//===--- SourceManager.cpp - Track and cache source files -----------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file was developed by Chris Lattner and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file implements the SourceManager interface.
//
//===----------------------------------------------------------------------===//

#include "clang/Basic/SourceManager.h"
#include "clang/Basic/FileManager.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/System/Path.h"
#include <algorithm>
#include <iostream>
#include <fcntl.h>

using namespace clang;
using namespace SrcMgr;
using llvm::MemoryBuffer;

SourceManager::~SourceManager() {
  for (std::map<const FileEntry *, FileInfo>::iterator I = FileInfos.begin(),
       E = FileInfos.end(); I != E; ++I) {
    delete I->second.Buffer;
    delete[] I->second.SourceLineCache;
  }
  
  for (std::list<InfoRec>::iterator I = MemBufferInfos.begin(), 
       E = MemBufferInfos.end(); I != E; ++I) {
    delete I->second.Buffer;
    delete[] I->second.SourceLineCache;
  }
}


// FIXME: REMOVE THESE
#include <unistd.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/fcntl.h>
#include <cerrno>

static const MemoryBuffer *ReadFileFast(const FileEntry *FileEnt) {
#if 0
  // FIXME: Reintroduce this and zap this function once the common llvm stuff
  // is fast for the small case.
  return MemoryBuffer::getFile(FileEnt->getName(), strlen(FileEnt->getName()),
                               FileEnt->getSize());
#endif
  
  // If the file is larger than some threshold, use 'read', otherwise use mmap.
  if (FileEnt->getSize() >= 4096*4)
    return MemoryBuffer::getFile(FileEnt->getName(), strlen(FileEnt->getName()),
                                 0, FileEnt->getSize());
  
  MemoryBuffer *SB = MemoryBuffer::getNewUninitMemBuffer(FileEnt->getSize(),
                                                         FileEnt->getName());
  char *BufPtr = const_cast<char*>(SB->getBufferStart());
  
  int FD = ::open(FileEnt->getName(), O_RDONLY);
  if (FD == -1) {
    delete SB;
    return 0;
  }
  
  unsigned BytesLeft = FileEnt->getSize();
  while (BytesLeft) {
    ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
    if (NumRead != -1) {
      BytesLeft -= NumRead;
      BufPtr += NumRead;
    } else if (errno == EINTR) {
      // try again
    } else {
      // error reading.
      close(FD);
      delete SB;
      return 0;
    }
  }
  close(FD);
  
  return SB;
}


/// getFileInfo - Create or return a cached FileInfo for the specified file.
///
const InfoRec *
SourceManager::getInfoRec(const FileEntry *FileEnt) {
  assert(FileEnt && "Didn't specify a file entry to use?");
  // Do we already have information about this file?
  std::map<const FileEntry *, FileInfo>::iterator I = 
    FileInfos.lower_bound(FileEnt);
  if (I != FileInfos.end() && I->first == FileEnt)
    return &*I;
  
  // Nope, get information.
  const MemoryBuffer *File = ReadFileFast(FileEnt);
  if (File == 0)
    return 0;

  const InfoRec &Entry =
    *FileInfos.insert(I, std::make_pair(FileEnt, FileInfo()));
  FileInfo &Info = const_cast<FileInfo &>(Entry.second);

  Info.Buffer = File;
  Info.SourceLineCache = 0;
  Info.NumLines = 0;
  return &Entry;
}


/// createMemBufferInfoRec - Create a new info record for the specified memory
/// buffer.  This does no caching.
const InfoRec *
SourceManager::createMemBufferInfoRec(const MemoryBuffer *Buffer) {
  // Add a new info record to the MemBufferInfos list and return it.
  FileInfo FI;
  FI.Buffer = Buffer;
  FI.SourceLineCache = 0;
  FI.NumLines = 0;
  MemBufferInfos.push_back(InfoRec(0, FI));
  return &MemBufferInfos.back();
}


/// createFileID - Create a new fileID for the specified InfoRec and include
/// position.  This works regardless of whether the InfoRec corresponds to a
/// file or some other input source.
unsigned SourceManager::createFileID(const InfoRec *File,
                                     SourceLocation IncludePos) {
  // If FileEnt is really large (e.g. it's a large .i file), we may not be able
  // to fit an arbitrary position in the file in the FilePos field.  To handle
  // this, we create one FileID for each chunk of the file that fits in a
  // FilePos field.
  unsigned FileSize = File->second.Buffer->getBufferSize();
  if (FileSize+1 < (1 << SourceLocation::FilePosBits)) {
    FileIDs.push_back(FileIDInfo::getNormalBuffer(IncludePos, 0, File));
    assert(FileIDs.size() < (1 << SourceLocation::FileIDBits) &&
           "Ran out of file ID's!");
    return FileIDs.size();
  }
  
  // Create one FileID for each chunk of the file.
  unsigned Result = FileIDs.size()+1;

  unsigned ChunkNo = 0;
  while (1) {
    FileIDs.push_back(FileIDInfo::getNormalBuffer(IncludePos, ChunkNo++, File));

    if (FileSize+1 < (1 << SourceLocation::FilePosBits)) break;
    FileSize -= (1 << SourceLocation::FilePosBits);
  }

  assert(FileIDs.size() < (1 << SourceLocation::FileIDBits) &&
         "Ran out of file ID's!");
  return Result;
}

/// getInstantiationLoc - Return a new SourceLocation that encodes the fact
/// that a token from physloc PhysLoc should actually be referenced from
/// InstantiationLoc.
SourceLocation SourceManager::getInstantiationLoc(SourceLocation VirtLoc,
                                                  SourceLocation InstantLoc) {
  // The specified source location may be a mapped location, due to a macro
  // instantiation or #line directive.  Strip off this information to find out
  // where the characters are actually located.
  SourceLocation PhysLoc = getPhysicalLoc(VirtLoc);
  
  // Resolve InstantLoc down to a real logical location.
  InstantLoc = getLogicalLoc(InstantLoc);
  
  unsigned InstantiationFileID;
  // If this is the same instantiation as was requested last time, return this
  // immediately.
  if (PhysLoc.getFileID() == LastInstantiationLoc_MacroFID &&
      InstantLoc == LastInstantiationLoc_InstantLoc) {
    InstantiationFileID = LastInstantiationLoc_Result;
  } else {
    // Add a FileID for this.  FIXME: should cache these!
    FileIDs.push_back(FileIDInfo::getMacroExpansion(InstantLoc,
                                                    PhysLoc.getFileID()));
    InstantiationFileID = FileIDs.size();
    
    // Remember this in the single-entry cache for next time.
    LastInstantiationLoc_MacroFID   = PhysLoc.getFileID();
    LastInstantiationLoc_InstantLoc = InstantLoc;
    LastInstantiationLoc_Result     = InstantiationFileID;
  }
  return SourceLocation(InstantiationFileID, PhysLoc.getRawFilePos());
}



/// getCharacterData - Return a pointer to the start of the specified location
/// in the appropriate MemoryBuffer.
const char *SourceManager::getCharacterData(SourceLocation SL) const {
  // Note that this is a hot function in the getSpelling() path, which is
  // heavily used by -E mode.
  unsigned FileID = SL.getFileID();
  assert(FileID && "Invalid source location!");
  
  return getFileInfo(FileID)->Buffer->getBufferStart() + getFilePos(SL);
}

/// getIncludeLoc - Return the location of the #include for the specified
/// FileID.
SourceLocation SourceManager::getIncludeLoc(unsigned FileID) const {
  const SrcMgr::FileIDInfo *FIDInfo = getFIDInfo(FileID);

  // For Macros, the physical loc is specified by the MacroTokenFileID.
  if (FIDInfo->IDType == SrcMgr::FileIDInfo::MacroExpansion)
    FIDInfo = &FileIDs[FIDInfo->u.MacroTokenFileID-1];
  
  return FIDInfo->IncludeLoc;
}  


/// getColumnNumber - Return the column # for the specified include position.
/// this is significantly cheaper to compute than the line number.  This returns
/// zero if the column number isn't known.
unsigned SourceManager::getColumnNumber(SourceLocation Loc) const {
  Loc = getLogicalLoc(Loc);
  unsigned FileID = Loc.getFileID();
  if (FileID == 0) return 0;
  
  unsigned FilePos = getFilePos(Loc);
  const MemoryBuffer *Buffer = getBuffer(FileID);
  const char *Buf = Buffer->getBufferStart();

  unsigned LineStart = FilePos;
  while (LineStart && Buf[LineStart-1] != '\n' && Buf[LineStart-1] != '\r')
    --LineStart;
  return FilePos-LineStart+1;
}

/// getSourceName - This method returns the name of the file or buffer that
/// the SourceLocation specifies.  This can be modified with #line directives,
/// etc.
std::string SourceManager::getSourceName(SourceLocation Loc) {
  Loc = getLogicalLoc(Loc);
  unsigned FileID = Loc.getFileID();
  if (FileID == 0) return "";
  return getFileInfo(FileID)->Buffer->getBufferIdentifier();
}


/// getLineNumber - Given a SourceLocation, return the physical line number
/// for the position indicated.  This requires building and caching a table of
/// line offsets for the MemoryBuffer, so this is not cheap: use only when
/// about to emit a diagnostic.
unsigned SourceManager::getLineNumber(SourceLocation Loc) {
  Loc = getLogicalLoc(Loc);
  unsigned FileID = Loc.getFileID();
  if (FileID == 0) return 0;
  FileInfo *FileInfo = getFileInfo(FileID);
  
  // If this is the first use of line information for this buffer, compute the
  /// SourceLineCache for it on demand. 
  if (FileInfo->SourceLineCache == 0) {
    const MemoryBuffer *Buffer = FileInfo->Buffer;
    
    // Find the file offsets of all of the *physical* source lines.  This does
    // not look at trigraphs, escaped newlines, or anything else tricky.
    std::vector<unsigned> LineOffsets;
    
    // Line #1 starts at char 0.
    LineOffsets.push_back(0);
    
    const unsigned char *Buf = (const unsigned char *)Buffer->getBufferStart();
    const unsigned char *End = (const unsigned char *)Buffer->getBufferEnd();
    unsigned Offs = 0;
    while (1) {
      // Skip over the contents of the line.
      // TODO: Vectorize this?  This is very performance sensitive for programs
      // with lots of diagnostics and in -E mode.
      const unsigned char *NextBuf = (const unsigned char *)Buf;
      while (*NextBuf != '\n' && *NextBuf != '\r' && *NextBuf != '\0')
        ++NextBuf;
      Offs += NextBuf-Buf;
      Buf = NextBuf;
      
      if (Buf[0] == '\n' || Buf[0] == '\r') {
        // If this is \n\r or \r\n, skip both characters.
        if ((Buf[1] == '\n' || Buf[1] == '\r') && Buf[0] != Buf[1])
          ++Offs, ++Buf;
        ++Offs, ++Buf;
        LineOffsets.push_back(Offs);
      } else {
        // Otherwise, this is a null.  If end of file, exit.
        if (Buf == End) break;
        // Otherwise, skip the null.
        ++Offs, ++Buf;
      }
    }
    LineOffsets.push_back(Offs);
    
    // Copy the offsets into the FileInfo structure.
    FileInfo->NumLines = LineOffsets.size();
    FileInfo->SourceLineCache = new unsigned[LineOffsets.size()];
    std::copy(LineOffsets.begin(), LineOffsets.end(),
              FileInfo->SourceLineCache);
  }

  // Okay, we know we have a line number table.  Do a binary search to find the
  // line number that this character position lands on.
  unsigned NumLines = FileInfo->NumLines;
  unsigned *SourceLineCache = FileInfo->SourceLineCache;
    
  // TODO: If this is performance sensitive, we could try doing simple radix
  // type approaches to make good (tight?) initial guesses based on the
  // assumption that all lines are the same average size.
  unsigned *Pos = std::lower_bound(SourceLineCache, SourceLineCache+NumLines,
                                   getFilePos(Loc)+1);
  return Pos-SourceLineCache;
}

/// getSourceFilePos - This method returns the *logical* offset from the start
/// of the file that the specified SourceLocation represents.  This returns
/// the location of the *logical* character data, not the physical file
/// position.  In the case of macros, for example, this returns where the
/// macro was instantiated, not where the characters for the macro can be
/// found.
unsigned SourceManager::getSourceFilePos(SourceLocation Loc) const {
 
  // If this is a macro, we need to get the instantiation location.
  const SrcMgr::FileIDInfo *FIDInfo = getFIDInfo(Loc.getFileID());
  while (FIDInfo->IDType == SrcMgr::FileIDInfo::MacroExpansion) {
    Loc = FIDInfo->IncludeLoc;
    FIDInfo = getFIDInfo(Loc.getFileID());
  }
  
  return getFilePos(Loc);
}


/// PrintStats - Print statistics to stderr.
///
void SourceManager::PrintStats() const {
  std::cerr << "\n*** Source Manager Stats:\n";
  std::cerr << FileInfos.size() << " files mapped, " << MemBufferInfos.size()
            << " mem buffers mapped, " << FileIDs.size() 
            << " file ID's allocated.\n";
  unsigned NumBuffers = 0, NumMacros = 0;
  for (unsigned i = 0, e = FileIDs.size(); i != e; ++i) {
    if (FileIDs[i].IDType == FileIDInfo::NormalBuffer)
      ++NumBuffers;
    else if (FileIDs[i].IDType == FileIDInfo::MacroExpansion)
      ++NumMacros;
    else
      assert(0 && "Unknown FileID!");
  }
  std::cerr << "  " << NumBuffers << " normal buffer FileID's, "
            << NumMacros << " macro expansion FileID's.\n";
    
  
  
  unsigned NumLineNumsComputed = 0;
  unsigned NumFileBytesMapped = 0;
  for (std::map<const FileEntry *, FileInfo>::const_iterator I = 
       FileInfos.begin(), E = FileInfos.end(); I != E; ++I) {
    NumLineNumsComputed += I->second.SourceLineCache != 0;
    NumFileBytesMapped  += I->second.Buffer->getBufferSize();
  }
  std::cerr << NumFileBytesMapped << " bytes of files mapped, "
            << NumLineNumsComputed << " files with line #'s computed.\n";
}