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LocalCacheFile Class Reference

Proxy class to copy a file locally in large chunks. More...

#include <Utilities/StorageFactory/interface/LocalCacheFile.h>

Inheritance diagram for LocalCacheFile:

List of all members.

Public Member Functions
virtual void	close (void)
virtual void	flush (void)
	LocalCacheFile (Storage *base, const std::string &tmpdir="")
virtual IOOffset	position (IOOffset offset, Relative whence=SET)
virtual bool	prefetch (const IOPosBuffer *what, IOSize n)
virtual IOSize	read (void *into, IOSize n, IOOffset pos)
virtual IOSize	read (void *into, IOSize n)
	Read into into at most n number of bytes.
virtual IOSize	readv (IOPosBuffer *into, IOSize n)
virtual IOSize	readv (IOBuffer *into, IOSize n)
	Read from the input stream into multiple scattered buffers.
virtual void	resize (IOOffset size)
virtual IOSize	write (const void *from, IOSize n, IOOffset pos)
virtual IOSize	write (const void *from, IOSize n)
	Write n bytes of data starting at address from.
virtual IOSize	writev (const IOPosBuffer *from, IOSize n)
virtual IOSize	writev (const IOBuffer *from, IOSize n)
	Write to the output stream from multiple buffers.
	~LocalCacheFile (void)
Private Member Functions
void	cache (IOOffset start, IOOffset end)
Private Attributes
File *	file_
IOOffset	image_
std::vector< char >	present_
Storage *	storage_

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Detailed Description

Proxy class to copy a file locally in large chunks.

Definition at line 10 of file LocalCacheFile.h.

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Constructor & Destructor Documentation

LocalCacheFile::LocalCacheFile	(	Storage *	base,
		const std::string &	tmpdir = ""
	)

Definition at line 22 of file LocalCacheFile.cc.

References CHUNK_SIZE, Exception, fd, file_, image_, mkstemp(), p, present_, File::resize(), and pyDBSRunClass::temp.

  : image_(base->size()),
    file_(0),
    storage_(base)
{
  present_.resize((image_ + CHUNK_SIZE - 1) / CHUNK_SIZE, 0);

  std::string pattern(tmpdir);
  if (pattern.empty())
    if (char *p = getenv("TMPDIR"))
      pattern = p;
  if (pattern.empty())
    pattern = "/tmp";
  pattern += "/cmssw-shadow-XXXXXX";

  std::vector<char> temp(pattern.c_str(), pattern.c_str()+pattern.size()+1);
  int fd = mkstemp(&temp[0]);
  if (fd == -1)
    throw cms::Exception("LocalCacheFile")
      << "Cannot create temporary file '" << pattern << "': "
      << strerror(errno) << " (error " << errno << ")";

  unlink(&temp[0]);
  file_ = new File(fd);
  file_->resize(image_);
}

LocalCacheFile::~LocalCacheFile

(

void

)

Definition at line 49 of file LocalCacheFile.cc.

References file_, and storage_.

{
  delete file_;
  delete storage_;
}

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Member Function Documentation

void LocalCacheFile::cache	(	IOOffset	start,
		IOOffset	end
	)			[private]

Definition at line 56 of file LocalCacheFile.cc.

References CHUNK_SIZE, e, Exception, IOChannel::fd(), file_, image_, index, len, min, mmap, present_, Storage::read(), storage_, and cms::Exception::what().

Referenced by prefetch(), read(), and readv().

{
  start = (start / CHUNK_SIZE) * CHUNK_SIZE;
  end = std::min(end, image_);

  IOSize nread = 0;
  IOSize index = start / CHUNK_SIZE;

  while (start < end)
  {
    IOSize len = std::min(image_ - start, CHUNK_SIZE);
    if (! present_[index])
    {
      void *window = mmap(0, len, PROT_READ | PROT_WRITE, MAP_SHARED, file_->fd(), start);
      if (window == MAP_FAILED)
        throw cms::Exception("LocalCacheFile")
          << "Unable to map a window of local cache file: "
          << strerror(errno) << " (error " << errno << ")";

      try
      {
        nread = storage_->read(window, len, start);
      }
      catch (cms::Exception &e)
      {
        munmap(window, len);
        throw cms::Exception("LocalCacheFile")
          << "Unable to cache " << len << " byte file segment at " << start
          << ": " << e.what();
      }

      munmap(window, len);

      if (nread != len)
        throw cms::Exception("LocalCacheFile")
          << "Unable to cache " << len << " byte file segment at " << start
          << ": got only " << nread << " bytes back";

      present_[index] = 1;
    }

    start += len;
    ++index;
  }
}

void LocalCacheFile::close

(

void

)

[virtual]

Reimplemented from Storage.

Definition at line 172 of file LocalCacheFile.cc.

References Storage::close(), File::close(), file_, and storage_.

{
  storage_->close();
  file_->close();
}

void LocalCacheFile::flush

(

void

)

[virtual]

Reimplemented from Storage.

Definition at line 168 of file LocalCacheFile.cc.

References nowrite().

{ nowrite("flush"); }

IOOffset LocalCacheFile::position	(	IOOffset	offset,
		Relative	whence = SET
	)			[virtual]

Implements Storage.

Definition at line 160 of file LocalCacheFile.cc.

References file_, and File::position().

{ return file_->position(offset, whence); }

bool LocalCacheFile::prefetch	(	const IOPosBuffer *	what,
		IOSize	n
	)			[virtual]

Reimplemented from Storage.

Definition at line 179 of file LocalCacheFile.cc.

References cache(), end, file_, i, IOPosBuffer::offset(), File::prefetch(), and IOPosBuffer::size().

{
  for (IOSize i = 0; i < n; ++i)
  {
    IOOffset start = what[i].offset();
    IOOffset end = start + what[i].size();
    cache(start, end);
  }
  
  return file_->prefetch(what, n);
}

IOSize LocalCacheFile::read	(	void *	into,
		IOSize	n,
		IOOffset	pos
	)			[virtual]

Reimplemented from Storage.

Definition at line 112 of file LocalCacheFile.cc.

References cache(), file_, and File::read().

{
  cache(pos, pos + n);
  return file_->read(into, n, pos);
}

IOSize LocalCacheFile::read	(	void *	into,
		IOSize	n
	)			[virtual]

Read into into at most n number of bytes.

If this is a blocking stream, the call will block until some data can be read, end of input is reached, or an exception is thrown. For a non-blocking stream the available input is returned. If none is available, an exception is thrown.

Returns:

The number of bytes actually read. This is less or equal to the size of the buffer. Zero indicates that the end of the input has been reached: end of file, or remote end closing for a connected channel like a pipe or a socket. Otherwise the value can be less than requested if limited amount of input is currently available for platform or implementation reasons.

Exceptions:

In

case of error, a IOError exception is thrown. This includes the situation where the input stream is in non-blocking mode and no input is currently available (FIXME: make this simpler; clarify which exception).

Implements IOInput.

Definition at line 103 of file LocalCacheFile.cc.

References cache(), file_, File::position(), and File::read().

{
  IOOffset here = file_->position();
  cache(here, here + n);

  return file_->read(into, n);
}

IOSize LocalCacheFile::readv	(	IOPosBuffer *	into,
		IOSize	n
	)			[virtual]

Reimplemented from Storage.

Definition at line 131 of file LocalCacheFile.cc.

References cache(), end, i, IOPosBuffer::offset(), Storage::readv(), IOPosBuffer::size(), and storage_.

{
  for (IOSize i = 0; i < n; ++i)
  {
    IOOffset start = into[i].offset();
    IOOffset end = start + into[i].size();
    cache(start, end);
  }

  return storage_->readv(into, n);
}

IOSize LocalCacheFile::readv	(	IOBuffer *	into,
		IOSize	buffers
	)			[virtual]

Read from the input stream into multiple scattered buffers.

There are buffers to fill in an array starting at into; the memory those buffers occupy does not need to be contiguous. The buffers are filled in the order given, eac buffer is filled fully before the subsequent buffers.

If this is a blocking stream, the call will block until some data can be read, end of input is reached, or an exception is thrown. For a non-blocking stream the available input is returned. If none is available, an exception is thrown.

The base class implementation uses read(void *, IOSize) method, but derived classes may implement a more efficient alternative.

Returns:

The number of bytes actually read. This is less or equal to the size of the buffer. Zero indicates that the end of the input has been reached: end of file, or remote end closing for a connected channel like a pipe or a socket. Otherwise the value can be less than requested if limited amount of input is currently available for platform or implementation reasons. Note that the return value indicates the number of bytes read, not the number of buffers; it is the sum total of bytes filled into all the buffers.

Exceptions:

In

case of error, a IOError exception is thrown. However if some data has already been read, the error is swallowed and the method returns the data read so far. It is assumed that persistent errors will occur anyway on the next read and sporadic errors like stream becoming unvailable can be ignored. Use xread() if a different policy is desirable.

Reimplemented from IOInput.

Definition at line 119 of file LocalCacheFile.cc.

References cache(), end, file_, i, File::position(), File::readv(), and Storage::size().

{
  IOOffset start = file_->position();
  IOOffset end = start;
  for (IOSize i = 0; i < n; ++i)
    end += into[i].size();
  cache(start, end);

  return file_->readv(into, n);
}

void LocalCacheFile::resize

(

IOOffset

size

)

[virtual]

Implements Storage.

Definition at line 164 of file LocalCacheFile.cc.

References nowrite().

{ nowrite("resize"); }

IOSize LocalCacheFile::write	(	const void *	from,
		IOSize	n,
		IOOffset	pos
	)			[virtual]

Reimplemented from Storage.

Definition at line 148 of file LocalCacheFile.cc.

References nowrite().

{ nowrite("write"); return 0; }

IOSize LocalCacheFile::write	(	const void *	from,
		IOSize	n
	)			[virtual]

Write n bytes of data starting at address from.

Returns:

The number of bytes written. Normally this will be n, but can be less, even zero, for example if the stream is non-blocking mode and cannot accept input at this time.

Exceptions:

In

case of error, an exception is thrown. However if the stream is in non-blocking mode and cannot accept output, it will not throw an exception -- the return value will be less than requested.

Implements IOOutput.

Definition at line 144 of file LocalCacheFile.cc.

References nowrite().

{ nowrite("write"); return 0; }

IOSize LocalCacheFile::writev	(	const IOPosBuffer *	from,
		IOSize	n
	)			[virtual]

Reimplemented from Storage.

Definition at line 156 of file LocalCacheFile.cc.

References nowrite().

{ nowrite("writev"); return 0; }

IOSize LocalCacheFile::writev	(	const IOBuffer *	from,
		IOSize	buffers
	)			[virtual]

Write to the output stream from multiple buffers.

There are buffers to fill in an array starting at from. The buffers are filled in the order given, each buffer fully before the subsequent buffers. The method uses write(const void *, IOSize), but may be implemented more efficiently in derived classes.

Note that derived classes should not normally call this method, as it simply routes the call back to derived class through the other virtual functions. Use this method only at the "outside edge" when transferring calls from one object to another, not in up/down calls in the inheritance tree.

Returns:

The number of bytes actually written. This is less or equal to the size of the buffers. The value can be less than requested if the stream is unable to accept all the output for platform or implementation reasons. Note that the return value indicates the number of bytes written, not the number of buffers; it is the sum total of bytes written from all the buffers.

Exceptions:

In

case of error, an exception is thrown. However if the stream is in non-blocking mode and cannot accept output, it will not throw an exception -- the return value will be less than requested.

Reimplemented from IOOutput.

Definition at line 152 of file LocalCacheFile.cc.

References nowrite().

{ nowrite("writev"); return 0; }

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Member Data Documentation

File* LocalCacheFile::file_ [private]

Definition at line 39 of file LocalCacheFile.h.

Referenced by cache(), close(), LocalCacheFile(), position(), prefetch(), read(), readv(), and ~LocalCacheFile().

IOOffset LocalCacheFile::image_ [private]

Definition at line 37 of file LocalCacheFile.h.

Referenced by cache(), and LocalCacheFile().

std::vector<char> LocalCacheFile::present_ [private]

Definition at line 38 of file LocalCacheFile.h.

Referenced by cache(), and LocalCacheFile().

Storage* LocalCacheFile::storage_ [private]

Definition at line 40 of file LocalCacheFile.h.

Referenced by cache(), close(), readv(), and ~LocalCacheFile().

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The documentation for this class was generated from the following files:

• Utilities/StorageFactory/interface/LocalCacheFile.h
• Utilities/StorageFactory/src/LocalCacheFile.cc

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