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      1 //===-- Regex.cpp - Regular Expression matcher implementation -------------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file implements a POSIX regular expression matcher.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "llvm/Support/Regex.h"
     15 #include "llvm/Support/ErrorHandling.h"
     16 #include "llvm/Support/raw_ostream.h"
     17 #include "llvm/ADT/SmallVector.h"
     18 #include "regex_impl.h"
     19 #include <string>
     20 using namespace llvm;
     21 
     22 Regex::Regex(StringRef regex, unsigned Flags) {
     23   unsigned flags = 0;
     24   preg = new llvm_regex();
     25   preg->re_endp = regex.end();
     26   if (Flags & IgnoreCase)
     27     flags |= REG_ICASE;
     28   if (Flags & Newline)
     29     flags |= REG_NEWLINE;
     30   error = llvm_regcomp(preg, regex.data(), flags|REG_EXTENDED|REG_PEND);
     31 }
     32 
     33 Regex::~Regex() {
     34   llvm_regfree(preg);
     35   delete preg;
     36 }
     37 
     38 bool Regex::isValid(std::string &Error) {
     39   if (!error)
     40     return true;
     41 
     42   size_t len = llvm_regerror(error, preg, NULL, 0);
     43 
     44   Error.resize(len);
     45   llvm_regerror(error, preg, &Error[0], len);
     46   return false;
     47 }
     48 
     49 /// getNumMatches - In a valid regex, return the number of parenthesized
     50 /// matches it contains.
     51 unsigned Regex::getNumMatches() const {
     52   return preg->re_nsub;
     53 }
     54 
     55 bool Regex::match(StringRef String, SmallVectorImpl<StringRef> *Matches){
     56   unsigned nmatch = Matches ? preg->re_nsub+1 : 0;
     57 
     58   // pmatch needs to have at least one element.
     59   SmallVector<llvm_regmatch_t, 8> pm;
     60   pm.resize(nmatch > 0 ? nmatch : 1);
     61   pm[0].rm_so = 0;
     62   pm[0].rm_eo = String.size();
     63 
     64   int rc = llvm_regexec(preg, String.data(), nmatch, pm.data(), REG_STARTEND);
     65 
     66   if (rc == REG_NOMATCH)
     67     return false;
     68   if (rc != 0) {
     69     // regexec can fail due to invalid pattern or running out of memory.
     70     error = rc;
     71     return false;
     72   }
     73 
     74   // There was a match.
     75 
     76   if (Matches) { // match position requested
     77     Matches->clear();
     78 
     79     for (unsigned i = 0; i != nmatch; ++i) {
     80       if (pm[i].rm_so == -1) {
     81         // this group didn't match
     82         Matches->push_back(StringRef());
     83         continue;
     84       }
     85       assert(pm[i].rm_eo >= pm[i].rm_so);
     86       Matches->push_back(StringRef(String.data()+pm[i].rm_so,
     87                                    pm[i].rm_eo-pm[i].rm_so));
     88     }
     89   }
     90 
     91   return true;
     92 }
     93 
     94 std::string Regex::sub(StringRef Repl, StringRef String,
     95                        std::string *Error) {
     96   SmallVector<StringRef, 8> Matches;
     97 
     98   // Reset error, if given.
     99   if (Error && !Error->empty()) *Error = "";
    100 
    101   // Return the input if there was no match.
    102   if (!match(String, &Matches))
    103     return String;
    104 
    105   // Otherwise splice in the replacement string, starting with the prefix before
    106   // the match.
    107   std::string Res(String.begin(), Matches[0].begin());
    108 
    109   // Then the replacement string, honoring possible substitutions.
    110   while (!Repl.empty()) {
    111     // Skip to the next escape.
    112     std::pair<StringRef, StringRef> Split = Repl.split('\\');
    113 
    114     // Add the skipped substring.
    115     Res += Split.first;
    116 
    117     // Check for terminimation and trailing backslash.
    118     if (Split.second.empty()) {
    119       if (Repl.size() != Split.first.size() &&
    120           Error && Error->empty())
    121         *Error = "replacement string contained trailing backslash";
    122       break;
    123     }
    124 
    125     // Otherwise update the replacement string and interpret escapes.
    126     Repl = Split.second;
    127 
    128     // FIXME: We should have a StringExtras function for mapping C99 escapes.
    129     switch (Repl[0]) {
    130       // Treat all unrecognized characters as self-quoting.
    131     default:
    132       Res += Repl[0];
    133       Repl = Repl.substr(1);
    134       break;
    135 
    136       // Single character escapes.
    137     case 't':
    138       Res += '\t';
    139       Repl = Repl.substr(1);
    140       break;
    141     case 'n':
    142       Res += '\n';
    143       Repl = Repl.substr(1);
    144       break;
    145 
    146       // Decimal escapes are backreferences.
    147     case '0': case '1': case '2': case '3': case '4':
    148     case '5': case '6': case '7': case '8': case '9': {
    149       // Extract the backreference number.
    150       StringRef Ref = Repl.slice(0, Repl.find_first_not_of("0123456789"));
    151       Repl = Repl.substr(Ref.size());
    152 
    153       unsigned RefValue;
    154       if (!Ref.getAsInteger(10, RefValue) &&
    155           RefValue < Matches.size())
    156         Res += Matches[RefValue];
    157       else if (Error && Error->empty())
    158         *Error = "invalid backreference string '" + Ref.str() + "'";
    159       break;
    160     }
    161     }
    162   }
    163 
    164   // And finally the suffix.
    165   Res += StringRef(Matches[0].end(), String.end() - Matches[0].end());
    166 
    167   return Res;
    168 }
    169