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[wxWidgets.git] / src / common / string.cpp

/////////////////////////////////////////////////////////////////////////////
// Name:        string.cpp
// Purpose:     wxString class
// Author:      Vadim Zeitlin
// Modified by:
// Created:     29/01/98
// RCS-ID:      $Id$
// Copyright:   (c) 1998 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

#ifdef __GNUG__
  #pragma implementation "string.h"
#endif

/*
 * About ref counting:
 *  1) all empty strings use g_strEmpty, nRefs = -1 (set in Init())
 *  2) AllocBuffer() sets nRefs to 1, Lock() increments it by one
 *  3) Unlock() decrements nRefs and frees memory if it goes to 0
 */

// ===========================================================================
// headers, declarations, constants
// ===========================================================================

// For compilers that support precompilation, includes "wx.h".
#include "wx/wxprec.h"

#ifdef __BORLANDC__
  #pragma hdrstop
#endif

#ifndef WX_PRECOMP
  #include "wx/defs.h"
  #include "wx/string.h"
  #include "wx/intl.h"
  #include "wx/thread.h"
#endif

#include <ctype.h>
#include <string.h>
#include <stdlib.h>

#ifdef __SALFORDC__
  #include <clib.h>
#endif

#if wxUSE_UNICODE
    #undef wxUSE_EXPERIMENTAL_PRINTF
    #ifndef wvsnprintf
        #define wxUSE_EXPERIMENTAL_PRINTF 1
    #endif
#endif

// allocating extra space for each string consumes more memory but speeds up
// the concatenation operations (nLen is the current string's length)
// NB: EXTRA_ALLOC must be >= 0!
#define EXTRA_ALLOC       (19 - nLen % 16)

// ---------------------------------------------------------------------------
// static class variables definition
// ---------------------------------------------------------------------------

#if defined(__VISAGECPP__) && __IBMCPP__ >= 400
// must define this static for VA or else you get multiply defined symbols
// everywhere
const unsigned int wxSTRING_MAXLEN = UINT_MAX - 100;
#endif // Visual Age

#ifdef  wxSTD_STRING_COMPATIBILITY
  const size_t wxString::npos = wxSTRING_MAXLEN;
#endif // wxSTD_STRING_COMPATIBILITY

// ----------------------------------------------------------------------------
// static data
// ----------------------------------------------------------------------------

// for an empty string, GetStringData() will return this address: this
// structure has the same layout as wxStringData and it's data() method will
// return the empty string (dummy pointer)
static const struct
{
  wxStringData data;
  wxChar dummy;
} g_strEmpty = { {-1, 0, 0}, wxT('\0') };

// empty C style string: points to 'string data' byte of g_strEmpty
extern const wxChar WXDLLEXPORT *wxEmptyString = &g_strEmpty.dummy;

// ----------------------------------------------------------------------------
// conditional compilation
// ----------------------------------------------------------------------------

#if !defined(__WXSW__) && wxUSE_UNICODE
  #ifdef wxUSE_EXPERIMENTAL_PRINTF
    #undef wxUSE_EXPERIMENTAL_PRINTF
  #endif
  #define wxUSE_EXPERIMENTAL_PRINTF 1
#endif

// we want to find out if the current platform supports vsnprintf()-like
// function: for Unix this is done with configure, for Windows we test the
// compiler explicitly.
//
// FIXME currently, this is only for ANSI (!Unicode) strings, so we call this
//       function wxVsnprintfA (A for ANSI), should also find one for Unicode
//       strings in Unicode build
#ifdef __WXMSW__
    #if defined(__VISUALC__) || (defined(__MINGW32__) && wxUSE_NORLANDER_HEADERS)
        #define wxVsnprintfA     _vsnprintf
    #endif
#elif defined(__WXMAC__)
    #define wxVsnprintfA       vsnprintf
#else   // !Windows
    #ifdef HAVE_VSNPRINTF
        #define wxVsnprintfA       vsnprintf
    #endif
#endif  // Windows/!Windows

#ifndef wxVsnprintfA
    // in this case we'll use vsprintf() (which is ANSI and thus should be
    // always available), but it's unsafe because it doesn't check for buffer
    // size - so give a warning
    #define wxVsnprintfA(buf, len, format, arg) vsprintf(buf, format, arg)

    #if defined(__VISUALC__)
        #pragma message("Using sprintf() because no snprintf()-like function defined")
    #elif defined(__GNUG__)
        #warning "Using sprintf() because no snprintf()-like function defined"
    #endif //compiler
#endif // no vsnprintf

#if defined(_AIX)
  // AIX has vsnprintf, but there's no prototype in the system headers.
  extern "C" int vsnprintf(char* str, size_t n, const char* format, va_list ap);
#endif

// ----------------------------------------------------------------------------
// global functions
// ----------------------------------------------------------------------------

#if defined(wxSTD_STRING_COMPATIBILITY) && wxUSE_STD_IOSTREAM

// MS Visual C++ version 5.0 provides the new STL headers as well as the old
// iostream ones.
//
// ATTN: you can _not_ use both of these in the same program!

wxSTD istream& operator>>(wxSTD istream& is, wxString& WXUNUSED(str))
{
#if 0
  int w = is.width(0);
  if ( is.ipfx(0) ) {
    streambuf *sb = is.rdbuf();
    str.erase();
    while ( true ) {
      int ch = sb->sbumpc ();
      if ( ch == EOF ) {
        is.setstate(ios::eofbit);
        break;
      }
      else if ( isspace(ch) ) {
        sb->sungetc();
        break;
      }

      str += ch;
      if ( --w == 1 )
        break;
    }
  }

  is.isfx();
  if ( str.length() == 0 )
    is.setstate(ios::failbit);
#endif
  return is;
}

wxSTD ostream& operator<<(wxSTD ostream& os, const wxString& str)
{
  os << str.c_str();
  return os;
}

#endif  //std::string compatibility

#ifndef wxVsnprintf
int WXDLLEXPORT wxVsnprintf(wxChar *buf, size_t len,
                            const wxChar *format, va_list argptr)
{
#if wxUSE_UNICODE
    wxString s;
    int iLen = s.PrintfV(format, argptr);
    if ( iLen != -1 )
    {
        wxStrncpy(buf, s.c_str(), len);
        buf[len-1] = wxT('\0');
    }

    return iLen;
#else // ANSI
    // vsnprintf() will not terminate the string with '\0' if there is not
    // enough place, but we want the string to always be NUL terminated
    int rc = wxVsnprintfA(buf, len - 1, format, argptr);
    if ( rc == -1 )
    {
        buf[len] = 0;
    }

    return rc;
#endif // Unicode/ANSI
}
#else
// GNU libc 2.2 only has for wxVsnprintf for Unicode called vswprintf
// so we imitate wxVsprintf using it.
int WXDLLEXPORT wxVsprintf(wxChar *buf,
                           const wxChar *format,
                           va_list argptr)
{
    return vswprintf( buf, 10000, format, argptr );
}
#endif

#ifndef wxSnprintf   
int WXDLLEXPORT wxSnprintf(wxChar *buf, size_t len,
                           const wxChar *format, ...)
{
    va_list argptr;
    va_start(argptr, format);

    int iLen = wxVsnprintf(buf, len, format, argptr);

    va_end(argptr);

    return iLen;
}
#else
// GNU libc 2.2 only has for wxSnprintf for Unicode called swprintf
// so we imitate wxSprintf using it.
int WXDLLEXPORT wxSprintf(wxChar *buf,
                          const wxChar *format,
                          ...) ATTRIBUTE_PRINTF_2
{
    va_list argptr;
    va_start(argptr, format);

    int iLen = swprintf(buf, 10000, format, argptr);

    va_end(argptr);

    return iLen;
}
#endif

// ----------------------------------------------------------------------------
// private classes
// ----------------------------------------------------------------------------

// this small class is used to gather statistics for performance tuning
//#define WXSTRING_STATISTICS
#ifdef  WXSTRING_STATISTICS
  class Averager
  {
  public:
    Averager(const char *sz) { m_sz = sz; m_nTotal = m_nCount = 0; }
   ~Averager()
   { printf("wxString: average %s = %f\n", m_sz, ((float)m_nTotal)/m_nCount); }

    void Add(size_t n) { m_nTotal += n; m_nCount++; }

  private:
    size_t m_nCount, m_nTotal;
    const char *m_sz;
  } g_averageLength("allocation size"),
    g_averageSummandLength("summand length"),
    g_averageConcatHit("hit probability in concat"),
    g_averageInitialLength("initial string length");

  #define STATISTICS_ADD(av, val) g_average##av.Add(val)
#else
  #define STATISTICS_ADD(av, val)
#endif // WXSTRING_STATISTICS

// ===========================================================================
// wxString class core
// ===========================================================================

// ---------------------------------------------------------------------------
// construction
// ---------------------------------------------------------------------------

// constructs string of <nLength> copies of character <ch>
wxString::wxString(wxChar ch, size_t nLength)
{
  Init();

  if ( nLength > 0 ) {
    if ( !AllocBuffer(nLength) ) {
      wxFAIL_MSG( _T("out of memory in wxString::wxString") );
      return;
    }

#if wxUSE_UNICODE
    // memset only works on char
    for (size_t n=0; n<nLength; n++) m_pchData[n] = ch;
#else
    memset(m_pchData, ch, nLength);
#endif
  }
}

// takes nLength elements of psz starting at nPos
void wxString::InitWith(const wxChar *psz, size_t nPos, size_t nLength)
{
  Init();

  // if the length is not given, assume the string to be NUL terminated
  if ( nLength == wxSTRING_MAXLEN ) {
    wxASSERT_MSG( nPos <= wxStrlen(psz), _T("index out of bounds") );

    nLength = wxStrlen(psz + nPos);
  }

  STATISTICS_ADD(InitialLength, nLength);

  if ( nLength > 0 ) {
    // trailing '\0' is written in AllocBuffer()
    if ( !AllocBuffer(nLength) ) {
      wxFAIL_MSG( _T("out of memory in wxString::InitWith") );
      return;
    }
    memcpy(m_pchData, psz + nPos, nLength*sizeof(wxChar));
  }
}

#ifdef  wxSTD_STRING_COMPATIBILITY

// poor man's iterators are "void *" pointers
wxString::wxString(const void *pStart, const void *pEnd)
{
  InitWith((const wxChar *)pStart, 0,
           (const wxChar *)pEnd - (const wxChar *)pStart);
}

#endif  //std::string compatibility

#if wxUSE_UNICODE

// from multibyte string
wxString::wxString(const char *psz, wxMBConv& conv, size_t nLength)
{
  // first get necessary size
  size_t nLen = psz ? conv.MB2WC((wchar_t *) NULL, psz, 0) : 0;

  // nLength is number of *Unicode* characters here!
  if ((nLen != (size_t)-1) && (nLen > nLength))
    nLen = nLength;

  // empty?
  if ( (nLen != 0) && (nLen != (size_t)-1) ) {
    if ( !AllocBuffer(nLen) ) {
      wxFAIL_MSG( _T("out of memory in wxString::wxString") );
      return;
    }
    conv.MB2WC(m_pchData, psz, nLen);
  }
  else {
    Init();
  }
}

#else // ANSI

#if wxUSE_WCHAR_T
// from wide string
wxString::wxString(const wchar_t *pwz, wxMBConv& conv, size_t nLength)
{
  // first get necessary size
  size_t nLen = 0;
  if (pwz)
  {
    if (nLength == wxSTRING_MAXLEN)
      nLen = conv.WC2MB((char *) NULL, pwz, 0);
    else
      nLen = nLength;
  }

  // empty?
  if ( (nLen != 0) && (nLen != (size_t)-1) ) {
    if ( !AllocBuffer(nLen) ) {
      wxFAIL_MSG( _T("out of memory in wxString::wxString") );
      return;
    }
    conv.WC2MB(m_pchData, pwz, nLen);
  }
  else {
    Init();
  }
}
#endif // wxUSE_WCHAR_T

#endif // Unicode/ANSI

// ---------------------------------------------------------------------------
// memory allocation
// ---------------------------------------------------------------------------

// allocates memory needed to store a C string of length nLen
bool wxString::AllocBuffer(size_t nLen)
{
  // allocating 0 sized buffer doesn't make sense, all empty strings should
  // reuse g_strEmpty
  wxASSERT( nLen >  0 );

  // make sure that we don't overflow
  wxASSERT( nLen < (INT_MAX / sizeof(wxChar)) -
                   (sizeof(wxStringData) + EXTRA_ALLOC + 1) );

  STATISTICS_ADD(Length, nLen);

  // allocate memory:
  // 1) one extra character for '\0' termination
  // 2) sizeof(wxStringData) for housekeeping info
  wxStringData* pData = (wxStringData*)
    malloc(sizeof(wxStringData) + (nLen + EXTRA_ALLOC + 1)*sizeof(wxChar));
  
  if ( pData == NULL ) {
    // allocation failures are handled by the caller
    return FALSE;
  }
  
  pData->nRefs        = 1;
  pData->nDataLength  = nLen;
  pData->nAllocLength = nLen + EXTRA_ALLOC;
  m_pchData           = pData->data();  // data starts after wxStringData
  m_pchData[nLen]     = wxT('\0');
  return TRUE;
}

// must be called before changing this string
bool wxString::CopyBeforeWrite()
{
  wxStringData* pData = GetStringData();

  if ( pData->IsShared() ) {
    pData->Unlock();                // memory not freed because shared
    size_t nLen = pData->nDataLength;
    if ( !AllocBuffer(nLen) ) {
      // allocation failures are handled by the caller
      return FALSE;
    }
    memcpy(m_pchData, pData->data(), nLen*sizeof(wxChar));
  }

  wxASSERT( !GetStringData()->IsShared() );  // we must be the only owner

  return TRUE;
}

// must be called before replacing contents of this string
bool wxString::AllocBeforeWrite(size_t nLen)
{
  wxASSERT( nLen != 0 );  // doesn't make any sense

  // must not share string and must have enough space
  wxStringData* pData = GetStringData();
  if ( pData->IsShared() || pData->IsEmpty() ) {
    // can't work with old buffer, get new one
    pData->Unlock();
    if ( !AllocBuffer(nLen) ) {
      // allocation failures are handled by the caller
      return FALSE;
    }
  }
  else {
    if ( nLen > pData->nAllocLength ) {
      // realloc the buffer instead of calling malloc() again, this is more
      // efficient
      STATISTICS_ADD(Length, nLen);

      nLen += EXTRA_ALLOC;

      pData = (wxStringData*)
          realloc(pData, sizeof(wxStringData) + (nLen + 1)*sizeof(wxChar));
      
      if ( pData == NULL ) {
        // allocation failures are handled by the caller
        // keep previous data since reallocation failed
        return FALSE;
      }

      pData->nAllocLength = nLen;
      m_pchData = pData->data();
    }

    // now we have enough space, just update the string length
    pData->nDataLength = nLen;
  }

  wxASSERT( !GetStringData()->IsShared() );  // we must be the only owner

  return TRUE;
}

// allocate enough memory for nLen characters
bool wxString::Alloc(size_t nLen)
{
  wxStringData *pData = GetStringData();
  if ( pData->nAllocLength <= nLen ) {
    if ( pData->IsEmpty() ) {
      nLen += EXTRA_ALLOC;

      wxStringData* pData = (wxStringData*)
          malloc(sizeof(wxStringData) + (nLen + 1)*sizeof(wxChar));

      if ( pData == NULL ) {
        // allocation failure handled by caller
        return FALSE;
      }
      
      pData->nRefs = 1;
      pData->nDataLength = 0;
      pData->nAllocLength = nLen;
      m_pchData = pData->data();  // data starts after wxStringData
      m_pchData[0u] = wxT('\0');
    }
    else if ( pData->IsShared() ) {
      pData->Unlock();                // memory not freed because shared
      size_t nOldLen = pData->nDataLength;
      if ( !AllocBuffer(nLen) ) {
        // allocation failure handled by caller
        return FALSE;
      }
      memcpy(m_pchData, pData->data(), nOldLen*sizeof(wxChar));
    }
    else {
      nLen += EXTRA_ALLOC;

      pData = (wxStringData *)
        realloc(pData, sizeof(wxStringData) + (nLen + 1)*sizeof(wxChar));

      if ( pData == NULL ) {
        // allocation failure handled by caller
        // keep previous data since reallocation failed
        return FALSE;
      }

      // it's not important if the pointer changed or not (the check for this
      // is not faster than assigning to m_pchData in all cases)
      pData->nAllocLength = nLen;
      m_pchData = pData->data();
    }
  }
  //else: we've already got enough
  return TRUE;
}

// shrink to minimal size (releasing extra memory)
bool wxString::Shrink()
{
  wxStringData *pData = GetStringData();

  size_t nLen = pData->nDataLength;
  void *p = realloc(pData, sizeof(wxStringData) + (nLen + 1)*sizeof(wxChar));

  if ( p == NULL) {
      wxFAIL_MSG( _T("out of memory reallocating wxString data") );
      // keep previous data since reallocation failed
      return FALSE;
  }

  if ( p != pData )
  {
      // contrary to what one might believe, some realloc() implementation do
      // move the memory block even when its size is reduced
      pData = (wxStringData *)p;

      m_pchData = pData->data();
  }

  pData->nAllocLength = nLen;

  return TRUE;
}

// get the pointer to writable buffer of (at least) nLen bytes
wxChar *wxString::GetWriteBuf(size_t nLen)
{
  if ( !AllocBeforeWrite(nLen) ) {
    // allocation failure handled by caller
    return NULL;
  }

  wxASSERT( GetStringData()->nRefs == 1 );
  GetStringData()->Validate(FALSE);

  return m_pchData;
}

// put string back in a reasonable state after GetWriteBuf
void wxString::UngetWriteBuf()
{
  GetStringData()->nDataLength = wxStrlen(m_pchData);
  GetStringData()->Validate(TRUE);
}

void wxString::UngetWriteBuf(size_t nLen)
{
  GetStringData()->nDataLength = nLen;
  GetStringData()->Validate(TRUE);
}

// ---------------------------------------------------------------------------
// data access
// ---------------------------------------------------------------------------

// all functions are inline in string.h

// ---------------------------------------------------------------------------
// assignment operators
// ---------------------------------------------------------------------------

// helper function: does real copy
bool wxString::AssignCopy(size_t nSrcLen, const wxChar *pszSrcData)
{
  if ( nSrcLen == 0 ) {
    Reinit();
  }
  else {
    if ( !AllocBeforeWrite(nSrcLen) ) {
      // allocation failure handled by caller
      return FALSE;
    }
    memcpy(m_pchData, pszSrcData, nSrcLen*sizeof(wxChar));
    GetStringData()->nDataLength = nSrcLen;
    m_pchData[nSrcLen] = wxT('\0');
  }
  return TRUE;
}

// assigns one string to another
wxString& wxString::operator=(const wxString& stringSrc)
{
  wxASSERT( stringSrc.GetStringData()->IsValid() );

  // don't copy string over itself
  if ( m_pchData != stringSrc.m_pchData ) {
    if ( stringSrc.GetStringData()->IsEmpty() ) {
      Reinit();
    }
    else {
      // adjust references
      GetStringData()->Unlock();
      m_pchData = stringSrc.m_pchData;
      GetStringData()->Lock();
    }
  }

  return *this;
}

// assigns a single character
wxString& wxString::operator=(wxChar ch)
{
  if ( !AssignCopy(1, &ch) ) {
    wxFAIL_MSG( _T("out of memory in wxString::operator=(wxChar)") );
  }
  return *this;
}


// assigns C string
wxString& wxString::operator=(const wxChar *psz)
{
  if ( !AssignCopy(wxStrlen(psz), psz) ) {
    wxFAIL_MSG( _T("out of memory in wxString::operator=(const wxChar *)") );
  }
  return *this;
}

#if !wxUSE_UNICODE

// same as 'signed char' variant
wxString& wxString::operator=(const unsigned char* psz)
{
  *this = (const char *)psz;
  return *this;
}

#if wxUSE_WCHAR_T
wxString& wxString::operator=(const wchar_t *pwz)
{
  wxString str(pwz);
  *this = str;
  return *this;
}
#endif

#endif

// ---------------------------------------------------------------------------
// string concatenation
// ---------------------------------------------------------------------------

// add something to this string
bool wxString::ConcatSelf(int nSrcLen, const wxChar *pszSrcData)
{
  STATISTICS_ADD(SummandLength, nSrcLen);

  // concatenating an empty string is a NOP
  if ( nSrcLen > 0 ) {
    wxStringData *pData = GetStringData();
    size_t nLen = pData->nDataLength;
    size_t nNewLen = nLen + nSrcLen;

    // alloc new buffer if current is too small
    if ( pData->IsShared() ) {
      STATISTICS_ADD(ConcatHit, 0);

      // we have to allocate another buffer
      wxStringData* pOldData = GetStringData();
      if ( !AllocBuffer(nNewLen) ) {
          // allocation failure handled by caller
          return FALSE;
      }
      memcpy(m_pchData, pOldData->data(), nLen*sizeof(wxChar));
      pOldData->Unlock();
    }
    else if ( nNewLen > pData->nAllocLength ) {
      STATISTICS_ADD(ConcatHit, 0);

      // we have to grow the buffer
      if ( !Alloc(nNewLen) ) {
          // allocation failure handled by caller
          return FALSE;
      }
    }
    else {
      STATISTICS_ADD(ConcatHit, 1);

      // the buffer is already big enough
    }

    // should be enough space
    wxASSERT( nNewLen <= GetStringData()->nAllocLength );

    // fast concatenation - all is done in our buffer
    memcpy(m_pchData + nLen, pszSrcData, nSrcLen*sizeof(wxChar));

    m_pchData[nNewLen] = wxT('\0');          // put terminating '\0'
    GetStringData()->nDataLength = nNewLen; // and fix the length
  }
  //else: the string to append was empty
  return TRUE;
}

/*
 * concatenation functions come in 5 flavours:
 *  string + string
 *  char   + string      and      string + char
 *  C str  + string      and      string + C str
 */

wxString operator+(const wxString& str1, const wxString& str2)
{
  wxASSERT( str1.GetStringData()->IsValid() );
  wxASSERT( str2.GetStringData()->IsValid() );

  wxString s = str1;
  s += str2;

  return s;
}

wxString operator+(const wxString& str, wxChar ch)
{
  wxASSERT( str.GetStringData()->IsValid() );

  wxString s = str;
  s += ch;

  return s;
}

wxString operator+(wxChar ch, const wxString& str)
{
  wxASSERT( str.GetStringData()->IsValid() );

  wxString s = ch;
  s += str;

  return s;
}

wxString operator+(const wxString& str, const wxChar *psz)
{
  wxASSERT( str.GetStringData()->IsValid() );

  wxString s;
  if ( !s.Alloc(wxStrlen(psz) + str.Len()) ) {
    wxFAIL_MSG( _T("out of memory in wxString::operator+") );
  }
  s = str;
  s += psz;

  return s;
}

wxString operator+(const wxChar *psz, const wxString& str)
{
  wxASSERT( str.GetStringData()->IsValid() );

  wxString s;
  if ( !s.Alloc(wxStrlen(psz) + str.Len()) ) {
    wxFAIL_MSG( _T("out of memory in wxString::operator+") );
  }
  s = psz;
  s += str;

  return s;
}

// ===========================================================================
// other common string functions
// ===========================================================================

// ---------------------------------------------------------------------------
// simple sub-string extraction
// ---------------------------------------------------------------------------

// helper function: clone the data attached to this string
bool wxString::AllocCopy(wxString& dest, int nCopyLen, int nCopyIndex) const
{
  if ( nCopyLen == 0 ) {
    dest.Init();
  }
  else {
    if ( !dest.AllocBuffer(nCopyLen) ) {
      // allocation failure handled by caller
      return FALSE;
    }
    memcpy(dest.m_pchData, m_pchData + nCopyIndex, nCopyLen*sizeof(wxChar));
  }
  return TRUE;
}

// extract string of length nCount starting at nFirst
wxString wxString::Mid(size_t nFirst, size_t nCount) const
{
  wxStringData *pData = GetStringData();
  size_t nLen = pData->nDataLength;

  // default value of nCount is wxSTRING_MAXLEN and means "till the end"
  if ( nCount == wxSTRING_MAXLEN )
  {
    nCount = nLen - nFirst;
  }

  // out-of-bounds requests return sensible things
  if ( nFirst + nCount > nLen )
  {
    nCount = nLen - nFirst;
  }

  if ( nFirst > nLen )
  {
    // AllocCopy() will return empty string
    nCount = 0;
  }

  wxString dest;
  if ( !AllocCopy(dest, nCount, nFirst) ) {
      wxFAIL_MSG( _T("out of memory in wxString::Mid") );
  }

  return dest;
}

// check that the tring starts with prefix and return the rest of the string
// in the provided pointer if it is not NULL, otherwise return FALSE
bool wxString::StartsWith(const wxChar *prefix, wxString *rest) const
{
    wxASSERT_MSG( prefix, _T("invalid parameter in wxString::StartsWith") );

    // first check if the beginning of the string matches the prefix: note
    // that we don't have to check that we don't run out of this string as
    // when we reach the terminating NUL, either prefix string ends too (and
    // then it's ok) or we break out of the loop because there is no match
    const wxChar *p = c_str();
    while ( *prefix )
    {
        if ( *prefix++ != *p++ )
        {
            // no match
            return FALSE;
        }
    }

    if ( rest )
    {
        // put the rest of the string into provided pointer
        *rest = p;
    }

    return TRUE;
}

// extract nCount last (rightmost) characters
wxString wxString::Right(size_t nCount) const
{
  if ( nCount > (size_t)GetStringData()->nDataLength )
    nCount = GetStringData()->nDataLength;

  wxString dest;
  if ( !AllocCopy(dest, nCount, GetStringData()->nDataLength - nCount) ) {
    wxFAIL_MSG( _T("out of memory in wxString::Right") );
  }
  return dest;
}

// get all characters after the last occurence of ch
// (returns the whole string if ch not found)
wxString wxString::AfterLast(wxChar ch) const
{
  wxString str;
  int iPos = Find(ch, TRUE);
  if ( iPos == wxNOT_FOUND )
    str = *this;
  else
    str = c_str() + iPos + 1;

  return str;
}

// extract nCount first (leftmost) characters
wxString wxString::Left(size_t nCount) const
{
  if ( nCount > (size_t)GetStringData()->nDataLength )
    nCount = GetStringData()->nDataLength;

  wxString dest;
  if ( !AllocCopy(dest, nCount, 0) ) {
    wxFAIL_MSG( _T("out of memory in wxString::Left") );
  }
  return dest;
}

// get all characters before the first occurence of ch
// (returns the whole string if ch not found)
wxString wxString::BeforeFirst(wxChar ch) const
{
  wxString str;
  for ( const wxChar *pc = m_pchData; *pc != wxT('\0') && *pc != ch; pc++ )
    str += *pc;

  return str;
}

/// get all characters before the last occurence of ch
/// (returns empty string if ch not found)
wxString wxString::BeforeLast(wxChar ch) const
{
  wxString str;
  int iPos = Find(ch, TRUE);
  if ( iPos != wxNOT_FOUND && iPos != 0 )
    str = wxString(c_str(), iPos);

  return str;
}

/// get all characters after the first occurence of ch
/// (returns empty string if ch not found)
wxString wxString::AfterFirst(wxChar ch) const
{
  wxString str;
  int iPos = Find(ch);
  if ( iPos != wxNOT_FOUND )
    str = c_str() + iPos + 1;

  return str;
}

// replace first (or all) occurences of some substring with another one
size_t wxString::Replace(const wxChar *szOld, const wxChar *szNew, bool bReplaceAll)
{
  size_t uiCount = 0;   // count of replacements made

  size_t uiOldLen = wxStrlen(szOld);

  wxString strTemp;
  const wxChar *pCurrent = m_pchData;
  const wxChar *pSubstr;
  while ( *pCurrent != wxT('\0') ) {
    pSubstr = wxStrstr(pCurrent, szOld);
    if ( pSubstr == NULL ) {
      // strTemp is unused if no replacements were made, so avoid the copy
      if ( uiCount == 0 )
        return 0;

      strTemp += pCurrent;    // copy the rest
      break;                  // exit the loop
    }
    else {
      // take chars before match
      if ( !strTemp.ConcatSelf(pSubstr - pCurrent, pCurrent) ) {
        wxFAIL_MSG( _T("out of memory in wxString::Replace") );
        return 0;
      }
      strTemp += szNew;
      pCurrent = pSubstr + uiOldLen;  // restart after match

      uiCount++;

      // stop now?
      if ( !bReplaceAll ) {
        strTemp += pCurrent;    // copy the rest
        break;                  // exit the loop
      }
    }
  }

  // only done if there were replacements, otherwise would have returned above
  *this = strTemp;

  return uiCount;
}

bool wxString::IsAscii() const
{
  const wxChar *s = (const wxChar*) *this;
  while(*s){
    if(!isascii(*s)) return(FALSE);
    s++;
  }
  return(TRUE);
}

bool wxString::IsWord() const
{
  const wxChar *s = (const wxChar*) *this;
  while(*s){
    if(!wxIsalpha(*s)) return(FALSE);
    s++;
  }
  return(TRUE);
}

bool wxString::IsNumber() const
{
  const wxChar *s = (const wxChar*) *this;
  if (wxStrlen(s))
     if ((s[0] == '-') || (s[0] == '+')) s++;
  while(*s){
    if(!wxIsdigit(*s)) return(FALSE);
    s++;
  }
  return(TRUE);
}

wxString wxString::Strip(stripType w) const
{
    wxString s = *this;
    if ( w & leading ) s.Trim(FALSE);
    if ( w & trailing ) s.Trim(TRUE);
    return s;
}

// ---------------------------------------------------------------------------
// case conversion
// ---------------------------------------------------------------------------

wxString& wxString::MakeUpper()
{
  if ( !CopyBeforeWrite() ) {
    wxFAIL_MSG( _T("out of memory in wxString::MakeUpper") );
    return *this;
  }
    
  for ( wxChar *p = m_pchData; *p; p++ )
    *p = (wxChar)wxToupper(*p);

  return *this;
}

wxString& wxString::MakeLower()
{
  if ( !CopyBeforeWrite() ) {
    wxFAIL_MSG( _T("out of memory in wxString::MakeLower") );
    return *this;
  }

  for ( wxChar *p = m_pchData; *p; p++ )
    *p = (wxChar)wxTolower(*p);

  return *this;
}

// ---------------------------------------------------------------------------
// trimming and padding
// ---------------------------------------------------------------------------

// some compilers (VC++ 6.0 not to name them) return TRUE for a call to