lib/Support/Regex.cpp

   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 }