40 lines
844 B
Go
40 lines
844 B
Go
package structs
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import "fmt"
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// Bitmap is a simple uncompressed bitmap
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type Bitmap []byte
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// NewBitmap returns a bitmap with up to size indexes
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func NewBitmap(size int) (Bitmap, error) {
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if size <= 0 {
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return nil, fmt.Errorf("bitmap must be positive size")
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}
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if size&7 != 0 {
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return nil, fmt.Errorf("bitmap must be byte aligned")
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}
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b := make([]byte, size>>3)
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return Bitmap(b), nil
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}
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// Set is used to set the given index of the bitmap
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func (b Bitmap) Set(idx uint) {
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bucket := idx >> 3
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mask := byte(1 << (idx & 7))
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b[bucket] |= mask
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}
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// Check is used to check the given index of the bitmap
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func (b Bitmap) Check(idx uint) bool {
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bucket := idx >> 3
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mask := byte(1 << (idx & 7))
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return (b[bucket] & mask) != 0
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}
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// Clear is used to efficiently clear the bitmap
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func (b Bitmap) Clear() {
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for i := range b {
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b[i] = 0
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}
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}
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