cpl_vsil_stdout.cpp

/**********************************************************************
 *
 * Project:  CPL - Common Portability Library
 * Purpose:  Implement VSI large file api for stdout
 * Author:   Even Rouault, <even dot rouault at spatialys.com>
 *
 **********************************************************************
 * Copyright (c) 2010-2013, Even Rouault <even dot rouault at spatialys.com>
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/

#include "cpl_port.h"
#include "cpl_vsi.h"

#include <cstddef>
#include <cstdio>
#include <cstring>
#if HAVE_FCNTL_H
#include <fcntl.h>
#endif

#include "cpl_error.h"
#include "cpl_vsi_virtual.h"

#ifdef _WIN32
#include <io.h>
#include <fcntl.h>
#endif

static VSIWriteFunction pWriteFunction = fwrite;
static FILE *pWriteStream = stdout;

/************************************************************************/
/*                        VSIStdoutSetRedirection()                     */
/************************************************************************/

/** Set an alternative write function and output file handle instead of
 *  fwrite() / stdout.
 *
 * @param pFct Function with same signature as fwrite()
 * @param stream File handle on which to output. Passed to pFct.
 *
 * @since GDAL 2.0
 */
void VSIStdoutSetRedirection(VSIWriteFunction pFct, FILE *stream)
{
    pWriteFunction = pFct;
    pWriteStream = stream;
}

//! @cond Doxygen_Suppress

/************************************************************************/
/* ==================================================================== */
/*                       VSIStdoutFilesystemHandler                     */
/* ==================================================================== */
/************************************************************************/

class VSIStdoutFilesystemHandler final : public VSIFilesystemHandler
{
    CPL_DISALLOW_COPY_ASSIGN(VSIStdoutFilesystemHandler)

  public:
    VSIStdoutFilesystemHandler() = default;

    VSIVirtualHandle *Open(const char *pszFilename, const char *pszAccess,
                           bool bSetError,
                           CSLConstList /* papszOptions */) override;
    int Stat(const char *pszFilename, VSIStatBufL *pStatBuf,
             int nFlags) override;

    bool SupportsRead(const char * /* pszPath */) override
    {
        return false;
    }
};

/************************************************************************/
/* ==================================================================== */
/*                        VSIStdoutHandle                               */
/* ==================================================================== */
/************************************************************************/

class VSIStdoutHandle final : public VSIVirtualHandle
{
    CPL_DISALLOW_COPY_ASSIGN(VSIStdoutHandle)

    vsi_l_offset m_nOffset = 0;
    bool m_bError = false;

  public:
    VSIStdoutHandle() = default;
    ~VSIStdoutHandle() override = default;

    int Seek(vsi_l_offset nOffset, int nWhence) override;
    vsi_l_offset Tell() override;
    size_t Read(void *pBuffer, size_t nSize, size_t nMemb) override;
    size_t Write(const void *pBuffer, size_t nSize, size_t nMemb) override;

    void ClearErr() override
    {
        m_bError = false;
    }

    int Error() override
    {
        return m_bError;
    }

    int Eof() override
    {
        return FALSE;
    }

    int Flush() override;
    int Close() override;
};

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

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

{
    if (nOffset == 0 && (nWhence == SEEK_END || nWhence == SEEK_CUR))
        return 0;
    if (nWhence == SEEK_SET && nOffset == Tell())
        return 0;
    CPLError(CE_Failure, CPLE_NotSupported, "Seek() unsupported on /vsistdout");
    return -1;
}

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

vsi_l_offset VSIStdoutHandle::Tell()
{
    return m_nOffset;
}

/************************************************************************/
/*                               Flush()                                */
/************************************************************************/

int VSIStdoutHandle::Flush()

{
    if (pWriteStream == stdout)
        return fflush(stdout);
    else
        return 0;
}

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

size_t VSIStdoutHandle::Read(void * /* pBuffer */, size_t nSize, size_t nCount)
{
    if (nSize > 0 && nCount > 0)
    {
        CPLError(CE_Failure, CPLE_NotSupported,
                 "Read() unsupported on /vsistdout");
        m_bError = true;
    }
    return 0;
}

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

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

{
    size_t nRet = pWriteFunction(pBuffer, nSize, nCount, pWriteStream);
    m_nOffset += nSize * nRet;
    return nRet;
}

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

int VSIStdoutHandle::Close()

{
    return Flush();
}

/************************************************************************/
/* ==================================================================== */
/*                       VSIStdoutFilesystemHandler                     */
/* ==================================================================== */
/************************************************************************/

/************************************************************************/
/*                                Open()                                */
/************************************************************************/

VSIVirtualHandle *
VSIStdoutFilesystemHandler::Open(const char * /* pszFilename */,
                                 const char *pszAccess, bool /* bSetError */,
                                 CSLConstList /* papszOptions */)
{
    if (strchr(pszAccess, 'r') != nullptr || strchr(pszAccess, '+') != nullptr)
    {
        CPLError(CE_Failure, CPLE_NotSupported,
                 "Read or update mode not supported on /vsistdout");
        return nullptr;
    }

#ifdef _WIN32
    if (strchr(pszAccess, 'b') != nullptr)
        setmode(fileno(stdout), O_BINARY);
#endif

    return new VSIStdoutHandle;
}

/************************************************************************/
/*                                Stat()                                */
/************************************************************************/

int VSIStdoutFilesystemHandler::Stat(const char * /* pszFilename */,
                                     VSIStatBufL *pStatBuf, int /* nFlags */)

{
    memset(pStatBuf, 0, sizeof(VSIStatBufL));

    return -1;
}

/************************************************************************/
/* ==================================================================== */
/*                   VSIStdoutRedirectFilesystemHandler                 */
/* ==================================================================== */
/************************************************************************/

class VSIStdoutRedirectFilesystemHandler final : public VSIFilesystemHandler
{
  public:
    VSIVirtualHandle *Open(const char *pszFilename, const char *pszAccess,
                           bool bSetError,
                           CSLConstList /* papszOptions */) override;
    int Stat(const char *pszFilename, VSIStatBufL *pStatBuf,
             int nFlags) override;

    bool SupportsRead(const char * /* pszPath */) override
    {
        return false;
    }
};

/************************************************************************/
/* ==================================================================== */
/*                        VSIStdoutRedirectHandle                       */
/* ==================================================================== */
/************************************************************************/

class VSIStdoutRedirectHandle final : public VSIVirtualHandle
{
    VSIVirtualHandle *m_poHandle = nullptr;
    bool m_bError = false;

    CPL_DISALLOW_COPY_ASSIGN(VSIStdoutRedirectHandle)

  public:
    explicit VSIStdoutRedirectHandle(VSIVirtualHandle *poHandle);
    ~VSIStdoutRedirectHandle() override;

    int Seek(vsi_l_offset nOffset, int nWhence) override;
    vsi_l_offset Tell() override;
    size_t Read(void *pBuffer, size_t nSize, size_t nMemb) override;
    size_t Write(const void *pBuffer, size_t nSize, size_t nMemb) override;

    void ClearErr() override
    {
        m_bError = false;
    }

    int Error() override
    {
        return m_bError;
    }

    int Eof() override
    {
        return FALSE;
    }

    int Flush() override;
    int Close() override;
};

/************************************************************************/
/*                        VSIStdoutRedirectHandle()                    */
/************************************************************************/

VSIStdoutRedirectHandle::VSIStdoutRedirectHandle(VSIVirtualHandle *poHandle)
    : m_poHandle(poHandle)
{
}

/************************************************************************/
/*                        ~VSIStdoutRedirectHandle()                    */
/************************************************************************/

VSIStdoutRedirectHandle::~VSIStdoutRedirectHandle()
{
    delete m_poHandle;
}

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

int VSIStdoutRedirectHandle::Seek(vsi_l_offset /* nOffset */, int /* nWhence */)
{
    CPLError(CE_Failure, CPLE_NotSupported,
             "Seek() unsupported on /vsistdout_redirect");
    return -1;
}

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

vsi_l_offset VSIStdoutRedirectHandle::Tell()
{
    return m_poHandle->Tell();
}

/************************************************************************/
/*                               Flush()                                */
/************************************************************************/

int VSIStdoutRedirectHandle::Flush()

{
    return m_poHandle->Flush();
}

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

size_t VSIStdoutRedirectHandle::Read(void * /* pBuffer */, size_t nSize,
                                     size_t nCount)
{
    if (nSize > 0 && nCount > 0)
    {
        CPLError(CE_Failure, CPLE_NotSupported,
                 "Read() unsupported on /vsistdout");
        m_bError = true;
    }
    return 0;
}

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

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

{
    return m_poHandle->Write(pBuffer, nSize, nCount);
}

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

int VSIStdoutRedirectHandle::Close()

{
    return m_poHandle->Close();
}

/************************************************************************/
/* ==================================================================== */
/*                 VSIStdoutRedirectFilesystemHandler                   */
/* ==================================================================== */
/************************************************************************/

/************************************************************************/
/*                                Open()                                */
/************************************************************************/

VSIVirtualHandle *VSIStdoutRedirectFilesystemHandler::Open(
    const char *pszFilename, const char *pszAccess, bool /* bSetError */,
    CSLConstList /* papszOptions */)

{
    if (strchr(pszAccess, 'r') != nullptr || strchr(pszAccess, '+') != nullptr)
    {
        CPLError(CE_Failure, CPLE_NotSupported,
                 "Read or update mode not supported on /vsistdout_redirect");
        return nullptr;
    }

    VSIVirtualHandle *poHandle = reinterpret_cast<VSIVirtualHandle *>(
        VSIFOpenL(pszFilename + strlen("/vsistdout_redirect/"), pszAccess));
    if (poHandle == nullptr)
        return nullptr;

    return new VSIStdoutRedirectHandle(poHandle);
}

/************************************************************************/
/*                                Stat()                                */
/************************************************************************/

int VSIStdoutRedirectFilesystemHandler::Stat(const char * /* pszFilename */,
                                             VSIStatBufL *pStatBuf,
                                             int /* nFlags */)
{
    memset(pStatBuf, 0, sizeof(VSIStatBufL));

    return -1;
}

//! @endcond

/************************************************************************/
/*                       VSIInstallStdoutHandler()                      */
/************************************************************************/

/*!
 \brief Install /vsistdout/ file system handler

 A special file handler is installed that allows writing to the standard
 output stream.

 The file operations available are of course limited to Write().

 A variation of this file system exists as the /vsistdout_redirect/ file
 system handler, where the output function can be defined with
 VSIStdoutSetRedirection().

 \verbatim embed:rst
 See :ref:`/vsistdout/ documentation <vsistdout>`
 \endverbatim

 @since GDAL 1.8.0
 */

void VSIInstallStdoutHandler()

{
    VSIFileManager::InstallHandler("/vsistdout/",
                                   new VSIStdoutFilesystemHandler);
    VSIFileManager::InstallHandler("/vsistdout_redirect/",
                                   new VSIStdoutRedirectFilesystemHandler);
}