Martino Ferrari
76 lines
1.6 KiB
Go
76 lines
1.6 KiB
Go
package pvdata
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import "io"
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// BitSet is a variable-length set of bit indices, encoded on the wire as:
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//
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// compact-size(n_bytes) + n_bytes of little-endian bits.
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//
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// Bit 0 of byte 0 is field index 0, bit 1 of byte 0 is field index 1, etc.
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// Used in pvData Monitor responses for "changed" and "overrun" masks.
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type BitSet struct {
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bits []byte
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}
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// NewBitSet returns an empty BitSet.
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func NewBitSet() BitSet { return BitSet{} }
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// Set sets bit i in the BitSet.
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func (bs *BitSet) Set(i int) {
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byteIdx := i / 8
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for len(bs.bits) <= byteIdx {
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bs.bits = append(bs.bits, 0)
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}
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bs.bits[byteIdx] |= 1 << (uint(i) % 8)
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}
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// Has reports whether bit i is set.
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func (bs *BitSet) Has(i int) bool {
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byteIdx := i / 8
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if byteIdx >= len(bs.bits) {
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return false
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}
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return bs.bits[byteIdx]&(1<<(uint(i)%8)) != 0
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}
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// ReadBitSet reads a BitSet from r.
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func ReadBitSet(r io.Reader) (BitSet, error) {
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n, err := ReadSize(r)
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if err != nil {
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return BitSet{}, err
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}
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if n == 0 {
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return BitSet{}, nil
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}
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buf := make([]byte, n)
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if _, err := io.ReadFull(r, buf); err != nil {
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return BitSet{}, err
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}
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return BitSet{bits: buf}, nil
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}
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// WriteBitSet writes bs to w.
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func WriteBitSet(w io.Writer, bs BitSet) error {
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if err := WriteSize(w, int64(len(bs.bits))); err != nil {
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return err
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}
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if len(bs.bits) == 0 {
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return nil
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}
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_, err := w.Write(bs.bits)
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return err
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}
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// FieldIndices returns all set bit indices in ascending order.
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func (bs *BitSet) FieldIndices() []int {
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var out []int
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for bi, b := range bs.bits {
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for bit := 0; bit < 8; bit++ {
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if b&(1<<uint(bit)) != 0 {
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out = append(out, bi*8+bit)
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}
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}
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}
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return out
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}
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