SeqFile Class Reference

A class to manage I/O for a chain of blocked files. More...

#include <SeqFile.h>

Collaboration diagram for SeqFile:

Public Member Functions
	SeqFile (const std::string &filename, const std::string &rwflag, char *streamerinfo=nullptr, int streamerinfo_size=0, bool filenameIsPattern=false)
	Constructor. More...
	~SeqFile ()
	Destructor.
	SeqFile (const SeqFile &)=delete
	No copying.
SeqFile &	operator= (const SeqFile &)=delete
	No assignment.
int	status () const
	Returns status after constructor call. More...
int	write (const char *buf)
	Write a record to a file. More...
int	read (char *buf, int max)
	Read a record from a file. More...

Private Member Functions
void	openFile (std::string filename, bool readonly)
	actually open the file

Private Attributes
std::string	m_filename
	Name of the opened file.
std::string	m_filenamePattern
	Pattern for creating the file from the sequence number.
int	m_fd { -1}
	file descriptor.
int	m_nb {0}
	when saving a file, the total number of bytes written, 0 when reading.
int	m_nfile {0}
	file counter, starting at 0 (files are split after c_MaxFileSize bytes).
bool	m_compressed {false}
	is file gzipped compressed?
std::unique_ptr< std::ios >	m_stream
	pointer to the filtering input or output stream
char *	m_streamerinfo
	StreamerInfo.
int	m_streamerinfo_size
	size(bytes) of StreamerInfo

Static Private Attributes
static const int	c_MaxFileSize {512000000 * 4}
	maximal size of one file (in Bytes).

Detailed Description

A class to manage I/O for a chain of blocked files.

Definition at line 22 of file SeqFile.h.

Constructor & Destructor Documentation

SeqFile()

SeqFile	(	const std::string &	filename,
		const std::string &	rwflag,
		char *	streamerinfo = nullptr,
		int	streamerinfo_size = 0,
		bool	filenameIsPattern = false
	)

Constructor.

Parameters

filename	name of the file
rwflag	should probably be r or rw
streamerinfo	String containing the streamer info
streamerinfo_size	Size of the string containing the streamer info
filenameIsPattern	if true interpret the filename as a boost::format pattern which takes the sequence number as argument instead of producing .sroot-N files

Definition at line 25 of file SeqFile.cc.

                                        :
  m_filename(filename)
{
  if (filename.empty()) {
    B2ERROR("SeqFile: Empty filename given");
    return;
  }
  bool readonly = rwflag.find('w') == std::string::npos;
  // is the file already compressed?
  m_compressed = filename.size() > 3 && filename.compare(filename.size() - 3, 3, ".gz") == 0;
  // strip .gz suffix to add it at the end automatically and correctly for subsequent files
  if (m_compressed) {
    m_filename = filename.substr(0, filename.size() - 3);
  }
  // check if we want different naming scheme using boost::format
  if (filenameIsPattern) {
    m_filenamePattern = m_filename;
    try {
      m_filename = (boost::format(m_filenamePattern) % m_nfile).str();
    } catch (std::exception& e) {
      B2FATAL("Cannot use filename pattern" << m_filenamePattern << ": " << e.what());
    }
  }
 
  // Store StreamerInfo 2017.5.8
  m_streamerinfo = nullptr;
  m_streamerinfo_size = 0;
  if (streamerinfo != nullptr && streamerinfo_size > 0) {
    m_streamerinfo_size = streamerinfo_size;
    m_streamerinfo = new char[ m_streamerinfo_size ];
    memcpy(m_streamerinfo, streamerinfo, m_streamerinfo_size);
  }
 
  // open the file
  openFile(m_filename, readonly);
  // if that fails and it's not already assumed to be compressed try again adding .gz to the name
  if (m_fd < 0 && !m_compressed) {
    B2WARNING("SeqFile: error opening '" << filename << "': " << strerror(errno)
              << ", trying again with '.gz'");
    m_compressed = true;
    openFile(m_filename, readonly);
  }
  // is the file open now?
  if (m_fd < 0) {
    B2ERROR("SeqFile: error opening '" << filename << "': " << strerror(errno));
  } else {
    B2INFO("SeqFile: " << m_filename << " opened (fd=" << m_fd << ")");
  }
 
}

Member Function Documentation

read()

int read	(	char *	buf,
		int	max
	)

Read a record from a file.

The record length is returned.

Definition at line 170 of file SeqFile.cc.

status()

int status

(

)

const

Returns status after constructor call.

If success, fd is returned. If not, -1

Definition at line 131 of file SeqFile.cc.

write()

int write

(

const char *

buf

)

Write a record to a file.

First word of the record should contain number of words.

Definition at line 136 of file SeqFile.cc.

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

• framework/pcore/include/SeqFile.h
• framework/pcore/src/SeqFile.cc