text: //===- GraphWriter.cpp - Implements GraphWriter support routines ----------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements misc. GraphWriter support routines.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/Support/GraphWriter.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/SmallVector.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Config/config.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/ErrorOr.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/Program.h"
  #include "llvm/Support/raw_ostream.h"
  #include <cassert>
  #include <system_error>
  #include <string>
  #include <vector>
  
  using namespace llvm;
  
  static cl::opt<bool> ViewBackground("view-background", cl::Hidden,
    cl::desc("Execute graph viewer in the background. Creates tmp file litter."));
  
  std::string llvm::DOT::EscapeString(const std::string &Label) {
    std::string Str(Label);
    for (unsigned i = 0; i != Str.length(); ++i)
    switch (Str[i]) {
      case '\n':
        Str.insert(Str.begin()+i, '\\');  // Escape character...
        ++i;
        Str[i] = 'n';
        break;
      case '\t':
        Str.insert(Str.begin()+i, ' ');  // Convert to two spaces
        ++i;
        Str[i] = ' ';
        break;
      case '\\':
        if (i+1 != Str.length())
          switch (Str[i+1]) {
            case 'l': continue; // don't disturb \l
            case '|': case '{': case '}':
              Str.erase(Str.begin()+i); continue;
            default: break;
          }
          LLVM_FALLTHROUGH;
      case '{': case '}':
      case '<': case '>':
      case '|': case '"':
        Str.insert(Str.begin()+i, '\\');  // Escape character...
        ++i;  // don't infinite loop
        break;
    }
    return Str;
  }
  
  /// Get a color string for this node number. Simply round-robin selects
  /// from a reasonable number of colors.
  StringRef llvm::DOT::getColorString(unsigned ColorNumber) {
    static const int NumColors = 20;
    static const char* Colors[NumColors] = {
      "aaaaaa", "aa0000", "00aa00", "aa5500", "0055ff", "aa00aa", "00aaaa",
      "555555", "ff5555", "55ff55", "ffff55", "5555ff", "ff55ff", "55ffff",
      "ffaaaa", "aaffaa", "ffffaa", "aaaaff", "ffaaff", "aaffff"};
    return Colors[ColorNumber % NumColors];
  }
  
  std::string llvm::createGraphFilename(const Twine &Name, int &FD) {
    FD = -1;
    SmallString<128> Filename;
    std::error_code EC = sys::fs::createTemporaryFile(Name, "dot", FD, Filename);
    if (EC) {
      errs() << "Error: " << EC.message() << "\n";
      return "";
    }
  
    errs() << "Writing '" << Filename << "'... ";
    return Filename.str();
  }
  
  // Execute the graph viewer. Return true if there were errors.
  static bool ExecGraphViewer(StringRef ExecPath, std::vector<StringRef> &args,
                              StringRef Filename, bool wait,
                              std::string &ErrMsg) {
    if (wait) {
      if (sys::ExecuteAndWait(ExecPath, args, None, {}, 0, 0, &ErrMsg)) {
        errs() << "Error: " << ErrMsg << "\n";
        return true;
      }
      sys::fs::remove(Filename);
      errs() << " done. \n";
    } else {
      sys::ExecuteNoWait(ExecPath, args, None, {}, 0, &ErrMsg);
      errs() << "Remember to erase graph file: " << Filename << "\n";
    }
    return false;
  }
  
  namespace {
  
  struct GraphSession {
    std::string LogBuffer;
  
    bool TryFindProgram(StringRef Names, std::string &ProgramPath) {
      raw_string_ostream Log(LogBuffer);
      SmallVector<StringRef, 8> parts;
      Names.split(parts, '|');
      for (auto Name : parts) {
        if (ErrorOr<std::string> P = sys::findProgramByName(Name)) {
          ProgramPath = *P;
          return true;
        }
        Log << "  Tried '" << Name << "'\n";
      }
      return false;
    }
  };
  
  } // end anonymous namespace
  
  static const char *getProgramName(GraphProgram::Name program) {
    switch (program) {
    case GraphProgram::DOT:
      return "dot";
    case GraphProgram::FDP:
      return "fdp";
    case GraphProgram::NEATO:
      return "neato";
    case GraphProgram::TWOPI:
      return "twopi";
    case GraphProgram::CIRCO:
      return "circo";
    }
    llvm_unreachable("bad kind");
  }
  
  bool llvm::DisplayGraph(StringRef FilenameRef, bool wait,
                          GraphProgram::Name program) {
    std::string Filename = FilenameRef;
    std::string ErrMsg;
    std::string ViewerPath;
    GraphSession S;
  
  #ifdef __APPLE__
    wait &= !ViewBackground;
    if (S.TryFindProgram("open", ViewerPath)) {
      std::vector<StringRef> args;
      args.push_back(ViewerPath);
      if (wait)
        args.push_back("-W");
      args.push_back(Filename);
      errs() << "Trying 'open' program... ";
      if (!ExecGraphViewer(ViewerPath, args, Filename, wait, ErrMsg))
        return false;
    }
  #endif
    if (S.TryFindProgram("xdg-open", ViewerPath)) {
      std::vector<StringRef> args;
      args.push_back(ViewerPath);
      args.push_back(Filename);
      errs() << "Trying 'xdg-open' program... ";
      if (!ExecGraphViewer(ViewerPath, args, Filename, wait, ErrMsg))
        return false;
    }
  
    // Graphviz
    if (S.TryFindProgram("Graphviz", ViewerPath)) {
      std::vector<StringRef> args;
      args.push_back(ViewerPath);
      args.push_back(Filename);
  
      errs() << "Running 'Graphviz' program... ";
      return ExecGraphViewer(ViewerPath, args, Filename, wait, ErrMsg);
    }
  
    // xdot
    if (S.TryFindProgram("xdot|xdot.py", ViewerPath)) {
      std::vector<StringRef> args;
      args.push_back(ViewerPath);
      args.push_back(Filename);
  
      args.push_back("-f");
      args.push_back(getProgramName(program));
  
      errs() << "Running 'xdot.py' program... ";
      return ExecGraphViewer(ViewerPath, args, Filename, wait, ErrMsg);
    }
  
    enum ViewerKind {
      VK_None,
      VK_OSXOpen,
      VK_XDGOpen,
      VK_Ghostview,
      VK_CmdStart
    };
    ViewerKind Viewer = VK_None;
  #ifdef __APPLE__
    if (!Viewer && S.TryFindProgram("open", ViewerPath))
      Viewer = VK_OSXOpen;
  #endif
    if (!Viewer && S.TryFindProgram("gv", ViewerPath))
      Viewer = VK_Ghostview;
    if (!Viewer && S.TryFindProgram("xdg-open", ViewerPath))
      Viewer = VK_XDGOpen;
  #ifdef _WIN32
    if (!Viewer && S.TryFindProgram("cmd", ViewerPath)) {
      Viewer = VK_CmdStart;
    }
  #endif
  
    // PostScript or PDF graph generator + PostScript/PDF viewer
    std::string GeneratorPath;
    if (Viewer &&
        (S.TryFindProgram(getProgramName(program), GeneratorPath) ||
         S.TryFindProgram("dot|fdp|neato|twopi|circo", GeneratorPath))) {
      std::string OutputFilename =
          Filename + (Viewer == VK_CmdStart ? ".pdf" : ".ps");
  
      std::vector<StringRef> args;
      args.push_back(GeneratorPath);
      if (Viewer == VK_CmdStart)
        args.push_back("-Tpdf");
      else
        args.push_back("-Tps");
      args.push_back("-Nfontname=Courier");
      args.push_back("-Gsize=7.5,10");
      args.push_back(Filename);
      args.push_back("-o");
      args.push_back(OutputFilename);
  
      errs() << "Running '" << GeneratorPath << "' program... ";
  
      if (ExecGraphViewer(GeneratorPath, args, Filename, true, ErrMsg))
        return true;
  
      // The lifetime of StartArg must include the call of ExecGraphViewer
      // because the args are passed as vector of char*.
      std::string StartArg;
  
      args.clear();
      args.push_back(ViewerPath);
      switch (Viewer) {
      case VK_OSXOpen:
        args.push_back("-W");
        args.push_back(OutputFilename);
        break;
      case VK_XDGOpen:
        wait = false;
        args.push_back(OutputFilename);
        break;
      case VK_Ghostview:
        args.push_back("--spartan");
        args.push_back(OutputFilename);
        break;
      case VK_CmdStart:
        args.push_back("/S");
        args.push_back("/C");
        StartArg =
            (StringRef("start ") + (wait ? "/WAIT " : "") + OutputFilename).str();
        args.push_back(StartArg);
        break;
      case VK_None:
        llvm_unreachable("Invalid viewer");
      }
  
      ErrMsg.clear();
      return ExecGraphViewer(ViewerPath, args, OutputFilename, wait, ErrMsg);
    }
  
    // dotty
    if (S.TryFindProgram("dotty", ViewerPath)) {
      std::vector<StringRef> args;
      args.push_back(ViewerPath);
      args.push_back(Filename);
  
  // Dotty spawns another app and doesn't wait until it returns
  #ifdef _WIN32
      wait = false;
  #endif
      errs() << "Running 'dotty' program... ";
      return ExecGraphViewer(ViewerPath, args, Filename, wait, ErrMsg);
    }
  
    errs() << "Error: Couldn't find a usable graph viewer program:\n";
    errs() << S.LogBuffer << "\n";
    return true;
  }
  