cpl_vsi_mem.cpp

用于读取TAB、MIF、SHP文件的类

/******************************************************************************
 * $Id: cpl_vsi_mem.cpp,v 1.12 2006/06/30 14:25:24 dron Exp $
 *
 * Project:  VSI Virtual File System
 * Purpose:  Implementation of Memory Buffer virtual IO functions.
 * Author:   Frank Warmerdam, [e-mail]
 *
 ******************************************************************************
 * Copyright (c) 2005, Frank Warmerdam <[e-mail]>
 *
 * 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, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 ******************************************************************************
 *
 * $Log: cpl_vsi_mem.cpp,v $
 * Revision 1.12  2006/06/30 14:25:24  dron
 * Avoid warnings on win/64.
 *
 * Revision 1.11  2006/03/27 15:24:41  fwarmerdam
 * buffer in FWrite is const
 *
 * Revision 1.10  2006/02/24 23:06:18  mloskot
 * Fix missing namespace in string type usage
 * Bug reported by Thom DeCarlo in the [Gdal-dev] problem compiling with VS.NET post on the list.
 *
 * Revision 1.9  2006/02/19 21:54:34  mloskot
 * [WINCE] Changes related to Windows CE port of CPL. Most changes are #ifdef wrappers.
 *
 * Revision 1.8  2006/01/19 23:54:07  fwarmerdam
 * Protect access to oFileList in VSIGetMemFileBuffer() and VSIFileFromMemBuffer().
 *
 * Revision 1.7  2006/01/11 02:35:56  fwarmerdam
 * Fixed mutex cleanup.
 *
 * Revision 1.6  2006/01/11 00:39:40  fwarmerdam
 * protect oFileList with a mutex (bug 1031)
 *
 * Revision 1.5  2005/10/07 00:26:27  fwarmerdam
 * add documentation
 *
 * Revision 1.4  2005/09/12 16:50:37  fwarmerdam
 * added VSIMemFile buffer fetcher
 *
 * Revision 1.3  2005/09/12 00:37:55  fwarmerdam
 * fixed ownership in buffer to file function
 *
 * Revision 1.2  2005/09/11 18:32:07  fwarmerdam
 * tweak bigint expression to avoid vc6 problems
 *
 * Revision 1.1  2005/09/11 18:00:30  fwarmerdam
 * New
 *
 */

/* Remove annoying warnings in eVC++ and VC++ 6.0 */
#if defined(WIN32CE)
#  pragma warning(disable:4786)
#endif

#include "cpl_vsi_private.h"
#include "cpl_string.h"
#include "cpl_multiproc.h"
#include <map>

#if defined(WIN32CE)
#  include <wce_errno.h>
#endif


CPL_CVSID("$Id: cpl_vsi_mem.cpp,v 1.12 2006/06/30 14:25:24 dron Exp $");

/*
** Notes on Multithreading:
**
** VSIMemFilesystemHandler: This class maintains a mutex to protect
** access and update of the oFileList array which has all the "files" in 
** the memory filesystem area.  It is expected that multiple threads would
** want to create and read different files at the same time and so might
** collide access oFileList without the mutex.
**
** VSIMemFile: In theory we could allow different threads to update the
** the same memory file, but for simplicity we restrict to single writer,
** multiple reader as an expectation on the application code (not enforced
** here), which means we don't need to do any protection of this class.
**
** VSIMemHandle: This is essentially a "current location" representing
** on accessor to a file, and is inherently intended only to be used in 
** a single thread. 
**
** In General:
**
** Multiple threads accessing the memory filesystem are ok as long as
**  1) A given VSIMemHandle (ie. FILE * at app level) isn't used by multiple 
**     threads at once. 
**  2) A given memory file isn't accessed by more than one thread unless
**     all threads are just reading.
*/ 

/************************************************************************/
/* ==================================================================== */
/*                              VSIMemFile                              */
/* ==================================================================== */
/************************************************************************/

class VSIMemFile
{
public:
    CPLString     osFilename;
    int           nRefCount;

    int           bIsDirectory;

    int           bOwnData;
    GByte        *pabyData;
    vsi_l_offset  nLength;
    vsi_l_offset  nAllocLength;

                  VSIMemFile();
    virtual       ~VSIMemFile();

    bool          SetLength( vsi_l_offset nNewSize );
};

/************************************************************************/
/* ==================================================================== */
/*                             VSIMemHandle                             */
/* ==================================================================== */
/************************************************************************/

class VSIMemHandle : public VSIVirtualHandle
{ 
  public:
    VSIMemFile    *poFile;
    vsi_l_offset  nOffset;

    virtual int       Seek( vsi_l_offset nOffset, int nWhence );
    virtual vsi_l_offset Tell();
    virtual size_t    Read( void *pBuffer, size_t nSize, size_t nMemb );
    virtual size_t    Write( const void *pBuffer, size_t nSize, size_t nMemb );
    virtual int       Eof();
    virtual int       Close();
};

/************************************************************************/
/* ==================================================================== */
/*                       VSIMemFilesystemHandler                        */
/* ==================================================================== */
/************************************************************************/

class VSIMemFilesystemHandler : public VSIFilesystemHandler 
{
public:
    std::map<CPLString,VSIMemFile*>   oFileList;
    void             *hMutex;

                     VSIMemFilesystemHandler();
    virtual          ~VSIMemFilesystemHandler();

    virtual VSIVirtualHandle *Open( const char *pszFilename, 
                                    const char *pszAccess);
    virtual int      Stat( const char *pszFilename, VSIStatBufL *pStatBuf );
    virtual int      Unlink( const char *pszFilename );
    virtual int      Mkdir( const char *pszDirname, long nMode );
    virtual int      Rmdir( const char *pszDirname );
    virtual char   **ReadDir( const char *pszDirname );
};

/************************************************************************/
/* ==================================================================== */
/*                              VSIMemFile                              */
/* ==================================================================== */
/************************************************************************/

/************************************************************************/
/*                             VSIMemFile()                             */
/************************************************************************/

VSIMemFile::VSIMemFile()

{
    nRefCount = 0;
    bIsDirectory = FALSE;
    bOwnData = TRUE;
    pabyData = NULL;
    nLength = 0;
    nAllocLength = 0;
}

/************************************************************************/
/*                            ~VSIMemFile()                             */
/************************************************************************/

VSIMemFile::~VSIMemFile()

{
    if( nRefCount != 0 )
        CPLDebug( "VSIMemFile", "Memory file %s deleted with %d references.",
                  osFilename.c_str(), nRefCount );

    if( bOwnData && pabyData )
        CPLFree( pabyData );
}

/************************************************************************/
/*                             SetLength()                              */
/************************************************************************/

bool VSIMemFile::SetLength( vsi_l_offset nNewLength )

{
/* -------------------------------------------------------------------- */
/*      Grow underlying array if needed.                                */
/* -------------------------------------------------------------------- */
    if( nNewLength > nAllocLength )
    {
        GByte *pabyNewData;
        vsi_l_offset nNewAlloc = (nNewLength + nNewLength / 10) + 5000;

        pabyNewData = (GByte *) CPLRealloc(pabyData, (size_t)nNewAlloc);
        if( pabyNewData == NULL )
            return false;

        pabyData = pabyNewData;
        nAllocLength = nNewAlloc;
    }

    nLength = nNewLength;

    return true;
}

/************************************************************************/
/* ==================================================================== */
/*                             VSIMemHandle                             */
/* ==================================================================== */
/************************************************************************/


/************************************************************************/
/*                               Close()                                */
/************************************************************************/

int VSIMemHandle::Close()

{
    poFile->nRefCount--;
    poFile = NULL;

    return 0;
}

/************************************************************************/
/*                                Seek()                                */
/************************************************************************/

int VSIMemHandle::Seek( vsi_l_offset nOffset, int nWhence )

{
    if( nWhence == SEEK_CUR )
        this->nOffset += nOffset;
    else if( nWhence == SEEK_SET )
        this->nOffset = nOffset;
    else if( nWhence == SEEK_END )
        this->nOffset = poFile->nLength + nOffset;
    else
    {
        errno = EINVAL;
        return -1;
    }

    if( this->nOffset < 0 )
    {
        this->nOffset = 0;
        return -1;
    }
    
    if( this->nOffset > poFile->nLength )
    {
        if( !poFile->SetLength( this->nOffset ) )
            return -1;
    }

    return 0;
}

/************************************************************************/
/*                                Tell()                                */
/************************************************************************/

vsi_l_offset VSIMemHandle::Tell()

{
    return nOffset;
}

/************************************************************************/
/*                                Read()                                */
/************************************************************************/

size_t VSIMemHandle::Read( void * pBuffer, size_t nSize, size_t nCount )

{
    // FIXME: Integer overflow check should be placed here:
    size_t nBytesToRead = nSize * nCount; 

    if( nBytesToRead + nOffset > poFile->nLength )
    {
        nBytesToRead = poFile->nLength - nOffset;
        nCount = nBytesToRead / nSize;
    }

    memcpy( pBuffer, poFile->pabyData + nOffset, (size_t)nBytesToRead );
    nOffset += nBytesToRead;

    return nCount;
}

/************************************************************************/
/*                               Write()                                */
/************************************************************************/

size_t VSIMemHandle::Write( const void * pBuffer, size_t nSize, size_t nCount )

{
    // FIXME: Integer overflow check should be placed here:
    size_t nBytesToWrite = nSize * nCount; 

    if( nBytesToWrite + nOffset > poFile->nLength )
    {
        if( !poFile->SetLength( nBytesToWrite + nOffset ) )
            return 0;
    }

    memcpy( poFile->pabyData + nOffset, pBuffer, nBytesToWrite );
    nOffset += nBytesToWrite;

    return nCount;
}

/************************************************************************/
/*                                Eof()                                 */
/************************************************************************/

int VSIMemHandle::Eof()

{
    return nOffset == poFile->nLength;
}

/************************************************************************/
/* ==================================================================== */
/*                       VSIMemFilesystemHandler                        */
/* ==================================================================== */
/************************************************************************/