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>
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  error = llvm_regcomp(preg, regex.data(), flags|REG_EXTENDED|REG_PEND);
31}
32
33Regex::~Regex() {
34  llvm_regfree(preg);
35  delete preg;
36}
37
38bool 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.
51unsigned Regex::getNumMatches() const {
52  return preg->re_nsub;
53}
54
55bool 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
94std::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