calculate_seek.go

Documentation: github.com/dsoprea/go-utility/v2/filesystem

     1  package rifs
     2  
     3  import (
     4  	"io"
     5  	"os"
     6  
     7  	"github.com/dsoprea/go-logging"
     8  )
     9  
    10  // SeekType is a convenience type to associate the different seek-types with
    11  // printable descriptions.
    12  type SeekType int
    13  
    14  // String returns a descriptive string.
    15  func (n SeekType) String() string {
    16  	if n == io.SeekCurrent {
    17  		return "SEEK-CURRENT"
    18  	} else if n == io.SeekEnd {
    19  		return "SEEK-END"
    20  	} else if n == io.SeekStart {
    21  		return "SEEK-START"
    22  	}
    23  
    24  	log.Panicf("unknown seek-type: (%d)", n)
    25  	return ""
    26  }
    27  
    28  // CalculateSeek calculates an offset in a file-stream given the parameters.
    29  func CalculateSeek(currentOffset int64, delta int64, whence int, fileSize int64) (finalOffset int64, err error) {
    30  	defer func() {
    31  		if state := recover(); state != nil {
    32  			err = log.Wrap(state.(error))
    33  			finalOffset = 0
    34  		}
    35  	}()
    36  
    37  	if whence == os.SEEK_SET {
    38  		finalOffset = delta
    39  	} else if whence == os.SEEK_CUR {
    40  		finalOffset = currentOffset + delta
    41  	} else if whence == os.SEEK_END {
    42  		finalOffset = fileSize + delta
    43  	} else {
    44  		log.Panicf("whence not valid: (%d)", whence)
    45  	}
    46  
    47  	if finalOffset < 0 {
    48  		finalOffset = 0
    49  	}
    50  
    51  	return finalOffset, nil
    52  }
    53
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