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
244 typedef PacketParserBase parser_base_type; ///< Base type of the next parser
246 ///////////////////////////////////////////////////////////////////////////
247 ///\name Structors and default members
250 // no default constructor
252 // default destructor
253 // no conversion constructors
256 ///////////////////////////////////////////////////////////////////////////
258 data_iterator i() const; ///< Return beginning of data to parse
259 /**< The parser is expected to interpret the data beginning
260 here. The size of the interpreted is given by
261 <tt>senf::bytes(</tt><em>parser
262 instance</em><tt>)</tt>. */
263 state_type state() const; ///< Return state of this parser
264 /**< The value returned should be interpreted as an opaque
265 value provided just to be forwarded to other
267 PacketData & data() const; ///< Access the packets raw data container
268 /**< This member will return the raw data container holding
269 the data which is parsed by \c this parser. */
271 void init() const; ///< Default implementation
272 /**< This is just an empty default
273 implementation. Re-implement this member in your own
274 parsers if needed. */
277 PacketParserBase(data_iterator i, state_type s); ///< Standard constructor
278 /**< This is the constructor used by most parsers. The
279 parameters are just forwarded from the derived classes
280 constructor parameters. */
281 PacketParserBase(data_iterator i, state_type s, size_type size);
282 ///< Size checking constructor
283 /**< In addition to the standard constructor, this
284 constructor will validate, that there is enough data in
285 the raw data container to parse \a size bytes after \a
288 This constructor is called by all 'final' parsers
289 (e.g. the integer parsers) and \e only by those
290 parsers. Most parsers do \e not check the validity of
291 the iterator, this is delayed until the very last
292 parser. This allows to partial parse truncated
295 \throw TruncatedPacketException if the raw data
296 container does not hold at least \a size bytes
297 beginning at \a i. */
299 bool check(size_type size) const; ///< Check size of data container
300 /**< \returns \c true, if the data container holds at least
301 \a size beginning at i(), \c false otherwise. */
302 void validate(size_type size) const; ///< Validate size of data container
303 /**< \throws TruncatedPacketException if the raw data
304 container does not hold at least \a size bytes
307 template <class Parser> Parser parse(data_iterator i) const; ///< Create sub-parser
308 /**< Creates a new instance of \a Parser to parse data
309 beginning at \a i. Automatically passes \a state() to
311 template <class Parser> Parser parse(size_type n) const; ///< Create sub-parser
312 /**< Creates a new instance of \a Parser to parse data
313 * beginning at i()<tt> + </tt>\a n. Automatically passes \a
314 state() to the new parser. */
316 void defaultInit() const; ///< Default implementation
317 /**< This is just an empty default
318 implementation. Re-implement this member in your own
319 parsers if needed. */
321 Packet packet() const; ///< Get packet this parser is parsing from
322 /**< \important This member should only be used from packet
323 parsers when access to previous or following packets is
324 needed e.g. for calculating checksums etc. */
327 data_iterator end() const;
332 template <class Parser> friend class SafePacketParser;
335 /** \brief Return raw size parsed by the given parser object
337 This function will either call <tt>p.bytes()</tt> or return <tt>Parser::fixed_bytes</tt>
338 depending on the type of parser.
340 The value returned does \e not take into account the amount of data actually available. So
341 you always need to validate this value against the packet size if you directly access the
342 data. The standard low-level parses all do this check automatically to guard against
345 \param[in] p Parser object to check
346 \returns number of bytes this parser expects to parser
347 \ingroup packetparser
349 template <class Parser>
350 PacketParserBase::size_type bytes(Parser p);
352 namespace detail { template <class Parser> class ParserInitBytes; }
354 /** \brief Return number of bytes to allocate to new object of given type
356 This meta-function is called like
358 senf::init_bytes<SomeParser>::value
361 This expression evaluates to a compile-time constant integral expression of type
362 senf::PacketParserBase::size_type. This meta-function will return \c Parser::fixed_bytes or
363 \c Parser::init_bytes depending on the type of parser.
365 \param[in] Parser The Parser to return init_bytes for
366 \returns Number of bytes to allocate to the new object
367 \ingroup packetparser
369 template <class Parser>
370 struct init_bytes : public detail::ParserInitBytes<Parser>
374 template <class Parser>
375 typename boost::enable_if<
376 boost::is_base_of<PacketParserBase, Parser>,
378 operator<<(Parser target, Parser source);
380 /** \brief Generic parser copying
383 This operator allows to copy the values of identical parsers. This operation does \e not
384 depend on the parsers detailed implementation, it will just replace the data bytes of the
385 target parser with those from the source parser. This allows to easily copy around complex
386 packet substructures.
388 This operation is different from the ordinary assignment operator: It does not change the \a
389 target parser, it changes the data referenced by the \a target parser.
391 \ingroup packetparser
393 template <class Parser>
394 Parser operator<<(Parser target, Parser source);
398 template <class Parser, class Value>
399 typename boost::enable_if_c <
400 boost::is_base_of<PacketParserBase, Parser>::value
401 && ! boost::is_base_of<PacketParserBase, Value>::value,
403 operator<<(Parser target, Value const & value);
405 /** \brief Generic parser value assignment
407 This operator allows to assign a value to parsers which implement a <tt>value(</tt>\a
408 value<tt>)</tt> member. This operator allows to use a common syntax for assigning values or
411 \ingroup packetparser
413 template <class Parser, class Value>
414 Parser operator<<(Parser target, Value const & value);
418 template <class Parser, class Value>
419 typename boost::enable_if_c <
420 boost::is_base_of<PacketParserBase, Parser>::value
421 && ! boost::is_base_of<PacketParserBase, Value>::value,
423 operator<<(Parser target, boost::optional<Value> const & value);
425 /** \brief Generic parser value assignment
427 This operator allows to assign a value to parsers which implement a <tt>value(</tt>\a
428 value<tt>)</tt> member. This special version allows to assign optional values: IF the
429 optional value is not set, the assignment will be skipped.
431 This operator allows to use a common syntax for assigning values or parsers to a parser.
433 \ingroup packetparser
435 template <class Parser, class Value>
436 Parser operator<<(Parser target, boost::optional<Value> const & value);
439 /** \brief Default parser parsing nothing
441 struct VoidPacketParser
442 : public PacketParserBase
444 # include SENF_FIXED_PARSER()
445 SENF_PARSER_FINALIZE(VoidPacketParser);
448 /** \brief Iterator re-validating Parser wrapper
450 An ordinary parser will be invalidated whenever the raw data container's size is
451 changed. This can complicate some algorithms considerably.
453 This wrapper will update the parsers iterator (the value returned by the i() member) on
454 every access. This ensures that the iterator will stay valid.
456 \attention Beware however, if you insert or remove data before the safe wrapper, the
457 location will \e not be updated accordingly and therefore the parser will be
460 Additionally a SafePacketParser has an uninitialized state. The only allowed operations in
461 this state are the boolean test for validity and assigning another parser.
463 \ingroup packetparser
465 template <class Parser>
466 class SafePacketParser
467 : public SafeBool< SafePacketParser<Parser> >
470 ///////////////////////////////////////////////////////////////////////////
473 ///////////////////////////////////////////////////////////////////////////
474 ///\name Structors and default members
477 // default copy constructor
478 // default copy assignment
479 // default destructor
480 SafePacketParser(); ///< Create an empty uninitialized SafePacketParser
482 // conversion constructors
483 SafePacketParser(Parser parser); ///< Initialize SafePacketParser from \a parser
485 SafePacketParser & operator=(Parser parser); ///< Assign \a parser to \c this
488 ///////////////////////////////////////////////////////////////////////////
490 Parser operator*() const; ///< Access the stored parser
491 /**< On every access, the stored parsers iterator will be
492 updated / re-validated. */
493 Parser const * operator->() const; ///< Access the stored parser
494 /**< On every access, the stored parsers iterator will be
495 updated / re-validated. */
496 bool boolean_test() const; ///< Check validity
501 mutable boost::optional<Parser> parser_;
502 senf::safe_data_iterator i_;
507 ///////////////////////////////hh.e////////////////////////////////////////
509 #if !defined(HH_Packets__decls_) && !defined(HH_PacketParser_i_)
510 #define HH_PacketParser_i_
511 #include "PacketParser.cci"
512 #include "PacketParser.ct"
513 #include "PacketParser.cti"
520 // c-file-style: "senf"
521 // indent-tabs-mode: nil
522 // ispell-local-dictionary: "american"
523 // compile-command: "scons -u test"
524 // comment-column: 40