assimp.assimp/code/Common/DefaultIOStream.cpp

/*
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Open Asset Import Library (assimp)
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  following disclaimer.

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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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*/
/** @file  DefaultIOStream.cpp
 *  @brief Default File I/O implementation for #Importer
 */

#include <assimp/DefaultIOStream.h>
#include <assimp/ai_assert.h>
#include <sys/stat.h>
#include <sys/types.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 (size_t)::_ftelli64(file);
}

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

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

// ----------------------------------------------------------------------------------
size_t DefaultIOStream::Read(void *pvBuffer,
        size_t pSize,
        size_t pCount) {
    ai_assert(nullptr != pvBuffer);
    ai_assert(0 != pSize);
    ai_assert(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(nullptr != pvBuffer);
    ai_assert(0 != pSize);

    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);
    }
}

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