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/*
Ousía
Copyright (C) 2014, 2015 Benjamin Paaßen, Andreas Stöckel
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _OUSIA_RESOURCE_LOCATOR_HPP_
#define _OUSIA_RESOURCE_LOCATOR_HPP_
#include <istream>
#include <memory>
#include "Resource.hpp"
namespace ousia {
// Forward declaration
class ResourceLocator;
/**
* A ResourceLocator is a class able to locate resources in some way, usually
* on the hard drive.
*
* We specify this as an abstract superclass to have an interface layer between
* the program core and possible future extensions in terms of resource
* locations (e.g. online resources, .zip files, etc.).
*/
class ResourceLocator {
protected:
/**
* The locate function uses this ResourceLocator to search for a given
* Resource name (path parameter). It returns a Location with the
* 'valid' flag set accordingly.
*
* @param resource reference to a Resource the will be set the the found
* location. The content of the variable will be only valid if the return
* value of this function is set to true.
* @param path is the resource name.
* @param relativeTo is an already resolved fully qualified name/canonical
* path that is to be used as base directory for this search. It is
* guaranteed that the path was produced by this locator instance. Otherwise
* this argument is set to an empty string.
* @param type is the type of this resource.
* @return true if a resource could be found, false otherwise.
*/
virtual bool doLocate(Resource &resource, const std::string &path,
const ResourceType type,
const std::string &relativeTo) const = 0;
/**
* This method returns a stream containing the data of the resource at the
* given location.
*
* @param location is a found location, most likely from a Location.
*
* @return a stream containing the data of the Resource at this
* location. This has to be a unique_pointer because the current
* C++11 compiler does not yet support move semantics for
* streams.
*/
virtual std::unique_ptr<std::istream> doStream(
const std::string &location) const = 0;
public:
/**
* Virtual destructor of the ResourceLocator interface.
*/
virtual ~ResourceLocator() {}
/**
* The locate function uses this ResourceLocator to search for a given
* Resource name (path parameter).
*
* @param resource reference to a Resource the will be set the the found
* location. The content of the variable will be only valid if the return
* value of this function is set to true.
* @param path is the resource name.
* @param relativeTo is an already resolved Resource.
* @param type is the type of this resource.
* @return true if a resource could be found, false otherwise.
*/
bool locate(Resource &resource, const std::string &path,
const ResourceType type = ResourceType::UNKNOWN,
const Resource &relativeTo = NullResource) const;
/**
* The locate function uses this ResourceLocator to search for a given
* Resource name (path parameter).
*
* @param resource reference to a Resource the will be set the the found
* location. The content of the variable will be only valid if the return
* value of this function is set to true.
* @param path is the resource name.
* @param type is the type of this resource.
* @param relativeTo is the location of an already resolved resource
* relative to which this resource should be located.
* @return true if a resource could be found, false otherwise.
*/
bool locate(Resource &resource, const std::string &path,
const ResourceType type,
const std::string &relativeTo) const;
/**
* This method returns a stream containing the data of the resource at the
* given location.
*
* @param location is a found location, most likely from a Location.
*
* @return a stream containing the data of the Resource at this
* location. This has to be a unique_pointer because the current
* C++11 compiler does not yet support move semantics for
* streams.
*/
std::unique_ptr<std::istream> stream(const std::string &location) const;
};
/**
* The StaticResourceLocator class stores a set of predefined resources in
* memory and allows to return these.
*/
class StaticResourceLocator : public ResourceLocator {
private:
/**
* Map containing the paths and the corresponding stored data.
*/
std::map<std::string, std::string> resources;
protected:
/**
* Always returns false.
*/
bool doLocate(Resource &resource, const std::string &path,
const ResourceType type,
const std::string &relativeTo) const override;
/**
* Returns an input stream containing an empty string.
*/
std::unique_ptr<std::istream> doStream(
const std::string &location) const override;
public:
/**
* Stores static (string) data for the given path.
*
* @param path is the path the resource should be stored with.
* @param data is the data that should be stored for that path.
*/
void store(const std::string &path, const std::string &data);
};
/**
* Implementation of the NullResourceLocator - contains a default implementation
* of the ResourceLocator class that does nothing. This class is e.g. used in
* the default constructor of the resource class. A instance of the class is
* provided as "NullResourceLocator".
*/
class NullResourceLocatorImpl : public ResourceLocator {
protected:
/**
* Always returns false.
*/
bool doLocate(Resource &resource, const std::string &path,
const ResourceType type,
const std::string &relativeTo) const override;
/**
* Returns an input stream containing an empty string.
*/
std::unique_ptr<std::istream> doStream(
const std::string &location) const override;
};
/**
* The NullResourceLocator is used as a fallback for invalid Resources.
*/
extern const NullResourceLocatorImpl NullResourceLocator;
}
#endif /* _RESOURCE_LOCATOR_HPP_ */
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