/**********************************************************************
 *
 * Project:  CPL - Common Portability Library
 * Purpose:  Implement VSI large file api for stdin
 * Author:   Even Rouault, <even dot rouault at spatialys.com>
 *
 **********************************************************************
 * Copyright (c) 2010-2012, Even Rouault <even dot rouault at spatialys.com>
 *
 * 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.
 ****************************************************************************/

//! @cond Doxygen_Suppress

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

#include <cstddef>
#include <cstdio>
#include <cstring>
#if HAVE_FCNTL_H
#  include <fcntl.h>
#endif
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif

#include <algorithm>

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

#ifdef WIN32
#include <io.h>
#include <fcntl.h>
#endif

CPL_CVSID("$Id: cpl_vsil_stdin.cpp a044c83f8091becdd11e27be6e9c08d0d3478126 2021-02-24 11:38:17 +0100 Even Rouault $")

// We buffer the first 1MB of standard input to enable drivers
// to autodetect data. In the first MB, backward and forward seeking
// is allowed, after only forward seeking will work.
// TODO(schwehr): Make BUFFER_SIZE a static const.
#define BUFFER_SIZE (1024 * 1024)

static GByte* pabyBuffer = nullptr;
static GUInt32 nBufferLen = 0;
static GUIntBig nRealPos = 0;

/************************************************************************/
/*                           VSIStdinInit()                             */
/************************************************************************/

static void VSIStdinInit()
{
    if( pabyBuffer == nullptr )
    {
#ifdef WIN32
        setmode( fileno( stdin ), O_BINARY );
#endif
        pabyBuffer = static_cast<GByte *>(CPLMalloc(BUFFER_SIZE));
    }
}

/************************************************************************/
/* ==================================================================== */
/*                       VSIStdinFilesystemHandler                     */
/* ==================================================================== */
/************************************************************************/

class VSIStdinFilesystemHandler final : public VSIFilesystemHandler
{
    CPL_DISALLOW_COPY_ASSIGN(VSIStdinFilesystemHandler)

  public:
    VSIStdinFilesystemHandler();
    ~VSIStdinFilesystemHandler() override;

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

/************************************************************************/
/* ==================================================================== */
/*                        VSIStdinHandle                               */
/* ==================================================================== */
/************************************************************************/

class VSIStdinHandle final : public VSIVirtualHandle
{
  private:
    CPL_DISALLOW_COPY_ASSIGN(VSIStdinHandle)

    GUIntBig nCurOff = 0;
    int               ReadAndCache( void* pBuffer, int nToRead );

  public:
    VSIStdinHandle() = default;
    ~VSIStdinHandle() 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;
    int Eof() override;
    int Close() override;
};

/************************************************************************/
/*                              ReadAndCache()                          */
/************************************************************************/

int VSIStdinHandle::ReadAndCache( void* pBuffer, int nToRead )
{
    CPLAssert(nCurOff == nRealPos);

    int nRead = static_cast<int>(fread(pBuffer, 1, nToRead, stdin));

    if( nRealPos < BUFFER_SIZE )
    {
        const int nToCopy =
            std::min(BUFFER_SIZE - static_cast<int>(nRealPos), nRead);
        memcpy(pabyBuffer + nRealPos, pBuffer, nToCopy);
        nBufferLen += nToCopy;
    }

    nCurOff += nRead;
    nRealPos = nCurOff;

    return nRead;
}

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

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

{
    if( nWhence == SEEK_SET && nOffset == nCurOff )
        return 0;

    VSIStdinInit();
    if( nRealPos < BUFFER_SIZE )
    {
        nRealPos += fread(pabyBuffer + nRealPos, 1,
                          BUFFER_SIZE - static_cast<int>(nRealPos), stdin);
        nBufferLen = static_cast<int>(nRealPos);
    }

    if( nWhence == SEEK_END )
    {
        if( nOffset != 0 )
        {
            CPLError(CE_Failure, CPLE_NotSupported,
                     "Seek(xx != 0, SEEK_END) unsupported on /vsistdin");
            return -1;
        }

        if( nBufferLen < BUFFER_SIZE )
        {
            nCurOff = nBufferLen;
            return 0;
        }

        CPLError(CE_Failure, CPLE_NotSupported,
                 "Seek(SEEK_END) unsupported on /vsistdin when stdin > 1 MB");
        return -1;
    }

    if( nWhence == SEEK_CUR )
        nOffset += nCurOff;

    if( nRealPos > nBufferLen && nOffset < nRealPos )
    {
        CPLError(CE_Failure, CPLE_NotSupported,
                 "backward Seek() unsupported on /vsistdin above first MB");
        return -1;
    }

    if( nOffset < nBufferLen )
    {
        nCurOff = nOffset;
        return 0;
    }

    if( nOffset == nCurOff )
        return 0;

    CPLDebug("VSI", "Forward seek from " CPL_FRMT_GUIB " to " CPL_FRMT_GUIB,
             nCurOff, nOffset);

    char abyTemp[8192] = {};
    nCurOff = nRealPos;
    while( true )
    {
        const vsi_l_offset nMaxToRead = 8192;
        const int nToRead = static_cast<int>(std::min(nMaxToRead,
                                                      nOffset - nCurOff));
        const int nRead = ReadAndCache(abyTemp, nToRead);

        if( nRead < nToRead )
            return -1;
        if( nToRead < 8192 )
            break;
    }

    return 0;
}

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

vsi_l_offset VSIStdinHandle::Tell()
{
    return nCurOff;
}

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

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

{
    VSIStdinInit();

    if( nCurOff < nBufferLen )
    {
        if( nCurOff + nSize * nCount < nBufferLen )
        {
            memcpy(pBuffer, pabyBuffer + nCurOff, nSize * nCount);
            nCurOff += nSize * nCount;
            return nCount;
        }

        const int nAlreadyCached = static_cast<int>(nBufferLen - nCurOff);
        memcpy(pBuffer, pabyBuffer + nCurOff, nAlreadyCached);

        nCurOff += nAlreadyCached;

        const int nRead =
            ReadAndCache( static_cast<GByte *>(pBuffer) + nAlreadyCached,
                          static_cast<int>(nSize*nCount - nAlreadyCached) );

        return (nRead + nAlreadyCached) / nSize;
    }

    int nRead = ReadAndCache( pBuffer, static_cast<int>(nSize * nCount) );
    return nRead / nSize;
}

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

size_t VSIStdinHandle::Write( const void * /* pBuffer */,
                              size_t /* nSize */,
                              size_t /* nCount */ )
{
    CPLError(CE_Failure, CPLE_NotSupported,
             "Write() unsupported on /vsistdin");
    return 0;
}

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

int VSIStdinHandle::Eof()

{
    if( nCurOff < nBufferLen )
        return FALSE;
    return feof(stdin);
}

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

int VSIStdinHandle::Close()

{
    return 0;
}

/************************************************************************/
/* ==================================================================== */
/*                       VSIStdinFilesystemHandler                     */
/* ==================================================================== */
/************************************************************************/

/************************************************************************/
/*                        VSIStdinFilesystemHandler()                   */
/************************************************************************/

VSIStdinFilesystemHandler::VSIStdinFilesystemHandler()
{
    pabyBuffer = nullptr;
    nBufferLen = 0;
    nRealPos = 0;
}

/************************************************************************/
/*                       ~VSIStdinFilesystemHandler()                   */
/************************************************************************/

VSIStdinFilesystemHandler::~VSIStdinFilesystemHandler()
{
    CPLFree(pabyBuffer);
    pabyBuffer = nullptr;
}

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

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

{
    if( strcmp(pszFilename, "/vsistdin/") != 0 )
        return nullptr;

    if( !CPLTestBool(CPLGetConfigOption("CPL_ALLOW_VSISTDIN", "YES")) )
    {
        CPLError(CE_Failure, CPLE_NotSupported,
                 "/vsistdin/ disabled. Set CPL_ALLOW_VSISTDIN to YES to "
                "enable it");
        return nullptr;
    }

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

    return new VSIStdinHandle;
}

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

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

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

    if( strcmp(pszFilename, "/vsistdin/") != 0 )
        return -1;

    if( !CPLTestBool(CPLGetConfigOption("CPL_ALLOW_VSISTDIN", "YES")) )
    {
        CPLError(CE_Failure, CPLE_NotSupported,
                 "/vsistdin/ disabled. Set CPL_ALLOW_VSISTDIN to YES to "
                "enable it");
        return -1;
    }

    if( nFlags & VSI_STAT_SIZE_FLAG )
    {
        VSIStdinInit();
        if( nBufferLen == 0 )
            nRealPos = nBufferLen =
                static_cast<int>(fread(pabyBuffer, 1, BUFFER_SIZE, stdin));

        pStatBuf->st_size = nBufferLen;
    }

    pStatBuf->st_mode = S_IFREG;
    return 0;
}

//! @endcond

/************************************************************************/
/*                       VSIInstallStdinHandler()                       */
/************************************************************************/

/**
 * \brief Install /vsistdin/ file system handler
 *
 * A special file handler is installed that allows reading from the standard
 * input stream.
 *
 * The file operations available are of course limited to Read() and
 * forward Seek() (full seek in the first MB of a file).
 *
 * @since GDAL 1.8.0
 */
void VSIInstallStdinHandler()

{
    VSIFileManager::InstallHandler("/vsistdin/", new VSIStdinFilesystemHandler);
}
