lib/Support/Regex.cpp

   1 //===-- Regex.cpp - Regular Expression matcher implementation -------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file implements a POSIX regular expression matcher.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Support/Regex.h"
  14 #include "llvm/ADT/SmallVector.h"
  15 #include "llvm/ADT/StringRef.h"
  16 #include "llvm/ADT/Twine.h"
  17 #include <string>
  18
  19 // Important this comes last because it defines "_REGEX_H_". At least on
  20 // Darwin, if included before any header that (transitively) includes
  21 // xlocale.h, this will cause trouble, because of missing regex-related types.
  22 #include "regex_impl.h"
  23
  24 using namespace llvm;
  25
  26 Regex::Regex() : preg(nullptr), error(REG_BADPAT) {}
  27
  28 Regex::Regex(StringRef regex, unsigned Flags) {
  29   unsigned flags = 0;
  30   preg = new llvm_regex();
  31   preg->re_endp = regex.end();
  32   if (Flags & IgnoreCase)
  33     flags |= REG_ICASE;
  34   if (Flags & Newline)
  35     flags |= REG_NEWLINE;
  36   if (!(Flags & BasicRegex))
  37     flags |= REG_EXTENDED;
  38   error = llvm_regcomp(preg, regex.data(), flags|REG_PEND);
  39 }
  40
  41 Regex::Regex(Regex &&regex) {
  42   preg = regex.preg;
  43   error = regex.error;
  44   regex.preg = nullptr;
  45   regex.error = REG_BADPAT;
  46 }
  47
  48 Regex::~Regex() {
  49   if (preg) {
  50     llvm_regfree(preg);
  51     delete preg;
  52   }
  53 }
  54
  55 namespace {
  56
  57 /// Utility to convert a regex error code into a human-readable string.
  58 void RegexErrorToString(int error, struct llvm_regex *preg,
  59                         std::string &Error) {
  60   size_t len = llvm_regerror(error, preg, nullptr, 0);
  61
  62   Error.resize(len - 1);
  63   llvm_regerror(error, preg, &Error[0], len);
  64 }
  65
  66 } // namespace
  67
  68 bool Regex::isValid(std::string &Error) const {
  69   if (!error)
  70     return true;
  71
  72   RegexErrorToString(error, preg, Error);
  73   return false;
  74 }
  75
  76 /// getNumMatches - In a valid regex, return the number of parenthesized
  77 /// matches it contains.
  78 unsigned Regex::getNumMatches() const {
  79   return preg->re_nsub;
  80 }
  81
  82 bool Regex::match(StringRef String, SmallVectorImpl<StringRef> *Matches,
  83                   std::string *Error) const {
  84   // Reset error, if given.
  85   if (Error && !Error->empty())
  86     *Error = "";
  87
  88   // Check if the regex itself didn't successfully compile.
  89   if (Error ? !isValid(*Error) : !isValid())
  90     return false;
  91
  92   unsigned nmatch = Matches ? preg->re_nsub+1 : 0;
  93
  94   // pmatch needs to have at least one element.
  95   SmallVector<llvm_regmatch_t, 8> pm;
  96   pm.resize(nmatch > 0 ? nmatch : 1);
  97   pm[0].rm_so = 0;
  98   pm[0].rm_eo = String.size();
  99
 100   int rc = llvm_regexec(preg, String.data(), nmatch, pm.data(), REG_STARTEND);
 101
 102   // Failure to match is not an error, it's just a normal return value.
 103   // Any other error code is considered abnormal, and is logged in the Error.
 104   if (rc == REG_NOMATCH)
 105     return false;
 106   if (rc != 0) {
 107     if (Error)
 108       RegexErrorToString(error, preg, *Error);
 109     return false;
 110   }
 111
 112   // There was a match.
 113
 114   if (Matches) { // match position requested
 115     Matches->clear();
 116
 117     for (unsigned i = 0; i != nmatch; ++i) {
 118       if (pm[i].rm_so == -1) {
 119         // this group didn't match
 120         Matches->push_back(StringRef());
 121         continue;
 122       }
 123       assert(pm[i].rm_eo >= pm[i].rm_so);
 124       Matches->push_back(StringRef(String.data()+pm[i].rm_so,
 125                                    pm[i].rm_eo-pm[i].rm_so));
 126     }
 127   }
 128
 129   return true;
 130 }
 131
 132 std::string Regex::sub(StringRef Repl, StringRef String,
 133                        std::string *Error) const {
 134   SmallVector<StringRef, 8> Matches;
 135
 136   // Return the input if there was no match.
 137   if (!match(String, &Matches, Error))
 138     return String;
 139
 140   // Otherwise splice in the replacement string, starting with the prefix before
 141   // the match.
 142   std::string Res(String.begin(), Matches[0].begin());
 143
 144   // Then the replacement string, honoring possible substitutions.
 145   while (!Repl.empty()) {
 146     // Skip to the next escape.
 147     std::pair<StringRef, StringRef> Split = Repl.split('\\');
 148
 149     // Add the skipped substring.
 150     Res += Split.first;
 151
 152     // Check for terminimation and trailing backslash.
 153     if (Split.second.empty()) {
 154       if (Repl.size() != Split.first.size() &&
 155           Error && Error->empty())
 156         *Error = "replacement string contained trailing backslash";
 157       break;
 158     }
 159
 160     // Otherwise update the replacement string and interpret escapes.
 161     Repl = Split.second;
 162
 163     // FIXME: We should have a StringExtras function for mapping C99 escapes.
 164     switch (Repl[0]) {
 165       // Treat all unrecognized characters as self-quoting.
 166     default:
 167       Res += Repl[0];
 168       Repl = Repl.substr(1);
 169       break;
 170
 171       // Single character escapes.
 172     case 't':
 173       Res += '\t';
 174       Repl = Repl.substr(1);
 175       break;
 176     case 'n':
 177       Res += '\n';
 178       Repl = Repl.substr(1);
 179       break;
 180
 181       // Decimal escapes are backreferences.
 182     case '0': case '1': case '2': case '3': case '4':
 183     case '5': case '6': case '7': case '8': case '9': {
 184       // Extract the backreference number.
 185       StringRef Ref = Repl.slice(0, Repl.find_first_not_of("0123456789"));
 186       Repl = Repl.substr(Ref.size());
 187
 188       unsigned RefValue;
 189       if (!Ref.getAsInteger(10, RefValue) &&
 190           RefValue < Matches.size())
 191         Res += Matches[RefValue];
 192       else if (Error && Error->empty())
 193         *Error = ("invalid backreference string '" + Twine(Ref) + "'").str();
 194       break;
 195     }
 196     }
 197   }
 198
 199   // And finally the suffix.
 200   Res += StringRef(Matches[0].end(), String.end() - Matches[0].end());
 201
 202   return Res;
 203 }
 204
 205 // These are the special characters matched in functions like "p_ere_exp".
 206 static const char RegexMetachars[] = "()^$|*+?.[]\\{}";
 207
 208 bool Regex::isLiteralERE(StringRef Str) {
 209   // Check for regex metacharacters.  This list was derived from our regex
 210   // implementation in regcomp.c and double checked against the POSIX extended
 211   // regular expression specification.
 212   return Str.find_first_of(RegexMetachars) == StringRef::npos;
 213 }
 214
 215 std::string Regex::escape(StringRef String) {
 216   std::string RegexStr;
 217   for (unsigned i = 0, e = String.size(); i != e; ++i) {
 218     if (strchr(RegexMetachars, String[i]))
 219       RegexStr += '\\';
 220     RegexStr += String[i];
 221   }
 222
 223   return RegexStr;
 224 }