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 <cassert>
18#include <string>
19
20// Important this comes last because it defines "_REGEX_H_". At least on
21// Darwin, if included before any header that (transitively) includes
22// xlocale.h, this will cause trouble, because of missing regex-related types.
23#include "regex_impl.h"
24
25using namespace llvm;
26
27Regex::Regex() : preg(nullptr), error(REG_BADPAT) {}
28
29Regex::Regex(StringRef regex, RegexFlags Flags) {
30  unsigned flags = 0;
31  preg = new llvm_regex();
32  preg->re_endp = regex.end();
33  if (Flags & IgnoreCase)
34    flags |= REG_ICASE;
35  if (Flags & Newline)
36    flags |= REG_NEWLINE;
37  if (!(Flags & BasicRegex))
38    flags |= REG_EXTENDED;
39  error = llvm_regcomp(preg, regex.data(), flags|REG_PEND);
40}
41
42Regex::Regex(StringRef regex, unsigned Flags)
43    : Regex(regex, static_cast<RegexFlags>(Flags)) {}
44
45Regex::Regex(Regex &&regex) {
46  preg = regex.preg;
47  error = regex.error;
48  regex.preg = nullptr;
49  regex.error = REG_BADPAT;
50}
51
52Regex::~Regex() {
53  if (preg) {
54    llvm_regfree(preg);
55    delete preg;
56  }
57}
58
59namespace {
60
61/// Utility to convert a regex error code into a human-readable string.
62void RegexErrorToString(int error, struct llvm_regex *preg,
63                        std::string &Error) {
64  size_t len = llvm_regerror(error, preg, nullptr, 0);
65
66  Error.resize(len - 1);
67  llvm_regerror(error, preg, &Error[0], len);
68}
69
70} // namespace
71
72bool Regex::isValid(std::string &Error) const {
73  if (!error)
74    return true;
75
76  RegexErrorToString(error, preg, Error);
77  return false;
78}
79
80/// getNumMatches - In a valid regex, return the number of parenthesized
81/// matches it contains.
82unsigned Regex::getNumMatches() const {
83  return preg->re_nsub;
84}
85
86bool Regex::match(StringRef String, SmallVectorImpl<StringRef> *Matches,
87                  std::string *Error) const {
88  // Reset error, if given.
89  if (Error && !Error->empty())
90    *Error = "";
91
92  // Check if the regex itself didn't successfully compile.
93  if (Error ? !isValid(*Error) : !isValid())
94    return false;
95
96  unsigned nmatch = Matches ? preg->re_nsub+1 : 0;
97
98  // pmatch needs to have at least one element.
99  SmallVector<llvm_regmatch_t, 8> pm;
100  pm.resize(nmatch > 0 ? nmatch : 1);
101  pm[0].rm_so = 0;
102  pm[0].rm_eo = String.size();
103
104  int rc = llvm_regexec(preg, String.data(), nmatch, pm.data(), REG_STARTEND);
105
106  // Failure to match is not an error, it's just a normal return value.
107  // Any other error code is considered abnormal, and is logged in the Error.
108  if (rc == REG_NOMATCH)
109    return false;
110  if (rc != 0) {
111    if (Error)
112      RegexErrorToString(error, preg, *Error);
113    return false;
114  }
115
116  // There was a match.
117
118  if (Matches) { // match position requested
119    Matches->clear();
120
121    for (unsigned i = 0; i != nmatch; ++i) {
122      if (pm[i].rm_so == -1) {
123        // this group didn't match
124        Matches->push_back(StringRef());
125        continue;
126      }
127      assert(pm[i].rm_eo >= pm[i].rm_so);
128      Matches->push_back(StringRef(String.data()+pm[i].rm_so,
129                                   pm[i].rm_eo-pm[i].rm_so));
130    }
131  }
132
133  return true;
134}
135
136std::string Regex::sub(StringRef Repl, StringRef String,
137                       std::string *Error) const {
138  SmallVector<StringRef, 8> Matches;
139
140  // Return the input if there was no match.
141  if (!match(String, &Matches, Error))
142    return std::string(String);
143
144  // Otherwise splice in the replacement string, starting with the prefix before
145  // the match.
146  std::string Res(String.begin(), Matches[0].begin());
147
148  // Then the replacement string, honoring possible substitutions.
149  while (!Repl.empty()) {
150    // Skip to the next escape.
151    std::pair<StringRef, StringRef> Split = Repl.split('\\');
152
153    // Add the skipped substring.
154    Res += Split.first;
155
156    // Check for terminimation and trailing backslash.
157    if (Split.second.empty()) {
158      if (Repl.size() != Split.first.size() &&
159          Error && Error->empty())
160        *Error = "replacement string contained trailing backslash";
161      break;
162    }
163
164    // Otherwise update the replacement string and interpret escapes.
165    Repl = Split.second;
166
167    // FIXME: We should have a StringExtras function for mapping C99 escapes.
168    switch (Repl[0]) {
169      // Treat all unrecognized characters as self-quoting.
170    default:
171      Res += Repl[0];
172      Repl = Repl.substr(1);
173      break;
174
175      // Single character escapes.
176    case 't':
177      Res += '\t';
178      Repl = Repl.substr(1);
179      break;
180    case 'n':
181      Res += '\n';
182      Repl = Repl.substr(1);
183      break;
184
185      // Decimal escapes are backreferences.
186    case '0': case '1': case '2': case '3': case '4':
187    case '5': case '6': case '7': case '8': case '9': {
188      // Extract the backreference number.
189      StringRef Ref = Repl.slice(0, Repl.find_first_not_of("0123456789"));
190      Repl = Repl.substr(Ref.size());
191
192      unsigned RefValue;
193      if (!Ref.getAsInteger(10, RefValue) &&
194          RefValue < Matches.size())
195        Res += Matches[RefValue];
196      else if (Error && Error->empty())
197        *Error = ("invalid backreference string '" + Twine(Ref) + "'").str();
198      break;
199    }
200    }
201  }
202
203  // And finally the suffix.
204  Res += StringRef(Matches[0].end(), String.end() - Matches[0].end());
205
206  return Res;
207}
208
209// These are the special characters matched in functions like "p_ere_exp".
210static const char RegexMetachars[] = "()^$|*+?.[]\\{}";
211
212bool Regex::isLiteralERE(StringRef Str) {
213  // Check for regex metacharacters.  This list was derived from our regex
214  // implementation in regcomp.c and double checked against the POSIX extended
215  // regular expression specification.
216  return Str.find_first_of(RegexMetachars) == StringRef::npos;
217}
218
219std::string Regex::escape(StringRef String) {
220  std::string RegexStr;
221  for (char C : String) {
222    if (strchr(RegexMetachars, C))
223      RegexStr += '\\';
224    RegexStr += C;
225  }
226
227  return RegexStr;
228}
229