Add Assimp library in thirdparty

From https://github.com/assimp/assimp repo at d2b45377e4b09a1f43be95e45553afcc06b03f4b

thirdparty/assimp/code/CInterfaceIOWrapper.cpp

@@ -0,0 +1,136 @@
+/*
+---------------------------------------------------------------------------
+Open Asset Import Library (assimp)
+---------------------------------------------------------------------------
+
+Copyright (c) 2006-2019, assimp team
+
+
+
+All rights reserved.
+
+Redistribution and use of this software in source and binary forms,
+with or without modification, are permitted provided that the following
+conditions are met:
+
+* Redistributions of source code must retain the above
+  copyright notice, this list of conditions and the
+  following disclaimer.
+
+* Redistributions in binary form must reproduce the above
+  copyright notice, this list of conditions and the
+  following disclaimer in the documentation and/or other
+  materials provided with the distribution.
+
+* Neither the name of the assimp team, nor the names of its
+  contributors may be used to endorse or promote products
+  derived from this software without specific prior
+  written permission of the assimp team.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+---------------------------------------------------------------------------
+*/
+
+/** @file aiFileIO -> IOSystem wrapper*/
+
+#include "CInterfaceIOWrapper.h"
+
+namespace Assimp    {
+
+CIOStreamWrapper::~CIOStreamWrapper(void)
+{
+    /* Various places depend on this destructor to close the file */
+    if (mFile) {
+        mIO->mFileSystem->CloseProc(mIO->mFileSystem, mFile);
+        mFile = nullptr;
+    }
+}
+
+// ...................................................................
+size_t CIOStreamWrapper::Read(void* pvBuffer,
+    size_t pSize,
+    size_t pCount
+){
+    // need to typecast here as C has no void*
+    return mFile->ReadProc(mFile,(char*)pvBuffer,pSize,pCount);
+}
+
+// ...................................................................
+size_t CIOStreamWrapper::Write(const void* pvBuffer,
+    size_t pSize,
+    size_t pCount
+){
+    // need to typecast here as C has no void*
+    return mFile->WriteProc(mFile,(const char*)pvBuffer,pSize,pCount);
+}
+
+// ...................................................................
+aiReturn CIOStreamWrapper::Seek(size_t pOffset,
+    aiOrigin pOrigin
+){
+    return mFile->SeekProc(mFile,pOffset,pOrigin);
+}
+
+// ...................................................................
+size_t CIOStreamWrapper::Tell(void) const {
+    return mFile->TellProc(mFile);
+}
+
+// ...................................................................
+size_t CIOStreamWrapper::FileSize() const {
+    return mFile->FileSizeProc(mFile);
+}
+
+// ...................................................................
+void CIOStreamWrapper::Flush () {
+    return mFile->FlushProc(mFile);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Custom IOStream implementation for the C-API
+bool CIOSystemWrapper::Exists( const char* pFile) const {
+    aiFile* p = mFileSystem->OpenProc(mFileSystem,pFile,"rb");
+    if (p){
+        mFileSystem->CloseProc(mFileSystem,p);
+        return true;
+    }
+    return false;
+}
+
+// ...................................................................
+char CIOSystemWrapper::getOsSeparator() const {
+#ifndef _WIN32
+    return '/';
+#else
+    return '\\';
+#endif
+}
+
+// ...................................................................
+IOStream* CIOSystemWrapper::Open(const char* pFile,const char* pMode) {
+    aiFile* p = mFileSystem->OpenProc(mFileSystem,pFile,pMode);
+    if (!p) {
+        return NULL;
+    }
+    return new CIOStreamWrapper(p, this);
+}
+
+// ...................................................................
+void CIOSystemWrapper::Close( IOStream* pFile) {
+    if (!pFile) {
+        return;
+    }
+    delete pFile;
+}
+
+}