FS_FileResolver.h

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/*
 * PROPRIETARY INFORMATION.  This software is proprietary to
 * Side Effects Software Inc., and is not to be reproduced,
 * transmitted, or disclosed in any way without written permission.
 *
 * NAME:        FS_FileResolver.h (FS  Library, C++)
 *
 * COMMENTS:    This class resolves the data specified by its name. The name can
 *              a file path or an "op:" path. 
 *
 *              In applications that can cook the op data (eg, Houdini and
 *              Batch), the resolver instance actually searches out the node and
 *              asks it for the data, then it creates a stream and returns it as
 *              a file reader object. To release this temporarily created
 *              stream, the requester needs to let the resolver know so that
 *              it can relinquish it.
 *
 *              In applications that don't have access to nodes (eg, Mantra),
 *              the resolver instance needs to rely on the data given to
 *              it (eg, inside the IFD stream). Since other entities (eg,
 *              shaders) still refer to the data as "op:", the resolver
 *              needs to figure out which data to return for each request.
 *              The data is returned in a form of FS_Reader, but the actual
 *              data may be in memory, in a temp file on disk, or elsewhere.
 *              The requester may notify the resolver that it is done with the
 *              data and to relinquish it, but the resolver will probably need
 *              to keep the data around for the future requests, since there is
 *              no source for that data (no nodes, and IFD has been already
 *              sourced before).
 *
 */

#ifndef __FS_FileResolver__
#define __FS_FileResolver__

#include "FS_API.h"
#include <SYS/SYS_Types.h>
#include <UT/UT_String.h>
#include <UT/UT_StringHolder.h>
#include <UT/UT_SymbolTable.h>

class UT_IStream;
class FS_Reader;


//============================================================================= 
/// Provides various options for creating and obtaining the file data.
class FS_API FS_FileResolverOptions
{
public:
    /// Constructor.
     FS_FileResolverOptions();
     FS_FileResolverOptions( const FS_FileResolverOptions & src );

    /// Assignment operator.
    const FS_FileResolverOptions &  operator=( 
                                        const FS_FileResolverOptions & src );

    /// Gets the time at which a node should be evaluated to obtain the data.
    fpreal                      getTime() const
                                { return myTime; }
    void                        setTime( fpreal time )
                                { myTime = time; }

    /// Gets the extension for the file that will contain the resolved data.
    /// It indirectly determines the data type for stream readers and writers.
    const UT_StringHolder       &getFileExtension() const
                                { return myFileExtension; }
    void                        setFileExtension(const UT_StringHolder &ext) 
                                { myFileExtension = ext; }

    /// Checks if the file should be treated as an environment map.
    bool                        getIsEnvMap() const
                                { return myIsEnvMap; }
    void                        setIsEnvMap( bool env_map )
                                { myIsEnvMap = env_map; }

   
private:
    UT_StringHolder     myFileExtension;    // extension of the data file
    fpreal              myTime;             // node evaluation time
    bool                myIsEnvMap;         // is environment map
};


//============================================================================= 
/// Maps the operator paths (eg, "op:/path"), and other data sources,
/// to file readers that access their data.
class FS_API FS_FileResolver
{
public:
    /// Constructor.
                                 FS_FileResolver();
    /// Destructor.
    virtual                     ~FS_FileResolver();

    /// Sets the instance that will resolve the operator paths to data files.
    static void                 setResolver( FS_FileResolver * resolver );

    /// Returns the currently set resolver.
    static FS_FileResolver *    getResolver();


    /// Checks if the resolver can provide the file data for the given name.
    // TODO: this method may need to take FS_FileResolverOptions argument
    virtual bool                getCanResolve( const char * name ) = 0;

    /// @brief Creates a new reader object given the file (or data) name. 
    ///
    /// The returned reader can be used to read the data, and when finished,
    /// it should be freed by passing it to the FS_FileResolver::deleteReader()
    /// method.
    ///
    /// @param  opts    The options that indicate how the data should be
    ///                 generated, if applicable. Eg, it contains the evaluation
    ///                 time for nodes or the file format in which the data
    ///                 should be available.
    ///
    /// @param  name    The name of the data to be read. Can be a file
    ///                 specified with "file:/path" or an operator node
    ///                 data specified with "op:/path", or any other standard
    ///                 way of specifying data in Houdini.
    //
    /// @return         The reader for the specified data.
    ///
    virtual FS_Reader *         newReader( const FS_FileResolverOptions & opts,
                                           const char * name ) = 0;


    /// Closes stream (if they are still open) and deletes the reader. 
    /// After this call, the reader pointer will no longer be valid.
    /// 
    /// @param  reader  The reader to be freed. 
    ///
    virtual void                deleteReader( FS_Reader * reader ) = 0;


    /// Obtains the file path to the data of a given name. On success,
    /// 'file_path' will contain a non-epnty file path. This file path
    /// should be then released using FS_FileResolver::relinquishFilePath().
    ///
    /// @param opts     The options that describe the data.
    /// @param name     The name of the data available in the file.
    /// @param file_path    The output parameter which will have the
    ///                 path of the file that contains the data. If
    ///                 the request fails, the path will be an empty string.
    virtual void                acquireFilePath( 
                                            const FS_FileResolverOptions & opts,
                                            const char * name,
                                            UT_String & file_path ) = 0;

    /// Releases the file path and allows the resolver to (optionally) free
    /// the file resources.
    /// 
    /// @param  file_path   The file path previously obtained with
    ///                     FS_FileResolver::acquireFilePath().
    virtual void                relinquishFilePath( const char * file_path ) = 0;

    /// Adds the data to the resolver, so that the resolver can handle
    /// future requests for the data given this name. 
    /// 
    /// @param  opts    Options describe how the data should be interpreted.
    ///
    /// @param  name    The name of the resource. Future requests for this
    ///                 resource using FS_FileResolver::newReader() will returno
    ///                 a reader that provides this data.
    ///
    /// @param  data    The stream containing the data. The resolver will
    ///                 read in and store this data for future use.
    virtual void                registerFile(const FS_FileResolverOptions &opts,
                                             const UT_StringHolder &name,
                                             UT_IStream & data );

    /// Returns an instance-unique identifier for a path that can be used to
    /// check if the underlying resource data has changed, and should be 
    /// re-read by the clients of this class.
    
    /// @param name     The name of the data to get the identifier for.
    /// 
    /// @return         The revision id of the data. Returns 0 if the resource
    ///                 does not exist or revision IDs are not supported.
    virtual int         getRevisionID(const char *name) = 0;
protected:

    /// Contains details about the data that the resolver can provide.
    class FS_API FS_ResolverFileEntry
    {
    public:
        // constructor
        FS_ResolverFileEntry(const UT_StringHolder &name,
                        const UT_StringHolder &file_name,
                        const FS_FileResolverOptions &opts);

        // Accessors.
        const UT_StringHolder   &getName() const { return myName; }
        const UT_StringHolder   &getFileName() const { return myFileName; }

        const FS_FileResolverOptions    &getOptions() const
                                                { return myOptions; }

    private:
        /// Name of the resource this entry represents.
        UT_StringHolder         myName;

        /// The file name in which the resource data is saved.
        UT_StringHolder         myFileName;

        /// Options with which the file has been crated.
        FS_FileResolverOptions  myOptions;
    };


    /// Adds the file to the table.
    /// The resolver takes ownership of the file and will delete it
    /// in the destructor, unless it is unregistered from the table beforehand,
    /// with FS_FileResolver::unregisterFile().
    void                        registerFile( 
                                        const FS_FileResolverOptions &opts,
                                        const UT_StringHolder &name,
                                        const UT_StringHolder &file_path );

    /// Removes the file from table, and deletes the file if 'delete_file' is
    /// true.
    void                        unregisterFile( const UT_StringRef &name,
                                                bool delete_file );

    /// Looks up the table entry for the given name key and returns the
    /// entry. If not found, returns NULL.
    FS_ResolverFileEntry *      findFileInTable( const char * name );
    
private:
    /// Adds the file to the table.
    void                        addFileToTable(const UT_StringHolder &name,
                                                FS_ResolverFileEntry *entry);

    /// Removes the file entry from the table.  If 'delete_file' is true,
    /// the file on disk is also deleted.
    void                        removeFileFromTable(const UT_StringRef &name,
                                                     bool delete_file);
                                                

    /// Deletes the entry and any temporary files that hold the resource data.
    /// If 'delete_file' is true, the file on disk is also deleted.
    void                        deleteEntry(FS_ResolverFileEntry *entry,
                                             bool delete_file );


private:
    /// The current resolver.
    static FS_FileResolver      *theResolver;

    /// The table that maps the data name to the file containing that data.
    UT_SymbolMap<FS_ResolverFileEntry *> myFileTable;
};


//============================================================================= 
/// Utility class for auto destruction and cleanup of the file resolver. 
class FS_API FS_AutoFileResolverDestroyer
{
public:
    /// Constructor
     FS_AutoFileResolverDestroyer( FS_FileResolver * resolver );

    /// Destructor. Deletes the resolver it holds (if not NULL), and if
    /// it is the same as the current global resolver, it resets it to NULL.
    ~FS_AutoFileResolverDestroyer();

    /// Accessor for the resolver it holds.
    FS_FileResolver *       getResolver() const
                            { return myResolver; }

    /// Sets the resolver it cleans up after.
    void                    setResolver( FS_FileResolver * resolver ) 
                            { myResolver = resolver; }

    /// Destroys the resolver right away rather than waiting for the
    /// destructor to be invoked.
    void                    destroyResolver();

private:
    // the resolver to clean up after
    FS_FileResolver *       myResolver;
                            
};

#endif