wxWidgets/include/wx/buffer.h

///////////////////////////////////////////////////////////////////////////////
// Name:        wx/buffer.h
// Purpose:     auto buffer classes: buffers which automatically free memory
// Author:      Vadim Zeitlin
// Modified by:
// Created:     12.04.99
// RCS-ID:      $Id$
// Copyright:   (c) 1998 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
// Licence:     wxWindows licence
///////////////////////////////////////////////////////////////////////////////

#ifndef _WX_BUFFER_H
#define _WX_BUFFER_H

#include "wx/chartype.h"
#include "wx/wxcrtbase.h"

#include <stdlib.h>             // malloc() and free()

class WXDLLIMPEXP_FWD_BASE wxCStrData;

// ----------------------------------------------------------------------------
// Special classes for (wide) character strings: they use malloc/free instead
// of new/delete
// ----------------------------------------------------------------------------

template <typename T>
class WXDLLIMPEXP_BASE wxCharTypeBuffer
{
public:
    typedef T CharType;

    wxCharTypeBuffer(const CharType *str = NULL)
        : m_str(str ? wxStrdup(str) : NULL),
          m_owned(true)
    {
    }

    wxCharTypeBuffer(size_t len)
        : m_str((CharType *)malloc((len + 1)*sizeof(CharType))),
          m_owned(true)
    {
        m_str[len] = (CharType)0;
    }

    static const wxCharTypeBuffer CreateNonOwned(const CharType *str)
    {
        wxCharTypeBuffer buf;
        buf.m_str = wx_const_cast(CharType*, str);
        buf.m_owned = false;
        return buf;
    }

    /* no need to check for NULL, free() does it */
    ~wxCharTypeBuffer()
    {
        if ( m_owned)
            free(m_str);
    }

    /*
        WARNING:

        the copy ctor and assignment operators change the passed in object
        even although it is declared as "const", so:

        a) it shouldn't be really const
        b) you shouldn't use it afterwards (or know that it was reset)

        This is very ugly but is unfortunately needed to make the normal use
        of wxCharTypeBuffer buffer objects possible and is very similar to what
        std::auto_ptr<> does (as if it were an excuse...)
    */

    /*
       because of the remark above, release() is declared const even if it
       isn't really const
     */
    CharType *release() const
    {
        wxASSERT_MSG( m_owned, _T("can't release non-owned buffer") );
        return DoRelease();
    }

    void reset()
    {
        if ( m_owned )
            free(m_str);
        m_str = NULL;
    }

    wxCharTypeBuffer(const wxCharTypeBuffer& src)
    {
        CopyFrom(src);
    }

    wxCharTypeBuffer& operator=(const CharType *str)
    {
        if ( m_owned )
            free(m_str);
        m_str = str ? wxStrdup(str) : NULL;
        m_owned = true;
        return *this;
    }

    wxCharTypeBuffer& operator=(const wxCharTypeBuffer& src)
    {
        if ( m_owned )
            free(m_str);
        CopyFrom(src);
        return *this;
    }

    bool extend(size_t len)
    {
        wxASSERT_MSG( m_owned, _T("cannot extend non-owned buffer") );

        CharType *
            str = (CharType *)realloc(m_str, (len + 1)*sizeof(CharType));
        if ( !str )
            return false;

        m_str = str;

        return true;
    }

    CharType *data() { return m_str; }
    const CharType *data() const { return m_str; }
    operator const CharType *() const { return m_str; }
    CharType operator[](size_t n) const { return m_str[n]; }


private:
    CharType *DoRelease() const
    {
        CharType *p = m_str;
        ((wxCharTypeBuffer *)this)->m_str = NULL;
        return p;
    }

    void CopyFrom(const wxCharTypeBuffer& src)
    {
        m_owned = src.m_owned;
        m_str = src.DoRelease();
    }

private:
    CharType *m_str;
    bool m_owned;
};

WXDLLIMPEXP_TEMPLATE_INSTANCE_BASE( wxCharTypeBuffer<char> )

class WXDLLIMPEXP_BASE wxCharBuffer : public wxCharTypeBuffer<char>
{
public:
    typedef wxCharTypeBuffer<char> wxCharTypeBufferBase;

    wxCharBuffer(const wxCharTypeBufferBase& buf)
        : wxCharTypeBufferBase(buf) {}

    wxCharBuffer(const CharType *str = NULL) : wxCharTypeBufferBase(str) {}
    wxCharBuffer(size_t len) : wxCharTypeBufferBase(len) {}

    wxCharBuffer(const wxCStrData& cstr);
};

#if wxUSE_WCHAR_T
WXDLLIMPEXP_TEMPLATE_INSTANCE_BASE( wxCharTypeBuffer<wchar_t> )

class WXDLLIMPEXP_BASE wxWCharBuffer : public wxCharTypeBuffer<wchar_t>
{
public:
    typedef wxCharTypeBuffer<wchar_t> wxCharTypeBufferBase;

    wxWCharBuffer(const wxCharTypeBufferBase& buf)
        : wxCharTypeBufferBase(buf) {}

    wxWCharBuffer(const CharType *str = NULL) : wxCharTypeBufferBase(str) {}
    wxWCharBuffer(size_t len) : wxCharTypeBufferBase(len) {}

    wxWCharBuffer(const wxCStrData& cstr);
};
#endif // wxUSE_WCHAR_T

// wxCharTypeBuffer<T> implicitly convertible to T*
template <typename T>
class wxWritableCharTypeBuffer : public wxCharTypeBuffer<T>
{
public:
    typedef typename wxCharTypeBuffer<T>::CharType CharType;

    wxWritableCharTypeBuffer(const wxCharTypeBuffer<T>& src)
        : wxCharTypeBuffer<T>(src) {}
    // FIXME-UTF8: this won't be needed after converting mb_str()/wc_str() to
    //             always return a buffer
    wxWritableCharTypeBuffer(const CharType *str = NULL)
        : wxCharTypeBuffer<T>(str) {}

    operator CharType*() { return this->data(); }
};

typedef wxWritableCharTypeBuffer<char> wxWritableCharBuffer;
typedef wxWritableCharTypeBuffer<wchar_t> wxWritableWCharBuffer;


#if wxUSE_UNICODE
    #define wxWxCharBuffer wxWCharBuffer

    #define wxMB2WXbuf wxWCharBuffer
    #define wxWX2MBbuf wxCharBuffer
    #if wxUSE_UNICODE_WCHAR
        #define wxWC2WXbuf wxChar*
        #define wxWX2WCbuf wxChar*
    #elif wxUSE_UNICODE_UTF8
        #define wxWC2WXbuf wxWCharBuffer
        #define wxWX2WCbuf wxWCharBuffer
    #endif
#else // ANSI
    #define wxWxCharBuffer wxCharBuffer

    #define wxMB2WXbuf wxChar*
    #define wxWX2MBbuf wxChar*
    #define wxWC2WXbuf wxCharBuffer
    #define wxWX2WCbuf wxWCharBuffer
#endif // Unicode/ANSI

// type of the value returned by wxString::utf8_str()
#if wxUSE_UNICODE_UTF8
    #define wxUTF8Buf char *
#else
    #define wxUTF8Buf wxCharBuffer
#endif

// ----------------------------------------------------------------------------
// A class for holding growable data buffers (not necessarily strings)
// ----------------------------------------------------------------------------

// This class manages the actual data buffer pointer and is ref-counted.
class wxMemoryBufferData
{
public:
    // the initial size and also the size added by ResizeIfNeeded()
    enum { DefBufSize = 1024 };

    friend class wxMemoryBuffer;

    // everyting is private as it can only be used by wxMemoryBuffer
private:
    wxMemoryBufferData(size_t size = wxMemoryBufferData::DefBufSize)
        : m_data(size ? malloc(size) : NULL), m_size(size), m_len(0), m_ref(0)
    {
    }
    ~wxMemoryBufferData() { free(m_data); }


    void ResizeIfNeeded(size_t newSize)
    {
        if (newSize > m_size)
        {
            void *dataOld = m_data;
            m_data = realloc(m_data, newSize + wxMemoryBufferData::DefBufSize);
            if ( !m_data )
            {
                free(dataOld);
            }

            m_size = newSize + wxMemoryBufferData::DefBufSize;
        }
    }

    void IncRef() { m_ref += 1; }
    void DecRef()
    {
        m_ref -= 1;
        if (m_ref == 0)  // are there no more references?
            delete this;
    }


    // the buffer containing the data
    void  *m_data;

    // the size of the buffer
    size_t m_size;

    // the amount of data currently in the buffer
    size_t m_len;

    // the reference count
    size_t m_ref;

    DECLARE_NO_COPY_CLASS(wxMemoryBufferData)
};


class WXDLLIMPEXP_BASE wxMemoryBuffer
{
public:
    // ctor and dtor
    wxMemoryBuffer(size_t size = wxMemoryBufferData::DefBufSize)
    {
        m_bufdata = new wxMemoryBufferData(size);
        m_bufdata->IncRef();
    }

    ~wxMemoryBuffer() { m_bufdata->DecRef(); }


    // copy and assignment
    wxMemoryBuffer(const wxMemoryBuffer& src)
        : m_bufdata(src.m_bufdata)
    {
        m_bufdata->IncRef();
    }

    wxMemoryBuffer& operator=(const wxMemoryBuffer& src)
    {
        m_bufdata->DecRef();
        m_bufdata = src.m_bufdata;
        m_bufdata->IncRef();
        return *this;
    }


    // Accessors
    void  *GetData() const    { return m_bufdata->m_data; }
    size_t GetBufSize() const { return m_bufdata->m_size; }
    size_t GetDataLen() const { return m_bufdata->m_len; }

    void   SetBufSize(size_t size) { m_bufdata->ResizeIfNeeded(size); }
    void   SetDataLen(size_t len)
    {
        wxASSERT(len <= m_bufdata->m_size);
        m_bufdata->m_len = len;
    }

    // Ensure the buffer is big enough and return a pointer to it
    void *GetWriteBuf(size_t sizeNeeded)
    {
        m_bufdata->ResizeIfNeeded(sizeNeeded);
        return m_bufdata->m_data;
    }

    // Update the length after the write
    void  UngetWriteBuf(size_t sizeUsed) { SetDataLen(sizeUsed); }

    // Like the above, but appends to the buffer
    void *GetAppendBuf(size_t sizeNeeded)
    {
        m_bufdata->ResizeIfNeeded(m_bufdata->m_len + sizeNeeded);
        return (char*)m_bufdata->m_data + m_bufdata->m_len;
    }

    // Update the length after the append
    void  UngetAppendBuf(size_t sizeUsed)
    {
        SetDataLen(m_bufdata->m_len + sizeUsed);
    }

    // Other ways to append to the buffer
    void  AppendByte(char data)
    {
        wxCHECK_RET( m_bufdata->m_data, _T("invalid wxMemoryBuffer") );

        m_bufdata->ResizeIfNeeded(m_bufdata->m_len + 1);
        *(((char*)m_bufdata->m_data) + m_bufdata->m_len) = data;
        m_bufdata->m_len += 1;
    }

    void  AppendData(const void *data, size_t len)
    {
        memcpy(GetAppendBuf(len), data, len);
        UngetAppendBuf(len);
    }

    operator const char *() const { return (const char*)GetData(); }

private:
    wxMemoryBufferData*  m_bufdata;
};

// ----------------------------------------------------------------------------
// template class for any kind of data
// ----------------------------------------------------------------------------

// TODO

#endif // _WX_BUFFER_H