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"1 strings to match" in a comment, which isn't gramatic. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113140 91177308-0d34-0410-b5e6-96231b3b80d8
137 lines
5.1 KiB
C++
137 lines
5.1 KiB
C++
//===- StringMatcher.cpp - Generate a matcher for input strings -----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the StringMatcher class.
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//
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//===----------------------------------------------------------------------===//
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#include "StringMatcher.h"
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#include "llvm/Support/raw_ostream.h"
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#include <map>
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using namespace llvm;
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/// FindFirstNonCommonLetter - Find the first character in the keys of the
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/// string pairs that is not shared across the whole set of strings. All
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/// strings are assumed to have the same length.
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static unsigned
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FindFirstNonCommonLetter(const std::vector<const
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StringMatcher::StringPair*> &Matches) {
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assert(!Matches.empty());
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for (unsigned i = 0, e = Matches[0]->first.size(); i != e; ++i) {
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// Check to see if letter i is the same across the set.
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char Letter = Matches[0]->first[i];
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for (unsigned str = 0, e = Matches.size(); str != e; ++str)
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if (Matches[str]->first[i] != Letter)
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return i;
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}
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return Matches[0]->first.size();
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}
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/// EmitStringMatcherForChar - Given a set of strings that are known to be the
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/// same length and whose characters leading up to CharNo are the same, emit
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/// code to verify that CharNo and later are the same.
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///
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/// \return - True if control can leave the emitted code fragment.
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bool StringMatcher::
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EmitStringMatcherForChar(const std::vector<const StringPair*> &Matches,
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unsigned CharNo, unsigned IndentCount) const {
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assert(!Matches.empty() && "Must have at least one string to match!");
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std::string Indent(IndentCount*2+4, ' ');
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// If we have verified that the entire string matches, we're done: output the
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// matching code.
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if (CharNo == Matches[0]->first.size()) {
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assert(Matches.size() == 1 && "Had duplicate keys to match on");
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// FIXME: If Matches[0].first has embeded \n, this will be bad.
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OS << Indent << Matches[0]->second << "\t // \"" << Matches[0]->first
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<< "\"\n";
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return false;
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}
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// Bucket the matches by the character we are comparing.
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std::map<char, std::vector<const StringPair*> > MatchesByLetter;
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for (unsigned i = 0, e = Matches.size(); i != e; ++i)
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MatchesByLetter[Matches[i]->first[CharNo]].push_back(Matches[i]);
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// If we have exactly one bucket to match, see how many characters are common
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// across the whole set and match all of them at once.
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if (MatchesByLetter.size() == 1) {
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unsigned FirstNonCommonLetter = FindFirstNonCommonLetter(Matches);
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unsigned NumChars = FirstNonCommonLetter-CharNo;
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// Emit code to break out if the prefix doesn't match.
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if (NumChars == 1) {
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// Do the comparison with if (Str[1] != 'f')
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// FIXME: Need to escape general characters.
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OS << Indent << "if (" << StrVariableName << "[" << CharNo << "] != '"
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<< Matches[0]->first[CharNo] << "')\n";
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OS << Indent << " break;\n";
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} else {
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// Do the comparison with if (Str.substr(1,3) != "foo").
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// FIXME: Need to escape general strings.
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OS << Indent << "if (" << StrVariableName << ".substr(" << CharNo << ","
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<< NumChars << ") != \"";
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OS << Matches[0]->first.substr(CharNo, NumChars) << "\")\n";
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OS << Indent << " break;\n";
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}
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return EmitStringMatcherForChar(Matches, FirstNonCommonLetter, IndentCount);
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}
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// Otherwise, we have multiple possible things, emit a switch on the
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// character.
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OS << Indent << "switch (" << StrVariableName << "[" << CharNo << "]) {\n";
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OS << Indent << "default: break;\n";
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for (std::map<char, std::vector<const StringPair*> >::iterator LI =
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MatchesByLetter.begin(), E = MatchesByLetter.end(); LI != E; ++LI) {
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// TODO: escape hard stuff (like \n) if we ever care about it.
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OS << Indent << "case '" << LI->first << "':\t // "
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<< LI->second.size() << " string";
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if (LI->second.size() != 1) OS << 's';
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OS << " to match.\n";
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if (EmitStringMatcherForChar(LI->second, CharNo+1, IndentCount+1))
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OS << Indent << " break;\n";
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}
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OS << Indent << "}\n";
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return true;
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}
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/// Emit - Top level entry point.
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///
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void StringMatcher::Emit() const {
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// First level categorization: group strings by length.
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std::map<unsigned, std::vector<const StringPair*> > MatchesByLength;
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for (unsigned i = 0, e = Matches.size(); i != e; ++i)
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MatchesByLength[Matches[i].first.size()].push_back(&Matches[i]);
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// Output a switch statement on length and categorize the elements within each
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// bin.
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OS << " switch (" << StrVariableName << ".size()) {\n";
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OS << " default: break;\n";
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for (std::map<unsigned, std::vector<const StringPair*> >::iterator LI =
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MatchesByLength.begin(), E = MatchesByLength.end(); LI != E; ++LI) {
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OS << " case " << LI->first << ":\t // " << LI->second.size()
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<< " strings to match.\n";
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if (EmitStringMatcherForChar(LI->second, 0, 0))
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OS << " break;\n";
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}
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OS << " }\n";
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}
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