79 lines
1.8 KiB
Go
79 lines
1.8 KiB
Go
/*
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Package bitfield provides a simple and efficient arbitrary size bit field implementation.
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It doesn't attempt to cover everything that could be done with bit fields,
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providing only things used by neo-go.
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*/
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package bitfield
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// Field is a bit field represented as a slice of uint64 values.
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type Field []uint64
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// Bits and bytes count in a basic element of Field.
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const elemBits = 64
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const elemBytes = 8
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// New creates a new bit field of specified length. Actual field length
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// can be rounded to the next multiple of 64, so it's a responsibility
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// of the user to deal with that.
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func New(n int) Field {
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return make(Field, 1+(n-1)/elemBits)
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}
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// Set sets one bit at specified offset. No bounds checking is done.
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func (f Field) Set(i int) {
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addr, offset := (i / elemBits), (i % elemBits)
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f[addr] |= (1 << offset)
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}
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// IsSet returns true if the bit with specified offset is set.
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func (f Field) IsSet(i int) bool {
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addr, offset := (i / elemBits), (i % elemBits)
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return (f[addr] & (1 << offset)) != 0
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}
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// Copy makes a copy of current Field.
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func (f Field) Copy() Field {
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fn := make(Field, len(f))
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copy(fn, f)
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return fn
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}
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// And implements logical AND between f's and m's bits saving the result into f.
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func (f Field) And(m Field) {
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l := len(m)
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for i := range f {
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if i >= l {
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f[i] = 0
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continue
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}
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f[i] &= m[i]
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}
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}
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// Equals compares two Fields and returns true if they're equal.
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func (f Field) Equals(o Field) bool {
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if len(f) != len(o) {
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return false
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}
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for i := range f {
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if f[i] != o[i] {
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return false
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}
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}
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return true
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}
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// IsSubset returns true when f is a subset of o (only has bits set that are
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// set in o).
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func (f Field) IsSubset(o Field) bool {
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if len(f) > len(o) {
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return false
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}
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for i := range f {
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r := f[i] & o[i]
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if r != f[i] {
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return false
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}
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}
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return true
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}
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