assimp/code/BaseImporter.h

/*
Open Asset Import Library (ASSIMP)
----------------------------------------------------------------------

Copyright (c) 2006-2008, ASSIMP Development Team
All rights reserved.

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  following disclaimer.

* Redistributions in binary form must reproduce the above
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  written permission of the ASSIMP Development Team.

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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 
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*/

/** @file Definition of the base class for all importer worker classes. */
#ifndef INCLUDED_AI_BASEIMPORTER_H
#define INCLUDED_AI_BASEIMPORTER_H

#include <string>
#include "./../include/aiTypes.h"

struct aiScene;

namespace Assimp	{

class IOSystem;
class Importer;

// utility to do char4 to uint32 in a portable manner
#define AI_MAKE_MAGIC(string) ((uint32_t)((string[0] << 24) + \
	(string[1] << 16) + (string[2] << 8) + string[3]))

// ---------------------------------------------------------------------------
/** Simple exception class to be thrown if an error occurs while importing. */
class ASSIMP_API ImportErrorException 
{
public:
	/** Constructor with arguments */
	ImportErrorException( const std::string& pErrorText)
	{
		mErrorText = pErrorText;
	}

	// -------------------------------------------------------------------
	/** Returns the error text provided when throwing the exception */
	inline const std::string& GetErrorText() const 
	{ return mErrorText; }

private:
	std::string mErrorText;
};

// ---------------------------------------------------------------------------
/** The BaseImporter defines a common interface for all importer worker 
 *  classes.
 *
 * The interface defines two functions: CanRead() is used to check if the 
 * importer can handle the format of the given file. If an implementation of 
 * this function returns true, the importer then calls ReadFile() which 
 * imports the given file. ReadFile is not overridable, it just calls 
 * InternReadFile() and catches any ImportErrorException that might occur.
 */
class ASSIMP_API BaseImporter
{
	friend class Importer;

protected:

	/** Constructor to be privately used by #Importer */
	BaseImporter();

	/** Destructor, private as well */
	virtual ~BaseImporter();

public:
	// -------------------------------------------------------------------
	/** Returns whether the class can handle the format of the given file.
	 *
	 * The implementation should be as quick as possible. A check for
	 * the file extension is enough. If no suitable loader is found with
	 * this strategy, CanRead() is called again, the 'checkSig' parameter
	 * set to true this time. Now the implementation is expected to
	 * perform a full check of the file format, possibly searching the
	 * first bytes of the file for magic identifiers or keywords.
	 *
	 * @param pFile Path and file name of the file to be examined.
	 * @param pIOHandler The IO handler to use for accessing any file.
	 * @param checkSig Set to true if this method is called a second time.
	 *   This time, the implementation may take more time to examine the
	 *   contents of the file to be loaded for magic bytes, keywords, etc
	 *   to be able to load files with unknown/not existent file extensions.
	 * @return true if the class can read this file, false if not.
	 *
	 * @note Sometimes ASSIMP uses this method to determine whether a
	 * a given file extension is generally supported. In this case the
	 * file extension is passed in the pFile parameter, pIOHandler is NULL
	 */
	virtual bool CanRead( const std::string& pFile, 
		IOSystem* pIOHandler, bool checkSig) const = 0;


	// -------------------------------------------------------------------
	/** Imports the given file and returns the imported data.
	 * If the import succeeds, ownership of the data is transferred to 
	 * the caller. If the import fails, NULL is returned. The function
	 * takes care that any partially constructed data is destroyed
	 * beforehand.
	 *
	 * @param pFile Path of the file to be imported. 
	 * @param pIOHandler IO-Handler used to open this and possible other files.
	 * @return The imported data or NULL if failed. If it failed a 
	 * human-readable error description can be retrieved by calling 
	 * GetErrorText()
	 *
	 * @note This function is not intended to be overridden. Implement 
	 * InternReadFile() to do the import. If an exception is thrown somewhere 
	 * in InternReadFile(), this function will catch it and transform it into
	 *  a suitable response to the caller.
	 */
	aiScene* ReadFile( const std::string& pFile, IOSystem* pIOHandler);


	// -------------------------------------------------------------------
	/** Returns the error description of the last error that occured. 
	 * @return A description of the last error that occured. An empty
	 * string if there was no error.
	 */
	const std::string& GetErrorText() const {
		return mErrorText;
	}


	// -------------------------------------------------------------------
	/** Called prior to ReadFile().
	 * The function is a request to the importer to update its configuration
	 * basing on the Importer's configuration property list.
	 * @param pImp Importer instance
	 * @param ppFlags Post-processing steps to be executed on the data
	 *  returned by the loaders. This value is provided to allow some
	 * internal optimizations.
	 */
	virtual void SetupProperties(const Importer* pImp /*,
		unsigned int ppFlags*/);

protected:

	// -------------------------------------------------------------------
	/** Called by Importer::GetExtensionList() for each loaded importer.
	 *  Importer implementations should append all file extensions
	 *  which they supported to the passed string.
	 *  Example: "*.blabb;*.quak;*.gug;*.foo" (no delimiter after the last!)
	 * @param append Output string
	 */
	virtual void GetExtensionList(std::string& append) = 0;

	// -------------------------------------------------------------------
	/** Imports the given file into the given scene structure. The 
	 * function is expected to throw an ImportErrorException if there is 
	 * an error. If it terminates normally, the data in aiScene is 
	 * expected to be correct. Override this function to implement the 
	 * actual importing.
	 * <br>
	 *  The output scene must meet the following requirements:<br>
	 * <ul>
	 * <li>At least a root node must be there, even if its only purpose
	 *     is to reference one mesh.</li>
	 * <li>aiMesh::mPrimitiveTypes may be 0. The types of primitives
	 *   in the mesh are determined automatically in this case.</li>
	 * <li>the vertex data is stored in a pseudo-indexed "verbose" format.
	 *   In fact this means that every vertex that is referenced by
	 *   a face is unique. Or the other way round: a vertex index may
	 *   not occur twice in a single aiMesh.</li>
	 * <li>aiAnimation::mDuration may be -1. Assimp determines the length
	 *   of the animation automatically in this case as the length of
	 *   the longest animation channel.</li>
	 * <li>aiMesh::mBitangents may be NULL if tangents and normals are
	 *   given. In this case bitangents are computed as the cross product
	 *   between normal and tangent.</li>
	 * <li>There needn't be a material. If none is there a default material
	 *   is generated. However, it is recommended practice for loaders
	 *   to generate a default material for yourself that matches the
	 *   default material setting for the file format better than Assimp's
	 *   generic default material. Note that default materials *should*
	 *   be named AI_DEFAULT_MATERIAL_NAME if they're just color-shaded
	 *   or AI_DEFAULT_TEXTURED_MATERIAL_NAME if they define a (dummy) 
	 *   texture. </li>
	 * </ul>
	 * If the AI_SCENE_FLAGS_INCOMPLETE-Flag is <b>not</b> set:<ul>
	 * <li> at least one mesh must be there</li>
	 * <li> there may be no meshes with 0 vertices or faces</li>
	 * </ul>
	 * This won't be checked (except by the validation step): Assimp will
	 * crash if one of the conditions is not met!
	 *
	 * @param pFile Path of the file to be imported.
	 * @param pScene The scene object to hold the imported data.
	 * NULL is not a valid parameter.
	 * @param pIOHandler The IO handler to use for any file access.
	 * NULL is not a valid parameter.
	 */
	virtual void InternReadFile( const std::string& pFile, 
		aiScene* pScene, IOSystem* pIOHandler) = 0;


	// -------------------------------------------------------------------
	/** A utility for CanRead().
	 *
	 *  The function searches the header of a file for a specific token
	 *  and returns true if this token is found. This works for text
	 *  files only. There is a rudimentary handling of UNICODE files.
	 *  The comparison is case independent.
	 *
	 *  @param pIOSystem IO System to work with
	 *  @param file File name of the file
	 *  @param tokens List of tokens to search for
	 *  @param numTokens Size of the token array
	 *  @param searchBytes Number of bytes to be searched for the tokens.
	 */
	static bool SearchFileHeaderForToken(IOSystem* pIOSystem, 
		const std::string&	file,
		const char**		tokens, 
		unsigned int		numTokens,
		unsigned int		searchBytes = 200);


	// -------------------------------------------------------------------
	/** @brief Check whether a file has a specific file extension
	 *  @param pFile Input file
	 *  @param ext0 Extension to check for. Lowercase characters only, no dot!
	 *  @param ext1 Optional second extension
	 *  @param ext2 Optional third extension
	 *  @note Case-insensitive
	 */
	static bool SimpleExtensionCheck (const std::string& pFile, 
		const char* ext0,
		const char* ext1 = NULL,
		const char* ext2 = NULL);

	// -------------------------------------------------------------------
	/** @brief Extract file extension from a string
	 *  @param pFile Input file
	 *  @return Extension without trailing dot, all lowercase
	 */
	static std::string GetExtension (const std::string& pFile);

	// -------------------------------------------------------------------
	/** @brief Check whether a file starts with one or more magic tokens
	 *  @param pFile Input file
	 *  @param pIOHandler IO system to be used
	 *  @param magic n magic tokens
	 *  @params num Size of magic
	 *  @param offset Offset from file start where tokens are located
	 *  @param Size of one token, in bytes. Maximally 16 bytes.
	 *  @return true if one of the given tokens was found
	 *
	 *  @note For convinence, the check is also performed for the
	 *  byte-swapped variant of all tokens (big endian). Only for
	 *  tokens of size 2,4.
	 */
	static bool CheckMagicToken(IOSystem* pIOHandler, const std::string& pFile, 
		const void* magic,
		unsigned int num,
		unsigned int offset = 0,
		unsigned int size   = 4);

#if 0 /** TODO **/
	// -------------------------------------------------------------------
	/** An utility for all text file loaders. It converts a file to our
	*  ASCII/UTF8 character set. Special unicode characters are lost.
	*
	*  @param buffer Input buffer. Needn't be terminated with zero.
	 *  @param length Length of the input buffer, in bytes. Receives the
	 *    number of output characters, excluding the terminal char.
	 *  @return true if the source format did not match our internal
	 *    format so it was converted.
	 */
	static bool ConvertToUTF8(const char* buffer, 
		unsigned int& length);
#endif

protected:

	/** Error description in case there was one. */
	std::string mErrorText;
};

struct BatchData;

// ---------------------------------------------------------------------------
/** A helper class that can be used by importers which need to load many
 *  extern meshes recursively.
 *
 *  The class uses several threads to load these meshes (or at least it
 *  could, this has not yet been implemented at the moment).
 *
 *  @note The class may not be used by more than one thread
 */
class ASSIMP_API BatchLoader
{
	// friend of Importer

public:

	/** Represents a full list of configuration properties
	 *  for the importer.
	 *
	 *  Properties can be set using SetGenericProperty
	 */
	struct PropertyMap
	{
		Importer::IntPropertyMap     ints;
		Importer::FloatPropertyMap   floats;
		Importer::StringPropertyMap  strings;

		bool operator == (const PropertyMap& prop) const {
			return ints == prop.ints && floats == prop.floats && strings == prop.strings; 
		}

		bool empty () const {
			return ints.empty() && floats.empty() && strings.empty();
		}
	};

public:
	

	/** Construct a batch loader from a given IO system
	 */
	BatchLoader(IOSystem* pIO);
	~BatchLoader();


	/** Sets the base path to be used for all subsequent load
	 *  calls. This is the working directory of Assimp. 
	 *
	 *  Every (inplicit) occurence of '.\' will be replaced with it.
	 *
	 *  @param pBase Base path. This *may* also be the path to
	 *  a file (the directory of the file is taken then, of course)
	 */
	void SetBasePath (const std::string& pBase);


	/** Add a new file to the list of files to be loaded.
	 *
	 *  @param file File to be loaded
	 *  @param steps Steps to be executed on the file
	 *  @param map Optional configuration properties
	 *  @return 'Load request channel' - an unique ID that can later
	 *    be used to access the imported file data.
	 */
	unsigned int AddLoadRequest	(const std::string& file,
		unsigned int steps = 0, const PropertyMap* map = NULL);


	/** Get an imported scene.
	 *
	 *  This polls the import from the internal request list.
	 *  If an import is requested several times, this function
	 *  can be called several times, too.
	 *
	 *  @param which LRWC returned by AddLoadRequest().
	 *  @return NULL if there is no scene with this file name
	 *  in the queue of the scene hasn't been loaded yet.
	 */
	aiScene* GetImport		(unsigned int which);


	/** Waits until all scenes have been loaded.
	 */
	void LoadAll();

private:

	// No need to have that in the public API ...
	BatchData* data;
};

} // end of namespace Assimp

#endif // AI_BASEIMPORTER_H_INC