haiku/docs/user/storage/PathFinder.dox

/*
 * Copyright 2013-2014 Haiku, Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Documentation by:
 *		John Scipione, jscipione@gmail.com
 *		Ingo Weinhold, ingo_weinhold@gmx.de
 *
 * Corresponds to:
 *		headers/os/storage/PathFinder.h	 hrev47402
 *		src/kits/storage/PathFinder.cpp	 hrev47402
 */


/*!
	\file PathFinder.h
	\ingroup storage
	\ingroup libbe
	\brief Provides the BPathFinder class interface.
*/


/*!
	\class BPathFinder
	\ingroup storage
	\ingroup libbe
	\brief Helper class to retrieve paths in the file system layout.

	The BPathFinder provides two sets of methods for retrieving paths:
	FindPath() for getting a single path in an installation location specified
	via a constructor or a SetTo() invocation, and the static FindPaths() for
	getting a list of paths for all installation locations.

	\since Haiku R1
*/


/*!
	\fn BPathFinder::BPathFinder(const void* codePointer,
		const char* dependency)
	\brief Creates an object referring to an installation location based on a
	       loaded image file.

	When initialized with this constructor a FindPath() method called afterward
	determines the path of the image (i.e. executable, library, or add-on) file
	associated with \a codePointer, a pointer to a location in the code or
	static data of an image loaded in the caller's team. Based on that path the
	path constant passed to FindPath() will be evaluated. In most cases that
	means first determining the path of the installation location from the path.

	If \a dependency is specified, instead of determining the installation
	location path from the image path, the installation location path of the
	dependency \a dependency of the package containing the image file is used.

	If the initialization fails, e.g. due to insufficient memory or invalid
	arguments, subsequent calls to FindPath() will return an error.

	\param codePointer A pointer to code or static data belonging to the image
	       based on which FindPath() shall compute the path. The special value
	       \c B_APP_IMAGE_SYMBOL (the default) can be used to refer to the
	       program image, and \c B_CURRENT_IMAGE_SYMBOL for the caller's image.
	\param dependency The name of the package's "requires" entry to be used for
	       resolving the installation location. Can be \c NULL (the default).

	\since Haiku R1
*/


/*!
	\fn BPathFinder::BPathFinder(const char* path, const char* dependency)
	\brief Creates an object referring to an installation location based on a
	       given \a path.

	When initialized with this constructor a FindPath() method called afterward
	evaluates the path constant passed to it based on \a path. In most cases
	that means first determining the path of the installation location from the
	given \a path.

	If \a dependency is specified, instead of determining the installation
	location path from the given path, the installation location path of the
	dependency \a dependency of the package containing the file referred to by
	\a path is used.

	If the initialization fails, e.g. due to insufficient memory or invalid
	arguments, subsequent calls to FindPath() will return an error.

	\param path A path based on which FindPath() shall compute the path.
	\param dependency The name of the package's "requires" entry to be used
	       for resolving the installation location. Can be \c NULL.

	\since Haiku R1
*/


/*!
	\fn BPathFinder::BPathFinder(const entry_ref& ref, const char* dependency)
	\brief Creates an object referring to an installation location based on a
	       given entry_ref.

	The constructor converts the given entry_ref \a ref to a path and then
	initializes the object like
	BPathFinder::BPathFinder(const char*, const char*).

	\param ref A reference to be resolved to a path based on which FindPath()
	       shall compute the path.
	\param dependency The name of the package's "requires" entry to be used
	       for resolving the installation location. Can be \c NULL.

	\see BPathFinder::BPathFinder(const char*, const char*)

	\since Haiku R1
*/


/*!
	\fn BPathFinder::BPathFinder(const BResolvableExpression& expression,
		const char* dependency)
	\brief Creates an object referring to an installation location based on
	       the path of a package satisfying the given resolvable expression.

	The constructor finds the latest package that satisfies the resolvable
	expression \a expression and then uses its path to initialize the object
	like BPathFinder::BPathFinder(const char*, const char*).

	\note When using this constructor linking against libpackage.so is
	      required.

	\param expression A resolvable expression to be resolved to the path of
	       the latest package satisfying it, based on which FindPath() shall
	       compute the path.
	\param dependency The name of the package's "requires" entry to be used
	       for resolving the installation location. Can be \c NULL.

	\see BPathFinder::BPathFinder(const char*, const char*)

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::SetTo(const void* codePointer,
		const char* dependency)
	\brief Reinitializes the object to refer to an installation location based
	       on a loaded image file.

	When reinitialized with this method a FindPath() method called afterward
	determines the path of the image (i.e. executable, library, or add-on)
	file associated with \a codePointer, a pointer to a location in the code
	or static data of an image loaded in the caller's team. Based on that path
	the path constant passed to FindPath() will be evaluated. In most cases
	that means first determining the path of the installation location from
	the path.

	If \a dependency is specified, instead of determining the installation
	location path from the image path, the installation location path of the
	dependency \a dependency of the package containing the image file is used.

	If the initialization fails, e.g. due to insufficient memory or invalid
	arguments, this method and subsequent calls to FindPath() will return an
	error.

	\param codePointer A pointer to code or static data belonging to the image
	       based on which FindPath() shall compute the path. The special value
	       \c B_APP_IMAGE_SYMBOL (the default) can be used to refer to the
	       program image, and \c B_CURRENT_IMAGE_SYMBOL for the caller's image.
	\param dependency The name of the package's "requires" entry to be used for
	       resolving the installation location. Can be \c NULL (the default).

	\return A status code.
	\retval B_OK Everything went fine.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::SetTo(const char* path, const char* dependency)
	\brief Reinitializes the object to refer to an installation location based
	       on a given \a path.

	When reinitialized with this method a FindPath() method called afterward
	evaluates the path constant passed to it based on \a path. In most cases
	that means first determining the path of the installation location from
	the given \a path.

	If \a dependency is specified, instead of determining the installation
	location path from the given path, the installation location path of the
	dependency \a dependency of the package containing the file referred to by
	\a path is used.

	If the initialization fails, e.g. due to insufficient memory or invalid
	arguments, this method and subsequent calls to FindPath() will return an
	error.

	\param path A path based on which FindPath() shall compute the path.
	\param dependency The name of the package's "requires" entry to be used for
	       resolving the installation location. Can be \c NULL.

	\return \c B_OK Everything if went fine or an error code otherwise.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::SetTo(const entry_ref& ref,
		const char* dependency)
	\brief Reinitializes the object to refer to an installation location based
	       on a given entry_ref.

	This method converts the given entry_ref \a ref to a path and then calls
	calls BPathFinder::SetTo(const char*, const char*).

	\param ref A reference to be resolved to a path based on which FindPath()
	       shall compute the path.
	\param dependency The name of the package's "requires" entry to be used
	       for resolving the installation location. Can be \c NULL.

	\see status_t BPathFinder::SetTo(const char*, const char*)

	\return \c B_OK Everything if went fine or an error code otherwise.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::SetTo(const BResolvableExpression& expression,
		const char* dependency)
	\brief Reinitializes the object to refer to an installation location based
		on a given resolvable expression.

	This method finds the latest package that satisfies the resolvable
	expression \a expression and then passes its path to
	BPathFinder::SetTo(const char*, const char*).

	\note When using this method linking against libpackage.so is required.

	\param expression A resolvable expression to be resolved to the path of the
		latest package satisfying it, based on which FindPath() shall compute
		the path.
	\param dependency The name of the package's "requires" entry to be used for
		resolving the installation location. Can be \c NULL.

	\see status_t BPathFinder::SetTo(const char*, const char*)

	\return \c B_OK Everything if went fine or an error code otherwise.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::FindPath(const char* architecture,
		path_base_directory baseDirectory, const char* subPath, uint32 flags,
		BPath& _path)
	\brief Retrieves a path in the file system layout based.

	Depending on how the object was initialized this method starts with a path
	(from an image file or as given) and based on it evaluates \a baseDirectory.
	In most cases that means first determining the path of the installation
	location from the path, then appending the relative path corresponding to
	the given \a baseDirectory constant, and finally appending \a subPath, if
	given.

	If a dependency string was passed to the previous constructor or SetTo()
	method, instead of determining the installation location path from the
	initial path, the installation location path of the dependency of the
	package containing the file the initial path refers to is used.

	If \a baseDirectory specifies a path that is architecture dependent,
	\a architecture is used for constructing the path. If \a architecture is
	\c NULL, the architecture associated with the initial path (as returned by
	guess_architecture_for_path()) is used. Note that if an image was specified,
	this is the same as the caller's architecture (as returned by
	get_architecture()).

	If \c B_FIND_PATH_IMAGE_PATH or \c B_FIND_PATH_PACKAGE_PATH are
	specified, \a subPath is ignored. In the former case, which is only valid,
	if an image was specified for initialization, \a dependency is ignored as
	well and the path of the image file is returned. In the latter case the path
	of the package containing the file the initial path refers to, respectively,
	if \a dependency was specified, that of the package \a dependency was
	resolved to is returned.

	\param architecture The name of the architecture to be used for resolving
	       \a architecture dependent paths. Can be \c NULL, in which case the
	       \a architecture associated with the initial path is used.
	\param baseDirectory Constant indicating which path to retrieve.
	\param subPath Relative subpath that shall be appended. Can be \c NULL.
	\param flags Bitwise OR of any of the following flags:
	       - \c B_FIND_PATH_CREATE_DIRECTORY: If the resulting path doesn't
	         exist, create it as a directory (including all missing ancestors).
	       - \c B_FIND_PATH_CREATE_PARENT_DIRECTORY: If the resulting path's
	         parent doesn't exist, create the parent directory (including all
	         missing ancestors).
	       - \c B_FIND_PATH_EXISTING_ONLY: If the resulting path doesn't exist,
	         fail with \c B_ENTRY_NOT_FOUND.
	\param _path The variable to be set to the resulting path on success.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND A file system entry required for retrieving the
	        path didn't exist, e.g. \c B_FIND_PATH_PACKAGE_PATH was specified
	        and the image file didn't belong to a package, or \c dependency
	        was specified, but wasn't a "requires" entry of the package, or
	        \c B_FIND_PATH_EXISTING_ONLY was specified and the resulting path
	        didn't exist.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::FindPath(path_base_directory baseDirectory,
		const char* subPath, uint32 flags, BPath& _path)
	\brief Retrieves a path in the file system layout based.

	Equivalent to a call to BPathFinder::FindPath(const char*,
	path_base_directory, const char*, uint32, BPath&) with a \c NULL
	architecture.

	\param baseDirectory Constant indicating which path to retrieve.
	\param subPath Relative subpath that shall be appended. Can be \c NULL.
	\param flags Bitwise OR of any of the following flags:
	       - \c B_FIND_PATH_CREATE_DIRECTORY: If the resulting path doesn't
	         exist, create it as a directory (including all missing ancestors).
	       - \c B_FIND_PATH_CREATE_PARENT_DIRECTORY: If the resulting path's
	         parent doesn't exist, create the parent directory (including all
	         missing ancestors).
	       - \c B_FIND_PATH_EXISTING_ONLY: If the resulting path doesn't exist,
	         fail with \c B_ENTRY_NOT_FOUND.
	\param _path The variable to be set to the resulting path on success.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND A file system entry required for retrieving the
	        path didn't exist, e.g. \c B_FIND_PATH_PACKAGE_PATH was specified
	        and the image file didn't belong to a package, or \c dependency
	        was specified, but wasn't a "requires" entry of the package, or
	        \c B_FIND_PATH_EXISTING_ONLY was specified and the resulting path
	        didn't exist.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::FindPath(path_base_directory baseDirectory,
		const char* subPath, BPath& _path)
	\brief Retrieves a path in the file system layout based.

	Equivalent to a call to BPathFinder::FindPath(const char*,
	path_base_directory, const char*, uint32, BPath&) with a \c NULL
	architecture and 0 flags.

	\param baseDirectory Constant indicating which path to retrieve.
	\param subPath Relative subpath that shall be appended. Can be \c NULL.
	\param _path The variable to be set to the resulting path on success.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND A file system entry required for retrieving the
		path didn't exist, e.g. \c B_FIND_PATH_PACKAGE_PATH was specified
		and the image file didn't belong to a package, or \c dependency was
		specified, but wasn't a "requires" entry of the package.
*/


/*!
	\fn status_t BPathFinder::FindPath(path_base_directory baseDirectory,
		BPath& _path)
	\brief Retrieves a path in the file system layout based.

	Equivalent to a call to BPathFinder::FindPath(const char*,
	path_base_directory, const char*, uint32, BPath&) with a \c NULL
	architecture, 0 flags, and \c NULL subpath.

	\param baseDirectory Constant indicating which path to retrieve.
	\param _path The variable to be set to the resulting path on success.
	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND A file system entry required for retrieving the
	        path didn't exist, e.g. \c B_FIND_PATH_PACKAGE_PATH was specified
	        and the image file didn't belong to a package, or \c dependency
	        was specified, but wasn't a "requires" entry of the package.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::FindPaths(const char* architecture,
		path_base_directory baseDirectory, const char* subPath, uint32 flags,
		BStringList& _paths)
	\brief Retrieves a list of paths in the file system layout.

	For each installation location -- in the order most specific to most
	generic, non-packaged before packaged -- the function evaluates
	\a baseDirectory to a path and appends \a subPath, if given.

	If \a baseDirectory specifies a path that is architecture dependent,
	\a architecture is used for constructing each path. If \a architecture is
	\c NULL, the caller's architecture (as returned by get_architecture()) is
	used.

	\c B_FIND_PATH_PACKAGE_PATH and \c B_FIND_PATH_IMAGE_PATH are not
	valid arguments for this function.

	\param architecture The name of the architecture to be used for resolving
	       \a architecture dependent paths. Can be \c NULL, in which case the
	       caller's \a architecture is used.
	\param baseDirectory Constant indicating which paths to retrieve.
	\param subPath Relative subpath that shall be appended. Can be \c NULL.
	\param flags Bitwise OR of any of the following flags:
	       - \c B_FIND_PATH_CREATE_DIRECTORY: If a resulting path doesn't
	         exist, create it as a directory (including all missing ancestors).
	       - \c B_FIND_PATH_CREATE_PARENT_DIRECTORY: If a resulting path's
	         parent doesn't exist, create the parent directory (including all
	         missing ancestors).
	       - \c B_FIND_PATH_EXISTING_ONLY: If a resulting path doesn't exist,
	         skip it. If none of the paths exist, fail with \c B_ENTRY_NOT_FOUND.
	\param _paths The BStringList variable where the retrieved paths shall be
	       stored. The list is emptied before adding the paths. It is also
	       emptied on error.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND A file system entry required for retrieving the
	        paths didn't exist, e.g. \c B_FIND_PATH_EXISTING_ONLY was
	        specified and none of the resulting paths existed.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::FindPaths(path_base_directory baseDirectory,
		const char* subPath, uint32 flags, BStringList& _paths)
	\brief Retrieves a list of paths in the file system layout.

	Equivalent to a call to BPathFinder::FindPaths(const char*,
	path_base_directory, const char*, uint32, BStringList&) with a \c NULL
	architecture.

	\param baseDirectory Constant indicating which paths to retrieve.
	\param subPath Relative subpath that shall be appended. Can be \c NULL.
	\param flags Bitwise OR of any of the following flags:
	       - \c B_FIND_PATH_CREATE_DIRECTORY: If a resulting path doesn't
	         exist, create it as a directory (including all missing ancestors).
	       - \c B_FIND_PATH_CREATE_PARENT_DIRECTORY: If a resulting path's
	         parent doesn't exist, create the parent directory (including all
	         missing ancestors).
	       - \c B_FIND_PATH_EXISTING_ONLY: If a resulting path doesn't exist,
	         skip it. If none of the paths exist, fail with
	         \c B_ENTRY_NOT_FOUND.
	\param _paths The BStringList variable where the retrieved paths shall be
	       stored. The list is emptied before adding the paths. It is also
	       emptied on error.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND A file system entry required for retrieving the
	        paths didn't exist, e.g. \c B_FIND_PATH_EXISTING_ONLY was specified
	        and none of the resulting paths existed.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::FindPaths(path_base_directory baseDirectory,
		const char* subPath, BStringList& _paths)
	\brief Retrieves a list of paths in the file system layout.

	Equivalent to a call to BPathFinder::FindPaths(const char*,
	path_base_directory, const char*, uint32, BStringList&) with a \c NULL
	architecture and 0 flags.

	\param baseDirectory Constant indicating which paths to retrieve.
	\param subPath Relative subpath that shall be appended. Can be \c NULL.
	\param _paths The BStringList variable where the retrieved paths shall be
	       stored. The list is emptied before adding the paths. It is also
	       emptied on error.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND A file system entry required for retrieving the
	        paths didn't exist, e.g. \c B_FIND_PATH_EXISTING_ONLY was specified
	        and none of the resulting paths existed.

	\since Haiku R1
*/


/*!
	\fn status_t BPathFinder::FindPaths(path_base_directory baseDirectory,
		BStringList& _paths)
	\brief Retrieves a list of paths in the file system layout.

	Equivalent to a call to BPathFinder::FindPaths(const char*,
	path_base_directory, const char*, uint32, BStringList&) with a \c NULL
	architecture, 0 flags, and \c NULL subpath.

	\param baseDirectory Constant indicating which paths to retrieve.
	\param _paths The BStringList variable where the retrieved paths shall be
	       stored. The list is emptied before adding the paths. It is also
	       emptied on error.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND A file system entry required for retrieving the
	        paths didn't exist, e.g. \c B_FIND_PATH_EXISTING_ONLY was specified
	        and none of the resulting paths existed.

	\since Haiku R1
*/