source/strings/regex.cpp

   1 #include <limits>
   2 #include <list>
   3 #include <stack>
   4 #include <vector>
   5 #include "format.h"
   6 #include "regex.h"
   7
   8 using namespace std;
   9
  10 namespace {
  11
  12 /** Writes an integer to a Regex code string, in little-endian order. */
  13 template<typename T>
  14 void write_int(T n, basic_string<unsigned char> &code)
  15 {
  16         for(unsigned i=0; i<sizeof(T); ++i)
  17                 code += (n>>(i*8))&0xFF;
  18 }
  19
  20 /** Reads an integer from a Regex code string, in little-endian order. */
  21 template<typename T>
  22 T read_int(basic_string<unsigned char>::const_iterator &c)
  23 {
  24         T result = 0;
  25         for(unsigned i=0; i<sizeof(T); ++i)
  26                 result += (*c++)<<(i*8);
  27         return result;
  28 }
  29
  30 }
  31
  32
  33 namespace Msp {
  34
  35 bad_regex::bad_regex(const string &w, const string &e, const string::const_iterator &i):
  36         logic_error(w+"\n"+make_where(e, i))
  37 { }
  38
  39 string bad_regex::make_where(const string &e, const string::const_iterator &i)
  40 {
  41         string result;
  42         string::size_type offset = i-e.begin();
  43         if(offset>40)
  44         {
  45                 result = e.substr(offset-40, 60);
  46                 offset = 40;
  47         }
  48         else
  49                 result = e.substr(0, 60);
  50         result += '\n';
  51         result.append(offset, ' ');
  52         result += '^';
  53         return result;
  54 }
  55
  56
  57 Regex::Regex(const string &expr)
  58 {
  59         n_groups = 0;
  60         auto iter = expr.begin();
  61         code = compile(expr, iter, n_groups, false);
  62         ++n_groups;
  63 }
  64
  65 Regex::Code Regex::compile(const string &expr, string::const_iterator &iter, unsigned &group, bool branch)
  66 {
  67         bool has_branches = false;
  68         stack<string::const_iterator> parens;
  69         bool escape = false;
  70         unsigned bracket = 0;
  71         string::const_iterator end;
  72         for(end=iter; end!=expr.end(); ++end)
  73         {
  74                 if(escape)
  75                         escape = false;
  76                 else if(bracket)
  77                 {
  78                         if(bracket==3 && *end==']')
  79                                 bracket = 0;
  80                         else if(bracket==1 && *end=='^')
  81                                 bracket = 2;
  82                         else
  83                                 bracket = 3;
  84                 }
  85                 else if(*end=='\\')
  86                         escape = true;
  87                 else if(*end=='(')
  88                         parens.push(end);
  89                 else if(*end==')')
  90                 {
  91                         if(parens.empty())
  92                         {
  93                                 if(group==0)
  94                                         throw bad_regex("unmatched ')'", expr, end);
  95                                 else
  96                                         break;
  97                         }
  98                         parens.pop();
  99                 }
 100                 else if(*end=='|' && parens.empty())
 101                 {
 102                         if(branch)
 103                                 break;
 104                         else
 105                                 has_branches = true;
 106                 }
 107                 else if(*end=='[')
 108                         bracket = 1;
 109         }
 110
 111         if(!parens.empty())
 112                 throw bad_regex("unmatched '('", expr, parens.top());
 113
 114         Code result;
 115
 116         unsigned this_group = group;
 117         if(!branch)
 118         {
 119                 result += GROUP_BEGIN;
 120                 write_int<Index>(this_group, result);
 121         }
 122
 123         const unsigned jump_size = 1+sizeof(Offset);
 124
 125         if(!has_branches)
 126         {
 127                 for(auto i=iter; i!=end;)
 128                 {
 129                         Code atom = parse_atom(expr, i, group);
 130
 131                         Count repeat_min = 1;
 132                         Count repeat_max = 1;
 133                         parse_repeat(expr, i, repeat_min, repeat_max);
 134
 135                         for(unsigned j=0; j<repeat_min; ++j)
 136                                 result += atom;
 137                         if(repeat_max==numeric_limits<Count>::max())
 138                         {
 139                                 if(repeat_min==0)
 140                                 {
 141                                         result += ND_JUMP;
 142                                         write_int<Offset>(atom.size()+jump_size, result);
 143                                         result += atom;
 144                                 }
 145                                 result += ND_JUMP;
 146                                 write_int<Offset>(-static_cast<Offset>(atom.size()+jump_size), result);
 147                         }
 148                         else if(repeat_max>repeat_min)
 149                         {
 150                                 for(unsigned j=repeat_min; j<repeat_max; ++j)
 151                                 {
 152                                         result += ND_JUMP;
 153                                         write_int<Offset>((repeat_max-j)*(atom.size()+jump_size)-jump_size, result);
 154                                         result += atom;
 155                                 }
 156                         }
 157                 }
 158         }
 159         else
 160         {
 161                 vector<Code> branches;
 162                 for(auto i=iter;;)
 163                 {
 164                         branches.push_back(compile(expr, i, group, true));
 165                         if(i==end)
 166                                 break;
 167                         ++i;
 168                 }
 169
 170                 unsigned n_branches = branches.size();
 171
 172                 Offset offset = (n_branches-1)*jump_size+branches.front().size();
 173                 for(auto i=++branches.begin(); i!=branches.end(); ++i)
 174                 {
 175                         result += ND_JUMP;
 176                         write_int<Offset>(offset, result);
 177                         offset += i->size();
 178                 }
 179
 180                 for(auto i=branches.begin(); i!=branches.end();)
 181                 {
 182                         result += *i;
 183                         offset -= i->size()+jump_size;
 184                         ++i;
 185                         if(i!=branches.end())
 186                         {
 187                                 result += JUMP;
 188                                 write_int<Offset>(offset, result);
 189                         }
 190                 }
 191         }
 192
 193         if(!branch)
 194         {
 195                 result += GROUP_END;
 196                 write_int<Index>(this_group, result);
 197         }
 198
 199         iter = end;
 200
 201         return result;
 202 }
 203
 204 Regex::Code Regex::parse_atom(const string &expr, string::const_iterator &i, unsigned &group)
 205 {
 206         Code result;
 207
 208         if(i==expr.end())
 209                 return result;
 210
 211         bool flag = false;
 212         if(*i=='\\')
 213         {
 214                 if(++i==expr.end())
 215                         throw bad_regex("stray backslash", expr, i-1);
 216                 flag = true;
 217         }
 218
 219         if(!flag)
 220         {
 221                 if(*i=='*' || *i=='{' || *i=='}' || *i=='+' || *i=='?' || *i=='|' || *i==')')
 222                         throw bad_regex("invalid atom", expr, i);
 223                 else if(*i=='[')
 224                         return parse_brackets(expr, i);
 225                 else if(*i=='.')
 226                         result += MATCH_ANY;
 227                 else if(*i=='^')
 228                         result += MATCH_BEGIN;
 229                 else if(*i=='$')
 230                         result += MATCH_END;
 231                 else if(*i=='(')
 232                 {
 233                         ++group;
 234                         result = compile(expr, ++i, group, false);
 235                 }
 236                 else
 237                         flag = true;
 238         }
 239
 240         if(flag)
 241         {
 242                 result += MATCH_CHAR;
 243                 result += *i;
 244         }
 245
 246         ++i;
 247
 248         return result;
 249 }
 250
 251 bool Regex::parse_repeat(const string &expr, string::const_iterator &i, Count &rmin, Count &rmax)
 252 {
 253         if(*i!='*' && *i!='+' && *i!='?' && *i!='{')
 254                 return false;
 255
 256         if(*i=='*' || *i=='+')
 257                 rmax = numeric_limits<Count>::max();
 258         if(*i=='*' || *i=='?')
 259                 rmin = 0;
 260         if(*i=='{')
 261         {
 262                 auto begin = i;
 263
 264                 rmin = 0;
 265                 for(++i; isdigit(*i); ++i)
 266                         rmin = rmin*10+(*i-'0');
 267
 268                 if(*i==',')
 269                 {
 270                         ++i;
 271                         if(*i!='}')
 272                         {
 273                                 rmax = 0;
 274                                 for(; isdigit(*i); ++i)
 275                                         rmax = rmax*10+(*i-'0');
 276                                 if(rmax<rmin)
 277                                         throw bad_regex("invalid bound", expr, begin);
 278                         }
 279                         else
 280                                 rmax = numeric_limits<Count>::max();
 281                 }
 282                 else
 283                         rmax = rmin;
 284                 if(*i!='}')
 285                         throw bad_regex("invalid bound", expr, begin);
 286         }
 287
 288         ++i;
 289
 290         return true;
 291 }
 292
 293 Regex::Code Regex::parse_brackets(const string &str, string::const_iterator &iter)
 294 {
 295         auto begin = iter;
 296         Code result;
 297
 298         ++iter;
 299         bool neg = false;
 300         if(*iter=='^')
 301         {
 302                 neg = true;
 303                 ++iter;
 304         }
 305
 306         auto end = iter;
 307         for(; (end!=str.end() && (end==iter || *end!=']')); ++end) ;
 308         if(end==str.end())
 309                 throw bad_regex("unmatched '['", str, begin);
 310
 311         unsigned char mask[32] = {0};
 312         unsigned type = 0;
 313         bool range = false;
 314         unsigned char first = 0, last = 0;
 315         for(auto i=iter; i!=end; ++i)
 316         {
 317                 unsigned char c = *i;
 318                 if(range)
 319                 {
 320                         last = c;
 321                         for(unsigned j=first; j<=c; ++j)
 322                                 mask[j>>3] |= 1<<(j&7);
 323                         range = false;
 324                         if(type<2)
 325                                 type = 2;
 326                 }
 327                 else if(c=='-' && i!=iter && end-i>1)
 328                         range = true;
 329                 else
 330                 {
 331                         first = c;
 332                         mask[c>>3] |= 1<<(c&7);
 333                         if(type==0)
 334                                 type = 1;
 335                         else
 336                                 type = 3;
 337                 }
 338         }
 339
 340         if(neg)
 341                 result += NEGATE;
 342
 343         if(type==1)
 344         {
 345                 result += MATCH_CHAR;
 346                 result += first;
 347         }
 348         else if(type==2)
 349         {
 350                 result += MATCH_RANGE;
 351                 result += first;
 352                 result += last;
 353         }
 354         else
 355         {
 356                 result += MATCH_MASK;
 357                 result.append(mask, 32);
 358         }
 359
 360         iter = end;
 361         ++iter;
 362
 363         return result;
 364 }
 365
 366 RegMatch Regex::match(const string &str) const
 367 {
 368         vector<RegMatch::Group> groups(n_groups);
 369
 370         for(auto i=str.begin(); i!=str.end(); ++i)
 371                 if(run(str, i, groups))
 372                         return RegMatch(str, groups);
 373
 374         return RegMatch();
 375 }
 376
 377 bool Regex::run(const string &str, const string::const_iterator &begin, vector<RegMatch::Group> &groups) const
 378 {
 379         bool result = false;
 380         list<RunContext> ctx;
 381         ctx.push_back(RunContext());
 382         ctx.front().citer = code.begin();
 383         ctx.front().groups.resize(groups.size());
 384
 385         for(auto i=begin;;)
 386         {
 387                 int c;
 388                 if(i!=str.end())
 389                         c = *i;
 390                 else
 391                         c = -1;
 392
 393                 for(auto j=ctx.begin(); j!=ctx.end();)
 394                 {
 395                         bool terminate = false;
 396                         bool negate_match = false;
 397                         for(; j->citer!=code.end();)
 398                         {
 399                                 Instruction instr = static_cast<Instruction>(*j->citer++);
 400
 401                                 if(instr==NEGATE)
 402                                         negate_match = true;
 403                                 else if(instr==JUMP)
 404                                 {
 405                                         Offset offset = read_int<Offset>(j->citer);
 406                                         j->citer += offset;
 407                                 }
 408                                 else if(instr==ND_JUMP)
 409                                 {
 410                                         Offset offset = read_int<Offset>(j->citer);
 411                                         ctx.push_back(*j);
 412                                         ctx.back().citer += offset;
 413                                 }
 414                                 else if(instr==GROUP_BEGIN)
 415                                 {
 416                                         Index n = read_int<Index>(j->citer);
 417                                         if(!j->groups[n].match)
 418                                                 j->groups[n].begin = i-str.begin();
 419                                 }
 420                                 else if(instr==GROUP_END)
 421                                 {
 422                                         Index n = read_int<Index>(j->citer);
 423                                         if(!j->groups[n].match)
 424                                         {
 425                                                 j->groups[n].match = true;
 426                                                 j->groups[n].end = i-str.begin();
 427                                                 j->groups[n].length = j->groups[n].end-j->groups[n].begin;
 428                                         }
 429
 430                                         if(n==0)
 431                                         {
 432                                                 result = true;
 433                                                 bool better = false;
 434                                                 for(unsigned k=0; (k<groups.size() && !better); ++k)
 435                                                 {
 436                                                         better = group_compare(j->groups[k], groups[k]);
 437                                                         if(group_compare(groups[k], j->groups[k]))
 438                                                                 break;
 439                                                 }
 440                                                 if(better)
 441                                                         groups = j->groups;
 442                                         }
 443                                 }
 444                                 else
 445                                 {
 446                                         bool match_result = false;
 447                                         bool input_consumed = false;
 448                                         if(instr==MATCH_BEGIN)
 449                                                 match_result = (i==str.begin());
 450                                         else if(instr==MATCH_END)
 451                                                 match_result = (i==str.end());
 452                                         else if(instr==MATCH_CHAR)
 453                                         {
 454                                                 match_result = (c==*j->citer++);
 455                                                 input_consumed = true;
 456                                         }
 457                                         else if(instr==MATCH_RANGE)
 458                                         {
 459                                                 unsigned char first = *j->citer++;
 460                                                 unsigned char last = *j->citer++;
 461                                                 match_result = (c>=first && c<=last);
 462                                                 input_consumed = true;
 463                                         }
 464                                         else if(instr==MATCH_MASK)
 465                                         {
 466                                                 if(c>=0 && c<=0xFF)
 467                                                 {
 468                                                         unsigned char m = *(j->citer+(c>>3));
 469                                                         match_result = m&(1<<(c&7));
 470                                                 }
 471                                                 input_consumed = true;
 472                                                 j->citer += 32;
 473                                         }
 474                                         else if(instr==MATCH_ANY)
 475                                         {
 476                                                 match_result = true;
 477                                                 input_consumed = true;
 478                                         }
 479                                         else
 480                                                 throw logic_error("invalid instruction in regex bytecode");
 481
 482                                         if(match_result==negate_match)
 483                                                 terminate = true;
 484                                         negate_match = false;
 485
 486                                         if(input_consumed || terminate)
 487                                                 break;
 488                                 }
 489                         }
 490
 491                         if(terminate || j->citer==code.end())
 492                                 j = ctx.erase(j);
 493                         else
 494                                 ++j;
 495                 }
 496
 497                 if(i==str.end() || ctx.empty())
 498                         break;
 499                 ++i;
 500         }
 501
 502         return result;
 503 }
 504
 505 bool Regex::group_compare(const RegMatch::Group &g1, const RegMatch::Group &g2) const
 506 {
 507         if(!g1.match)
 508                 return false;
 509
 510         // Any match is better than no match
 511         if(!g2.match)
 512                 return true;
 513
 514         // Earlier match is better
 515         if(g1.begin<g2.begin)
 516                 return true;
 517         if(g1.begin>g2.begin)
 518                 return false;
 519
 520         // Longer match at same position is better
 521         return g1.end>g2.end;
 522 }
 523
 524 string Regex::disassemble() const
 525 {
 526         string result;
 527
 528         for(auto i=code.begin(); i!=code.end();)
 529         {
 530                 auto j = i;
 531                 Offset offset = i-code.begin();
 532                 string decompiled = disassemble_instruction(i);
 533                 string bytes;
 534                 for(; j!=i; ++j)
 535                         bytes += format(" %02X", *j);
 536                 result += format("%3d:%-9s  ", offset, bytes);
 537                 if(bytes.size()>9)
 538                         result += "\n               ";
 539                 result += decompiled;
 540                 result += '\n';
 541         }
 542
 543         return result;
 544 }
 545
 546 string Regex::disassemble_instruction(Code::const_iterator &i) const
 547 {
 548         Instruction instr = static_cast<Instruction>(*i++);
 549
 550         switch(instr)
 551         {
 552         case JUMP:
 553                 {
 554                         Offset offset = read_int<Offset>(i);
 555                         return format("JUMP %+d (%d)", offset, (i-code.begin())+offset);
 556                 }
 557         case ND_JUMP:
 558                 {
 559                         Offset offset = read_int<Offset>(i);
 560                         return format("ND_JUMP %+d (%d)", offset, (i-code.begin())+offset);
 561                 }
 562         case GROUP_BEGIN:
 563                 return format("GROUP_BEGIN %d", read_int<Index>(i));
 564         case GROUP_END:
 565                 return format("GROUP_END %d", read_int<Index>(i));
 566         case NEGATE:
 567                 return "NEGATE";
 568         case MATCH_BEGIN:
 569                 return "MATCH_BEGIN";
 570         case MATCH_END:
 571                 return "MATCH_END";
 572         case MATCH_CHAR:
 573                 {
 574                         unsigned char c = *i++;
 575                         if(c>=0x20 && c<=0x7E)
 576                                 return format("MATCH_CHAR '%c'", c);
 577                         else
 578                                 return format("MATCH_CHAR %d", c);
 579                 }
 580                 break;
 581         case MATCH_RANGE:
 582                 {
 583                         int begin = *i++;
 584                         int end = *i++;
 585                         return format("MATCH_RANGE %d-%d", begin, end);
 586                 }
 587         case MATCH_MASK:
 588                 {
 589                         string result = "MATCH_MASK";
 590                         for(unsigned j=0; j<32; ++j)
 591                                 result += format(" %02X", *i++);
 592                         return result;
 593                 }
 594         case MATCH_ANY:
 595                 return "MATCH_ANY";
 596         default:
 597                 return format("UNKNOWN %d", instr);
 598         }
 599 }
 600
 601 } // namespace Msp