filereader.go

package main

/**
- Phani Teja Kesha (KP38691)
- Seshagopalan Narasimhan (XP27536)
- Siddhant Goenka (VI91418)
- Vamshi Krishna Sai Nagabandi (SO03137)
*/
import "os"

/* Structure to save file information */
type fileInfo struct	{
	filename string
	filesize uint64
	start, end uint64
}

/* Method to update file information like file size, used to distribute load to workers   */
func (freader *fileInfo) info()	{

		file, err := os.Open(freader.filename)

		if check(err)	{
			freader.filesize = getFileSize(file)
			logger.Infof("[%s] Filesize: %d bytes", freader.filename , freader.filesize)
			file.Close()
		}else {
			logger.Alert("Unable to open file:", freader.filename)
			logger.Critical("Closing application...")
			panic("Need filesize to distribute load to workers")
		}//end of file open check

}//end of method


/* Reads the file, based on start and end location specified in the structure */
func (freader *fileInfo) read() []byte {

	file, err := os.Open(freader.filename)

	if check(err)	{

		freader.filesize = getFileSize(file)

		/* Double check seek endpoints */
		/* No need of freader.start>=0 check, as its unsigned int */
		if freader.start<freader.end && freader.end<=freader.filesize	{

			offset := int( freader.end - freader.start + 1 )
			_, err := file.Seek( int64(freader.start), 0 )

			if check(err)	{
				var data = make([]byte, offset)
				logger.Debugf(" Reading %d bytes from %s ", offset, freader.filename )
				file.Read(data);
				return data
			}else {
				logger.Errorf("Unable to read file using seek values [%d,%d] ", freader.start, freader.end )
			}

		}else if freader.start==0 && freader.end==0 {
			/* Only if start and end is not defined the values of both would be 0, implying read the whole file */
			var data = make([]byte, freader.filesize)
			logger.Debugf(" Reading whole file %s ", freader.filename )
			file.Read(data)
			return data
		}else {
			logger.Errorf("Invalid Seek options to read file [%d,%d] ", freader.start, freader.end )
		}

		file.Close()

	}else {
		logger.Error("Unable to open file: ", freader.filename)
		panic("Error opening file...Exit initiated! ")
	}//end of file open check

	logger.Warningf("[%s] NO Bytes to return ", freader.filename )
	return make([]byte, 0)

}//end of method



func getFileSize(file *os.File) uint64	{
	stat, err := file.Stat()
	if check(err)	{
		return uint64(stat.Size())
	}else {
		logger.Alert("Unable to get filesize")
		logger.Critical("Closing application...")
		panic("Need filesize to distribute load to workers")
	}
}