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/*=============================================================================
Copyright (c) 2002-2003 Joel de Guzman
http://spirit.sourceforge.net/
Use, modification and distribution is subject to the Boost Software
License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
http://www.boost.org/LICENSE_1_0.txt)
=============================================================================*/
#include <boost/spirit/include/classic_core.hpp>
#include <boost/spirit/include/classic_push_back_actor.hpp>
#include <boost/spirit/include/classic_if.hpp>
#include <boost/spirit/include/classic_for.hpp>
#include <boost/spirit/include/phoenix1.hpp>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
///////////////////////////////////////////////////////////////////////////////
//
// Sample parser for binary data. This sample highlights the use of dynamic
// parsing where the result of actions direct the actual parsing behavior.
// We shall demonstrate 1) the use of phoenix to implement lambda (unnamed)
// functions, 2) dynamic looping using for_p, 3) the push_back_a actor for
// stuffing data into a vector, and 4) the if_p parser for choosing parser
// branches based on semantic conditions.
//
// << Sample idea by Florian Weimer >>
//
// For simplicity, we shall use bytes as atoms (and not 16-bit quantities
// in big-endian format or something similar, which would be more realistic)
// and PASCAL strings.
//
// A packet is the literal octet with value 255, followed by a variable
// octet N (denoting the total length of the packet), followed by N-2 octets
// (the payload). The payload contains a variable-length header, followed
// by zero or more elements.
//
// The header contains a single PASCAL string.
//
// An element is a PASCAL string (alternative: an element is an octet M,
// followed by [M/8] bytes, i.e. the necessary number of bytes to store M
// bits).
//
// (This data structure is inspired by the format of a BGP UPDATE message.)
//
// Packet layout:
//
// .-------------------.
// | 0xff | ^
// +-------------------+ |
// | packet length | |
// +-------------------+ | number of bytes indicated by packet length
// : : |
// : payload : |
// | | v
// `-------------------'
//
// Payload layout:
//
// .-------------------.
// | header length |
// +-------------------+
// | header octets | ^
// : : | number of octets given by header length
// : : |
// : : v
// +-------------------+
// | IPv4 prefix | ^
// : : | IPv4 prefixes have variable length (see
// +-------------------+ | below). The number of prefixes is
// | IPv4 prefix | | determined by the packet length.
// : : |
// +-------------------+ |
// : : |
// : : v
//
//
// IPv4 prefix layout comes in five variants, depending on the first
// octet:
//
// .-------------------.
// | 0x00 | single octet, corresponds to 0.0.0.0/0
// `-------------------'
//
// .-------------------.
// | 0x01 to 0x08 | two octets, prefix lengths up to /8.
// +-------------------+
// | MSB of network |
// `-------------------'
//
// .-------------------.
// | 0x09 to 0x10 | three octets, prefix lengths up to /16.
// +-------------------+
// | MSB of network |
// +-------------------+
// | next octet |
// `-------------------'
//
// .-------------------.
// | 0x11 to 0x18 | four octets, prefix lengths up to /24.
// +-------------------+
// | MSB of network |
// +-------------------+
// | next octet |
// +-------------------+
// | next octet |
// `-------------------'
//
// .-------------------.
// | 0x19 to 0x20 | five octets, prefix lengths up to /32.
// +-------------------+
// | MSB of network |
// +-------------------+
// | next octet |
// +-------------------+
// | next octet |
// +-------------------+
// | LSB of network |
// `-------------------'
//
///////////////////////////////////////////////////////////////////////////////
using namespace std;
using namespace BOOST_SPIRIT_CLASSIC_NS;
using namespace phoenix;
struct ipv4_prefix_data
{
char prefix_len, n0, n1, n2, n3;
ipv4_prefix_data()
: prefix_len(0),n0(0),n1(0),n2(0),n3(0) {}
};
struct ipv4_data
{
char packet_len, header_len;
std::string header;
std::vector<ipv4_prefix_data> prefixes;
ipv4_data()
: packet_len(0),header_len(0){}
};
struct ipv4 : public grammar<ipv4>
{
template <typename ScannerT>
struct definition
{
definition(ipv4 const& self)
{
packet =
'\xff'
>> anychar_p[var(self.data.packet_len) = arg1]
>> payload
;
payload =
anychar_p[var(self.data.header_len) = arg1]
>> for_p(var(i) = 0, var(i) < var(self.data.header_len), ++var(i))
[
anychar_p[var(self.data.header) += arg1]
]
>> *ipv4_prefix
;
ipv4_prefix =
anychar_p
[
var(temp.prefix_len) = arg1,
var(temp.n0) = 0,
var(temp.n1) = 0,
var(temp.n2) = 0,
var(temp.n3) = 0
]
>> if_p(var(temp.prefix_len) > 0x00)
[
anychar_p[var(temp.n0) = arg1]
>> if_p(var(temp.prefix_len) > 0x08)
[
anychar_p[var(temp.n1) = arg1]
>> if_p(var(temp.prefix_len) > 0x10)
[
anychar_p[var(temp.n2) = arg1]
>> if_p(var(temp.prefix_len) > 0x18)
[
anychar_p[var(temp.n3) = arg1]
]
]
]
]
[
push_back_a(self.data.prefixes, temp)
]
;
}
int i;
ipv4_prefix_data temp;
rule<ScannerT> packet, payload, ipv4_prefix;
rule<ScannerT> const&
start() const { return packet; }
};
ipv4(ipv4_data& data)
: data(data) {}
ipv4_data& data;
};
////////////////////////////////////////////////////////////////////////////
//
// Main program
//
////////////////////////////////////////////////////////////////////////////
int
as_byte(char n)
{
if (n < 0)
return n + 256;
return n;
}
void
print_prefix(ipv4_prefix_data const& prefix)
{
cout << "prefix length = " << as_byte(prefix.prefix_len) << endl;
cout << "n0 = " << as_byte(prefix.n0) << endl;
cout << "n1 = " << as_byte(prefix.n1) << endl;
cout << "n2 = " << as_byte(prefix.n2) << endl;
cout << "n3 = " << as_byte(prefix.n3) << endl;
}
void
parse_ipv4(char const* str, unsigned len)
{
ipv4_data data;
ipv4 g(data);
parse_info<> info = parse(str, str+len, g);
if (info.full)
{
cout << "-------------------------\n";
cout << "Parsing succeeded\n";
cout << "packet length = " << as_byte(data.packet_len) << endl;
cout << "header length = " << as_byte(data.header_len) << endl;
cout << "header = " << data.header << endl;
for_each(data.prefixes.begin(), data.prefixes.end(), print_prefix);
cout << "-------------------------\n";
}
else
{
cout << "Parsing failed\n";
cout << "stopped at:";
for (char const* s = info.stop; s != str+len; ++s)
cout << static_cast<int>(*s) << endl;
}
}
// Test inputs:
// The string in the header is "empty", the prefix list is empty.
char const i1[8] =
{
0xff,0x08,0x05,
'e','m','p','t','y'
};
// The string in the header is "default route", the prefix list
// has just one element, 0.0.0.0/0.
char const i2[17] =
{
0xff,0x11,0x0d,
'd','e','f','a','u','l','t',' ',
'r','o','u','t','e',
0x00
};
// The string in the header is "private address space", the prefix list
// has the elements 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
char const i3[32] =
{
0xff,0x20,0x15,
'p','r','i','v','a','t','e',' ',
'a','d','d','r','e','s','s',' ',
's','p','a','c','e',
0x08,0x0a,
0x0c,0xac,0x10,
0x10,0xc0,0xa8
};
int
main()
{
parse_ipv4(i1, sizeof(i1));
parse_ipv4(i2, sizeof(i2));
parse_ipv4(i3, sizeof(i3));
return 0;
}
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