haiku/docs/user/storage/Node.dox

/*
 * Copyright 2002-2014 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/Node.h	hrev47402
 *		src/kits/storage/Node.cpp	hrev47402
 */


/*!
	\file Node.h
	\ingroup storage
	\ingroup libbe
	\brief Provides the BNode class and node_ref struct.
*/


/*!
	\struct node_ref
	\ingroup storage
	\ingroup libbe
	\brief Reference structure to a particular vnode on a device.

	\since BeOS R3
*/


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

	\since BeOS R3
*/


/*!
	\fn node_ref::node_ref(const node_ref& other)
	\brief Creates a copy of the given node_ref object.

	\param other the node_ref to be copied.

	\since BeOS R3
*/


/*!
	\name Operators
*/


//! @{


/*!
	\fn bool node_ref::operator==(const node_ref& other) const
	\brief Tests whether this node_ref and the supplied one are equal.

	\param other The node_ref to be compared against.

	\return \c true, if the objects are equal, \c false otherwise.

	\since BeOS R3
*/


/*!
	\fn bool node_ref::operator!=(const node_ref& other) const
	\brief Tests whether this node_ref and the supplied one are NOT equal.

	\param other The node_ref to be compared against.

	\return \c true, if the objects are \b NOT equal, \c false otherwise.

	\since BeOS R3
*/


/*!
	\fn bool node_ref::operator<(const node_ref& other) const
	\brief Tests whether this node_ref is less than the supplied one.

	\param other The node_ref to be compared against.

	\return \c true, if this node_ref is less than \a other,
	        \c false otherwise.

	\since Haiku R1
*/


/*!
	\fn node_ref& node_ref::operator=(const node_ref& other)
	\brief Makes this node ref a copy of the supplied one.

	\param other The node_ref to be copied.

	\return A reference to this object.

	\since BeOS R3
*/


//! @}


/*!
	\var node_ref::device
	\brief The device number on which the node is located.

	\since BeOS R3
*/


/*!
	\var node_ref::node
	\brief The node's inode number.

	\since BeOS R3
*/


/*!
	\class BNode
	\ingroup storage
	\ingroup libbe
	\brief A BNode represents a chunk of data in the filesystem.

	The BNode class provides an interface for manipulating the data and
	attributes belonging to filesystem entries. The BNode is unaware of the
	name that refers to it in the filesystem (i.e. its entry), instead, a
	BNode is concerned solely with the entry's data and attributes.

	\since BeOS R3
*/


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

	\see SetTo()

	\since BeOS R3
*/


/*!
	\fn BNode::BNode(const entry_ref* ref)
	\brief Creates a BNode object and initializes it to the specified
	       entry_ref.

	\param ref The entry_ref referring to the node.

	\since BeOS R3
*/


/*!
	\fn BNode::BNode(const BEntry* entry)
	\brief Creates a BNode object and initializes it to the specified
	       filesystem entry.

	\param entry The BEntry referring to the node.

	\since BeOS R3
*/


/*!
	\fn BNode::BNode(const char* path)
	\brief Creates a BNode object and initializes it to the entry referred
	       to by the specified path.

	\param path The \a path referring to the node.

	\since BeOS R3
*/


/*!
	\fn BNode::BNode(const BDirectory* dir, const char* path)
	\brief Creates a BNode object and initializes it to the entry referred
	       to by the specified path rooted in the specified directory.

	\param dir The base BDirectory.
	\param path The \a path name relative to \a dir.

	\since BeOS R3
*/


/*!
	\fn BNode::BNode(const BNode& other)
	\brief Creates a copy of the given BNode.

	\param other The BNode to be copied.

	\since BeOS R3
*/


/*!
	\fn BNode::~BNode()
	\brief Frees all resources associated with the BNode.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::GetStat(struct stat* stat) const
	\brief Fills in the given stat structure with the <tt>stat()</tt>
	       information for this object.

	\param stat A pointer to a stat structure to be filled in.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE: \c NULL \a stat.

	\since Haiku R1
*/


/*!
	\fn int BNode::Dup()
	\brief Gets the POSIX file descriptor referred to by this node.

	Remember to call close() on the file descriptor when you're through
	with it.

	\returns A valid file descriptor, or -1 if something went wrong.

	\since Haiku R1
*/


/*!
	\name Constructor Helpers
*/


//! @{


/*!
	\fn status_t BNode::InitCheck() const
	\brief Checks whether the object has been properly initialized or not.

	\returns \c B_OK if the object has been properly initialized, or
	         \c B_NO_INIT otherwise.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::SetTo(const entry_ref* ref)
	\brief Initializes the object to the specified entry_ref.

	\param ref The entry_ref referring to the entry.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK: Everything went fine.
	\retval B_BAD_VALUE: \a ref was \c NULL.
	\retval B_ENTRY_NOT_FOUND: The entry could not be found.
	\retval B_BUSY: The entry was locked.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::SetTo(const BEntry* entry)
	\brief Initializes the object to the specified filesystem \a entry.

	\param entry The BEntry representing the entry.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a entry was \c NULL.
	\retval B_ENTRY_NOT_FOUND The \a entry could not be found.
	\retval B_BUSY The \a entry was locked.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::SetTo(const char* path)
	\brief Initializes the object to the specified \a path.

	\param path The entry's path name; \a path can be relative or absolute,
	       and can contain "." and ".." elements. If path is relative, it uses
	       the current working directory as the base directory.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a path was \c NULL.
	\retval B_ENTRY_NOT_FOUND The entry could not be found.
	\retval B_BUSY The entry of was locked.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::SetTo(const BDirectory* dir, const char* path)
	\brief Initializes the object to the entry referred by the
	       specified \a path relative to the the specified directory.

	\param dir The base BDirectory.
	\param path The path name relative to \a dir.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a dir was \c NULL.
	\retval B_ENTRY_NOT_FOUND The entry could not be found.
	\retval B_BUSY The entry was locked.

	\since BeOS R3
*/


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

	\since BeOS R3
*/


//! @}


/*!
	\name Locking Methods
*/


//! @{


/*!
	\fn status_t BNode::Lock()
	\brief Attains an exclusive lock on the data referred to by this node
	       so that it may not be modified by any other objects or methods.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_FILE_ERROR The object is not initialized.
	\retval B_BUSY The node is already locked.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::Unlock()
	\brief Unlocks the date referred to by this node.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_FILE_ERROR The object is not initialized.
	\retval B_BAD_VALUE The node is not locked.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::Sync()
	\brief Immediately performs any pending disk actions on the node.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_FILE_ERROR Something went wrong.

	\since BeOS R3
*/


//! @}


/*!
	\name Attribute Methods
*/


//! @{


/*!
	\fn ssize_t BNode::WriteAttr(const char* attr, type_code type,
		off_t offset, const void* buffer, size_t length)
	\brief Writes data from a buffer to an attribute.

	Write \a length bytes of data from \a buffer to the attribute specified
	by \a name after erasing any data that existed previously. The type
	specified by \a type \em is remembered, and may be queried with
	GetAttrInfo(). The value of \a offset is currently ignored.

	\param attr The name of the attribute.
	\param type The type of the attribute.
	\param offset The index at which to write the data (currently ignored).
	\param buffer The buffer containing the data to be written.
	\param length The number of bytes to be written.

	\return The number of bytes actually written.
	\retval B_BAD_VALUE \a attr or \a buffer was \c NULL.
	\retval B_FILE_ERROR The object was not initialized or the node it refers
	        to was read only.
	\retval B_NOT_ALLOWED The node resides on a read only volume.
	\retval B_DEVICE_FULL There was insufficient disk space to complete the
	        operation.
	\retval B_NO_MEMORY There was insufficient memory to complete the
	        operation.

	\since BeOS R3
*/


/*!
	\fn ssize_t BNode::ReadAttr(const char* attr, type_code type,
		off_t offset, void* buffer, size_t length) const
	\brief Reads data from an attribute into \a buffer.

	Reads \a length bytes of data from the attribute given by \a name into
	\a buffer. \a type and \a offset are currently ignored.

	\param attr The name of the attribute.
	\param type The type of the attribute (currently ignored).
	\param offset The index from which to read the data (currently ignored).
	\param buffer The buffer for the data to be read.
	\param length The number of bytes to be read.

	\return The number of bytes actually read.
	\retval B_BAD_VALUE \a attr or \a buffer was \c NULL.
	\retval B_FILE_ERROR The object was not initialized.
	\retval B_ENTRY_NOT_FOUND The node had no attribute \a attr.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::RemoveAttr(const char* name)
	\brief Deletes the attribute given by \a name.

	\param name The name of the attribute to remove.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a name was \c NULL.
	\retval B_FILE_ERROR The object was not initialized or the node it
	        referred to was read-only.
	\retval B_ENTRY_NOT_FOUND The node had no attribute \a name.
	\retval B_NOT_ALLOWED The node resided on a read-only volume.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::RenameAttr(const char* oldName, const char* newName)
	\brief Moves the attribute given by \a oldName to \a newName.

	If \a newName already exists, the data is clobbered.

	\param oldName The name of the attribute to be renamed.
	\param newName The new name for the attribute.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a oldName or \a newName was \c NULL.
	\retval B_FILE_ERROR The object was not initialized or the node it
	        referred to was read only.
	\retval B_ENTRY_NOT_FOUND The node had no attribute \a oldName.
	\retval B_NOT_ALLOWED The node resided on a read-only volume.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::GetAttrInfo(const char* name,
		struct attr_info* info) const
	\brief Fills in the pre-allocated attr_info struct pointed to by \a info
	       with information about the attribute specified by \a name.

	\param name The name of the attribute.
	\param info The attr_info structure to be filled in.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a name was \c NULL.
	\retval B_FILE_ERROR The object was not initialized.
	\retval B_ENTRY_NOT_FOUND The node had no attribute \a name.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::GetNextAttrName(char* buffer)
	\brief Copies the name of the attribute into \c buffer and then advances
	       the pointer to the next attribute.

	The name of the node is first copied into \a buffer, which should be at
	least \c B_ATTR_NAME_LENGTH characters long. The copied node name is
	\0 terminated. Once the name is copied the attribute list pointer
	is advanced to the next attribute in the list. When GetNextAttrName()
	reaches the end of the list it returns \c B_ENTRY_NOT_FOUND.

	\param buffer A buffer to copy the name of the attribute into.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK The Attribute name was copied and there are more attribute
	        names to copy.
	\retval B_BAD_VALUE passed in \a buffer was \c NULL.
	\retval B_FILE_ERROR The object was not initialized.
	\retval B_ENTRY_NOT_FOUND There were no more attributes, the last attribute
	        name had already been copied.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::RewindAttrs()
	\brief Resets the object's attribute pointer to the first attribute in the
	       list.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_FILE_ERROR Some other error occurred.

	\since BeOS R3
*/


/*!
	\fn status_t BNode::WriteAttrString(const char* name, const BString* data)
	\brief Writes the specified string to the specified attribute, clobbering
	       any previous data.

	\param name the name of the attribute.
	\param data the BString to be written to the attribute.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a name or \a data was \c NULL.
	\retval B_FILE_ERROR The object was not initialized or the node it
	        referred to was read-only.
	\retval B_NOT_ALLOWED The node resided on a read-only volume.
	\retval B_DEVICE_FULL There was insufficient disk space to complete the
	        operation.
	\retval B_NO_MEMORY There was insufficient memory to complete the
	        operation.

	\since Haiku R1
*/


/*!
	\fn status_t BNode::ReadAttrString(const char* name, BString* result) const
	\brief Reads the data of the specified attribute into the pre-allocated
	       \a result.

	\param name the name of the attribute.
	\param result the BString to be set to the value of the attribute.

	\return \c B_OK on success or an error code otherwise.
	\retval B_OK Everything went fine.
	\retval B_BAD_VALUE \a name or \a result was \c NULL.
	\retval B_FILE_ERROR The object was not initialized.
	\retval B_ENTRY_NOT_FOUND The node had no attribute \a attr.

	\since Haiku R1
*/


//! @}


/*!
	\name Operators
*/


//! @{


/*!
	\fn BNode& BNode::operator=(const BNode& other)
	\brief Initializes the object as a copy of \a other.

	\param other the BNode to be copied.

	\returns A reference to this BNode object.

	\since BeOS R3
*/


/*!
	\fn bool BNode::operator==(const BNode &node) const
	\brief Tests whether this and the supplied BNode object are equal.

	Two BNode objects are said to be equal if they're set to the same node,
	or if they're both unintialized

	\param node The BNode to be compared against.

	\return \c true, if the BNode objects are equal, \c false otherwise.

	\since BeOS R3
*/


/*!
	\fn bool BNode::operator!=(const BNode &node) const
	\brief Tests whether this and the supplied BNode object are not equal.

	Two BNode objects are said to be equal if they're set to the same node,
	or if they're both unintialized.

	\param node The BNode to be compared with

	\return \c false, if the BNode objects are equal, \c true otherwise.

	\since BeOS R3
*/


//! @}