic_string& replace (size_type pos, size_type n1, const charT* s,
size_type n2);
basic_string& replace (size_type pos, size_type n1, const charT* s)
{ return replace (pos, n1, s, traits::length (s)); }
basic_string& replace (size_type pos, size_type n1, size_type n2, charT c);
basic_string& replace (size_type pos, size_type n, charT c)
{ return replace (pos, n, 1, c); }
basic_string& replace (iterator i1, iterator i2, const basic_string& str)
{ return replace (i1 - ibegin (), i2 - i1, str); }
basic_string& replace (iterator i1, iterator i2, const charT* s, size_type n)
{ return replace (i1 - ibegin (), i2 - i1, s, n); }
basic_string& replace (iterator i1, iterator i2, const charT* s)
{ return replace (i1 - ibegin (), i2 - i1, s); }
basic_string& replace (iterator i1, iterator i2, size_type n, charT c)
{ return replace (i1 - ibegin (), i2 - i1, n, c); }
#ifdef __STL_MEMBER_TEMPLATES
template<class InputIterator>
basic_string& replace(iterator i1, iterator i2,
InputIterator j1, InputIterator j2);
#else
basic_string& replace(iterator i1, iterator i2,
const_iterator j1, const_iterator j2);
#endif

private:
static charT eos () { return traits::eos (); }
void unique () { if (rep ()->ref > 1) alloc (length (), true); }
void selfish () { unique (); rep ()->selfish = true; }

public:
charT operator[] (size_type pos) const
{
if (pos == length ())
return eos ();
return data ()[pos];
}

reference operator[] (size_type pos)
{ selfish (); return (*rep ())[pos]; }

reference at (size_type pos)
{
OUTOFRANGE (pos >= length ());
return (*this)[pos];
}
const_reference at (size_type pos) const
{
OUTOFRANGE (pos >= length ());
return data ()[pos];
}

private:
void terminate () const
{ traits::assign ((*rep ())[length ()], eos ()); }

public:
const charT* c_str () const
{ if (length () == 0) return ""; terminate (); return data (); }
void resize (size_type n, charT c);
void resize (size_type n)
{ resize (n, eos ()); }
void reserve (size_type) { }

size_type copy (charT* s, size_type n, size_type pos = 0) const;

size_type find (const basic_string& str, size_type pos = 0) const
{ return find (str.data(), pos, str.length()); }
size_type find (const charT* s, size_type pos, size_type n) const;
size_type find (const charT* s, size_type pos = 0) const
{ return find (s, pos, traits::length (s)); }
size_type find (charT c, size_type pos = 0) const;

size_type rfind (const basic_string& str, size_type pos = npos) const
{ return rfind (str.data(), pos, str.length()); }
size_type rfind (const charT* s, size_type pos, size_type n) const;
size_type rfind (const charT* s, size_type pos = npos) const
{ return rfind (s, pos, traits::length (s)); }
size_type rfind (charT c, size_type pos = npos) const;

size_type find_first_of (const basic_string& str, size_type pos = 0) const
{ return find_first_of (str.data(), pos, str.length()); }
size_type find_first_of (const charT* s, size_type pos, size_type n) const;
size_type find_first_of (const charT* s, size_type pos = 0) const
{ return find_first_of (s, pos, traits::length (s)); }
size_type find_first_of (charT c, size_type pos = 0) const
{ return find (c, pos); }

size_type find_last_of (const basic_string& str, size_type pos = npos) const
{ return find_last_of (str.data(), pos, str.length()); }
size_type find_last_of (const charT* s, size_type pos, size_type n) const;
size_type find_last_of (const charT* s, size_type pos = npos) const
{ return find_last_of (s, pos, traits::length (s)); }
size_type find_last_of (charT c, size_type pos = npos) const
{ return rfind (c, pos); }

size_type find_first_not_of (const basic_string& str, size_type pos = 0) const
{ return find_first_not_of (str.data(), pos, str.length()); }
size_type find_first_not_of (const charT* s, size_type pos, size_type n) const;
size_type find_first_not_of (const charT* s, size_type pos = 0) const
{ return find_first_not_of (s, pos, traits::length (s)); }
size_type find_first_not_of (charT c, size_type pos = 0) const;

size_type find_last_not_of (const basic_string& str, size_type pos = npos) const
{ return find_last_not_of (str.data(), pos, str.length()); }
size_type find_last_not_of (const charT* s, size_type pos, size_type n) const;
size_type find_last_not_of (const charT* s, size_type pos = npos) const
{ return find_last_not_of (s, pos, traits::length (s)); }
size_type find_last_not_of (charT c, size_type pos = npos) const;

basic_string substr (size_type pos = 0, size_type n = npos) const
{ return basic_string (*this, pos, n); }

int compare (const basic_string& str, size_type pos = 0, size_type n = npos) const;
// There is no 'strncmp' equivalent for charT pointers.
int compare (const charT* s, size_type pos, size_type n) const;
int compare (const charT* s, size_type pos = 0) const
{ return compare (s, pos, traits::length (s)); }

iterator begin () { selfish (); return &(*this)[0]; }
iterator end () { selfish (); return &(*this)[length ()]; }

private:
iterator ibegin () const { return &(*rep ())[0]; }
iterator iend () const { return &(*rep ())[length ()]; }

public:
const_iterator begin () const { return ibegin (); }
const_iterator end () const { return iend (); }

reverse_iterator rbegin() { return reverse_iterator (end ()); }
const_reverse_iterator rbegin() const
{ return const_reverse_iterator (end ()); }
reverse_iterator rend() { return reverse_iterator (begin ()); }
const_reverse_iterator rend() const
{ return const_reverse_iterator (begin ()); }

private:
void alloc (size_type size, bool save);
static size_type _find (const charT* ptr, charT c, size_type xpos, size_type len);
inline bool check_realloc (size_type s) const;

static Rep nilRep;
charT *dat;
};

template <class charT, class traits, class Allocator>
inline bool
operator== (const basic_string <charT, traits, Allocator>& lhs,
const basic_string <charT, traits, Allocator>& rhs)
{
return (lhs.compare (rhs) == 0);
}

template <class charT, class traits, class Allocator>
inline bool
operator== (const charT* lhs, const basic_string <charT, traits, Allocator>& rhs)
{
return (rhs.compare (lhs) == 0);
}

template <class charT, class traits, class Allocator>
inline bool
operator== (const basic_string <charT, traits, Allocator>& lhs, const charT* rhs)
{
return (lhs.compare (rhs) == 0);
}

Using code tags might get me to take a second look.:rolleyes: