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  1. #include <sstream>
  2. #include <istream>
  3. #include <iostream>
  4.  
  5. void fill_testdata(std::ostream& os);
  6.  
  7. struct FormatData {
  8.     std::string signature, header; // e.g. 4 + 16 = 20 bytes - could be different, of course
  9.     std::string payload;           // 16bit length prefixed
  10. };
  11.  
  12. FormatData parse(std::istream& is);
  13.  
  14. int main() {
  15.     std::stringstream ss;
  16.     fill_testdata(ss);
  17.  
  18.     try {
  19.         FormatData data = parse(ss);
  20.  
  21.         std::cout << "actual payload bytes: " << data.payload.length() << "\n";
  22.         std::cout << "payload: '" << data.payload << "'\n";
  23.     } catch(std::runtime_error const& e) {
  24.         std::cout << "Error: " << e.what() << "\n";
  25.     }
  26. }
  27.  
  28. // some testdata
  29. void fill_testdata(std::ostream& os)
  30. {
  31.     char data[] = { 
  32.         'S'   , 'I'   , 'G'   , 'N'   , '\x00'   , // 0..4
  33.         '\x00', '\x00', '\x00', '\x00', '\x00'   , // 5..9
  34.         '\x00', '\x00', '\x00', '\x00', '\x00'   , // 10..14
  35.         '\x00', '\x00', '\x00', '\x00', '\x00'   , // 15..19
  36.         '\x0b', '\x00', 'H'   , 'e'   , 'l'      , // 20..24
  37.         'l'   , 'o'   , ' '   , 'w'   , 'o'      , // 25..29
  38.         'r'   , 'l'   , 'd'   , '!'   , // 30..33
  39.     };
  40.     os.write(data, sizeof(data));
  41. }
  42.  
  43. //#define BOOST_SPIRIT_DEBUG
  44. #include <boost/fusion/adapted/struct.hpp>
  45. #include <boost/spirit/include/qi.hpp>
  46. #include <boost/spirit/include/phoenix.hpp>
  47. namespace qi = boost::spirit::qi;
  48.  
  49. BOOST_FUSION_ADAPT_STRUCT(FormatData, signature, header, payload)
  50.  
  51. template <typename It>
  52. struct FileFormat : qi::grammar<It, FormatData()> {
  53.     FileFormat() : FileFormat::base_type(start) {
  54.         using namespace qi;
  55.  
  56.         signature  = string("SIGN");     // 4 byte signature, just for example
  57.         header     = repeat(16) [byte_]; // 16 byte header, same
  58.  
  59.         payload   %= omit[little_word[_len=_1]] >> repeat(_len) [byte_];
  60.         start      = signature >> header >> payload;
  61.  
  62.         //BOOST_SPIRIT_DEBUG_NODES((start)(signature)(header)(payload))
  63.     }
  64.   private:
  65.     qi::rule<It, FormatData()> start;
  66.     qi::rule<It, std::string()> signature, header;
  67.  
  68.     qi::_a_type _len;
  69.     qi::rule<It, std::string(), qi::locals<uint16_t> > payload;
  70. };
  71.  
  72. FormatData parse(std::istream& is) {
  73.     using it = boost::spirit::istream_iterator;
  74.  
  75.     FormatData data;
  76.     it f(is >> std::noskipws), l;
  77.     bool ok = parse(f, l, FileFormat<it>{}, data);
  78.  
  79.     if (!ok)
  80.         throw std::runtime_error("parse failure\n");
  81.  
  82.     return data;
  83. }
  84.  
Success #stdin #stdout 0s 15272KB
comments (?)
stdin 
Standard input is empty
stdout 
actual payload bytes: 11
payload: 'Hello world'
https://ideone.com/5y07p5
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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