BlobIOSystem.h

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

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*/

/** @file Provides cheat implementations for IOSystem and IOStream to
 *  redirect exporter output to a blob chain.*/

#ifndef AI_BLOBIOSYSTEM_H_INCLUDED
#define AI_BLOBIOSYSTEM_H_INCLUDED

namespace Assimp	{
	class BlobIOSystem;

// --------------------------------------------------------------------------------------------
/** Redirect IOStream to a blob */
// --------------------------------------------------------------------------------------------
class BlobIOStream : public IOStream
{
public:

	BlobIOStream(BlobIOSystem* creator, const std::string& file, size_t initial = 4096)
		: buffer()
		, cur_size()
		, file_size()
		, cursor()
		, initial(initial)
		, file(file)
		, creator(creator)
	{
	}


	virtual ~BlobIOStream();

public:

	// -------------------------------------------------------------------
	aiExportDataBlob* GetBlob()
	{
		aiExportDataBlob* blob = new aiExportDataBlob();
		blob->size = file_size;
		blob->data = buffer;

		buffer = NULL;

		return blob;
	}


public:


	// -------------------------------------------------------------------
    virtual size_t Read(void* pvBuffer, 
		size_t pSize, 
		size_t pCount) 
	{
		return 0;
	}

	// -------------------------------------------------------------------
    virtual size_t Write(const void* pvBuffer, 
		size_t pSize,
		size_t pCount) 
	{
		pSize *= pCount;
		if (cursor + pSize > cur_size) {
			Grow(cursor + pSize);
		}

		memcpy(buffer+cursor, pvBuffer, pSize);
		cursor += pSize;

		file_size = std::max(file_size,cursor);
		return pCount; 
	}

	// -------------------------------------------------------------------
	virtual aiReturn Seek(size_t pOffset,
		aiOrigin pOrigin)
	{
		switch(pOrigin) 
		{
		case aiOrigin_CUR:
			cursor += pOffset;

		case aiOrigin_END:
			cursor = file_size - pOffset;

		case aiOrigin_SET:
			cursor = pOffset;
			break;

		default:
			return AI_FAILURE;
		}

		if (cursor > file_size) {
			Grow(cursor);
		}

		file_size = std::max(cursor,file_size);
		return AI_SUCCESS;
	}

	// -------------------------------------------------------------------
    virtual size_t Tell() const
	{
		return cursor;
	}

	// -------------------------------------------------------------------
	virtual size_t FileSize() const
	{
		return file_size;
	}

	// -------------------------------------------------------------------
	virtual void Flush() 
	{
		// ignore
	}



private:

	// -------------------------------------------------------------------
	void Grow(size_t need = 0) 
	{
		// 1.5 and phi are very heap-friendly growth factors (the first
		// allows for frequent re-use of heap blocks, the second
		// forms a fibonacci sequence with similar characteristics -
		// since this heavily depends on the heap implementation 
		// and other factors as well, i'll just go with 1.5 since
		// it is quicker to compute).
		size_t new_size = std::max(initial, std::max( need, cur_size+(cur_size>>1) ));

		const uint8_t* const old = buffer;
		buffer = new uint8_t[new_size];

		if (old) {
			memcpy(buffer,old,cur_size);
			delete[] old;
		}

		cur_size = new_size;
	}

private:

	uint8_t* buffer;
	size_t cur_size,file_size, cursor, initial;

	const std::string file;
	BlobIOSystem* const creator;
};


#define AI_BLOBIO_MAGIC "$blobfile"

// --------------------------------------------------------------------------------------------
/** Redirect IOSystem to a blob */
// --------------------------------------------------------------------------------------------
class BlobIOSystem : public IOSystem
{

	friend class BlobIOStream;
	typedef std::pair<std::string, aiExportDataBlob*> BlobEntry;

public:

	BlobIOSystem()
	{
	}

	virtual ~BlobIOSystem()
	{
		BOOST_FOREACH(BlobEntry& blobby, blobs) {
			delete blobby.second;
		}
	}

public:

	// -------------------------------------------------------------------
	const char* GetMagicFileName() const 
	{
		return AI_BLOBIO_MAGIC;
	}


	// -------------------------------------------------------------------
	aiExportDataBlob* GetBlobChain()
	{
		// one must be the master
		aiExportDataBlob* master = NULL, *cur;
		BOOST_FOREACH(const BlobEntry& blobby, blobs) {
			if (blobby.first == AI_BLOBIO_MAGIC) {
				master = blobby.second;
				break;
			}
		}
		if (!master) {
			DefaultLogger::get()->error("BlobIOSystem: no data written or master file was not closed properly.");
			return NULL;
		}

		master->name.Set("");

		cur = master;
		BOOST_FOREACH(const BlobEntry& blobby, blobs) {
			if (blobby.second == master) {
				continue;
			}

			cur->next = blobby.second;
			cur = cur->next;

			// extract the file extension from the file written
			const std::string::size_type s = blobby.first.find_first_of('.');
			cur->name.Set(s == std::string::npos ? blobby.first : blobby.first.substr(s+1));
		}

		// give up blob ownership
		blobs.clear();
		return master;
	}

public:

	// -------------------------------------------------------------------
	virtual bool Exists( const char* pFile) const {
		return created.find(std::string(pFile)) != created.end();
	}


	// -------------------------------------------------------------------
	virtual char getOsSeparator() const {
		return '/';
	}


	// -------------------------------------------------------------------
	virtual IOStream* Open(const char* pFile,
		const char* pMode)
	{
		if (pMode[0] != 'w') {
			return NULL;
		}

		created.insert(std::string(pFile));
		return new BlobIOStream(this,std::string(pFile));
	}

	// -------------------------------------------------------------------
	virtual void Close( IOStream* pFile) 
	{
		delete pFile;
	}

private:

	// -------------------------------------------------------------------
	void OnDestruct(const std::string& filename, BlobIOStream* child) 
	{	
		// we don't know in which the files are closed, so we
		// can't reliably say that the first must be the master 
		// file ...
		blobs.push_back( BlobEntry(filename,child->GetBlob()) );
	}

private:
	std::set<std::string> created;
	std::vector< BlobEntry > blobs;
};


// --------------------------------------------------------------------------------------------
BlobIOStream :: ~BlobIOStream() 
{
	creator->OnDestruct(file,this);
	delete[] buffer;
}

	
} // end Assimp

#endif