go-bitmask-check

what is bitmask check in Go

tags: learning go programming

content

• im seeing this code:

if segmentedLine.Flags&parser.Elided == parser.Elided {
	break
}

• type of segmentedLine is GraphRowLine

type GraphRowLine struct {
	// other fields
	Flags    RowLineFlags
}

• and we have

type RowLineFlags int
const (
	Revision RowLineFlags = 1 << iota
	Highlightable
	Elided
)

• this involves:
  • go-bit-wise-operator
  • go-why-use-bit-wise-iota

if segmentedLine.Flags&parser.Elided == parser.Elided {
	break
}

• in other words, this condition checks:

  • does segmented.Flags contain parser.Elided flag?

• in an more Go idiomatic way:

if segmentedLine.Flags & parser.Elided != 0 {
	// do something
}

• because every flag only has 1 bit activated,
  • after AND operation, the result could only be 0 or parser.Elided
  • if it’s not zero, it means Flags contains Elided flag

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