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Add Regex::sub, for doing regular expression substitution with backreferences.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96503 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -56,6 +56,19 @@ namespace llvm {
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///
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/// This returns true on a successful match.
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bool match(const StringRef &String, SmallVectorImpl<StringRef> *Matches=0);
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/// sub - Return the result of replacing the first match of the regex in
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/// \arg String with the \arg Repl string. Backreferences like "\0" in the
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/// replacement string are replaced with the appropriate match substring.
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///
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/// Note that the replacement string has backslash escaping performed on
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/// it. Invalid backreferences are ignored (replaced by empty strings).
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///
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/// \param Error If non-null, any errors in the substitution (invalid
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/// backreferences, trailing backslashes) will be recorded as a non-empty
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/// string.
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std::string sub(StringRef Repl, StringRef String, std::string *Error = 0);
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private:
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struct llvm_regex *preg;
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int error;
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@ -90,3 +90,79 @@ bool Regex::match(const StringRef &String, SmallVectorImpl<StringRef> *Matches){
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return true;
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}
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std::string Regex::sub(StringRef Repl, StringRef String,
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std::string *Error) {
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SmallVector<StringRef, 8> Matches;
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// Reset error, if given.
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if (Error && !Error->empty()) *Error = "";
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// Return the input if there was no match.
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if (!match(String, &Matches))
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return String;
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// Otherwise splice in the replacement string, starting with the prefix before
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// the match.
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std::string Res(String.begin(), Matches[0].begin());
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// Then the replacement string, honoring possible substitutions.
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while (!Repl.empty()) {
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// Skip to the next escape.
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std::pair<StringRef, StringRef> Split = Repl.split('\\');
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// Add the skipped substring.
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Res += Split.first;
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// Check for terminimation and trailing backslash.
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if (Split.second.empty()) {
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if (Repl.size() != Split.first.size() &&
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Error && Error->empty())
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*Error = "replacement string contained trailing backslash";
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break;
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}
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// Otherwise update the replacement string and interpret escapes.
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Repl = Split.second;
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// FIXME: We should have a StringExtras function for mapping C99 escapes.
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switch (Repl[0]) {
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// Treat all unrecognized characters as self-quoting.
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default:
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Res += Repl[0];
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Repl = Repl.substr(1);
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break;
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// Single character escapes.
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case 't':
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Res += '\t';
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Repl = Repl.substr(1);
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break;
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case 'n':
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Res += '\n';
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Repl = Repl.substr(1);
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break;
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// Decimal escapes are backreferences.
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case '0': case '1': case '2': case '3': case '4':
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case '5': case '6': case '7': case '8': case '9': {
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// Extract the backreference number.
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StringRef Ref = Repl.slice(0, Repl.find_first_not_of("0123456789"));
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Repl = Repl.substr(Ref.size());
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unsigned RefValue;
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if (!Ref.getAsInteger(10, RefValue) &&
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RefValue < Matches.size())
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Res += Matches[RefValue];
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else if (Error && Error->empty())
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*Error = "invalid backreference string '" + Ref.str() + "'";
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break;
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}
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}
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}
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// And finally the suffix.
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Res += StringRef(Matches[0].end(), String.end() - Matches[0].end());
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return Res;
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}
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@ -62,4 +62,33 @@ TEST_F(RegexTest, Basics) {
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EXPECT_TRUE(r5.match(String));
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}
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TEST_F(RegexTest, Substitution) {
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std::string Error;
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EXPECT_EQ("aNUMber", Regex("[0-9]+").sub("NUM", "a1234ber"));
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// Standard Escapes
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EXPECT_EQ("a\\ber", Regex("[0-9]+").sub("\\\\", "a1234ber", &Error));
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EXPECT_EQ(Error, "");
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EXPECT_EQ("a\nber", Regex("[0-9]+").sub("\\n", "a1234ber", &Error));
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EXPECT_EQ(Error, "");
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EXPECT_EQ("a\tber", Regex("[0-9]+").sub("\\t", "a1234ber", &Error));
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EXPECT_EQ(Error, "");
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EXPECT_EQ("ajber", Regex("[0-9]+").sub("\\j", "a1234ber", &Error));
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EXPECT_EQ(Error, "");
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EXPECT_EQ("aber", Regex("[0-9]+").sub("\\", "a1234ber", &Error));
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EXPECT_EQ(Error, "replacement string contained trailing backslash");
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// Backreferences
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EXPECT_EQ("aa1234bber", Regex("a[0-9]+b").sub("a\\0b", "a1234ber", &Error));
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EXPECT_EQ(Error, "");
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EXPECT_EQ("a1234ber", Regex("a([0-9]+)b").sub("a\\1b", "a1234ber", &Error));
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EXPECT_EQ(Error, "");
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EXPECT_EQ("aber", Regex("a[0-9]+b").sub("a\\100b", "a1234ber", &Error));
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EXPECT_EQ(Error, "invalid backreference string '100'");
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}
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}
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