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Diffstat (limited to 'src/core/resource/ResourceLocator.hpp')
| -rw-r--r-- | src/core/resource/ResourceLocator.hpp | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/src/core/resource/ResourceLocator.hpp b/src/core/resource/ResourceLocator.hpp new file mode 100644 index 0000000..c1d0807 --- /dev/null +++ b/src/core/resource/ResourceLocator.hpp @@ -0,0 +1,193 @@ +/* + 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_ */ + |