StreamInterceptor Class Reference

Base class with all necessary features to intercept output to a file descriptor. More...

#include <IOIntercept.h>

Inheritance diagram for StreamInterceptor:

Collaboration diagram for StreamInterceptor:

Public Member Functions
	StreamInterceptor (std::ostream &stream, FILE *fileObject)
	Construct keeping a reference to the std::ostream and the file descriptor which are associated with this stream as well as a file descriptor for the replacement.
	~StreamInterceptor ()
	close file descriptors
bool	start ()
	start intercepting the stream.
bool	finish ()
	stop intercepting the stream.

Protected Member Functions
void	setReplacementFD (int fd)
	set the replacement file descriptor, should be called in the constructor of derived classes
bool	replaceFD (int fileDescriptor)
	Replace the file descriptor of m_fileObject with the one passed.

Static Protected Member Functions
static void	readFD (int fd, std::string &out)
	Read the contents of a file descriptor until there is no more input and place them in out.

Protected Attributes
std::ostream &	m_stream
	C++ stream object, only needed to flush before replacement.
FILE *	m_fileObject
	File object of the file we want to replace, needed to obtain file descriptor and to flush.
int	m_savedFD { -1}
	Saved file descriptor: a duplicate of the file descriptor of m_fileObject.
int	m_replacementFD { -1}
	Replacement file descriptor to be used while capturing.
bool	m_capturing {false}
	Check whether we are already capturing.

Detailed Description

Base class with all necessary features to intercept output to a file descriptor.

Definition at line 23 of file IOIntercept.h.

Constructor & Destructor Documentation

StreamInterceptor()

StreamInterceptor	(	std::ostream &	stream,
		FILE *	fileObject
	)

Construct keeping a reference to the std::ostream and the file descriptor which are associated with this stream as well as a file descriptor for the replacement.

Parameters

stream	C++ ostream which is associated with the file descriptor we want to intercept
fileObject	file object which is associated with the file descriptor we want to intercept

Definition at line 88 of file IOIntercept.cc.

                                                                          :
    m_stream(stream), m_fileObject(fileObject), m_savedFD(dup(fileno(m_fileObject)))
  {
    if (m_savedFD < 0) {
      B2ERROR("Error duplicating file descriptor: " << std::strerror(errno));
    }
  }

~StreamInterceptor()

~StreamInterceptor

(

)

close file descriptors

Definition at line 95 of file IOIntercept.cc.

  {
    finish();
    if (m_savedFD >= 0) close(m_savedFD);
    if (m_replacementFD >= 0) close(m_replacementFD);
  }

Member Function Documentation

finish()

bool finish ( )

inline

stop intercepting the stream.

Returns

true if the object was capturing and stream could be restored

Definition at line 46 of file IOIntercept.h.

      {
        if (!m_capturing) return false;
        m_capturing = false;
        return replaceFD(m_savedFD);
      }

readFD()

void readFD ( int  fd, std::string &  out  )

staticprotected

Read the contents of a file descriptor until there is no more input and place them in out.

Parameters

fd	file descriptor to read, should be opened in non blocking mode O_NOBLOCK
out	string to be replaced with all the bytes read from fd

Definition at line 102 of file IOIntercept.cc.

  {
    out.clear();
    if (fd <= 0) return;
    // need a buffer to read
    static std::unique_ptr<char[]> buffer(new char[1024]);
    // so then, read everything
    while (true) {
      ssize_t size = read(fd, buffer.get(), 1024);
      if (size <= 0) {
        // in case we get interrupted by signal, try again
        if (size < 0 && errno == EINTR)  continue;
        break;
      }
      out.append(buffer.get(), static_cast<size_t>(size));
    }
  }

replaceFD()

bool replaceFD ( int  fileDescriptor )

protected

Replace the file descriptor of m_fileObject with the one passed.

Parameters

fileDescriptor

file descriptor to be set for m_fileObject using dup2()

Definition at line 120 of file IOIntercept.cc.

  {
    // obviously we don't want to replace invalid descriptors
    if (fileDescriptor < 0) return false;
    // flush existing stream
    m_stream << std::flush;
    std::fflush(m_fileObject);
    // and clear the bad bits we might have gotten when pipe capacity is reached
    m_stream.clear();
    // and then replace the file descriptor
    const int currentFD = fileno(m_fileObject);
    if (currentFD < 0) {
      B2ERROR("Error obtaining file descriptor: " << std::strerror(errno));
      return false;
    }
    while (dup2(fileDescriptor, currentFD) < 0) {
      if (errno != EINTR && errno != EBUSY) {
        B2ERROR("Error in dup2(), cannot replace file descriptor: " << std::strerror(errno));
        return false;
      }
      // interrupted or busy, let's try again
    }
    return true;
  }

setReplacementFD()

void setReplacementFD ( int  fd )

inlineprotected

set the replacement file descriptor, should be called in the constructor of derived classes

Definition at line 54 of file IOIntercept.h.

{ m_replacementFD = fd; }

start()

bool start ( )

inline

start intercepting the stream.

Returns

true on success, false on any error

Definition at line 38 of file IOIntercept.h.

      {
        // only start if we are not already running
        if (!m_capturing) m_capturing = replaceFD(m_replacementFD);
        return m_capturing;
      }

Member Data Documentation

m_capturing

bool m_capturing {false}

protected

Check whether we are already capturing.

Definition at line 73 of file IOIntercept.h.

m_fileObject

FILE* m_fileObject

protected

File object of the file we want to replace, needed to obtain file descriptor and to flush.

Definition at line 67 of file IOIntercept.h.

m_replacementFD

int m_replacementFD { -1}

protected

Replacement file descriptor to be used while capturing.

Definition at line 71 of file IOIntercept.h.

m_savedFD

int m_savedFD { -1}

protected

Saved file descriptor: a duplicate of the file descriptor of m_fileObject.

Definition at line 69 of file IOIntercept.h.

m_stream

std::ostream& m_stream

protected

C++ stream object, only needed to flush before replacement.

Definition at line 65 of file IOIntercept.h.

---

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

• framework/utilities/include/IOIntercept.h
• framework/utilities/src/IOIntercept.cc