00001 00030 #include <itpp/comm/crc.h> 00031 #include <itpp/base/specmat.h> 00032 #include <itpp/base/matfunc.h> 00033 00034 00035 namespace itpp { 00036 00037 void CRC_Code::set_generator(const bvec &poly) 00038 { 00039 //it_assert(poly(0) == 1 && poly(poly.size()-1) == 1, "CRC_Code::set_polynomial: not a valid polynomial"); 00040 it_assert(poly(0) == 1, "CRC_Code::set_polynomial: not a valid polynomial"); 00041 polynomial = poly; 00042 no_parity = polynomial.size()-1; 00043 } 00044 00046 00047 std::string crccode[18][2] = { 00048 {"CRC-4","1 1 1 1 1"}, 00049 {"CRC-7","1 1 0 1 0 0 0 1"}, 00050 {"CRC-8","1 1 1 0 1 0 1 0 1"}, 00051 {"CRC-12","1 1 0 0 0 0 0 0 0 1 1 1 1"}, 00052 {"CRC-24","1 1 0 0 0 0 0 0 0 0 1 0 1 0 0 0 1 0 0 0 0 0 0 0 1"}, 00053 {"CRC-32","1 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 1 0 0 1 1 0 0 0 1 1 1 0 0 0 1 0"}, 00054 {"CCITT-4","1 0 0 1 1"}, 00055 {"CCITT-5","1 1 0 1 0 1"}, 00056 {"CCITT-6","1 0 0 0 0 1 1"}, 00057 {"CCITT-16","1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1"}, 00058 {"CCITT-32","1 0 0 0 0 0 1 0 0 1 1 0 0 0 0 0 1 0 0 0 1 1 1 0 1 1 0 1 1 0 1 1 1"}, 00059 {"WCDMA-8","1 1 0 0 1 1 0 1 1"}, 00060 {"WCDMA-12","1 1 0 0 0 0 0 0 0 1 1 1 1"}, 00061 {"WCDMA-16","1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 0 1"}, 00062 {"WCDMA-24","1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 0 0 0 1 1"}, 00063 {"ATM-8","1 0 0 0 0 0 1 1 1"}, 00064 {"ANSI-16","1 1 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1"}, 00065 {"SDLC-16","1 1 0 1 0 0 0 0 0 1 0 0 1 0 1 1 1"}, 00066 }; 00067 00069 00070 void CRC_Code::set_code(const std::string &code) 00071 { 00072 bvec poly; 00073 for (int i=0; i<18;i++) { 00074 if (crccode[i][0] == code) 00075 poly = bvec(crccode[i][1]); 00076 } 00077 00078 if ( (code=="WCDMA-8") || (code=="WCDMA-12") || (code=="WCDMA-16") || (code=="WCDMA-24") ) { 00079 reverse_parity = true; 00080 } 00081 00082 it_assert(poly.size()>0, "This CRC code doesn't exist in the tables"); 00083 set_generator(poly); 00084 } 00085 00086 // Not optimized for speed! 00087 void CRC_Code::parity(const bvec &in_bits, bvec &out) const 00088 { 00089 bvec temp = concat(in_bits, zeros_b(no_parity)); 00090 00091 for (int i=0; i<temp.size()-polynomial.size()+1; i++) { 00092 if (temp(i) == 1) { 00093 temp.set_subvector(i,i+no_parity, temp(i,i+no_parity) + polynomial); 00094 } 00095 } 00096 00097 out = temp(temp.size()-no_parity,temp.size()-1); 00098 00099 if (reverse_parity) { 00100 out = reverse( out ); 00101 } 00102 00103 } 00104 00105 // Not optimized for speed 00106 bool CRC_Code::check_parity(const bvec &coded_bits) const 00107 { 00108 int n = coded_bits.size(); 00109 bvec temp; 00110 00111 if (reverse_parity) { 00112 temp = concat( coded_bits.left(n-no_parity), reverse( coded_bits.right( no_parity ) ) ); 00113 } else { 00114 temp = coded_bits; 00115 } 00116 00117 for (int i=0; i<temp.size()-polynomial.size()+1; i++) { 00118 if (temp(i) == 1) { 00119 temp.set_subvector(i,i+no_parity, temp(i,i+no_parity) + polynomial); 00120 } 00121 } 00122 00123 if ( temp(temp.size()-no_parity,temp.size()-1) == zeros_b(no_parity) ) 00124 return true; 00125 else 00126 return false; 00127 } 00128 00129 void CRC_Code::encode(const bvec &in_bits, bvec &out) const 00130 { 00131 bvec p; 00132 parity(in_bits, p); 00133 out = concat(in_bits, p); 00134 } 00135 00136 bvec CRC_Code::encode(const bvec &in_bits) const 00137 { 00138 bvec temp; 00139 encode(in_bits, temp); 00140 return temp; 00141 } 00142 00143 bool CRC_Code::decode(const bvec &coded_bits, bvec &out) const 00144 { 00145 out = coded_bits(0, coded_bits.size()-no_parity-1); 00146 if (check_parity(coded_bits)) { 00147 return true; 00148 } else 00149 return false; 00150 } 00151 00152 bool CRC_Code::decode(bvec &coded_bits) const 00153 { 00154 //coded_bits = coded_bits(0, coded_bits.size()-no_parity-1); <-- OLD CODE 00155 if (check_parity(coded_bits)) { 00156 return true; 00157 } else 00158 return false; 00159 } 00160 00161 } // namespace itpp
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