assimp/code/Common/DefaultIOStream.cpp

/*
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Open Asset Import Library (assimp)
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Copyright (c) 2006-2019, assimp team



All rights reserved.

Redistribution and use of this software in source and binary forms,
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  copyright notice, this list of conditions and the
  following disclaimer.

* Redistributions in binary form must reproduce the above
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* Neither the name of the assimp team, nor the names of its
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  derived from this software without specific prior
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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*/
/** @file  DefaultIOStream.cpp
 *  @brief Default File I/O implementation for #Importer
 */


#include <assimp/ai_assert.h>
#include <assimp/DefaultIOStream.h>
#include <sys/types.h>
#include <sys/stat.h>

using namespace Assimp;

namespace
{
    template<size_t sizeOfPointer>
    size_t select_ftell(FILE* file)
    {
        return ::ftell(file);
    }

    template<size_t sizeOfPointer>
    int select_fseek(FILE* file, int64_t offset, int origin)
    {
        return ::fseek(file, static_cast<long>(offset), origin);
    }

#if defined _WIN32 && (!defined __GNUC__ || __MSVCRT_VERSION__ >= 0x0601)
    template<>
    size_t select_ftell<8>(FILE* file)
    {
        return ::_ftelli64(file);
    }

    template<>
    int select_fseek<8>(FILE* file, int64_t offset, int origin)
    {
        return ::_fseeki64(file, offset, origin);
    }
#endif
}

// ----------------------------------------------------------------------------------
DefaultIOStream::~DefaultIOStream()
{
    if (mFile) {
        ::fclose(mFile);
        mFile = nullptr;
    }
}

// ----------------------------------------------------------------------------------
size_t DefaultIOStream::Read(void* pvBuffer,
    size_t pSize,
    size_t pCount)
{
    ai_assert(NULL != pvBuffer && 0 != pSize && 0 != pCount);
    return (mFile ? ::fread(pvBuffer, pSize, pCount, mFile) : 0);
}

// ----------------------------------------------------------------------------------
size_t DefaultIOStream::Write(const void* pvBuffer,
    size_t pSize,
    size_t pCount)
{
    ai_assert(NULL != pvBuffer && 0 != pSize && 0 != pCount);
    return (mFile ? ::fwrite(pvBuffer, pSize, pCount, mFile) : 0);
}

// ----------------------------------------------------------------------------------
aiReturn DefaultIOStream::Seek(size_t pOffset,
     aiOrigin pOrigin)
{
    if (!mFile) {
        return AI_FAILURE;
    }

    // Just to check whether our enum maps one to one with the CRT constants
    static_assert(aiOrigin_CUR == SEEK_CUR &&
        aiOrigin_END == SEEK_END && aiOrigin_SET == SEEK_SET, "aiOrigin_CUR == SEEK_CUR && \
        aiOrigin_END == SEEK_END && aiOrigin_SET == SEEK_SET");

    // do the seek
    return (0 == select_fseek<sizeof(void*)>(mFile, (int64_t)pOffset,(int)pOrigin) ? AI_SUCCESS : AI_FAILURE);
}

// ----------------------------------------------------------------------------------
size_t DefaultIOStream::Tell() const
{
    if (!mFile) {
        return 0;
    }
    return select_ftell<sizeof(void*)>(mFile);
}

// ----------------------------------------------------------------------------------
size_t DefaultIOStream::FileSize() const
{
    if (! mFile || mFilename.empty()) {
        return 0;
    }

    if (SIZE_MAX == mCachedSize ) {

        // Although fseek/ftell would allow us to reuse the existing file handle here,
        // it is generally unsafe because:
        //  - For binary streams, it is not technically well-defined
        //  - For text files the results are meaningless
        // That's why we use the safer variant fstat here.
        //
        // See here for details:
        // https://www.securecoding.cert.org/confluence/display/seccode/FIO19-C.+Do+not+use+fseek()+and+ftell()+to+compute+the+size+of+a+regular+file
#if defined _WIN32 && (!defined __GNUC__ || __MSVCRT_VERSION__ >= 0x0601)
        struct __stat64 fileStat;
        //using fileno + fstat avoids having to handle the filename
        int err = _fstat64(  _fileno(mFile), &fileStat );
        if (0 != err)
            return 0;
        mCachedSize = (size_t) (fileStat.st_size);
#elif defined __GNUC__ || defined __APPLE__ || defined __MACH__ || defined __FreeBSD__
        struct stat fileStat;
        int err = stat(mFilename.c_str(), &fileStat );
        if (0 != err)
            return 0;
        const unsigned long long cachedSize = fileStat.st_size;
        mCachedSize = static_cast< size_t >( cachedSize );
#else
#   error "Unknown platform"
#endif
    }
    return mCachedSize;
}

// ----------------------------------------------------------------------------------
void DefaultIOStream::Flush()
{
    if (mFile) {
        ::fflush(mFile);
    }
}

// ----------------------------------------------------------------------------------