ArchiveWriter.cpp

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//===-- ArchiveWriter.cpp - Write LLVM archive files ----------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Builds up an LLVM archive file (.a) containing LLVM bitcode.
//
//===----------------------------------------------------------------------===//

#include "llvm/Bitcode/Archive.h"
#include "ArchiveInternals.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/Bitcode/ReaderWriter.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/system_error.h"
#include <fstream>
#include <iomanip>
#include <ostream>
using namespace llvm;

// Write an integer using variable bit rate encoding. This saves a few bytes
// per entry in the symbol table.
static inline void writeInteger(unsigned num, std::ofstream& ARFile) {
  while (1) {
    if (num < 0x80) { // done?
      ARFile << (unsigned char)num;
      return;
    }

    // Nope, we are bigger than a character, output the next 7 bits and set the
    // high bit to say that there is more coming...
    ARFile << (unsigned char)(0x80 | ((unsigned char)num & 0x7F));
    num >>= 7;  // Shift out 7 bits now...
  }
}

// Compute how many bytes are taken by a given VBR encoded value. This is needed
// to pre-compute the size of the symbol table.
static inline unsigned numVbrBytes(unsigned num) {

  // Note that the following nested ifs are somewhat equivalent to a binary
  // search. We split it in half by comparing against 2^14 first. This allows
  // most reasonable values to be done in 2 comparisons instead of 1 for
  // small ones and four for large ones. We expect this to access file offsets
  // in the 2^10 to 2^24 range and symbol lengths in the 2^0 to 2^8 range,
  // so this approach is reasonable.
  if (num < 1<<14) {
    if (num < 1<<7)
      return 1;
    else
      return 2;
  }
  if (num < 1<<21)
    return 3;

  if (num < 1<<28)
    return 4;
  return 5; // anything >= 2^28 takes 5 bytes
}

// Create an empty archive.
Archive* Archive::CreateEmpty(const sys::Path& FilePath, LLVMContext& C) {
  Archive* result = new Archive(FilePath, C);
  return result;
}

// Fill the ArchiveMemberHeader with the information from a member. If
// TruncateNames is true, names are flattened to 15 chars or less. The sz field
// is provided here instead of coming from the mbr because the member might be
// stored compressed and the compressed size is not the ArchiveMember's size.
// Furthermore compressed files have negative size fields to identify them as
// compressed.
bool
Archive::fillHeader(const ArchiveMember &mbr, ArchiveMemberHeader& hdr,
                    int sz, bool TruncateNames) const {

  // Set the permissions mode, uid and gid
  hdr.init();
  char buffer[32];
  sprintf(buffer, "%-8o", mbr.getMode());
  memcpy(hdr.mode,buffer,8);
  sprintf(buffer,  "%-6u", mbr.getUser());
  memcpy(hdr.uid,buffer,6);
  sprintf(buffer,  "%-6u", mbr.getGroup());
  memcpy(hdr.gid,buffer,6);

  // Set the last modification date
  uint64_t secondsSinceEpoch = mbr.getModTime().toEpochTime();
  sprintf(buffer,"%-12u", unsigned(secondsSinceEpoch));
  memcpy(hdr.date,buffer,12);

  // Get rid of trailing blanks in the name
  std::string mbrPath = mbr.getPath().str();
  size_t mbrLen = mbrPath.length();
  while (mbrLen > 0 && mbrPath[mbrLen-1] == ' ') {
    mbrPath.erase(mbrLen-1,1);
    mbrLen--;
  }

  // Set the name field in one of its various flavors.
  bool writeLongName = false;
  if (mbr.isStringTable()) {
    memcpy(hdr.name,ARFILE_STRTAB_NAME,16);
  } else if (mbr.isSVR4SymbolTable()) {
    memcpy(hdr.name,ARFILE_SVR4_SYMTAB_NAME,16);
  } else if (mbr.isBSD4SymbolTable()) {
    memcpy(hdr.name,ARFILE_BSD4_SYMTAB_NAME,16);
  } else if (mbr.isLLVMSymbolTable()) {
    memcpy(hdr.name,ARFILE_LLVM_SYMTAB_NAME,16);
  } else if (TruncateNames) {
    const char* nm = mbrPath.c_str();
    unsigned len = mbrPath.length();
    size_t slashpos = mbrPath.rfind('/');
    if (slashpos != std::string::npos) {
      nm += slashpos + 1;
      len -= slashpos +1;
    }
    if (len > 15)
      len = 15;
    memcpy(hdr.name,nm,len);
    hdr.name[len] = '/';
  } else if (mbrPath.length() < 16 && mbrPath.find('/') == std::string::npos) {
    memcpy(hdr.name,mbrPath.c_str(),mbrPath.length());
    hdr.name[mbrPath.length()] = '/';
  } else {
    std::string nm = "#1/";
    nm += utostr(mbrPath.length());
    memcpy(hdr.name,nm.data(),nm.length());
    if (sz < 0)
      sz -= mbrPath.length();
    else
      sz += mbrPath.length();
    writeLongName = true;
  }

  // Set the size field
  if (sz < 0) {
    buffer[0] = '-';
    sprintf(&buffer[1],"%-9u",(unsigned)-sz);
  } else {
    sprintf(buffer, "%-10u", (unsigned)sz);
  }
  memcpy(hdr.size,buffer,10);

  return writeLongName;
}

// Insert a file into the archive before some other member. This also takes care
// of extracting the necessary flags and information from the file.
bool
Archive::addFileBefore(const sys::Path& filePath, iterator where,
                        std::string* ErrMsg) {
  bool Exists;
  if (sys::fs::exists(filePath.str(), Exists) || !Exists) {
    if (ErrMsg)
      *ErrMsg = "Can not add a non-existent file to archive";
    return true;
  }

  ArchiveMember* mbr = new ArchiveMember(this);

  mbr->data = 0;
  mbr->path = filePath;
  const sys::FileStatus *FSInfo = mbr->path.getFileStatus(false, ErrMsg);
  if (!FSInfo) {
    delete mbr;
    return true;
  }
  mbr->info = *FSInfo;

  unsigned flags = 0;
  bool hasSlash = filePath.str().find('/') != std::string::npos;
  if (hasSlash)
    flags |= ArchiveMember::HasPathFlag;
  if (hasSlash || filePath.str().length() > 15)
    flags |= ArchiveMember::HasLongFilenameFlag;

  sys::fs::file_magic type;
  if (sys::fs::identify_magic(mbr->path.str(), type))
    type = sys::fs::file_magic::unknown;
  switch (type) {
    case sys::fs::file_magic::bitcode:
      flags |= ArchiveMember::BitcodeFlag;
      break;
    default:
      break;
  }
  mbr->flags = flags;
  members.insert(where,mbr);
  return false;
}

// Write one member out to the file.
bool
Archive::writeMember(
  const ArchiveMember& member,
  std::ofstream& ARFile,
  bool CreateSymbolTable,
  bool TruncateNames,
  std::string* ErrMsg
) {

  unsigned filepos = ARFile.tellp();
  filepos -= 8;

  // Get the data and its size either from the
  // member's in-memory data or directly from the file.
  size_t fSize = member.getSize();
  const char *data = (const char*)member.getData();
  MemoryBuffer *mFile = 0;
  if (!data) {
    OwningPtr<MemoryBuffer> File;
    if (error_code ec = MemoryBuffer::getFile(member.getPath().c_str(), File)) {
      if (ErrMsg)
        *ErrMsg = ec.message();
      return true;
    }
    mFile = File.take();
    data = mFile->getBufferStart();
    fSize = mFile->getBufferSize();
  }

  // Now that we have the data in memory, update the
  // symbol table if it's a bitcode file.
  if (CreateSymbolTable && member.isBitcode()) {
    std::vector<std::string> symbols;
    std::string FullMemberName = archPath.str() + "(" + member.getPath().str()
      + ")";
    Module* M =
      GetBitcodeSymbols(data, fSize, FullMemberName, Context, symbols, ErrMsg);

    // If the bitcode parsed successfully
    if ( M ) {
      for (std::vector<std::string>::iterator SI = symbols.begin(),
           SE = symbols.end(); SI != SE; ++SI) {

        std::pair<SymTabType::iterator,bool> Res =
          symTab.insert(std::make_pair(*SI,filepos));

        if (Res.second) {
          symTabSize += SI->length() +
                        numVbrBytes(SI->length()) +
                        numVbrBytes(filepos);
        }
      }
      // We don't need this module any more.
      delete M;
    } else {
      delete mFile;
      if (ErrMsg)
        *ErrMsg = "Can't parse bitcode member: " + member.getPath().str()
          + ": " + *ErrMsg;
      return true;
    }
  }

  int hdrSize = fSize;

  // Compute the fields of the header
  ArchiveMemberHeader Hdr;
  bool writeLongName = fillHeader(member,Hdr,hdrSize,TruncateNames);

  // Write header to archive file
  ARFile.write((char*)&Hdr, sizeof(Hdr));

  // Write the long filename if its long
  if (writeLongName) {
    ARFile.write(member.getPath().str().data(),
                 member.getPath().str().length());
  }

  // Write the (possibly compressed) member's content to the file.
  ARFile.write(data,fSize);

  // Make sure the member is an even length
  if ((ARFile.tellp() & 1) == 1)
    ARFile << ARFILE_PAD;

  // Close the mapped file if it was opened
  delete mFile;
  return false;
}

// Write out the LLVM symbol table as an archive member to the file.
void
Archive::writeSymbolTable(std::ofstream& ARFile) {

  // Construct the symbol table's header
  ArchiveMemberHeader Hdr;
  Hdr.init();
  memcpy(Hdr.name,ARFILE_LLVM_SYMTAB_NAME,16);
  uint64_t secondsSinceEpoch = sys::TimeValue::now().toEpochTime();
  char buffer[32];
  sprintf(buffer, "%-8o", 0644);
  memcpy(Hdr.mode,buffer,8);
  sprintf(buffer, "%-6u", sys::Process::GetCurrentUserId());
  memcpy(Hdr.uid,buffer,6);
  sprintf(buffer, "%-6u", sys::Process::GetCurrentGroupId());
  memcpy(Hdr.gid,buffer,6);
  sprintf(buffer,"%-12u", unsigned(secondsSinceEpoch));
  memcpy(Hdr.date,buffer,12);
  sprintf(buffer,"%-10u",symTabSize);
  memcpy(Hdr.size,buffer,10);

  // Write the header
  ARFile.write((char*)&Hdr, sizeof(Hdr));

#ifndef NDEBUG
  // Save the starting position of the symbol tables data content.
  unsigned startpos = ARFile.tellp();
#endif

  // Write out the symbols sequentially
  for ( Archive::SymTabType::iterator I = symTab.begin(), E = symTab.end();
        I != E; ++I)
  {
    // Write out the file index
    writeInteger(I->second, ARFile);
    // Write out the length of the symbol
    writeInteger(I->first.length(), ARFile);
    // Write out the symbol
    ARFile.write(I->first.data(), I->first.length());
  }

#ifndef NDEBUG
  // Now that we're done with the symbol table, get the ending file position
  unsigned endpos = ARFile.tellp();
#endif

  // Make sure that the amount we wrote is what we pre-computed. This is
  // critical for file integrity purposes.
  assert(endpos - startpos == symTabSize && "Invalid symTabSize computation");

  // Make sure the symbol table is even sized
  if (symTabSize % 2 != 0 )
    ARFile << ARFILE_PAD;
}

// Write the entire archive to the file specified when the archive was created.
// This writes to a temporary file first. Options are for creating a symbol
// table, flattening the file names (no directories, 15 chars max) and
// compressing each archive member.
bool
Archive::writeToDisk(bool CreateSymbolTable, bool TruncateNames,
                     std::string* ErrMsg)
{
  // Make sure they haven't opened up the file, not loaded it,
  // but are now trying to write it which would wipe out the file.
  if (members.empty() && mapfile && mapfile->getBufferSize() > 8) {
    if (ErrMsg)
      *ErrMsg = "Can't write an archive not opened for writing";
    return true;
  }

  // Create a temporary file to store the archive in
  sys::Path TmpArchive = archPath;
  if (TmpArchive.createTemporaryFileOnDisk(ErrMsg))
    return true;

  // Make sure the temporary gets removed if we crash
  sys::RemoveFileOnSignal(TmpArchive);

  // Create archive file for output.
  std::ios::openmode io_mode = std::ios::out | std::ios::trunc |
                               std::ios::binary;
  std::ofstream ArchiveFile(TmpArchive.c_str(), io_mode);

  // Check for errors opening or creating archive file.
  if (!ArchiveFile.is_open() || ArchiveFile.bad()) {
    TmpArchive.eraseFromDisk();
    if (ErrMsg)
      *ErrMsg = "Error opening archive file: " + archPath.str();
    return true;
  }

  // If we're creating a symbol table, reset it now
  if (CreateSymbolTable) {
    symTabSize = 0;
    symTab.clear();
  }

  // Write magic string to archive.
  ArchiveFile << ARFILE_MAGIC;

  // Loop over all member files, and write them out. Note that this also
  // builds the symbol table, symTab.
  for (MembersList::iterator I = begin(), E = end(); I != E; ++I) {
    if (writeMember(*I, ArchiveFile, CreateSymbolTable,
                     TruncateNames, ErrMsg)) {
      TmpArchive.eraseFromDisk();
      ArchiveFile.close();
      return true;
    }
  }

  // Close archive file.
  ArchiveFile.close();

  // Write the symbol table
  if (CreateSymbolTable) {
    // At this point we have written a file that is a legal archive but it
    // doesn't have a symbol table in it. To aid in faster reading and to
    // ensure compatibility with other archivers we need to put the symbol
    // table first in the file. Unfortunately, this means mapping the file
    // we just wrote back in and copying it to the destination file.
    sys::Path FinalFilePath = archPath;

    // Map in the archive we just wrote.
    {
    OwningPtr<MemoryBuffer> arch;
    if (error_code ec = MemoryBuffer::getFile(TmpArchive.c_str(), arch)) {
      if (ErrMsg)
        *ErrMsg = ec.message();
      return true;
    }
    const char* base = arch->getBufferStart();

    // Open another temporary file in order to avoid invalidating the
    // mmapped data
    if (FinalFilePath.createTemporaryFileOnDisk(ErrMsg))
      return true;
    sys::RemoveFileOnSignal(FinalFilePath);

    std::ofstream FinalFile(FinalFilePath.c_str(), io_mode);
    if (!FinalFile.is_open() || FinalFile.bad()) {
      TmpArchive.eraseFromDisk();
      if (ErrMsg)
        *ErrMsg = "Error opening archive file: " + FinalFilePath.str();
      return true;
    }

    // Write the file magic number
    FinalFile << ARFILE_MAGIC;

    // If there is a foreign symbol table, put it into the file now. Most
    // ar(1) implementations require the symbol table to be first but llvm-ar
    // can deal with it being after a foreign symbol table. This ensures
    // compatibility with other ar(1) implementations as well as allowing the
    // archive to store both native .o and LLVM .bc files, both indexed.
    if (foreignST) {
      if (writeMember(*foreignST, FinalFile, false, false, ErrMsg)) {
        FinalFile.close();
        TmpArchive.eraseFromDisk();
        return true;
      }
    }

    // Put out the LLVM symbol table now.
    writeSymbolTable(FinalFile);

    // Copy the temporary file contents being sure to skip the file's magic
    // number.
    FinalFile.write(base + sizeof(ARFILE_MAGIC)-1,
      arch->getBufferSize()-sizeof(ARFILE_MAGIC)+1);

    // Close up shop
    FinalFile.close();
    } // free arch.

    // Move the final file over top of TmpArchive
    if (FinalFilePath.renamePathOnDisk(TmpArchive, ErrMsg))
      return true;
  }

  // Before we replace the actual archive, we need to forget all the
  // members, since they point to data in that old archive. We need to do
  // this because we cannot replace an open file on Windows.
  cleanUpMemory();

  if (TmpArchive.renamePathOnDisk(archPath, ErrMsg))
    return true;

  // Set correct read and write permissions after temporary file is moved
  // to final destination path.
  if (archPath.makeReadableOnDisk(ErrMsg))
    return true;
  if (archPath.makeWriteableOnDisk(ErrMsg))
    return true;

  return false;
}