ml
48 lines
1.6 KiB
Go
48 lines
1.6 KiB
Go
package compression
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// ControlWordParamLimit is the highest number the param property of a control word can take.
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const ControlWordParamLimit = 0x1FFFF
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// ControlWord describes the current compression action.
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type ControlWord uint32
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// ControlWordOf returns a word with the given parameters.
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func ControlWordOf(count int, controlType ControlType, param uint32) ControlWord {
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return (ControlWord(count) << 20) | (ControlWord(controlType&0x7) << 17) | ControlWord(param&ControlWordParamLimit)
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}
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// LongOffsetOf returns a word that indicates a long offset with given value.
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func LongOffsetOf(offset uint32) ControlWord {
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return ControlWord(offset & 0xFFFFF)
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}
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// Packed returns the control word packed in a PackedControlWord with the given number of times.
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func (word ControlWord) Packed(times int) PackedControlWord {
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return PackedControlWord((uint32(word) & 0x00FFFFFF) | (uint32(times) << 24))
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}
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// Count returns the count value of the control.
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func (word ControlWord) Count() int {
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return int((uint32(word) >> 20) & 0xF)
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}
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// IsLongOffset returns true if Count() returns 0.
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func (word ControlWord) IsLongOffset() bool {
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return word.Count() == 0
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}
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// LongOffset returns the long offset value. Only relevant if IsLongOffset() returns true.
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func (word ControlWord) LongOffset() uint32 {
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return (uint32(word) >> 0) & 0xFFFFF
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}
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// Type returns the type of the control. Only relevant if IsLongOffset() returns false.
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func (word ControlWord) Type() ControlType {
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return ControlType((uint32(word) >> 17) & 0x7)
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}
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// Parameter returns the type specific parameter value.
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func (word ControlWord) Parameter() uint32 {
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return (uint32(word) >> 0) & ControlWordParamLimit
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}
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