source/regex.cpp

   1 /* $Id$
   2
   3 This file is part of libmspstrings
   4 Copyright © 2007 Mikko Rasa
   5 Distributed under the LGPL
   6 */
   7
   8 #include <stack>
   9 #include <limits>
  10 #include <msp/core/except.h>
  11 #include "formatter.h"
  12 #include "regex.h"
  13
  14 using namespace std;
  15
  16 namespace {
  17
  18 /**
  19 Writes an integer to a Regex code string, in little-endian order.
  20 */
  21 template<typename T>
  22 void write_int(T n, Msp::Regex::Code &code)
  23 {
  24         for(unsigned i=0; i<sizeof(T); ++i)
  25                 code+=(n>>i*8)&0xFF;
  26 }
  27
  28 /**
  29 Reads an integer from a Regex code stream, in little-endian order.
  30 */
  31 template<typename T>
  32 T read_int(Msp::Regex::Code::const_iterator &c)
  33 {
  34         T result=0;
  35         for(unsigned i=0; i<sizeof(T); ++i)
  36                 result+=static_cast<unsigned char>(*c++)<<i*8;
  37         return result;
  38 }
  39
  40 }
  41
  42 namespace Msp {
  43
  44 Regex::Regex(const string &expr)
  45 {
  46         n_groups=0;
  47         string::const_iterator iter=expr.begin();
  48         code=compile(expr, iter, n_groups, false);
  49         ++n_groups;
  50 }
  51
  52 RegMatch Regex::match(const string &str) const
  53 {
  54         RegMatch::GroupArray groups(n_groups);
  55
  56         for(string::const_iterator i=str.begin(); i!=str.end(); ++i)
  57                 if(run(str, i, groups))
  58                         return RegMatch(str, groups);
  59
  60         return RegMatch();
  61 }
  62
  63 string Regex::disassemble() const
  64 {
  65         ostringstream ss;
  66
  67         for(Code::const_iterator i=code.begin(); i!=code.end();)
  68         {
  69                 Code::const_iterator j=i;
  70                 Offset offset=i-code.begin();
  71                 string decompiled=disassemble_instruction(i);
  72                 string bytes;
  73                 for(; j!=i; ++j)
  74                         bytes+=format(" %02X", static_cast<int>(*j)&0xFF);
  75                 ss<<Fmt("%3d")<<offset<<':'<<Fmt("%-9s")<<bytes;
  76                 if(bytes.size()>9)
  77                         ss<<"\n"<<Fmt("%15s");
  78                 ss<<"  "<<decompiled<<'\n';
  79         }
  80
  81         return ss.str();
  82 }
  83
  84 Regex::Code Regex::compile(const string &expr, string::const_iterator &iter, unsigned &group, bool branch)
  85 {
  86         bool has_branches=false;
  87         unsigned level=0;
  88         bool escape=false;
  89         string::const_iterator end;
  90         for(end=iter; end!=expr.end(); ++end)
  91         {
  92                 if(escape)
  93                         escape=false;
  94                 else if(*end=='\\')
  95                         escape=true;
  96                 else if(*end=='(')
  97                         ++level;
  98                 else if(*end==')')
  99                 {
 100                         if(level==0)
 101                         {
 102                                 if(group==0)
 103                                         throw InvalidParameterValue("Unexpected )");
 104                                 else
 105                                         break;
 106                         }
 107                         --level;
 108                 }
 109                 else if(*end=='|')
 110                 {
 111                         if(branch)
 112                                 break;
 113                         else if(level==0)
 114                                 has_branches=true;
 115                 }
 116         }
 117
 118         if(level>0)
 119                 throw InvalidParameterValue("Unmatched (");
 120
 121         Code result;
 122
 123         unsigned this_group=group;
 124         if(!branch)
 125         {
 126                 result+=GROUP_BEGIN;
 127                 write_int<Index>(this_group, result);
 128         }
 129
 130         const unsigned jump_size=1+sizeof(Offset);
 131
 132         if(!has_branches)
 133         {
 134                 for(string::const_iterator i=iter; i!=end;)
 135                 {
 136                         Code atom=parse_atom(expr, i, group);
 137
 138                         Count repeat_min=1;
 139                         Count repeat_max=1;
 140                         parse_repeat(i, repeat_min, repeat_max);
 141
 142                         for(unsigned j=0; j<repeat_min; ++j)
 143                                 result+=atom;
 144                         if(repeat_max==numeric_limits<Count>::max())
 145                         {
 146                                 if(repeat_min==0)
 147                                 {
 148                                         result+=ND_JUMP;
 149                                         write_int<Offset>(atom.size()+jump_size, result);
 150                                         result+=atom;
 151                                 }
 152                                 result+=ND_JUMP;
 153                                 write_int<Offset>(-(atom.size()+jump_size), result);
 154                         }
 155                         else if(repeat_max>repeat_min)
 156                         {
 157                                 for(unsigned j=repeat_min; j<repeat_max; ++j)
 158                                 {
 159                                         result+=ND_JUMP;
 160                                         write_int<Offset>((repeat_max-j)*(atom.size()+jump_size)-jump_size, result);
 161                                         result+=atom;
 162                                 }
 163                         }
 164                 }
 165         }
 166         else
 167         {
 168                 list<Code> branches;
 169                 for(string::const_iterator i=iter;;)
 170                 {
 171                         branches.push_back(compile(expr, i, group, true));
 172                         if(i==end)
 173                                 break;
 174                         ++i;
 175                 }
 176
 177                 unsigned n_branches=branches.size();
 178
 179                 Offset offset=(n_branches-1)*jump_size+branches.front().size();
 180                 for(list<Code>::iterator i=++branches.begin(); i!=branches.end(); ++i)
 181                 {
 182                         result+=ND_JUMP;
 183                         write_int<Offset>(offset, result);
 184                         offset+=i->size();
 185                 }
 186
 187                 for(list<Code>::iterator i=branches.begin(); i!=branches.end();)
 188                 {
 189                         result+=*i;
 190                         offset-=i->size()+jump_size;
 191                         ++i;
 192                         if(i!=branches.end())
 193                         {
 194                                 result+=JUMP;
 195                                 write_int<Offset>(offset, result);
 196                         }
 197                 }
 198         }
 199
 200         if(!branch)
 201         {
 202                 result+=GROUP_END;
 203                 write_int<Index>(this_group, result);
 204         }
 205
 206         iter=end;
 207
 208         return result;
 209 }
 210
 211 Regex::Code Regex::parse_atom(const string &expr, string::const_iterator &i, unsigned &group)
 212 {
 213         Code result;
 214
 215         if(i==expr.end())
 216                 return result;
 217
 218         bool flag=false;
 219         if(*i=='\\')
 220         {
 221                 if(++i==expr.end())
 222                         throw InvalidParameterValue("Stray backslash");
 223                 flag=true;
 224         }
 225
 226         if(!flag)
 227         {
 228                 if(*i=='*' || *i=='{' || *i=='}' || *i=='+' || *i=='?' || *i=='|' || *i==')')
 229                         throw InvalidParameterValue("Invalid atom");
 230                 else if(*i=='[')
 231                         return parse_brackets(expr, i);
 232                 else if(*i=='.')
 233                         result+=MATCH_ANY;
 234                 else if(*i=='^')
 235                         result+=MATCH_BEGIN;
 236                 else if(*i=='$')
 237                         result+=MATCH_END;
 238                 else if(*i=='(')
 239                 {
 240                         ++group;
 241                         result=compile(expr, ++i, group, false);
 242                 }
 243                 else
 244                         flag=true;
 245         }
 246
 247         if(flag)
 248         {
 249                 result+=MATCH_CHAR;
 250                 result+=*i;
 251         }
 252
 253         ++i;
 254
 255         return result;
 256 }
 257
 258 bool Regex::parse_repeat(string::const_iterator &i, Count &rmin, Count &rmax)
 259 {
 260         if(*i!='*' && *i!='+' && *i!='?' && *i!='{')
 261                 return false;
 262
 263         if(*i=='*' || *i=='+')
 264                 rmax=numeric_limits<Count>::max();
 265         if(*i=='*' || *i=='?')
 266                 rmin=0;
 267         if(*i=='{')
 268         {
 269                 rmin=0;
 270                 for(++i; isdigit(*i); ++i)
 271                         rmin=rmin*10+(*i-'0');
 272
 273                 if(*i==',')
 274                 {
 275                         ++i;
 276                         if(*i!='}')
 277                         {
 278                                 rmax=0;
 279                                 for(; isdigit(*i); ++i)
 280                                         rmax=rmax*10+(*i-'0');
 281                                 if(rmax<rmin)
 282                                         throw InvalidParameterValue("Invalid bound");
 283                         }
 284                         else
 285                                 rmax=numeric_limits<Count>::max();
 286                 }
 287                 else
 288                         rmax=rmin;
 289                 if(*i!='}')
 290                         throw InvalidParameterValue("Invalid bound");
 291         }
 292
 293         ++i;
 294
 295         return true;
 296 }
 297
 298 Regex::Code Regex::parse_brackets(const string &str, string::const_iterator &iter)
 299 {
 300         Code result;
 301
 302         ++iter;
 303         bool neg=false;
 304         if(*iter=='^')
 305         {
 306                 neg=true;
 307                 ++iter;
 308         }
 309
 310         string::const_iterator end=iter;
 311         for(; (end!=str.end() && (end==iter || *end!=']')); ++end) ;
 312         if(end==str.end())
 313                 throw InvalidParameterValue("Unmatched '['");
 314
 315         uint8_t mask[32]={0};
 316         unsigned type=0;
 317         bool range=false;
 318         unsigned char first=0, last=0;
 319         for(string::const_iterator i=iter; i!=end; ++i)
 320         {
 321                 unsigned char c=*i;
 322                 if(range)
 323                 {
 324                         last=c;
 325                         for(unsigned j=first; j<=c; ++j)
 326                                 mask[j>>3]|=1<<(j&7);
 327                         range=false;
 328                         if(type<2)
 329                                 type=2;
 330                 }
 331                 else if(c=='-' && i!=iter && end-i>1)
 332                         range=true;
 333                 else
 334                 {
 335                         first=c;
 336                         mask[c>>3]|=1<<(c&7);
 337                         if(type==0)
 338                                 type=1;
 339                         else
 340                                 type=3;
 341                 }
 342         }
 343
 344         if(neg)
 345                 result+=NEGATE;
 346
 347         if(type==1)
 348         {
 349                 result+=MATCH_CHAR;
 350                 result+=first;
 351         }
 352         else if(type==2)
 353         {
 354                 result+=MATCH_RANGE;
 355                 result+=first;
 356                 result+=last;
 357         }
 358         else
 359         {
 360                 result+=MATCH_MASK;
 361                 result.append(reinterpret_cast<char *>(mask), 32);
 362         }
 363
 364         iter=end;
 365         ++iter;
 366
 367         return result;
 368 }
 369
 370 bool Regex::run(const string &str, const string::const_iterator &begin, RegMatch::GroupArray &groups) const
 371 {
 372         bool result=false;
 373         list<RunContext> ctx;
 374         ctx.push_back(RunContext());
 375         ctx.front().citer=code.begin();
 376         ctx.front().groups.resize(groups.size());
 377
 378         for(string::const_iterator i=begin;;)
 379         {
 380                 int c;
 381                 if(i!=str.end())
 382                         c=static_cast<unsigned char>(*i);
 383                 else
 384                         c=-1;
 385
 386                 for(list<RunContext>::iterator j=ctx.begin(); j!=ctx.end();)
 387                 {
 388                         bool terminate=false;
 389                         bool negate_match=false;
 390                         for(; j->citer!=code.end();)
 391                         {
 392                                 Instruction instr=static_cast<Instruction>(*j->citer++);
 393
 394                                 if(instr==NEGATE)
 395                                         negate_match=true;
 396                                 else if(instr==JUMP)
 397                                 {
 398                                         Offset offset=read_int<Offset>(j->citer);
 399                                         j->citer+=offset;
 400                                 }
 401                                 else if(instr==ND_JUMP)
 402                                 {
 403                                         Offset offset=read_int<Offset>(j->citer);
 404                                         ctx.push_back(*j);
 405                                         ctx.back().citer+=offset;
 406                                 }
 407                                 else if(instr==GROUP_BEGIN)
 408                                 {
 409                                         Index n=read_int<Index>(j->citer);
 410                                         if(!j->groups[n].match)
 411                                                 j->groups[n].begin=i-str.begin();
 412                                 }
 413                                 else if(instr==GROUP_END)
 414                                 {
 415                                         Index n=read_int<Index>(j->citer);
 416                                         if(!j->groups[n].match)
 417                                         {
 418                                                 j->groups[n].match=true;
 419                                                 j->groups[n].end=i-str.begin();
 420                                                 j->groups[n].length=j->groups[n].end-j->groups[n].begin;
 421                                         }
 422
 423                                         if(n==0)
 424                                         {
 425                                                 result=true;
 426                                                 bool better=false;
 427                                                 for(unsigned k=0; (k<groups.size() && !better); ++k)
 428                                                 {
 429                                                         better=group_compare(j->groups[k], groups[k]);
 430                                                         if(group_compare(groups[k], j->groups[k]))
 431                                                                 break;
 432                                                 }
 433                                                 if(better)
 434                                                         groups=j->groups;
 435                                         }
 436                                 }
 437                                 else
 438                                 {
 439                                         bool match_result=false;
 440                                         bool input_consumed=false;
 441                                         if(instr==MATCH_BEGIN)
 442                                                 match_result=(i==str.begin());
 443                                         else if(instr==MATCH_END)
 444                                                 match_result=(i==str.end());
 445                                         else if(instr==MATCH_CHAR)
 446                                         {
 447                                                 match_result=(c==*j->citer++);
 448                                                 input_consumed=true;
 449                                         }
 450                                         else if(instr==MATCH_RANGE)
 451                                         {
 452                                                 unsigned char first=*j->citer++;
 453                                                 unsigned char last=*j->citer++;
 454                                                 match_result=(c>=first && c<=last);
 455                                                 input_consumed=true;
 456                                         }
 457                                         else if(instr==MATCH_MASK)
 458                                         {
 459                                                 uint8_t mask[32];
 460                                                 for(unsigned k=0; k<32; ++k)
 461                                                         mask[k]=*j->citer++;
 462                                                 match_result=mask[c>>3]&(1<<(c&7));
 463                                                 input_consumed=true;
 464                                         }
 465                                         else if(instr==MATCH_ANY)
 466                                         {
 467                                                 match_result=true;
 468                                                 input_consumed=true;
 469                                         }
 470                                         else
 471                                                 throw Exception("Invalid instruction");
 472
 473                                         if(match_result==negate_match)
 474                                                 terminate=true;
 475                                         negate_match=false;
 476
 477                                         if(input_consumed || terminate)
 478                                                 break;
 479                                 }
 480                         }
 481
 482                         if(terminate || j->citer==code.end())
 483                                 j=ctx.erase(j);
 484                         else
 485                                 ++j;
 486                 }
 487
 488                 if(i==str.end() || ctx.empty())
 489                         break;
 490                 ++i;
 491         }
 492
 493         return result;
 494 }
 495
 496 bool Regex::group_compare(const RegMatch::Group &g1, const RegMatch::Group &g2) const
 497 {
 498         if(!g1.match)
 499                 return false;
 500
 501         // Any match is better than no match
 502         if(!g2.match)
 503                 return true;
 504
 505         // Earlier match is better
 506         if(g1.begin<g2.begin)
 507                 return true;
 508         if(g2.begin>g2.begin)
 509                 return false;
 510
 511         // Longer match at same position is better
 512         return g1.end>g2.end;
 513 }
 514
 515 string Regex::disassemble_instruction(Code::const_iterator &i) const
 516 {
 517         Instruction instr=static_cast<Instruction>(*i++);
 518
 519         ostringstream result;
 520         switch(instr)
 521         {
 522         case JUMP:
 523                 {
 524                         Offset offset=read_int<Offset>(i);
 525                         result<<"JUMP "<<Fmt("%+d")<<offset<<" ("<<Fmt("%d")<<i-code.begin()+offset<<')';
 526                 }
 527                 break;
 528         case ND_JUMP:
 529                 {
 530                         Offset offset=read_int<Offset>(i);
 531                         result<<"ND_JUMP "<<Fmt("%+d")<<offset<<" ("<<Fmt("%d")<<i-code.begin()+offset<<')';
 532                 }
 533                 break;
 534         case GROUP_BEGIN:
 535                 result<<"GROUP_BEGIN "<<read_int<Index>(i);
 536                 break;
 537         case GROUP_END:
 538                 result<<"GROUP_END "<<read_int<Index>(i);
 539                 break;
 540         case NEGATE:
 541                 result<<"NEGATE";
 542                 break;
 543         case MATCH_BEGIN:
 544                 result<<"MATCH_BEGIN";
 545                 break;
 546         case MATCH_END:
 547                 result<<"MATCH_END";
 548                 break;
 549         case MATCH_CHAR:
 550                 {
 551                         char c=*i++;
 552                         result<<"MATCH_CHAR ";
 553                         if(c>=0x20 && c<=0x7E)
 554                                 result<<'\''<<c<<'\'';
 555                         else
 556                                 result<<(static_cast<int>(c)&0xFF);
 557                 }
 558                 break;
 559         case MATCH_RANGE:
 560                 result<<"MATCH_RANGE "<<(static_cast<int>(*i++)&0xFF);
 561                 result<<'-'<<(static_cast<int>(*i++)&0xFF);
 562                 break;
 563         case MATCH_MASK:
 564                 result<<"MATCH_MASK";
 565                 for(unsigned j=0; j<32; ++j)
 566                         result<<' '<<Fmt("%02X")<<(static_cast<int>(*i++)&0xFF);
 567                 break;
 568         case MATCH_ANY:
 569                 result<<"MATCH_ANY";
 570                 break;
 571         default:
 572                 result<<"UNKNOWN "<<instr;
 573         }
 574
 575         return result.str();
 576 }
 577
 578 } // namespace Msp