Regex.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338 
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 "regex_impl.h"
16#include "llvm/ADT/SmallVector.h"
17#include "llvm/Support/ErrorHandling.h"
18#include "llvm/Support/raw_ostream.h"
19#include <string>
20using namespace llvm;
21
22Regex::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  if (!(Flags & BasicRegex))
31    flags |= REG_EXTENDED;
32  error = llvm_regcomp(preg, regex.data(), flags|REG_PEND);
33}
34
35Regex::~Regex() {
36  if (preg) {
37    llvm_regfree(preg);
38    delete preg;
39  }
40}
41
42bool Regex::isValid(std::string &Error) {
43  if (!error)
44    return true;
45
46  size_t len = llvm_regerror(error, preg, NULL, 0);
47
48  Error.resize(len - 1);
49  llvm_regerror(error, preg, &Error[0], len);
50  return false;
51}
52
53/// getNumMatches - In a valid regex, return the number of parenthesized
54/// matches it contains.
55unsigned Regex::getNumMatches() const {
56  return preg->re_nsub;
57}
58
59bool Regex::match(StringRef String, SmallVectorImpl<StringRef> *Matches){
60  unsigned nmatch = Matches ? preg->re_nsub+1 : 0;
61
62  // pmatch needs to have at least one element.
63  SmallVector<llvm_regmatch_t, 8> pm;
64  pm.resize(nmatch > 0 ? nmatch : 1);
65  pm[0].rm_so = 0;
66  pm[0].rm_eo = String.size();
67
68  int rc = llvm_regexec(preg, String.data(), nmatch, pm.data(), REG_STARTEND);
69
70  if (rc == REG_NOMATCH)
71    return false;
72  if (rc != 0) {
73    // regexec can fail due to invalid pattern or running out of memory.
74    error = rc;
75    return false;
76  }
77
78  // There was a match.
79
80  if (Matches) { // match position requested
81    Matches->clear();
82
83    for (unsigned i = 0; i != nmatch; ++i) {
84      if (pm[i].rm_so == -1) {
85        // this group didn't match
86        Matches->push_back(StringRef());
87        continue;
88      }
89      assert(pm[i].rm_eo >= pm[i].rm_so);
90      Matches->push_back(StringRef(String.data()+pm[i].rm_so,
91                                   pm[i].rm_eo-pm[i].rm_so));
92    }
93  }
94
95  return true;
96}
97
98std::string Regex::sub(StringRef Repl, StringRef String,
99                       std::string *Error) {
100  SmallVector<StringRef, 8> Matches;
101
102  // Reset error, if given.
103  if (Error && !Error->empty()) *Error = "";
104
105  // Return the input if there was no match.
106  if (!match(String, &Matches))
107    return String;
108
109  // Otherwise splice in the replacement string, starting with the prefix before
110  // the match.
111  std::string Res(String.begin(), Matches[0].begin());
112
113  // Then the replacement string, honoring possible substitutions.
114  while (!Repl.empty()) {
115    // Skip to the next escape.
116    std::pair<StringRef, StringRef> Split = Repl.split('\\');
117
118    // Add the skipped substring.
119    Res += Split.first;
120
121    // Check for terminimation and trailing backslash.
122    if (Split.second.empty()) {
123      if (Repl.size() != Split.first.size() &&
124          Error && Error->empty())
125        *Error = "replacement string contained trailing backslash";
126      break;
127    }
128
129    // Otherwise update the replacement string and interpret escapes.
130    Repl = Split.second;
131
132    // FIXME: We should have a StringExtras function for mapping C99 escapes.
133    switch (Repl[0]) {
134      // Treat all unrecognized characters as self-quoting.
135    default:
136      Res += Repl[0];
137      Repl = Repl.substr(1);
138      break;
139
140      // Single character escapes.
141    case 't':
142      Res += '\t';
143      Repl = Repl.substr(1);
144      break;
145    case 'n':
146      Res += '\n';
147      Repl = Repl.substr(1);
148      break;
149
150      // Decimal escapes are backreferences.
151    case '0': case '1': case '2': case '3': case '4':
152    case '5': case '6': case '7': case '8': case '9': {
153      // Extract the backreference number.
154      StringRef Ref = Repl.slice(0, Repl.find_first_not_of("0123456789"));
155      Repl = Repl.substr(Ref.size());
156
157      unsigned RefValue;
158      if (!Ref.getAsInteger(10, RefValue) &&
159          RefValue < Matches.size())
160        Res += Matches[RefValue];
161      else if (Error && Error->empty())
162        *Error = "invalid backreference string '" + Ref.str() + "'";
163      break;
164    }
165    }
166  }
167
168  // And finally the suffix.
169  Res += StringRef(Matches[0].end(), String.end() - Matches[0].end());
170
171  return Res;
172}
173
174// These are the special characters matched in functions like "p_ere_exp".
175static const char RegexMetachars[] = "()^$|*+?.[]\\{}";
176
177bool Regex::isLiteralERE(StringRef Str) {
178  // Check for regex metacharacters.  This list was derived from our regex
179  // implementation in regcomp.c and double checked against the POSIX extended
180  // regular expression specification.
181  return Str.find_first_of(RegexMetachars) == StringRef::npos;
182}
183
184std::string Regex::escape(StringRef String) {
185  std::string RegexStr;
186  for (unsigned i = 0, e = String.size(); i != e; ++i) {
187    if (strchr(RegexMetachars, String[i]))
188      RegexStr += '\\';
189    RegexStr += String[i];
190  }
191
192  return RegexStr;
193}
194