2 // Fraunhofer Institut fuer offene Kommunikationssysteme (FOKUS)
3 // Kompetenzzentrum fuer Satelitenkommunikation (SatCom)
4 // Stefan Bund <g0dil@berlios.be>
6 // This program is free software; you can redistribute it and/or modify
7 // it under the terms of the GNU General Public License as published by
8 // the Free Software Foundation; either version 2 of the License, or
9 // (at your option) any later version.
11 // This program is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
16 // You should have received a copy of the GNU General Public License
17 // along with this program; if not, write to the
18 // Free Software Foundation, Inc.,
19 // 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
22 \brief PacketParser public header */
24 /** \defgroup packetparser The PacketParser facility
26 The PacketParser facility provides a framework to implement very lightweight classes which parse
27 the raw content of a packet into meaningful values. PacketParsers are always passed around
28 <em>by value</em>, they can be understood as pointers into the packet data with added type
29 information providing parsing functions.
31 Packet parsers are \e only used within the packet framework. You should never allocate a new
32 parser instance directly, you should the Packet library let that do for you (either by having
33 the parser as a packet parser in a packet type or by having a member in the packet parser which
34 allocates the parser as a sub-parser).
36 Parsers are built hierarchically. A high-level parser will return other parsers when accessing
37 an element (Example: Asking an EthernetParser for the ethertype field by calling the parsers \c
38 type() member will return an \c UInt16 parser). The lowest level building blocks then return the
39 values. This hierarchical structure greatly simplifies building complex parsers.
41 Since parsers are very lightweight and are passed by value, packet fields are accessed using the
42 corresponding accessor method:
47 // Assign new value to an integer parser
50 // Write out above value
51 std::cerr << p->someField() << "\n";
53 // Use the generic parser-assignment operator '<<' to copy field values
54 p->someVector()[1].someOtherField() << q->someField();
55 p->someVector() << q->someVector()
58 Here \c someField(), \c someOtherField() and \c someVector() are accessor methods named after
59 the field name. Each returns a parser object. Simple parsers can be used like their
60 corresponding basic type (e.g. a Parse_UInt16 field can be used like an unsigned integer), more
61 complex parsers provide type specific access members. Assigning a value to a parser will change
62 the underlying representation (the packet data).
64 Parsers can be grouped into several categories. These categories are not all defined rigorously
65 but are nevertheless helpful when working with the parsers:
66 \li <em>\ref parserimpl_value</em> provide the lowest level parsers (e.g. senf::Parse_UInt16 which
67 returns an integer value).
68 \li <em>\ref parserimpl_collection</em> are parsers which model a collection of sub-elements like
69 senf::Parse_List or senf::Parse_Vector.
70 \li <em>\ref parserimpl_composite</em> collect several fields of arbitrary type into a new
71 parser. Parsers defined using the \ref packetparsermacros fall under this category.
72 \li <em>\ref parserimpl_packet</em> are used to define a packet type.
74 \warning Parsers are like iterators: They are invalidated <em>whenever the size of the packet's
75 data is changed</em>. You should not store a parser anywhere. If you want to keep a parser
76 reference, use the senf::SafePacketParser wrapper. You still will need to take extra care to
77 ensure the parser is not invalidated.
79 \section parserimpl Packet parser categories
81 Every parser is derived from senf::PacketParserBase. This class provides the necessary
82 housekeeping information and provides the parsers with access to the data. You may in principle
83 define arbitrary methods as parser members (e.g. methods to calculate a checksum, methods
84 processing fields in some way and so on). You should however be very wary to access data outside
85 the range assigned to the packet (the range starting at \c i() and with a size of senf::bytes()
88 Each parser type has specific features
90 \subsection parserimpl_value Value parsers
92 For a parser \a SomeParser to be a value parser, the following expressions must be valid:
94 // SomeParser must have a 'value_type', The 'value_type' must be default constructible, copy
95 // constructible and assignable
96 SomeParser::value_type v;
98 // An instance of 'SomeParser' must have a 'value' member which returns a value which may be
99 // assigned to a variable of type 'value_type'
100 v = p.someParserField().value()
102 // It must be possible to assign a new value using the 'value' member
103 p.someParserField().value(v)
106 If at all possible, the 'value_type' should not reference the packet data using iterators or
107 pointers, it should hold a copy of the value (it's Ok for \c value() to return such a reference
108 as long as assigning it to a \c value_type variable will copy the value).
110 \subsection parserimpl_collection Collection parsers
112 A collection parser \a SomeParser should model STL containers. The parsers themselves will
113 probably only // provide a reduced interface, but the collection parser should have a \c
114 collection member which is a wrapper providing the full interface.
116 SomeParser::container c (p.someParserField());
119 You will probably only very seldom need to implement a completely new collection
120 parser. Instead, you can rely on senf::Parse_Vector or senf::Parse_List and implement new
123 \subsection parserimpl_composite Composite parsers
125 If possible, composite parsers should be implemented using the \ref packetparsermacros. In
126 addition to the normal parser requirements, these macros ensure, that for each field,
127 <em>fieldname</em><tt>_t</tt> is a typedef for the fields parser and
128 <em>fieldname</em><tt>_offset</tt> is the offset of the field in bytes from the beginning of the
129 parser (either a constant for fixed size parsers or a member function for dynamically sized
130 parsers). When defining composite parsers without the help of the \ref packetparsermacros, you
131 should provide those same members.
133 \subsection parserimpl_packet Packet parsers
135 Packet parsers are composite parsers with relaxed requirements. Since a packet parser will never
136 be used as a sub-parser (it will not be used within another composite parser or as value type in
137 a collection parser), the value returned by senf::bytes for this parser must not necessarily
138 cover the complete packet (e.g. if the packet has a trailer, the trailer will live outside the
139 range given by senf::bytes). You may define any member you want to have in your packets field
140 interface. These members may access the packet data in any way. You just need to ensure, that
141 the integration into the packet-type is correct (the senf::PacketTypeMixin will by default use
142 senf::bytes() to find the end of the header).
147 #ifndef HH_PacketParser_
148 #define HH_PacketParser_ 1
151 #include <boost/utility/enable_if.hpp>
152 #include <boost/type_traits.hpp>
153 #include <boost/optional.hpp>
154 #include "../Utils/SafeBool.hh"
155 #include "PacketTypes.hh"
156 #include "PacketData.hh"
157 #include "ParseHelpers.hh"
159 //#include "PacketParser.mpp"
160 ///////////////////////////////hh.p////////////////////////////////////////
166 /** \brief Parser Base class
168 Parsers come in two flavors: fixed and dynamically sized parsers. A <em>fixed size
169 parser</em> has a constant size, it will always parse a fixed number of bytes. The low-level
170 'final' parsers (like the integer parsers) are fixed size parsers as are composite parsers
171 built up only of fixed-size fields.
173 A <em>dynamically sized</em> parser on the other hand infers it's size from the contents of
174 the data parsed. Any parser containing at least one dynamically sized sub-parser will itself
175 be dynamically sized.
177 Both kinds of parser need to derive from PacketParserBase and implement several required
178 members. Which members to implement depends on the parsers flavor. There are two ways how to
180 \li If the parser just consists of a simple sequence of consecutive fields (sub-parsers),
181 the \ref SENF_PACKET_PARSER_DEFINE_FIELDS and \ref
182 SENF_PACKET_PARSER_DEFINE_FIXED_FIELDS macros provide a simple and convenient way to
184 \li In more complex cases, you need to implement the necessary members manually.
186 This documentation is about the manual implementation. You should nevertheless read through
187 this to understand, what above macros are doing.
189 The following example documents the interface (which must be) provided by a parser:
191 struct FooParser : public PacketParserBase
193 FooParser(data_iterator i, state_type s) : PacketParserBase(i,s) {}
195 // If this parser has a fixed size, you must define this size here This definition
196 // allows the parser to be used within the list, vector and array parsers static
197 static const size_type fixed_bytes = some_constant_size;
199 // If the parser does not have a fixed size, you must implement the bytes() member to
200 // return the size. ONLY EVER DEFINE ONE OF fixed_bytes OR bytes().
201 size_type bytes() const;
203 // If you define bytes(), you also need to define the init_bytes. This is the number
204 // of bytes to allocate when creating a new object
205 static const size_type init_bytes = some_constant_size;
207 // You also may define an init() member. This will be called to initialize a newly
208 // created data object. The default implementation just does nothing.
211 // ////////////////////////////////////////////////////////////////////////
213 // Add here members returning (sub-)parsers for the fields. The 'parse' member is
214 // used to construct the sub-parsers. This member either takes an iterator to the
215 // data to be parsed or just an offset in bytes.
217 senf::Parse_UInt16 type() const { return parse<Parse_UInt16>( 0 ); }
218 senf::Parse_UInt16 size() const { return parse<Parse_UInt16>( 2 ); }
222 You should never call the \c bytes() member of a parser directly. Instead you should use the
223 freestanding senf::bytes() function. This function will return the correct size irrespective
224 of the parsers flavor. You may access \c fixed_bytes directly, however be aware that this
225 will restrict your code to fixed size parsers (which depending on the circumstances may be
226 exactly what you want).
228 In the same way, don't access \c init_bytes directly, always use the senf::init_bytes
229 meta-function class which correctly supports fixed size parsers.
231 \ingroup packetparser
233 class PacketParserBase
236 ///////////////////////////////////////////////////////////////////////////
239 typedef detail::packet::iterator data_iterator; ///< Raw data iterator type
240 typedef detail::packet::size_type size_type; ///< Unsigned integral type
241 typedef detail::packet::difference_type difference_type; ///< Signed integral type
242 typedef detail::packet::byte byte; ///< Unsigned 8bit value, the raw value type
243 typedef PacketData * state_type; ///< Type of the 'state' parameter
245 ///////////////////////////////////////////////////////////////////////////
246 ///\name Structors and default members
249 // no default constructor
251 // default destructor
252 // no conversion constructors
255 ///////////////////////////////////////////////////////////////////////////
257 data_iterator i() const; ///< Return beginning of data to parse
258 /**< The parser is expected to interpret the data beginning
259 here. The size of the interpreted is given by
260 <tt>senf::bytes(</tt><em>parser
261 instance</em><tt>)</tt>. */
262 state_type state() const; ///< Return state of this parser
263 /**< The value returned should be interpreted as an opaque
264 value provided just to be forwarded to other
266 PacketData & data() const; ///< Access the packets raw data container
267 /**< This member will return the raw data container holding
268 the data which is parsed by \c this parser. */
270 void init() const; ///< Default implementation
271 /**< This is just an empty default
272 implementation. Re-implement this member in your own
273 parsers if needed. */
276 PacketParserBase(data_iterator i, state_type s); ///< Standard constructor
277 /**< This is the constructor used by most parsers. The
278 parameters are just forwarded from the derived classes
279 constructor parameters. */
280 PacketParserBase(data_iterator i, state_type s, size_type size);
281 ///< Size checking constructor
282 /**< In addition to the standard constructor, this
283 constructor will validate, that there is enough data in
284 the raw data container to parse \a size bytes after \a
287 This constructor is called by all 'final' parsers
288 (e.g. the integer parsers) and \e only by those
289 parsers. Most parsers do \e not check the validity of
290 the iterator, this is delayed until the very last
291 parser. This allows to partial parse truncated
294 \throw TruncatedPacketException if the raw data
295 container does not hold at least \a size bytes
296 beginning at \a i. */
298 bool check(size_type size) const; ///< Check size of data container
299 /**< \returns \c true, if the data container holds at least
300 \a size beginning at i(), \c false otherwise. */
301 void validate(size_type size) const; ///< Validate size of data container
302 /**< \throws TruncatedPacketException if the raw data
303 container does not hold at least \a size bytes
306 template <class Parser> Parser parse(data_iterator i) const; ///< Create sub-parser
307 /**< Creates a new instance of \a Parser to parse data
308 beginning at \a i. Automatically passes \a state() to
310 template <class Parser> Parser parse(size_type n) const; ///< Create sub-parser
311 /**< Creates a new instance of \a Parser to parse data
312 * beginning at i()<tt> + </tt>\a n. Automatically passes \a
313 state() to the new parser. */
315 void defaultInit() const; ///< Default implementation
316 /**< This is just an empty default
317 implementation. Re-implement this member in your own
318 parsers if needed. */
320 Packet packet() const; ///< Get packet this parser is parsing from
321 /**< \important This member should only be used from packet
322 parsers when access to previous or following packets is
323 needed e.g. for calculating checksums etc. */
326 data_iterator end() const;
331 template <class Parser> friend class SafePacketParser;
334 /** \brief Return raw size parsed by the given parser object
336 This function will either call <tt>p.bytes()</tt> or return <tt>Parser::fixed_bytes</tt>
337 depending on the type of parser.
339 The value returned does \e not take into account the amount of data actually available. So
340 you always need to validate this value against the packet size if you directly access the
341 data. The standard low-level parses all do this check automatically to guard against
344 \param[in] p Parser object to check
345 \returns number of bytes this parser expects to parser
346 \ingroup packetparser
348 template <class Parser>
349 PacketParserBase::size_type bytes(Parser p);
351 namespace detail { template <class Parser> class ParserInitBytes; }
353 /** \brief Return number of bytes to allocate to new object of given type
355 This meta-function is called like
357 senf::init_bytes<SomeParser>::value
360 This expression evaluates to a compile-time constant integral expression of type
361 senf::PacketParserBase::size_type. This meta-function will return \c Parser::fixed_bytes or
362 \c Parser::init_bytes depending on the type of parser.
364 \param[in] Parser The Parser to return init_bytes for
365 \returns Number of bytes to allocate to the new object
366 \ingroup packetparser
368 template <class Parser>
369 struct init_bytes : public detail::ParserInitBytes<Parser>
373 template <class Parser>
374 typename boost::enable_if<
375 boost::is_base_of<PacketParserBase, Parser>,
377 operator<<(Parser target, Parser source);
379 /** \brief Generic parser copying
382 This operator allows to copy the values of identical parsers. This operation does \e not
383 depend on the parsers detailed implementation, it will just replace the data bytes of the
384 target parser with those from the source parser. This allows to easily copy around complex
385 packet substructures.
387 This operation is different from the ordinary assignment operator: It does not change the \a
388 target parser, it changes the data referenced by the \a target parser.
390 \ingroup packetparser
392 template <class Parser>
393 Parser operator<<(Parser target, Parser source);
397 template <class Parser, class Value>
398 typename boost::enable_if_c <
399 boost::is_base_of<PacketParserBase, Parser>::value
400 && ! boost::is_base_of<PacketParserBase, Value>::value,
402 operator<<(Parser target, Value const & value);
404 /** \brief Generic parser value assignment
406 This operator allows to assign a value to parsers which implement a <tt>value(</tt>\a
407 value<tt>)</tt> member. This operator allows to use a common syntax for assigning values or
410 \ingroup packetparser
412 template <class Parser, class Value>
413 Parser operator<<(Parser target, Value const & value);
417 template <class Parser, class Value>
418 typename boost::enable_if_c <
419 boost::is_base_of<PacketParserBase, Parser>::value
420 && ! boost::is_base_of<PacketParserBase, Value>::value,
422 operator<<(Parser target, boost::optional<Value> const & value);
424 /** \brief Generic parser value assignment
426 This operator allows to assign a value to parsers which implement a <tt>value(</tt>\a
427 value<tt>)</tt> member. This special version allows to assign optional values: IF the
428 optional value is not set, the assignment will be skipped.
430 This operator allows to use a common syntax for assigning values or parsers to a parser.
432 \ingroup packetparser
434 template <class Parser, class Value>
435 Parser operator<<(Parser target, boost::optional<Value> const & value);
438 /** \brief Default parser parsing nothing
440 struct VoidPacketParser
441 : public PacketParserBase
443 # include SENF_FIXED_PARSER()
444 SENF_PARSER_FINALIZE(VoidPacketParser);
447 /** \brief Iterator re-validating Parser wrapper
449 An ordinary parser will be invalidated whenever the raw data container's size is
450 changed. This can complicate some algorithms considerably.
452 This wrapper will update the parsers iterator (the value returned by the i() member) on
453 every access. This ensures that the iterator will stay valid.
455 \attention Beware however, if you insert or remove data before the safe wrapper, the
456 location will \e not be updated accordingly and therefore the parser will be
459 Additionally a SafePacketParser has an uninitialized state. The only allowed operations in
460 this state are the boolean test for validity and assigning another parser.
462 \ingroup packetparser
464 template <class Parser>
465 class SafePacketParser
466 : public SafeBool< SafePacketParser<Parser> >
469 ///////////////////////////////////////////////////////////////////////////
472 ///////////////////////////////////////////////////////////////////////////
473 ///\name Structors and default members
476 // default copy constructor
477 // default copy assignment
478 // default destructor
479 SafePacketParser(); ///< Create an empty uninitialized SafePacketParser
481 // conversion constructors
482 SafePacketParser(Parser parser); ///< Initialize SafePacketParser from \a parser
484 SafePacketParser & operator=(Parser parser); ///< Assign \a parser to \c this
487 ///////////////////////////////////////////////////////////////////////////
489 Parser operator*() const; ///< Access the stored parser
490 /**< On every access, the stored parsers iterator will be
491 updated / re-validated. */
492 Parser const * operator->() const; ///< Access the stored parser
493 /**< On every access, the stored parsers iterator will be
494 updated / re-validated. */
495 bool boolean_test() const; ///< Check validity
500 mutable boost::optional<Parser> parser_;
501 senf::safe_data_iterator i_;
506 ///////////////////////////////hh.e////////////////////////////////////////
508 #if !defined(HH_Packets__decls_) && !defined(HH_PacketParser_i_)
509 #define HH_PacketParser_i_
510 #include "PacketParser.cci"
511 #include "PacketParser.ct"
512 #include "PacketParser.cti"
519 // c-file-style: "senf"
520 // indent-tabs-mode: nil
521 // ispell-local-dictionary: "american"
522 // compile-command: "scons -u test"
523 // comment-column: 40