Programming Languages Suite/ProgLangD.iso/C++-7/DISK10/MFC/SRC/STRING.CP$/string

Text File | 1992-03-10 | 7.0 KB | 292 lines

// This is a part of the Microsoft Foundation Classes C++ library.
// Copyright (C) 1992 Microsoft Corporation
// All rights reserved.
//
// This source code is only intended as a supplement to the
// Microsoft Foundation Classes Reference and Microsoft
// QuickHelp documentation provided with the library.
// See these sources for detailed information regarding the
// Microsoft Foundation Classes product.


#include "afx.h"
#pragma hdrstop
#include <limits.h>

#ifdef AFX_CORE_SEG
#pragma code_seg(AFX_CORE_SEG)
#endif

#ifdef _DEBUG
#undef THIS_FILE
static char BASED_CODE THIS_FILE[] = __FILE__;
#endif

#define new DEBUG_NEW

/////////////////////////////////////////////////////////////////////////////
// static class data, special inlines

char _afxChNil = '\0';

// For an empty string, m_???Data will point here
// (note: avoids a lot of NULL pointer tests when we call standard
//  C runtime libraries

extern const CString NEAR afxEmptyString;
const CString NEAR afxEmptyString;

void CString::Init()
{
    m_nDataLength = m_nAllocLength = 0;
    m_pchData = &_afxChNil;
}

//////////////////////////////////////////////////////////////////////////////
// Construction/Destruction

CString::CString()
{
    Init();
}

CString::CString(const CString& stringSrc)
{
    // if constructing a CString from another CString, we make a copy of the
    // original string data to enforce value semantics (i.e. each string
    // gets a copy of it's own

    stringSrc.AllocCopy(*this, stringSrc.m_nDataLength, 0, 0);
}

void CString::AllocBuffer(int nLen)
 // always allocate one extra character for '\0' termination
 // assumes [optimistically] that data length will equal allocation length
{
    ASSERT(nLen >= 0);
    ASSERT(nLen < INT_MAX - 1); // max size (enough room for 1 extra)

    if (nLen == 0)
    {
        Init();
    }
    else
    {
        m_pchData = new char[nLen+1];       // may throw an exception
        m_pchData[nLen] = '\0';
        m_nDataLength = nLen;
        m_nAllocLength = nLen;
    }
}

void CString::Empty()
{
    if (m_pchData != &_afxChNil)
    {
        delete [] m_pchData;
        Init();
    }
    ASSERT(m_nDataLength == 0);
    ASSERT(m_nAllocLength == 0);
}

CString::~CString()
 //  free any attached data
{
    if (m_pchData != &_afxChNil)
        delete [] m_pchData;        // NOTE: not type safe
}

//////////////////////////////////////////////////////////////////////////////
// Helpers for the rest of the implementation

static inline int SafeStrlen(const char* psz)
    { return (psz == NULL) ? NULL : strlen(psz); }

void CString::AllocCopy(CString& dest, int nCopyLen, int nCopyIndex,
     int nExtraLen) const
{
    // will clone the data attached to this string
    // allocating 'nExtraLen' characters
    // Places results in uninitialized string 'dest'
    // Will copy the part or all of original data to start of new string

    int nNewLen = nCopyLen + nExtraLen;

    if (nNewLen == 0)
    {
        dest.Init();
    }
    else
    {
        dest.AllocBuffer(nNewLen);
        memcpy(dest.m_pchData, &m_pchData[nCopyIndex], nCopyLen);
    }
}

//////////////////////////////////////////////////////////////////////////////
// More sophisticated construction

CString::CString(const char* psz)
{
    int nLen;
    if ((nLen = SafeStrlen(psz)) == 0)
        Init();
    else
    {
        AllocBuffer(nLen);
        memcpy(m_pchData, psz, nLen);
    }
}

//////////////////////////////////////////////////////////////////////////////
// Diagnostic support

#ifdef _DEBUG

CDumpContext&
operator <<(CDumpContext& dc, const CString& string)
{
    dc << string.m_pchData;
    return dc;
}

#endif //_DEBUG

//////////////////////////////////////////////////////////////////////////////
// Assignment operators
//  All assign a new value to the string
//      (a) first see if the buffer is big enough
//      (b) if enough room, copy on top of old buffer, set size and type
//      (c) otherwise free old string data, and create a new one
//
//  All routines return the new string (but as a 'const CString&' so that
//      assigning it again will cause a copy, eg: s1 = s2 = "hi there".
//

void CString::AssignCopy(int nSrcLen, const char* pszSrcData)
{
    // check if it will fit
    if (nSrcLen > m_nAllocLength)
    {
        // it won't fit, allocate another one
        Empty();
        AllocBuffer(nSrcLen);
    }
    if (nSrcLen != 0)
        memcpy(m_pchData, pszSrcData, nSrcLen);
    m_nDataLength = nSrcLen;
    m_pchData[nSrcLen] = '\0';
}

const CString&
CString::operator =(const CString& stringSrc)
{
    AssignCopy(stringSrc.m_nDataLength, stringSrc.m_pchData);
    return *this;
}

const CString&
CString::operator =(const char* psz)
{
    AssignCopy(SafeStrlen(psz), psz);
    return *this;
}


//////////////////////////////////////////////////////////////////////////////
// concatenation

// NOTE: "operator +" is done as friend functions for simplicity
//      There are three variants:
//          CString + CString
// and for ? = char, const char*
//          CString + ?
//          ? + CString

void
CString::ConcatCopy(int nSrc1Len, const char* pszSrc1Data,
        int nSrc2Len, const char* pszSrc2Data)
{
  // -- master concatenation routine
  // Concatenate two sources
  // -- assume that 'this' is a new CString object

    int nNewLen = nSrc1Len + nSrc2Len;
    AllocBuffer(nNewLen);
    memcpy(m_pchData, pszSrc1Data, nSrc1Len);
    memcpy(&m_pchData[nSrc1Len], pszSrc2Data, nSrc2Len);
}

CString
operator +(const CString& string1, const CString& string2)
{
    CString s;
    s.ConcatCopy(string1.m_nDataLength, string1.m_pchData,
        string2.m_nDataLength, string2.m_pchData);
    return s;
}

CString
operator +(const CString& string, const char* psz)
{
    CString s;
    s.ConcatCopy(string.m_nDataLength, string.m_pchData, SafeStrlen(psz), psz);
    return s;
}


CString
operator +(const char* psz, const CString& string)
{
    CString s;
    s.ConcatCopy(SafeStrlen(psz), psz, string.m_nDataLength, string.m_pchData);
    return s;
}

//////////////////////////////////////////////////////////////////////////////
// concatenate in place

void
CString::ConcatInPlace(int nSrcLen, const char* pszSrcData)
{
    //  -- the main routine for += operators

    // if the buffer is too small, or we have a width mis-match, just
    //   allocate a new buffer (slow but sure)
    if (m_nDataLength + nSrcLen > m_nAllocLength)
    {
        // we have to grow the buffer, use the Concat in place routine
        char* pszOldData = m_pchData;
        ConcatCopy(m_nDataLength, pszOldData, nSrcLen, pszSrcData);
        ASSERT(pszOldData != NULL);
        if (pszOldData != &_afxChNil)
            delete [] pszOldData;
    }
    else
    {
        // fast concatenation when buffer big enough
        memcpy(&m_pchData[m_nDataLength], pszSrcData, nSrcLen);
        m_nDataLength += nSrcLen;
    }
    ASSERT(m_nDataLength <= m_nAllocLength);
    m_pchData[m_nDataLength] = '\0';
}

const CString&
CString::operator +=(const char* psz)
{
    ConcatInPlace(SafeStrlen(psz), psz);
    return *this;
}

const CString&
CString::operator +=(const CString& string)
{
    ConcatInPlace(string.m_nDataLength, string.m_pchData);
    return *this;
}


///////////////////////////////////////////////////////////////////////////////