haiku/docs/user/storage/Resources.dox

/*
 * Copyright 2001-2006 Ingo Weinhold, bonefish@cs.tu-berlin.de
 * Copyright 2013 Haiku Inc. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		John Scipione, jscipione@gmail.com
 *		Ingo Weinhold, bonefish@users.sf.net
 *
 * Corresponds to:
 *		headers/os/storage/Resources.h	hrev45283
 *		src/kits/storage/Resources.cpp	hrev45283
 */


/*!
	\file Resources.h
	\ingroup storage
	\ingroup libbe
	\brief Provides the BResources class.
*/


/*!
	\class BResources
	\ingroup storage
	\ingroup libbe
	\brief Provides an interface for accessing and manipulating file
	       resources.

	BResources delegates most of the work to ResourcesContainer and
	ResourceFile. The former manages a collections of ResourceItem objects's
	(the actual resources) whereas the latter provides the file I/O
	functionality.

	An InitCheck() method is not needed, since a BResources object will
	never be invalid. It always serves as a resources container, even if
	it is not associated with a file. It is always possible to WriteTo()
	the resources BResources contains to a file (a valid one of course).
*/


/*!
	\fn BResources::BResources()
	\brief Creates an uninitialized BResources object.

	\see SetTo()
*/


/*!
	\fn BResources::BResources(const BFile* file, bool clobber)
	\brief Creates a BResources object that represents the resources of the
	       supplied \a file.

	If the \a clobber argument is \c true, the data of the file are erased
	and it is turned into an empty resource file. Otherwise \a file
	must refer either to a resource file or to an executable (ELF or PEF
	binary). If the file has been opened \c B_READ_ONLY, only read access
	to its resources is possible.

	The BResources object makes a copy of \a file, that is the caller remains
	owner of the BFile object.

	\param file The file to create a BResource object from.
	\param clobber If \c true, the data of the file are erased.
*/


/*!
	\fn BResources::BResources(const char* path, bool clobber)
	\brief Creates a BResources object that represents the resources of the
	       file referenced by the supplied \a path.

	If the \a clobber argument is \c true, the data of the file are erased
	and it is turned into an empty resource file. Otherwise \a path
	must refer either to a resource file or to an executable (ELF or PEF
	binary).

	\param path A path referring to the file to create a BResource object
	       from.
	\param clobber If \c true, the data of the file are erased.
*/


/*!
	\fn BResources::BResources(const entry_ref* ref, bool clobber)
	\brief Creates a BResources object that represents the resources of the
	       file referenced by the supplied \a ref.

	If the \a clobber argument is \c true, the data of the file are erased
	and it is turned into an empty resource file. Otherwise \a ref
	must refer either to a resource file or to an executable (ELF or PEF
	binary).

	\param ref An entry_ref referring to the file to create a BResource object
	       from.
	\param clobber If \c true, the data of the file are erased.
*/


/*!
	\fn BResources::~BResources()
	\brief Destroys the BResources object and frees any associated resources.

	Sync() is first called to make sure that the changes are written back to
	the file.
*/


/*!
	\name SetTo methods

	What happens, if \a clobber is \c true, depends on the type of the file.
	If the file is capable of containing resources, that is, is a resource
	file or an executable (ELF or PEF), its resources are removed. Otherwise
	the file's data are erased and it is turned into an empty resource file.
	If \a clobber is \c false, \a file must refer to a file that is capable
	of containing resources.

	If the file has been opened \c B_READ_ONLY, only read access
	to its resources is possible.

	The BResources object makes a copy of \a file, that is the caller remains
	owner of the BFile object.
*/


//! @{


/*!
	\fn status_t BResources::SetTo(const BFile* file, bool clobber)
	\brief Initializes the BResources object to represent the resources of
	       the supplied file.

	\param file The file to initialize the BResources object from.
	\param clobber If \c true, the data of the file are erased.

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a file was \c NULL or uninitialized.
	\retval B_ERROR Failed to initialize the object.
*/


/*!
	\fn status_t BResources::SetTo(const char* path, bool clobber)
	\brief Initialized the BResources object to represent the resources of
	       the file referred to by the supplied \a path.

	\param path A path referring to the file to create a BResource object
	       from.
	\param clobber If \c true, the data of the file are erased.

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a path was \c NULL.
	\retval B_ENTRY_NOT_FOUND The file referenced by \a path couldn't be found.
	\retval B_ERROR Failed to initialize the object.
*/


/*!
	\fn status_t BResources::SetTo(const entry_ref* ref, bool clobber)
	\brief Initialized the BResources object to represent the resources of the
	       file referenced by the supplied \a ref.

	\param ref An entry_ref referring to the file to create a BResource object
	       from.
	\param clobber If \c true, the data of the file are erased.

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a ref was \c NULL.
	\retval B_ENTRY_NOT_FOUND The file referenced by \a ref couldn't be found.
	\retval B_ERROR Failed to initialize the object.
*/


/*!
	\fn status_t BResources::SetToImage(image_id image, bool clobber)
	\brief Initialized the BResources object to represent the resources of
	       the file from which the specified \a image has been loaded.

	If \a clobber is \c true, the file's resources are removed.

	\param image ID of a loaded image.
	\param clobber If \c true, the data of the file are erased.

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_ENTRY_NOT_FOUND The file referenced by \a ref couldn't be found.
	\retval B_ERROR Failed to initialize the object.
*/


/*!
	\fn status_t BResources::SetToImage(const void* codeOrDataPointer,
		bool clobber)
	\brief Initialized the BResources object to represent the resources of
	       the file from which the specified pointer has been loaded.

	The image belongs to the current team and is identified by a pointer into
	it's code (aka text) or data segment, i.e. any pointer to a function or a
	static (or global) variable will do.

	If \a clobber is \c true, the file's resources are removed.

	\param codeOrDataPointer Pointer to the text or data segment of the image.
	\param clobber If \c true, the data of the file are erased.

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a codeOrDataPointer was \c NULL.
	\retval B_ENTRY_NOT_FOUND The image or the file couldn't be found.
	\retval B_ERROR Failed to initialize the object.
*/


//! @}


/*!
	\name Constructor helper methods
*/


//! @{


/*!
	\fn void BResources::Unset()
	\brief Returns the BResources object to an uninitialized state.

	If the object represented resources that had been modified, the data are
	written back to the file.

	\note This method is not found in BeOS R5.
*/


/*!
	\fn status_t BResources::InitCheck() const
	\brief Gets the initialization status of the object.

	Unlike other Storage Kit classes a BResources object is always properly
	initialized, unless it couldn't allocate memory for some important
	internal structures. Thus even after a call to SetTo() that reported an
	error, InitCheck() is likely to return \c B_OK.

	\note This method is not found in BeOS R5.

	\return \c B_OK if the objects is properly initialized,
	        \c B_NO_MEMORY otherwise.
*/


//! @}


/*!
	\name LoadResources methods

	A resource is loaded into memory only once. A second call with the same
	parameters will result in the same pointer. The BResources object is the
	owner of the allocated memory and the pointer to it will be valid until
	the object is destroyed or the resource is removed or modified.
*/


//! @{


/*!
	\fn const void* BResources::LoadResource(type_code type, int32 id,
		size_t* _size)
	\brief Loads a resource identified by \a type and \a id into memory.

	\param type The type of the resource to be loaded.
	\param id The ID of the resource to be loaded.
	\param _size A pointer to a variable into which the size of the resource
	       shall be written.

	\return A pointer to the resource data if everything went fine, or
			\c NULL if the file does not have a resource that matches the
			parameters or an error occurred.
*/


/*!
	\fn const void* BResources::LoadResource(type_code type, const char* name,
		size_t* _size)
	\brief Loads a resource identified by \a type and \a name into memory.

	\note Since a type and name pair may not identify a resource uniquely,
		  this method always returns the first resource that matches the
		  parameters, that is the one with the smallest index.

	\param type The type of the resource to be loaded.
	\param name The name of the resource to be loaded.
	\param _size A pointer to a variable into which the size of the resource
		   shall be written.

	\return A pointer to the resource data if everything went fine, or
			\c NULL if the file does not have a resource that matches the
			parameters or an error occurred.
*/


/*!
	\fn status_t BResources::PreloadResourceType(type_code type)
	\brief Loads all resources of the specified \a type into memory.

	If \a type is 0, all resources are loaded. This might be useful for
	performance reasons.

	\param type The type of resources to be loaded.

	\returns One of the following status codes or the negation of the number
	         of errors that occurred.
	\retval B_OK Everything went fine.
	\retval B_BAD_FILE The resource map is empty???
*/


//! @}


/*!
	\fn const BFile& BResources::File() const
	\brief Gets a reference to the internal BFile object.

	\return A reference to the internal BFile object.
*/


/*!
	\fn status_t BResources::Sync()
	\brief Writes all changes to the resources to the file.

	Since AddResource() and RemoveResource() may change the resources only in
	memory, this method can be used to make sure, that all changes are
	actually written to the file.

	The BResources object's destructor calls Sync() before cleaning up.

	\note When a resource is written to the file its data is converted
	      to the endianness of the file. When reading a resource the
	      data is converted to the endianness of the host. This of course
	      only works for known types, i.e. those that swap_data() is able to
	      understand.

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_FILE The resource map is empty???
	\retval B_FILE_ERROR A file error occurred.
	\retval B_IO_ERROR An error occurred while writing the resources.
	\retval B_NOT_ALLOWED The file was opened read only.
*/


/*!
	\fn status_t BResources::MergeFrom(BFile* fromFile)
	\brief Adds the resources of \a fromFile to the internal file of the
	       BResources object.

	\param fromFile The file whose resources are to be be copied from.

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_FILE The resource map is empty???
	\retval B_BAD_VALUE \a fromFile was \c NULL.
	\retval B_FILE_ERROR A file error occurred.
	\retval B_IO_ERROR An error occurred while writing the resources.
*/


/*!
	\fn status_t BResources::WriteTo(BFile* file)
	\brief Writes the resources to a new file.

	The resources formerly contained in the target file (if any) are erased.
	When the method returns, the BResources object refers to the new file.

	\warning If the resources have been modified, but Sync() has not been
	         called, the old file remains unmodified.

	\param file The file that the resources shall be written to.

	\return \c B_OK if everything went fine or an error code otherwise.
*/


/*!
	\fn status_t BResources::AddResource(type_code type, int32 id,
		const void* data, size_t length, const char* name)
	\brief Adds a new resource to the file.

	If a resource already exists with the same \a type and \a id it is
	replaced. The caller keeps the ownership of the supplied chunk of memory
	containing the resource data.

	Supplying an empty \a name (\c "") is equivalent to supplying a \c NULL
	\a name.

	\param type The type of the resource.
	\param id The ID of the resource.
	\param data The resource data.
	\param length The size of the data in bytes.
	\param name The name of the resource (may be empty or \c NULL).

	\returns A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a data was \c NULL.
	\retval B_FILE_ERROR A file error occurred.
	\retval B_NO_MEMORY Not enough memory for the operation.
	\retval B_NOT_ALLOWED The file was opened read only.
*/


/*!
	\fn bool BResources::HasResource(type_code type, int32 id)
	\brief Returns whether the file contains a resource with the specified
	       \a type and \a id.

	\param type The resource type to check.
	\param id The ID of the resource to check.

	\return \c true if the file contains a matching resource,
	        \c false otherwise.
*/


/*!
	\fn bool BResources::HasResource(type_code type, const char* name)
	\brief Returns whether the file contains a resource with the specified
	       \a type and \a name.

	\param type The resource type to check.
	\param name The name of the resource to check.

	\return \c true, if the file contains a matching resource,
	        \c false otherwise.
*/


/*!
	\fn bool BResources::GetResourceInfo(int32 byIndex, type_code* typeFound,
		int32* idFound, const char** nameFound, size_t* lengthFound)
	\brief Gets information about a resource identified by \a byindex.

	\param byIndex The index of the resource in the file.
	\param typeFound A pointer to a variable the type of the found resource
	       shall be written into.
	\param idFound A pointer to a variable the ID of the found resource
	       shall be written into.
	\param nameFound A pointer to a variable the name pointer of the found
	       resource shall be written into.
	\param lengthFound A pointer to a variable the data size of the found
	       resource shall be written into.

	\return \c true, if a matching resource could be found,
	        \c false otherwise.
*/


/*!
	\fn bool BResources::GetResourceInfo(type_code byType, int32 andIndex,
		int32* idFound, const char** nameFound, size_t* lengthFound)
	\brief Gets information about a resource identified by \a byType and
	       \a andIndex.

	\param byType The resource type.
	\param andIndex The index into a array of resources of type \a byType.
	\param idFound A pointer to a variable the ID of the found resource
	       shall be written into.
	\param nameFound A pointer to a variable the name pointer of the found
	       resource shall be written into.
	\param lengthFound A pointer to a variable the data size of the found
	       resource shall be written into.

	\return \c true, if a matching resource could be found,
	        \c false otherwise.
*/


/*!
	\fn bool BResources::GetResourceInfo(type_code byType, int32 andID,
		const char** nameFound, size_t* lengthFound)
	\brief Gets information about a resource identified by \a byType and
	       \a andID.

	\param byType The resource type.
	\param andID The resource ID.
	\param nameFound A pointer to a variable the name pointer of the found
	       resource shall be written into.
	\param lengthFound A pointer to a variable the data size of the found
	       resource shall be written into.

	\return \c true, if a matching resource could be found,
	        \c false otherwise.
*/


/*!
	\fn bool BResources::GetResourceInfo(type_code byType, const char* andName,
		int32* idFound, size_t* lengthFound)
	\brief Gets information about a resource identified by \a byType and
	       \a andName.

	\param byType The resource type.
	\param andName The resource name.
	\param idFound A pointer to a variable the ID of the found resource
	       shall be written into.
	\param lengthFound A pointer to a variable the data size of the found
	       resource shall be written into.

	\return \c true, if a matching resource could be found,
	        \c false otherwise.
*/


/*!
	\fn bool BResources::GetResourceInfo(const void* byPointer,
		type_code* typeFound, int32* idFound, size_t* lengthFound,
		const char** nameFound)
	\brief Gets information about a resource identified by \a byPointer.

	\param byPointer The pointer to the resource data (formerly returned by
	       LoadResource()).
	\param typeFound A pointer to a variable the type of the found resource
	       shall be written into.
	\param idFound A pointer to a variable the ID of the found resource
	       shall be written into.
	\param lengthFound A pointer to a variable the data size of the found
	       resource shall be written into.
	\param nameFound A pointer to a variable the name pointer of the found
	       resource shall be written into.

	\return \c true, if a matching resource could be found,
	        \c false otherwise.
*/


/*!
	\fn status_t BResources::RemoveResource(const void* resource)
	\brief Removes a resource identified by \a resource.

	\param resource The pointer to the resource data (formerly returned by
	       LoadResource()).

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a resource was \c NULL or invalid (didn't point to
	        any resource data of this file).
	\retval B_ERROR An error occurred while removing the resource.
	\retval B_FILE_ERROR A file error occurred.
	\retval B_NOT_ALLOWED The file was opened read only.
*/


/*!
	\fn status_t BResources::RemoveResource(type_code type, int32 id)
	\brief Removes a resource identified by \a type and \a id.

	\param type The type of the resource to remove.
	\param id The ID of the resource to remove.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE No such resource was found.
	\retval B_ERROR An error occurred while removing the resource.
	\retval B_FILE_ERROR A file error occurred.
	\retval B_NOT_ALLOWED The file was opened read only.
*/


/*!
	\name Deprecated methods

	These methods are deprecated and should not be used as there is a better
	method. See the method description for the replacement method to use.
*/


//! @{


/*!
	\fn status_t BResources::WriteResource(type_code type, int32 id,
		const void* data, off_t offset, size_t length)
	\brief Writes data into an existing resource.
	       (deprecated, use AddResource() instead)

	\deprecated Use AddResource() instead.

	If writing the data would exceed the bounds of the resource, it is
	enlarged respectively. If \a offset is past the end of the resource,
	padding with unspecified data is inserted.

	\param type The type of the resource to write data to.
	\param id The ID of the resource to write data to.
	\param data The data to be written.
	\param offset The byte offset relative to the beginning of the resource at
		   which the data shall be written.
	\param length The size of the data to be written.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a data was \c NULL or \a type and \a id did not
	        identify an existing resource.
	\retval B_ERROR Error writing data.
	\retval B_NO_MEMORY Not enough memory for this operation.
*/


/*!
	\fn status_t BResources::ReadResource(type_code type, int32 id,
		void* data, off_t offset, size_t length)
	\brief Reads data from an existing resource.
	       (deprecated, use LoadResource() instead)

	\deprecated Use LoadResource() instead.

	If more data than existing are requested, this method does not fail. It
	will then read only the existing data. As a consequence an offset past
	the end of the resource will not cause the method to fail, but no data
	will be read at all.

	\param type The type of the resource to be read.
	\param id The ID of the resource to be read.
	\param data A pointer to a buffer into which the data shall be read
	\param offset The byte offset relative to the beginning of the resource
		   from which the data shall be read.
	\param length The size of the data to be read.

	\return A status code.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a data was \c NULL or \a type and \a id did not
	        identify an existing resource.
	\retval B_ERROR Error reading data.
	\retval B_NO_MEMORY Not enough memory for this operation.
*/


/*!
	\fn void* BResources::FindResource(type_code type, int32 id,
		size_t* lengthFound)
	\brief Finds a resource by \a type and \a id and returns a pointer to a
	       copy of its data. (deprecated, use LoadResource() instead)

	\deprecated Use LoadResource() instead.

	\warning The caller is responsible for calling free() to release the
	         memory used by the returned data.

	\param type The type of the resource to find.
	\param id The ID of the resource to find.
	\param lengthFound A pointer to a variable into which the size of the
		   resource data shall be written.

	\return A pointer to the resource data if everything went fine or \c NULL
	        if an error occurred.
*/


/*!
	\fn void* BResources::FindResource(type_code type, const char* name,
		size_t* lengthFound)
	\brief Finds a resource by \a type and \a name and returns a pointer to a
	       copy of its data. (deprecated, use LoadResource() instead)

	\deprecated Use LoadResource() instead.

	\warning The caller is responsible for calling free() to release the
	         memory used by the returned data.

	\param type The type of the resource to find.
	\param name The name of the resource to find.
	\param lengthFound A pointer to a variable into which the size of the
		   resource data shall be written.

	\return A pointer to the resource data if everything went fine or \c NULL
	        if an error occurred.
*/


//! @}