X-Git-Url: http://g0dil.de/git?a=blobdiff_plain;f=Socket%2FSocketPolicy.hh;h=507eafdf6e1c8828730503cd9ee42e3ec6221bbb;hb=04dd5d565dc0a5888f8d26bbcb12e9d325d6a4e5;hp=be96da217a891f94528ff2430d6baf77bc99140b;hpb=85ab07d100a382467a42e19d741d403a7a96c951;p=senf.git
diff --git a/Socket/SocketPolicy.hh b/Socket/SocketPolicy.hh
index be96da2..507eafd 100644
--- a/Socket/SocketPolicy.hh
+++ b/Socket/SocketPolicy.hh
@@ -23,20 +23,16 @@
/** \file
\brief Policy Framework public header
- \todo We should probably remove BufferingPolicy from the
- interface, it does not make much sense (how did I come to
- include it ??)
-
- \todo Do we want to support separate read and write policies. This
- allows to treat pipes within this framework however, is this
- worth the effort?
-
- \idea Creating a new Socket will create 4 (!) new instances (The
- handle, the body, the policy and the protocol) of which 3
- (argh) (body, policy and protocol) live on the heap. This is
- expensive. We should convert all the policy classes to
- singletons and assign the same instance to all socket bodies
- with the same policy. This would reduce the number of heap
+ \todo We should probably remove BufferingPolicy from the interface, it does not make much sense
+ (how did I come to include it ??)
+
+ \todo Do we want to support separate read and write policies. This allows to treat pipes within
+ this framework however, is this worth the effort?
+
+ \idea Creating a new Socket will create 4 (!) new instances (The handle, the body, the policy
+ and the protocol) of which 3 (argh) (body, policy and protocol) live on the heap. This is
+ expensive. We should convert all the policy classes to singletons and assign the same
+ instance to all socket bodies with the same policy. This would reduce the number of heap
allocations per socket handle to two.
*/
@@ -46,157 +42,167 @@
\section policy_group_introduction Introduction to the Policy Framework
- The policy framework conceptually implements a list of parallel
- inheritance hierarchies each covering a specific interface aspect
- of the socket handle. The socket handle itself only provides
- minimal functionality. All further functionality is relayed to a
- policy class, or more precisely, to a group of policy classes, one
- for each policy axis. The policy axis are
+ The policy framework conceptually implements a list of parallel inheritance hierarchies each
+ covering a specific interface aspect of the socket handle. The socket handle itself only
+ provides minimal functionality. All further functionality is relayed to a policy class, or more
+ precisely, to a group of policy classes, one for each policy axis. The policy axis are
-
- - addressingPolicy
- - configures, whether a socket is
- addressable and if so, configures the address type
+ - addressingPolicy
- configures, whether a socket is addressable and if
+ so, configures the address type
- - framingPolicy
- - configures the type of framing the socket provides: either no
- framing providing a simple i/o stream or packet framing
+ - framingPolicy
- configures the type of framing the socket provides: either
+ no framing providing a simple i/o stream or packet framing
- - communicationPolicy
- - configures,if and how the communication partner is
+
- communicationPolicy
- configures,if and how the communication partner is
selected
- - readPolicy
- - configures the readability of the socket
+ - readPolicy
- configures the readability of the socket
+
+ - writePolicy
- configures the writability of the socket
+
+ - bufferingPolicy
- configures, if and how buffering is configured for a
+ socket
+
+ The template senf::SocketPolicy combines these policy axis to form a concrete socket policy. In
+ a concrete policy, each of these policy axis is assigned a value, the policy value. This value
+ is identified by a class type, a policy class. E.g. possible values for framingPolicy
+ are DatagramFramingPolicy or StreamFramingPolicy which are classes derived
+ from the axis base class FramingPolicyBase. This base class also doubles as
+ UnspecifiedFramingPolicy (which is just a typedef alias). If a policy axis is assigned
+ this Unspecified type, the axis is left unspecified, the concrete policy will be incomplete.
+
+ The senf::SocketPolicy template defines the behavior of a socket handle. The socket handle
+ instances do not implement any socket functionality themselves instead defering the
+ implementation to the policy classes. The SocketHandle interface is therefore \e not implemented
+ using virtual members, all important socket functions can be inlined by the compiler to create
+ highly efficient code.
+
+ A senf::SocketPolicy instance can be incomplete. In this case it does \e not completely specify
+ the socket interface, it leaves some aspects open by assigning the Unspecified value to one or
+ more of the policy axis. A senf::SocketHandle based on such a policy will have a reduced
+ interface: It will only support those members for wich the corresponding policies are defined.
+
+ To build a senf::SocketPolicy instance the senf::MakeSocketPolicy helper is provided. This
+ helper template takes any number (it is really limited to 6 Arguments but more arguments don't
+ make sense) of policy classes as it's argument. The MakeSocketPolicy helper will take the
+ arguments in the order they are specified and for each argument will check to which axis the
+ policy class belongs (by checking the base classes of that class) and assign it to the correct
+ policy axis in the senf::SocketPolicy template. If any policy axis are not specified, they are
+ defaulted to their corresponding Unspecified value. This helper frees you to specify the policy
+ classes in any order. An additional feature is, that you may specify a complete policy as a
+ first argument. This policy will then be used to provide default values for unspecified axis.
+
+ Two senf::SocketHandle's with different policies can be \e compatible. If they are, the more
+ specific SocketHandle can be converted (assigned to) the more basic SocketHandle. A SocketHandle
+ is more specific then another SocketHandle if the policy of the former is more specific then
+ that of the latter which means, that for each policy axis separately, the value of that axis of
+ the more specific policy is derived from or the same as the value of that axis in the more basic
+ policy. This is like converting a derived class pointer to a base class pointer, only it happens
+ separately but at the same time for each policy axis:
- - writePolicy
- - configures the writability of the socket
+ \code
+ // This defines an incomplete policy where addressingPolicy, writePolicy and bufferingPolicy
+ // are unspecified
+ typedef senf::MakeSocketPolicy<
+ senf::StreamFramingPolicy,
+ senf::ConnectedCommunicationPolicy,
+ senf::ReadablePolicy
+ >::policy MyReadableSocketPolicy
+
+ typedef senf::ClientSocketHandle MyReadableHandle;
+
+ // TCPv4ClientSocketHandle is a socket handle with the policy equivalent to
+ // senf::MakeSocketPolicy<
+ // INet4AddressingPolicy,
+ // StreamFramingPolicy,
+ // ConnectedCommunicationPolicy,
+ // ReadablePolicy,
+ // WritablePolicy,
+ // SocketBufferingPolicy>::policy
+ senf::TCPv4ClientSocketHandle tcpHandle (...);
+
+ MyReadableHandle myHandle (tcpHandle); // Conversion to more basic socket handle
+ \endcode
- - bufferingPolicy
- - configures, if and how buffering is configured for a socket
-
+ \section policy_group_details The Policy Framework Classes
- Every Policy value is identified by a class type. The policy
- classes themselves built an inheritance hierarchy for each policy
- axis. For each policy axis, the root of this tree is the class
- named \e Policy \c Base (e.g. \p AddressingPolicyBase).
+ In the following discussion, deeper insight into C++ and especially the concepts of template
+ meta-programming are needed. Hoewever, this information is only needed if you want to write new
+ policy classes or want to use the policy framework explicitly for your own involved
+ optimizations ... or if you are just plain curious :-)
+
+ In the following discussion we will use the following conventions:
+ \li \e Axis is one or \c AddressingPolicy, \c FramingPolicy, \c CommunicationPolicy, \c
+ ReadPolicy, \c WritePolicy or \c BufferingPolicy
+ \li \e socketPolicy is any socket policy (that is, an instantiation of the SocketPolicy
+ template)
+ \li \e trait is an any policy class (that is, any class derived from one of the axis base
+ classes)
- The senf::SocketPolicy defines the complete policy of a socket. It
- combines a set of policy classes, one for each policy
- axis. Together, they define the behavior of a socket handle. The
- socket handle instances do not implement any socket functionality
- themselves instead defering the implementation to the policy
- classes. The SocketHandle interface is therefore \e not
- implemented using virtual members, all important socket functions
- can be inlined by the compiler to create highly efficient code.
+ Each axis is comprised of a number of classes and templates (all in namespace senf of course):
- A SocketPolicy can be incomplete. In this case it does \e not
- completely specify the socket interface, it leaves some aspects
- open. A SocketHandle based on such a policy will have a reduced
- interface: It will only support those members for wich the
- corresponding policies are defined.
+ - \e Axis \c Base (ex: AddressingPolicyBase)
- Baseclass of all policies in this
+ axis
- Two SocketHandle's with different policies can be \e
- compatible. If they are, the more derived SocketHandle can be
- converted (assigned to) the more basic SocketHandle.
+ - \c Unspecified \e Axis (ex: \ref UnspecifiedAddressingPolicy)
- An alias (typedef)
+ for \e Axis \c Base
- \section policy_group_details The Policy Framework Classes
+ - \e Axis \c Is < \e socketPolicy, \e trait > (ex: AddressingPolicyIs)
- A template
+ metafunction returning \c boost::true_type, if \e trait (any class derived from \e Axis \c
+ Base) is a compatible policy value of the given \e socketPolicy
- In the following discussion we will use the following conventions:
- \li \e Policy is one or \c AddressingPolicy, \c FramingPolicy, \c
- CommunicationPolicy, \c ReadPolicy, \c WritePolicy or \c
- BufferingPolicy
- \li \e socketPolicy is any socket policy (that is, an
- instantiation of the SocketPolicy template)
- \li \e trait is an any policy class (that is, any class derived
- from one of the axis base classes)
-
- Each axis is comprised of a number of classes and templates (all
- in namespace senf of course):
-
-
- - \e Policy \c Base (ex: AddressingPolicyBase)
- - Baseclass of all policies in this axis
-
- - \c Unspecified \e Policy (ex: \ref UnspecifiedAddressingPolicy)
- - An alias (typedef) for \e Policy \c Base
-
- - \e Policy \c Is < \e socketPolicy, \e trait > (ex: AddressingPolicyIs)
- - A template metafunction returning \c boost::true_type, if \e
- trait (any class derived from \e Policy \c Base) is a compatible
- policy value of the given \e socketPolicy
-
- - \c If \e Policy \c Is < \e socketPolicy, \e trait > (ex: IfAddressingPolicyIs)
- - This is a combination of \e Policy \c Is and \c boost::enable_if
-
- - \c If \e Policy \c IsNot < \e socketPolicy, \e trait > (ex: IfAddressingPolicyIsNot)
- - The inverse of above
-
-
- These classes form the basis of the policy framework. To bind the
- policy axis together, there are some more classes and templates.
-
-
- - \c class \c SocketPolicyBase
- - This class is the base class of the SocketPolicy template. It
- is used to validate, that a class is really a SocketPolicy (by
- checking, that it derives from SocketPolicyBase. This is simpler
- than chacking the template directly).
-
- - \c template \c SocketPolicy < \e addressingPolicy, \e
- framingPolicy, \e communicationPolicy, \e readPolicy, \e
- writePolicy, \e bufferingPolicy >
- - This is the central SocketPolicy template. It combines a
- complete set of policy classes, one for each axis.
-
- - \c template \c MakeSocketPolicy < \e args >
- - \c MakeSocketPolicy is a template metafunction which
- simplifies building SocketPolicy instantiations. It takes any
- number (ok, up to a maximum of 6) of policy classes as an
- argument (in any order). It will sort these arguments into the
- SocketPolicy template arguments. If for some axis no class is
- specified, it's slot will be filled with \c Unspecified \e
- Policy. Additionally, the first Argument may optionally be ab
- arbitrary SocketPolicy. It will provide default values for
- unspecified axis
-
- - \c template \c SocketPolicyIsBaseOf < \e base, \e derived >
- - This template metafunction will check, wether the socket
- policy \e derived is convertible to \e base. This means, that for
- each axis, the corresponding policy class in \e derived must be
- derived or be the same as the one on \e base.
-
-
- \implementation All these classes are created automatically. The
- \c SENF_SOCKET_POLICIES makro is a Boost.Preprocessor style
- sequence listing all policy axis. The Boost.Preprocessor library
+ - \c If \e Axis \c Is < \e socketPolicy, \e trait > (ex: IfAddressingPolicyIs)
- This
+ is a combination of \e Axis \c Is and \c boost::enable_if
+
+ - \c If \e Axis \c IsNot < \e socketPolicy, \e trait > (ex: IfAddressingPolicyIsNot)
+ - The inverse of above
+
+ These classes form the basis of the policy framework. To bind the policy axis together, there
+ are some more classes and templates.
+
+ - \c class \c SocketPolicyBase
- This class is the base class of the SocketPolicy
+ template. It is used to validate, that a class is really a SocketPolicy (by checking, that it
+ derives from SocketPolicyBase. This is simpler than chacking the template directly).
+
+ - \c template \c SocketPolicy < \e addressingPolicy, \e framingPolicy, \e communicationPolicy,
+ \e readPolicy, \e writePolicy, \e bufferingPolicy >
- This is the central SocketPolicy
+ template. It combines a complete set of policy classes, one for each axis.
+
+ - \c template \c MakeSocketPolicy < \e args >
- \c MakeSocketPolicy is a template
+ metafunction which simplifies building SocketPolicy instantiations. It takes any number (ok, up
+ to a maximum of 6) of policy classes as an argument (in any order). It will sort these arguments
+ into the SocketPolicy template arguments. If for some axis no class is specified, it's slot will
+ be filled with \c Unspecified \e Axis. Additionally, the first Argument may optionally be ab
+ arbitrary SocketPolicy. It will provide default values for unspecified axis
+
+ - \c template \c SocketPolicyIsBaseOf < \e base, \e derived >
- This template
+ metafunction will check, wether the socket policy \e derived is convertible to \e base. This
+ means, that for each axis, the corresponding policy class in \e derived must be derived or be
+ the same as the one on \e base.
+
+ \implementation All these classes are created automatically. The \c SENF_SOCKET_POLICIES makro
+ is a Boost.Preprocessor style sequence listing all policy axis. The Boost.Preprocessor library
is then used to generate the respective classes.
\section policy_implement Implementing Policy Classes
- To define a new policy class, derive from the corresponding base
- class for your policy axies. The only policy axis which might
- possibly need to be extended are the addressing policy
- (AddressingPolicyBase) and the buffering policy
- (BufferingPolicyBase). See the Documentation of these classes for
- more information on which members can be implemented.
-
- All members you define must be static. For any of the policy
- classes, you must only define those members which are supported by
- your implementation. If you leave out a member you automatically
- disable the corresponding functionality in the
- ClientSocketHandle/ServerSocketHandle interface.
-
- The member prototypes given in the base class documentation only
- specify the call signature not the way, the member must be defined
- (FileHandle really is not a FileHandle but an arbitrary
+ To define a new policy class, derive from the corresponding base class for your policy
+ axies. The only policy axis which might possibly need to be extended are the addressing policy
+ (AddressingPolicyBase) and the buffering policy (BufferingPolicyBase). See the Documentation of
+ these classes for more information on which members can be implemented.
+
+ All members you define must be static. For any of the policy classes, you must only define those
+ members which are supported by your implementation. If you leave out a member you automatically
+ disable the corresponding functionality in the ClientSocketHandle/ServerSocketHandle interface.
+
+ The member prototypes given in the base class documentation only specify the call signature not
+ the way, the member must be defined (FileHandle really is not a FileHandle but an arbitrary
SocketHandle).
- If the existence of a member depends on other policies, you should
- use the If
SomePolicyIs
and
- If
SomePolicyIsNot
templates to
- dynamically enable/disable the member depending on some other
- policy:
+ If the existence of a member depends on other policies, you should use the
+ If
SomePolicyIs
and
+ If
SomePolicyIsNot
templates to dynamically enable/disable the
+ member depending on some other policy:
\code
struct ExampleAddressingPolicy
@@ -208,24 +214,21 @@
};
\endcode
- The \c connect member in this example will only be enabled, it
- the communication policy of the socket handle is
- ConnectedCommunicationPolicy (or a derived type). See Boost.Enable_If
- for a discussion of the third argument (\c
- senf::ConnectedCommunicationPolicyIs is based on the \c
- boost::enable_if template).
+ The \c connect member in this example will only be enabled, it the communication policy of the
+ socket handle is ConnectedCommunicationPolicy (or a derived type). See Boost.Enable_If for a discussion of
+ the third argument (\c senf::ConnectedCommunicationPolicyIs is based on the \c boost::enable_if
+ template).
\see \ref extend_policy \n
The Boost enable_if utility \n
The Boost.MPL library \n
The Boost.Preprocessor library
- \idea We could combine all the \e Policy \c Is templates into a
- single template. Since the \e trait argument will automatically
- specify the axis to be used, it is not necessary to specify that
- axis in the tempalte functor's name. We could even combine this
- with \c SocketPolicyIsBaseOf.
+ \idea We could combine all the \e Axis \c Is templates into a single template. Since the \e
+ trait argument will automatically specify the axis to be used, it is not necessary to specify
+ that axis in the tempalte functor's name. We could even combine this with \c
+ SocketPolicyIsBaseOf.
*/
/** \defgroup policy_impl_group Policy Implementation classes
@@ -251,9 +254,8 @@ namespace senf {
/// \addtogroup policy_group
/// @{
- // This may be adapted to change the supported policies (however,
- // ClientSocketHandle and ServerSocketHandle will probably have to
- // be adjusted accordingly)
+ // This may be adapted to change the supported policies (however, ClientSocketHandle and
+ // ServerSocketHandle will probably have to be adjusted accordingly)
/** \brief List all policy axis
@@ -439,7 +441,7 @@ namespace senf {
/** \brief Check single policy axis
- This template is an example of the \e Policy \c Is family of
+ This template is an example of the \e Axis \c Is family of
tempalte metafunctions. It will check, wether \c Trait is a
valid compatible Policy class of \c SocketPolicy. \c Trait
must be derived from AddressingPolicyBase (respectively \i
@@ -453,11 +455,11 @@ namespace senf {
/** \brief Enable template overload depending on policy value
- This template is an exmaple of the \c If \e Policy \c Is
+ This template is an exmaple of the \c If \e Axis \c Is
family of templates. It is used like Boost.enable_if
to enable a templated overload only, if the AddressingPolicy
- of \e Policy is compatible with \c Trait (that is the
+ of \e Axis is compatible with \c Trait (that is the
AddressingPolicy of \c Policy is derived from \c Trait).
\see policy_group
@@ -508,7 +510,7 @@ namespace senf {
A SocketPolicy can be complete or incomplete. An incomplete
SocketPolicy will have at least one axis set to \c Undefined
- \e Policy (or a generic derived class which is used to group
+ \e Axis (or a generic derived class which is used to group
some other policies but does not (completely) define the
policy behavior). A complete SocketPolicy will have a
concrete definition of the desired behavior for each policy
@@ -541,7 +543,7 @@ namespace senf {
SocketPolicy instantiation. It takes any number (that is up to
6) of Policy classes as arguments in any Order. It will create
a SocketPolicy from these policy classes. Any axis not
- specified will be left as \c Unspecified \e Policy.
+ specified will be left as \c Unspecified \e Axis.
\see policy_group
*/