code::ProgressiveReader Class Reference

Inheritance diagram for code::ProgressiveReader:

List of all members.

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Detailed Description

This interface allows for reading a file as it is arriving.

Author:

Lakshman

Version:

Id

code_ProgressiveReader.h,v 1.6 2009/06/02 20:17:39 lakshman Exp

See also:

ProgressiveFileReader

CompressedFileReader

Public Member Functions
	ProgressiveReader (const URL &url)
virtual	~ProgressiveReader ()
virtual bool	readNext (Buffer *dataBuf, size_t *bytes_read)=0
	Progressive readers, on successive calls to this method will read further and further into the file.
Static Public Member Functions
static SmartPtr< ProgressiveReader >	getReader (const URL &url)
	return a ProgressiveReader that can handle this file.
Protected Attributes
URL	url

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Constructor & Destructor Documentation

code::ProgressiveReader::ProgressiveReader

(

const URL &

url

)

virtual code::ProgressiveReader::~ProgressiveReader

(

)

[inline, virtual]

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Member Function Documentation

static SmartPtr<ProgressiveReader> code::ProgressiveReader::getReader

(

const URL &

url

)

[static]

return a ProgressiveReader that can handle this file.

Currently, the implementation assumes that if a file is compressed, it should be read using the CompleteFileReader else using the ProgressiveFileReader.

virtual bool code::ProgressiveReader::readNext	(	Buffer *	dataBuf,
		size_t *	bytes_read
	)			[pure virtual]

Progressive readers, on successive calls to this method will read further and further into the file.

Parameters:

	dataBuf	the Buffer to be modified with this method call dataBuf should be initialized to a reasonable size e.g: 1MB
	bytes_read	will be filled in with the number of bytes of dataBuf that have been filled in.

Returns:

isComplete whether or not this method should be called again to get more data

Example code:

    size_t tot_bytes = 0;

read the file ...
    bool complete = false;
    do {
read bytes
      size_t bytes_read = 0;
      complete = reader->readNext( &dataBuf , &bytes_read );

notify handlers
      if ( bytes_read > 0 ){
do something with the data
      }

update running total
      tot_bytes += bytes_read;
    } while ( !complete );
  }
do something with tot_bytes
  

Note that if the file is being filled in (in real-time), even if the readNext returns complete on one call, a subsequent call may return valid data (more data may have arrived in the intermediate time). Knowledge of when the file is complete is external, such as through knowing the file format.

Implemented in code::ProgressiveFileReader, and code::CompleteFileReader.

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Member Data Documentation

URL code::ProgressiveReader::url [protected]

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