X-Git-Url: http://g0dil.de/git?a=blobdiff_plain;f=Socket%2FMainpage.dox;h=5485c7e76b1d6735c4cf6de1b63086de7aa213c0;hb=5443435c4c2b6e4386c5334b5b8358273f2bae93;hp=29496dc37f201d7b12fbe423c836a8c7e15bd7e0;hpb=5a5c6d7f0fae7ad6c0af49d7742955cb6cf618cf;p=senf.git diff --git a/Socket/Mainpage.dox b/Socket/Mainpage.dox index 29496dc..5485c7e 100644 --- a/Socket/Mainpage.dox +++ b/Socket/Mainpage.dox @@ -1,200 +1,350 @@ +// $Id$ +// +// Copyright (C) 2007 +// Fraunhofer Institute for Open Communication Systems (FOKUS) +// Competence Center NETwork research (NET), St. Augustin, GERMANY +// Stefan Bund +// +// 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 2 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, write to the +// Free Software Foundation, Inc., +// 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + namespace senf { /** \mainpage The SENF Socket Library - The Socket library provides a high level and object oriented - abstraction of the BSD socket API. The abstraction is based on - several concepts: - - \li The basic visible interface is a \link handle_group handle - object \endlink - \li The socket interface relies on a \link policy_group policy - framework \endlink to configure it's functionality - \li The rest of the socket API is accessible using a classic - inheritance hierarchy of \link protocol_group protocol classes - \endlink - - The handle/body architecture provides automatic reference counted - management of socket instances, the policy framework provides - highly efficient access to the most important socket functions - (like reading and writing) and the inheritance hierarchy provides - convenient access to the multitude of special and protocol - dependent options. - - \see \ref usage \n - \ref handle_group \n - \ref policy_group \n - \ref protocol_group \n - \ref extend \n - \ref implementation - */ + The Socket library provides a high level and object oriented abstraction based on the BSD socket + API (but not limited to it). + + \autotoc + + \section socket_intro Introduction + \seechapter \ref structure \n + \seechapter \ref usage + + The socket library abstraction is based on several concepts: -/** \page usage Using the Socket Library + \li The basic visible interface is a \link handle_group handle object\endlink + \li The socket interface relies on a \link policy_group policy framework \endlink to configure + it's functionality + \li The rest of the socket API is accessible using a classic inheritance hierarchy of \link + protocol_group protocol classes \endlink + \li There is a family of auxilliary \ref addr_group to supplement the socket library - Whenever you use the socket library, what you will be dealing with - are FileHandle derived instances. The socket library relies - on reference counting to automatically manage the underlying - socket representation. This frees you of having to manage the - socket lifetime explicitly. - \section usage_create Creating a Socket Handle + \section socket_handle Socket Handles + \seechapter \ref handle_group \n + \seechapter \ref concrete_protocol_group - To create a new socket handle (opening a socket), you will need to - use ProtocolClientSocketHandle or - ProtocolServerSocketHandle. You will probably not use these - templates as is but use proper typedefs (for example - TCPv4ClientSocketHandle or PacketSocketHandle). The - documentation for these socket handles are found in the protocol - class (for example TCPv4SocketProtocol or - PacketProtocol). + The handle/body architecture provides automatic reference counted management of socket + instances. This is the visible interface to the socket library. - \section usage_reusable Writing Reusable Components + Each specific protocol is used primarily via a protocol specific handle (a typedef + symbol). However, more generic kinds of handles can be defined for more generic functionality. - To make your code more flexible, you should not pass around your - socket in this form. Most of your code will be using only a small - subset of the ProtocolClientSocketHandle or - ProtocolServerSocketHandle API. If instead of using the - fully specified handle type you use a more incomplete type, you - allow your code to be used with all socket which fulfill the - minimal requirements of your code. - This works, by defining a special reduced policy or handle for - your code: + + \section socket_policy The Policy interface + \seechapter \ref policy_group - \code - typedef ClientSocketHandle< - MakeSocketPolicy< - ReadablePolicy, - StreamFramingPolicy, - ConnectedCommunicationPolicy > > MyReadableHandle; - - \endcode + The policy framework configures the exact features, a specific type of socket handle + provides. This offers highly efficient access to the most important socket functions (like + reading and writing). The policy interface however is a \e static, non-polymorphic interface. - This defines \c MyReadableHandle as a ClientSocketHandle - which will have only read functionality. Your code expects a - stream interface (in contrast to a packet or datagram based - interface). You will not have \c write or \c readfrom members. \c - write will be disabled since the WritePolicy is unknown, \c - readfrom will be disabled since a socket with the - ConnectedCommunicationPolicy does not have a \c readfrom - member. - */ + + \section socket_protocol The Protocol interface + \seechapter \ref protocol_group + The protocol interface provides further protocol dependent and (possibly) polymorphic access to + further socket funcitonality. On the other hand, this type of interface is not as flexible, + generic and fast as the policy interface. -/** \page extend Extending the Library + \section socket_addr Auxilliary Addressing classes + \seechapter \ref addr_group + + To supplement the socket library, there are a multitude of addressing classes. These come in two + basic groups: + \li Protocol specific addresses (e.g. INet4Address, MACAddress) + \li Socket addresses (\c sockaddr) (e.g. INet4SocketAddress, LLSocketAddress) + + Whereas the protocol specific addresses are custom value types which represent their + corresponding low-level address, the socket addresses are based on the corresponding \c sockaddr + structures. - There are two layers, on which the socket library can be - extended: On the protocol layer and on the policy layer. Extending - the protocol layer is quite simple and works as long as the - desired protocol does use the same BSD API used by the standard - internet protocols as implemented in the standard policies - (i.e. it uses ordinary read() and write() or rcvfrom() or sendto() - calls and so on). - - If however the implementation of a policy feature needs to be - changed, a new policy class has to be written. This also is not - very complicated however the integration is more complex. + \section socket_further Going further + \seechapter \ref extend \n + \seechapter \ref implementation - \section extend_protocol Writing a new protocol class + The socket library is highly flexible and extensible. The implementation is not restricted to + plain BSD sockets: Any type of read/write communication can be wrapped into the socket library + (one Example is the TapSocketHandle which provides access to a Linux \c tap device). + + */ + +/** \page structure Overview of the Socket Library Structure + + \image html Handle.png + + This diagram tries to give a structural overview of the Socket Library, it does \e not directly + show, how the library is implemented. This will be explained later. + + The outside interface to the library is a Handle object. This is the only object, the library + user directly interacts with. Every handle references some socket. This is like the ordinary + POSIX API: the file descriptor (also called file handle, an integer number) references a socket + structure which lives in kernel space. In this library, the Handle object (which is not a simple + integer any more but an object) references the Socket (which is part of the + implementation). Several handles may reference the same Socket. In contrast to the kernel API, + the library employs reference counting to release a socket when the last Handle to it goes out + of scope. + + The behavior of a Socket is defined by it's Protocol. It is divided into two parts: the + policy interface and the protocol interface. Together they provide the + complete API for a specific type of Socket as defined by the Protocol. The policy + interface provides highly efficient access to the most frequently used operations whereas + the protocol interface completes the interface by providing a complete set of all + protocol specific operations not found in the policy interface. This structure allows us to + combine the benefits of two design methodologies: The policy interface utilizes a policy based + design technique and is highly efficient albeit more complex to implement, whereas the protocol + interface is based on a more common inheritance architecture which is not as optimized for + performance but much simpler to implement. We reduce the complexity of the implementation by + reducing the policy interface to a minimal sensible subset of the complete API. + + \section over_policy The Policy Interface - Most protocols can be implemented by just implementing a new - protocol class. The protocol class must be derived from - ConcreteSocketProtocol and takes the socket policy (as - created by MakeSocketPolicy) as a template argument. See the - documentation of this class for the interface. - - \attention You may want to use multiple inheritance as it is used - in the implementation of the standard protocols (See \ref - protocol_group). You must however be extra careful to ensure, that - every class ultimately has SocketPolicy as a public \e - virtual base. - - After the protocol class has been defined, you will probably want to - provide typedefs for the new protocol sockets. If the new protocol - is connection oriented, this will be like + The policy of a Socket consists of several parts, called policy axis. Each axis + corresponds to one specific interface aspect of the Socket. The exact meaning of the policy axis + are defined elsewhere (see \ref policy_group). The Protocol will always provide a complete set + of policy classes, one for each axis. + + This complete socket policy defines the policy interface of the protocol. This + interface is carried over into the Handle. The socket policy as defined in the Handle however + may be incomplete. This mans, that the \e accessible interface of the Socket depends on + the type of Handle used. The inherent interface does not change but the view of this interface + does if the Handle does not provide the \e complete policy interface. This feature is very + important. It allows to define generic Handle types. A generic Handle with an incompletely + defined policy can point to an arbitrary Socket as long as all those policy axis which \e are + defined match those defined in that Socket's protocol. Using such a generic handle decouples the + implementation parts using this handle from the other socket aspects (e.g. you may define a + generic socket handle for TCP based communication leaving the addressingPolicy undefined which + makes your code independent of the type of addressing, IPv4 or IPv6). + + This can be described as generalized compile-time polymorphism: A base class reference to some + derived class will only give access to a reduced interface (the base class interface) of a + class. The class still is of it's derived type (and inherently has the complete interface) but + only part of it is accessible via the base class reference. Likewise a generic handle (aka base + class reference) will only provide a reduced interface (aka base class interface) to the derived + class instance (aka socket). + + \section over_protocol The Protocol Interface + + The protocol interface is provided by a set of protocol facets. Each facet provides a + part of the interface. Whereas the policy interface is strictly defined (the number and type of + policy axis is fixed and also the possible members provided by the policy interface are fixed), + the protocol interface is much more flexible. Any member needed to provide a complete API for + the specific protocol may be defined, the number and type of facets combined to provide the + complete interface is up to the Protocol implementor. This flexibility is necessary to provide a + complete API for every possible protocol. + + However this flexibility comes at a cost: To access the protocol interface the user must know + the exact protocol of the socket. With other words, the protocol is only accessible if the + handle you use is a protocol specific handle. A protocol specific Handle differs from a + generic Handle in two ways: It always has a complete policy and it knows the exact protocol type + of the socket (which generic handles don't). This allows to access to the complete protocol + interface. + + \section over_impl Implementation of the Socket Libarary Structure + + In the Implementation, the socket policy is identified by an instance of the senf::SocketPolicy + template. The Socket representation is internally represented in a senf::SocketBody which is not + outside visible. The Handle is provided by a hierarchy of handle templates. Each Handle template + uses template arguments for the policy and/or protocol as needed (see \ref handle_group). + + The Handle hierarchy divides the interface into two separate strains: the client interface + (senf::ClientSocketHandle and senf::ProtocolClientSocketHandle) provides the interface of a + client socket whereas the server interface (senf::ServerSocketHandle and + senf::ProtocolServerSocketHandle) provides the interface as used by server sockets. + + The protocol interface is implemented using inheritance: The Protocol class inherits from each + protocol facet using multiple (virtual public) inheritance. The Protocol class therefore + provides the complete protocol API in a unified (see \ref protocol_group). + */ + +/** \page usage Using the Socket Library + + Whenever you use the socket library, what you will be dealing with are FileHandle derived + instances. The socket library relies on reference counting to automatically manage the + underlying socket representation. This frees you of having to manage the socket lifetime + explicitly. + + \section usage_create Creating a Socket Handle + + To create a new socket handle (opening a socket), you will need to use + ProtocolClientSocketHandle or ProtocolServerSocketHandle. You will probably not use these + templates as is but use proper typedefs (for example TCPv4ClientSocketHandle or + PacketSocketHandle). The documentation for these socket handles are found in the protocol class + (for example TCPv4SocketProtocol or PacketSocketProtocol). + + \section usage_reusable Writing Reusable Components + + To make your code more flexible, you should not pass around your socket in this form. Most of + your code will be using only a small subset of the ProtocolClientSocketHandle or + ProtocolServerSocketHandle API. + + If instead of using the fully specified handle type you use a more incomplete type, you allow + your code to be used with all sockets which fulfill the minimal requirements of your code. These + types are based on the ClientSocketHandle and ServerSocketHandle templates which implement the + policy interface without providing the concrete protocol interface. To use those templates you + may define a special reduced policy or handle for your code. By giving only an incomplete policy + you thereby reduce the interface to that required by your module: + \code - typedef ProtocolClientSocketHandle MyProtocolClientSocketHandle; - typedef ProtocolServerSocketHandle MyProtocolServerSocketHandle; - \endcode + typedef ClientSocketHandle< + MakeSocketPolicy< + ReadablePolicy, + StreamFramingPolicy, + ConnectedCommunicationPolicy > > MyReadableHandle; - \section extend_policy Extending the policy framework + \endcode - If you have to extend the policy framework, you will need to be - aware of some important limitations of the socket library: - - \li When you define a new policy for some axis, this new policy - must not be derived from one of the existing concrete - policy classes (except of course the respective policy axis - base class). This is important since the policy type is \e not - polymorphic. The policy to be used is selected by the compiler - using the \e static type, which is exactly what is desired, - since this allows calls to be efficiently inlined. - - \li Therefore, extending the policy framework will make the new - socket probably \e incompatible with generic code which relies - on the policy axis which is extended. Example: If you write a - new write policy because your protocol does not use ordinary - write() system calls but some protocol specific API, Then any - generic function relying on WritablePolicy will \e not - work with the new socket, since the socket does \e not have - this policy, it has some other kind of write policy. - - Therefore you need to be careful of what you are doing. The first - step is to find out, which policy you will have to implement. For - this, find the ClientSocketHandle and/or - ServerSocketHandle members you want to change (see \ref - ClientSocketHandle and \ref ServerSocketHandle). Not - all policy axis directly contribute to the SocketHandle - interface. However, some policy members additionally depend on - other policy axis (example: AddressingPolicy::connect is only - defined if the communication policy is - ConnectedCommunication). + This defines \c MyReadableHandle as a ClientSocketHandle which will have only read + functionality. Your code expects a stream interface (in contrast to a packet or datagram based + interface). You will not have \c write or \c readfrom members. \c write will be disabled since + the WritePolicy is unknown, \c readfrom will be disabled since a socket with the + ConnectedCommunicationPolicy does not have a \c readfrom member. - \see policy_group + \see + \ref policy_group \n + \ref handle_group \n + \ref protocol_group */ -/** \page glossary Glossary - - +/** \page extend Extending the Library - + There are two layers, on which the socket library can be extended: On the protocol layer and on + the policy layer. Extending the protocol layer is quite simple and works as long as the desired + protocol does use the same BSD API used by the standard internet protocols as implemented in the + standard policies (i.e. it uses ordinary read() and write() or rcvfrom() or sendto() calls and + so on). - + If however the implementation of a policy feature needs to be changed, a new policy class has to + be written. This also is not very complicated however the integration is more complex. - + \section extend_protocol Writing a new protocol class - + Most protocols can be implemented by just implementing a new protocol class. The protocol class + must be derived from ConcreteSocketProtocol and takes the socket policy (as created by + MakeSocketPolicy) as a template argument. See the documentation of this class for the interface. - + \attention You may want to use multiple inheritance as it is used in the implementation of the + standard protocols (See \ref protocol_group). You must however be extra careful to ensure, that + every class ultimately has SocketPolicy as a public \e virtual base. - + After the protocol class has been defined, you will probably want to provide typedefs for the + new protocol sockets. If the new protocol is connection oriented, this will be like + \code + typedef ProtocolClientSocketHandle MySocketProtocolClientSocketHandle; + typedef ProtocolServerSocketHandle MySocketProtocolServerSocketHandle; + \endcode - + \section extend_policy Extending the policy framework - - - + If you have to extend the policy framework, you will need to be aware of some important + limitations of the socket library: + + \li When you define a new policy for some axis, this new policy must not be derived + from one of the existing concrete policy classes (except of course the respective policy + axis base class). This is important since the policy type is \e not polymorphic. The policy + to be used is selected by the compiler using the \e static type, which is exactly what is + desired, since this allows calls to be efficiently inlined. + + \li Therefore, extending the policy framework will make the new socket probably \e incompatible + with generic code which relies on the policy axis which is extended. Example: If you write a + new write policy because your protocol does not use ordinary write() system calls but some + protocol specific API, Then any generic function relying on WritablePolicy will \e not work + with the new socket, since the socket does \e not have this policy, it has some other kind + of write policy. + + Therefore you need to be careful of what you are doing. The first step is to find out, which + policy you will have to implement. For this, find the ClientSocketHandle and/or + ServerSocketHandle members you want to change (see \ref ClientSocketHandle and \ref + ServerSocketHandle). Not all policy axis directly contribute to the SocketHandle + interface. However, some policy members additionally depend on other policy axis (example: + AddressingPolicy::connect is only defined if the communication policy is + ConnectedCommunication). -
policy collection of policy classes, one for each - policy axis, instantiation of the SocketPolicy template
policy axis one aspect defined in the socket - policy, typedef and member of the SocketPolicy template
policy class implementation of a single policy - axis, class derived from the axis base class
complete policy socket policy where each - axis is specified completely
incomplete policy socket policy, where at - least one axis is not fully specified
protocol class definition of a protocol as a - class, class inheriting from ConcreteSocketProtocol.
protocol facet a class providing some subset of - the protocol interface, class derived from SocketProtocol but not - from ConcreteSocketProtocol
policy interface interface directly provided by - ClientSocketHandle/ServerSocketHandle and defined through the - policy
protocol interface interface provided by the - protocol class and accessible via the - ProtocolClientSocketHandle::protocol()/ProtocolServerSocketHandle::protocol() - member
+ \see policy_group */ /** \page implementation Implementation notes - \image html SocketLibrary-classes.png + \section class_diagram Class Diagram + +
+ \ref IPv4Protocol + \ref WritePolicyBase + \ref SocketBufferingPolicy + \ref NoAddressingPolicy + \ref NotReadablePolicy + \ref AdressableBSDSocketProtocol + \ref BufferingPolicyBase + \ref FramingPolicyBase + \ref FileBody + \ref DatagramFramingPolicy + \ref INet6AddressingPolicy + \ref BSDSocketProtocol + \ref INet4AddressingPolicy + \ref ProtocolServerSocketHandle + \ref PolicyBase + \ref TCPProtocol + \ref ReadablePolicy + \ref SocketPolicy + \ref CommunicationPolicyBase + \ref TCPv6Protocol + \ref SocketProtocol + \ref ConnectedCommunicationPolicy + \ref ProtocolClientSocketHandle + \ref IPv6Protocol + \ref WritablePolicy + \ref SocketBody + \ref PacketProtocol + \ref NotWritablePolicy + \ref ReadPolicyBase + \ref SocketHandle + \ref ClientSocketHandle + \ref UnconnectedCommunicationPolicy + \ref ConcreteSocketProtocol + \ref TCPv4Protocol + \ref StreamFramingPolicy + \ref AddressingPolicyBase + \ref FileHandle + \ref LLAddressingPolicy + \ref ServerSocketHandle +
+ \htmlonly SocketLibrary-classes \endhtmlonly + + \section impl_notes Arbitrary Implementation Notes + + \li The implementation tries to isolate the library user as much as possible from the system + header files since those headers define a lot of define symbols and introduce a host of + symbols into the global namespace. This is, why some classes define their own \c enum types + to replace system defined define constants. This also precludes inlining some functionality. + + \li To reduce overhead, template functions/members which are more than one-liners are often + implemented in terms of a non-template function/member. This is also used to further the + isolation from system headers as defined above (template code must always be included into + every compilation unit together with all headers need for the implementation). */ } @@ -202,7 +352,11 @@ namespace senf { // Local Variables: // mode: c++ +// fill-column: 100 +// c-file-style: "senf" +// indent-tabs-mode: nil +// ispell-local-dictionary: "american" // mode: flyspell // mode: auto-fill -// ispell-local-dictionary: "american" +// compile-command: "scons -u doc" // End: